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Interactions between growth, sex, reproduction, and activity levels in control and fast-growing strains.. 1998

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INTERACTIONS BETWEEN GROWTH, SEX, REPRODUCTION, A N D ACTIVITY LEVELS IN CONTROL A N D FAST-GROWING STRAINS OF NILE TILAPIA (Oreochrotnis niloticus) CHANTELLE CAROLE BOZYNSKI B.Sc, The University of British Columbia, 1995 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of Zoology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA June 1998 © Chantelle Carole Bozynski, 1998 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of ZcXp\ The University of British Columbia Vancouver, Canada DE-6 (2/88) 11 Abstract Cultured fish play an important role i n meeting increasing demands of human consumption around the world . To meet consumer demand for larger-sized fish, fish culturist seek strains that possess a high growth rate and reach harvestable size before attaining sexual maturation. G i v e n the importance for farmers of understanding growth phenomena and controlling sexual maturation in fish stocks, this thesis examined the relationship between growth, behavioural activity, and sexual maturation i n control strains of Ni le tilapia, Oreochromis niloticus, and i n strains resulting from a project devoted to the Genetic Improvement of Farmed Tilapias (GIFT). Behavioural activity of fish groups was videorecorded each month of the three month study period. Under laboratory conditions, the fast-growing GIFT fish performed less locomotory and agonistic activity than the slow-growing control fish. Mir ror image stimulation tests performed on individual males supported the finding that controls are more aggressive than GIFT fish. In the comparison of females and males, the fast-growing male GIFT performed less locomotory, but more agonistic behaviour than the slow- growing female GIFT. In the controls, growth rates of males and females were relatively similar even though, the male controls performed more locomotory and agonistic behaviour than the female control fish. In all, low growth was associated wi th a high activity level; however, a few experimental observations appear to deviate from this relationship and are discussed. Ml Nesting behaviour, which is often the first indication of sexual maturity, was observed only i n males. Male controls performed more nesting behaviour than male GIFT fish. Also , significantly more nests were built by the control than GIFT fish. This suggest, at least i n males, that the slow-growing control fish became sexually mature sooner, and at a smaller size than the fast-growing GIFT fish. Furthermore, male GIFT fish required more time to complete their nest(s), and built fewer nests than male control fish. iv Table of Contents Abstract ii List of Tables vi List of Figures vii Acknowledgements — viii CHAPTER I General Introduction and Background Information 1 Introduction to the Problem 1 Background 2 Wild vs. Hatchery-reared fish 2 Sexual dimorphism in size 3 Nile tilapia (Oreochromis niloticus) 5 Objectives of the present study 7 CHAPTER II General Materials and Methods 8 Experimental Animals 8 Holding and Experimental Facilities 8 Videocamera Set-up 9 Fish Identification 10 Determination of Sex 11 Procedure for Recording Weight and Length Measurements 11 Behavioural Measures :.. 12 Swimming 12 Resting 12 Chasing/Escaping 12 Tail-beating 12 Nipping 13 Confronting 13 Jaw Lock 13 Opercular Flare 13 Gulping 13 Feeding 14 Nesting 14 Statistical Analyses 15 CHAPTER III Experiment I: Growth, behavioural activity, and sexual maturation in control and GIFT strains of Nile tilapia 16 Introduction : 16 Materials and Methods 17 Results 18 V CHAPTER IV Experiment II: Aggressive behaviour of males of control and GIFT strain of Nile tilapia in response to a mirror image 41 Introduction 41 Materials and Methods 42 Results .: : 43 CHAPTER V Experiment III: Nest building in male fish of the control and GIFT strains of Nile tilapia 45 Introduction 45 Materials and Methods 45 Results 47 CHAPTER VI Discussion :' 52 Concluding Remarks 64 References : 66 Appendix I 76 Appendix II 101 Appendix III 104 Appendix IV 106 Appendix V : 108 List of Tables v i Table I Total time two strains of juvenile Ni le tilapia (control and GIFT) performed swimming and resting acts each month of the three month study 21 Table II Number of bouts of locomotory and agonistic behaviours the control and GIFT strains of juvenile Ni le tilapia performed each month of the three month study 23 Table IE Total time the female and male juvenile Ni le tilapia (control and GIFT strains) performed swimming and resting acts each month of the three month study 28 Table IV Number of bouts of agonistic and escape behaviours performed by the female and male juvenile Nile tilapia (control and GIFT strains) each month of the three month study 31 Table V Number of bouts of locomotory behaviours performed by the female and male juvenile Nile tilapia (control and GIFT strains) each month of the three month study 35 Table V I Size-specific mortality i n the two strains of Ni le tilapia (control and GIFT) during the three month study period 39 Table VII Size-specific mortality in the male and female fish of the control strain Ni le tilapia 40 Table VIII Total time required to build a nest, the size of the nest at completion, nest diameter relative to fish length, and the number of nests built per fish were examined in the male fish of two strains of Ni le tilapia (control and GIFT) 51 List of Figures vi i Figure 1 Weight of fish from two strains of Nile tilapia (control and GIFT) 19 Figure 2 Length of fish from two strains of Nile tilapia (control and GIFT) 20 Figure 3 Weight of females and males from two strains of Ni le tilapia (control and GIFT) 25 Figure 4 Length of females and males from two strains of Ni le tilapia (control and GIFT) 26 Figure 5 Number of nests present in the experimental aquaria (control and GIFT strain of Nile tilapia) 37 Figure 6 Number of mirror-directed biting and tail-beating performed by the male fish from two strains of Ni le tilapia (control and GIFT) during the two behavioural trials 44 Figure 7 Weight of the nesting and non-nesting male fish from two strains of Nile tilapia (control and GIFT) 48 Figure 8 Length of the nesting and non-nesting male fish from two strains of Nile tilapia (control and GIFT) 49 Acknowledgements v m I would like to thank my supervisors, Dr . Robin Liley and Dr. Daniel Pauly for their assistance and support throughout the project. I w o u l d also like to thank my committee members, Dr . George Iwama and Dr . Dav id Randall , for their helpful criticisms and suggestions on the manuscript. I w o u l d l ike to thank the International Center for L i v i n g Aquat ic Resources Management ( I C L A R M ) for donating the two strains of Ni le tilapia for my study. I would also like to thank everyone from the U B C Zoology Department workshop, especially Bruce Gillespie, who helped me with the videocamera set-up. In addition, I am indebted to Patrick Shiu for his unswerving support and valuable advice throughout the study. Last, but certainly not the least, I would like to thank my family for their constant support and understanding, but especially my mother whose guidance has put me on the path of true fulfilment. CHAPTER I 1 General Introduction and Background Information Introduction to the Problem Rearing of cultured fish i n fish farms has become a fast growing industry. W i t h the increase i n demand for fish products on wor ld markets and the reduction i n w i l d fish stocks due to overexploitation of natural fish populations, cultured fish play an important role i n meeting the increasing demand of fish for h u m a n consumption around the world . One important production trait of farmed fish is its size at first sexual maturation. Fish strains that possess a high growth rate and reach harvestable size before attaining sexual maturation are sought by fish culturists because sexual maturation and spawning complicate production operations and/or affect product quality. This is especially important for the tilapias (mainly Oreochromis and Tilapia, Fam. Cichlidae), fish of African origin, which is now farmed for local and export markets i n over 80 countries (e.g., Phil ippines, Taiwan, Israel, and United States). When tilapia are stocked i n an unpopulated pond or another aquaculture facility, the fish often shift towards a more altricial life style, characterized by a shorter period of somatic growth, an earlier onset of reproductive maturity, and more numerous, smaller eggs (Fryer and lies, 1972; Noakes and Balon, 1982). The fish become "stunted," i n that they are smaller than other adults of the same species. The real phenomenon is that the fish are 2 not "small for their age," but "old for their size" (Noakes and Balon, 1982). These stunted individuals are unsuitable for the market, thus causing problems i n the fish industry. This provides the overall background for the work presented here. Background Wild vs. Hatchery-reared fish Growth rate comparisons have been made between w i l d and hatchery-reared fish. Vincent (1960), and Flick and Webster (1964) observed i n the brook trout, Salvelinus fontinalis, that under hatchery conditions, farmed fish grew faster than w i l d stocks. E i n u m and Fleming (1997), and Fleming and E i n u m (1997) also observed, under hatchery conditions, faster growth i n farmed Atlantic salmon, Salmo solar, than i n w i l d stock. Even under natural conditions, w i l d stock had a lower growth rate than farmed fish (Einum and Fleming, 1997). Furthermore, Davis and Fenderson (1971) observed i n Atlantic salmon that, even though hatchery and w i l d parr were matched for size when introduced to a divided outdoor stream aquarium, hatchery parr were on average larger i n size than w i l d parr as the study progressed. Overall , hatchery-reared fish seem to have a growth advantage over w i l d fish stocks. W i l d and hatchery-reared fish differ not only i n growth rates, but also i n their behavioural activity. Bachman (1984) observed i n the brown trout, Salmo trutta, that hatchery-reared fish fed less than w i l d fish. A similar feeding pattern was observed i n Atlantic salmon (Fenderson et al, 1968; Sosiak et al., 1979). Davis and Fenderson (1971), and Sosiak (1978) also observed i n Atlantic salmon that 3 hatchery parr were less shelter-oriented and more mobile than w i l d parr, and exhibited higher frequencies of agonistic behaviours. N o r m a n (1987), i n contrast, found Atlantic salmon fry of the hatchery stocks to be less aggressive. H o l m and Ferno (1978) went a step further i n their study, by examining the connection between aggressive activity and growth rate. They observed that aggressive Atlantic salmon parr grew less rapidly, while parr wi th the most rapid growth performed aggressive actions less often (Holm and Ferno, 1978). These results imply a negative relationship between aggressive activity and growth. Furthermore, Robinson and Doyle (1990) found a negative correlation between aggression and growth i n the tilapia hybrid, Oreochromis mossambicus x O. hornorum. Unfortunately, there is little information on the relationship between activity and growth i n farmed-reared and w i l d fish stocks. Thus, more research is needed to examine these relationships to see to what extent growth differences between farmed-reared and w i l d fish can be attributed to differences i n locomotory and/ or aggressive activity levels of fish stocks. Sexual dimorphism in size A s information has accumulated on growth rates of various fish species, it has become apparent that either a) the males and females of a given species grow at the same rate and have similar max imum sizes (e.g., herrings), b) the females have faster growth rates and reach larger size than the males (e.g., codfishes), or c) the males have faster growth rates and become larger than the females (e.g., cichlids) (Fryer and lies, 1972). The sex-related growth differences i n cichlids, 4 including N i l e tilapia, are wel l established (van Someren and Whitehead, 1959; Mabaye, 1971; Fryer and lies, 1972; Lowe-McConnel l , 1975, 1982; Balarin and Hatton, 1979; Palada-de Vera and Eknath, 1993; Toguyeni et al, 1996,1997). The causes of male growth superiority i n cichlids have been examined; however, no single explanation of sexual d imorphism i n size has been widely accepted. One hypothesis is that tilapia females put so much more energy into egg production, producing eggs at very frequent intervals, which may result i n costs to growth; also the females almost cease to feed while mouthbrooding their eggs and young (Lowe-McConnell , 1975). Another is that male sex hormones have an anabolic or growth promoting effect, and thus could result i n the higher growth of males (Donaldson et al., 1979; Ufodike and Madu , 1986). In addition, thyroid hormones (T 3 and T 4 ) also participate i n regulating growth and development. Toguyeni et al. (1996, 1997) observed, i n N i l e tilapia, that plasma T 3 levels were higher i n males than females, which could account for the males' growth advantage. It was also suggested that the difference i n growth may be related to a sex-linked genetic characteristic which gives the male an advantage either through efficiency of food conversion, or through aggressive feeding behaviour (Mabaye, 1971). Behavioural activity and its association wi th larger-sized males compared to females is an area that remains to be explored. Toguyeni et al. (1997) observed, i n mixed sex groups of N i l e tilapia, an increase i n activity and a decrease i n growth; however, no connection was made between the higher growth of males and their activity level. Therefore, more experimentation is needed to study the relationship between growth and activity level i n both sexes. 5 Nile tilapia (Oreochromis niloticus) Oreochromis niloticus originates from the upper N i l e i n Uganda. It has moved southwards, colonizing al l the western Rift lakes down to Lake Tanganyika, and has colonized central and western Africa, by the Chad and Niger basins. Its expansion is still taking place; it has not yet reached some of the tributaries of the upper Niger and it is rare i n the coastal rivers of western Africa (Philippart and Ruwet, 1982). It is found not only i n several of the great lakes of Africa but even outside Africa i n at least one coastal river of Israel (Fryer and lies, 1972). Oreochromis niloticus, a maternal mouthbrooding cichlid, has a lek-based breeding system analogous to those seen i n lekking birds (Fryer and lies, 1972; McKaye, 1984). Males congregate i n shallow waters where they excavate a shallow, saucer-like depression, to which they attract a succession of females. In the study of McKaye (1986), the term bower' was given to this bowl-shaped depression instead of "nest' because it is used only as a site for courting females, and mating (Borgia, 1985); it is constructed independently of the need to care for eggs and young (McKaye, 1986). However, both terms (i.e., nest and bower) have been used to describe the depression i n the sand, and thus both terms are used here. As eggs are being deposited i n the bower, the female quickly takes eggs and sperm into her mouth, where fertilization takes place, and then leaves for brooding grounds. The embryos and fry are brooded i n the female's mouth for approximately 20-30 days and then released (Fryer and lies, 1972). 6 In mouthbrooding cichlids, body size does not appear to be a major consideration i n mate choice, as observed i n substratum-spawning cichlids (McKaye, 1986). Males appear to court al l females indiscriminately, while females choose males on the basis of the character and/or location of the bower (McKaye, 1984). It was observed that a large bower is preferred by females (McKaye et al., 1990), and thus males who bui ld large bowers should experience a higher mating success. Due to the importance of nest characters on mating success of males, more informat ion on nest bui lding by mouthbrooding cichlids, such as N i l e tilapia, would be of interest. Ni le tilapia has dominated global tilapia culture since the 1980's, and its share of total tilapia production has increased dramatically from 33% or 66,000 mt i n 1984 to 72% or 474,000 mt i n 1995 (Rana, 1997). However, P u l l i n and Capi l i (1988) found that little attention had been given to the genetic improvement of farmed populations of N i l e tilapia (see also Pul l in , 1998). In 1988, an international workshop confirmed the findings of Pu l l i n and Capi l i that tilapia broodstocks used for aquaculture outside Africa were l imited i n genetic diversity (Pul l in , 1988; as cited i n Pu l l in , 1998). It was concluded that more investment i n research for the genetic improvement of tilapias was needed. Based upon these findings, the International Center for L i v i n g Aquatic Resources Management ( I C L A R M ) and its collaborators initiated the Genetic Improvement of Farmed Tilapias (GIFT) project i n the Philippines. Four new wi ld founder populations of N i l e tilapia (from Egypt, Ghana, Kenya, and Senegal) and populations of four strains of Ni le tilapia i n current use by farmers i n As ia (Israel' , Singapore, Taiwan, and 7 Thailand) were assembled. The genetic material from the best families of a l l strains were incorporated, according to their performance rankings, i n a synthetic strain termed GIFT ' strain. This synthetic strain has since been subjected to selective breeding for good growth (Pullin, 1998). A recent project found the estimated yield potential of the GIFT strain to be significantly higher than that of some of the existing farmed strains i n As i a ( I C L A R M - A D B , 1998; as cited i n Pul l in , 1998). Objectives of the present study It was wi th the ini t ial a im of examining the relationship that exist between growth rate and activity level of fish from two strains of N i l e tilapia (control and GIFT) that I commenced my preliminary observations i n March, 1997. Dur ing the following 12 months, three experiments were undertaken. The first experiment examined a) the differences i n the growth rates of the control and GIFT fish under controlled laboratory conditions, b) the relationship between growth rate and activity level, and c) the onset of sexual maturity as it relates to the differences i n growth rates. The second experiment examined, i n more detail, the differences i n the offensive aggression between male fish of both strains. Lastly, the third experiment examined nest bui lding i n male fish f rom the control and GIFT strains of N i l e tilapia. CHAPTER II 8 General Materials and Methods Experimental Animals The two strains of Ni le tilapia (Oreochromis niloticus), a fish of African origin, were imported into Vancouver, Canada from the International Center for L i v i n g Aquatic Resources Management ( ICLARM) , Bureau of Fisheries and Aquatic Resources (BFAR) / National Freshwater Fisheries Technology Research Center (NFFTRC), Munoz , Nueva Ecija, Philippines. The two strains are: 4th generation of GIFT fish (see Background on Ni l e tilapia) and v control ' N i l e tilapia from Bulacan Province, Philippines, typical of those fish farmed i n A s i a n countries where selective breeding has not yet been widely applied. Holding and Experimental Facilities O n arrival at the University of Brit ish Columbia (January 30th), the fish were placed i n 55 and 102 L stock tanks wi th similar fish densities (approximately 5.5 L of water per fish) for a five week period to acclimatize the fish to the laboratory conditions; the fish were then transferred to the experimental aquaria. A l l experimental aquaria were maintained at 24.0 + 0.5°C; the water temperature was similar to both pond sources i n the Philippines (i.e., 24-25°C). The temperature of the water i n the experimental tanks was maintained by the use of a r o o m heater which kept the room temperature at approximately 27°C. Each experimental tank, wi th dimensions of 61.0 cm x 30.5 cm x 30.5 cm, was provided 9 wi th a layer of gravel (depth of 2.5 cm), and a box charcoal filter. A l l four sides of the tanks were covered wi th beige paper to prevent visual interaction between neighbouring fish. I l luminat ion was provided, over a 12-h photoperiod, by fluorescent lights mounted 2 m above each row of tanks. The light strips were positioned upwards to minimize light reflection from the water surface f rom entering the camera lens during videorecording. Dur ing behavioural recording, two extra light strips, housed i n a wooden frame, were placed on either side of the row of aquaria to allow the fish to be seen clearly. These two extra light strips were turned on 30 m i n prior to the observation sessions to acclimatize the fish to the higher light intensity. The fish were fed commercially prepared catfish feed (Otter Co-op, Aldergrove, Brit ish Columbia) at 3% wet weight of fish daily. The quantity of feed given was adjusted monthly following the recording of standard length and weight of each fish. Videocamera Set-up Locomotory and agonistic behaviours were recorded using a colour pro843 R C A videocamera supported by a 4-wheeled a lumin ium stand placed on two a lumin ium tracks. This stand enabled the videocamera to be positioned lens down approximately 75 cm above the r i m of each experimental tank. A cable to a Panasonic video monitor, allowed fish behaviours to be observed while being videorecorded. 10 Fish Identification The fish were marked by attaching a coloured bead to each indiv idua l . The beads were attached 10 days prior to the start of the behavioural recordings. The fish were anaesthetized by being immersed i n a buffered 0.03% w / v solution of methane tricaine sulfonate (MS 222, Syndel Laboratories, Vancouver, Canada). When a fish was nearly motionless, on its side, and respiring slowly, the fish was removed from the solution and placed on a moist sponge. A 0.25 m m diameter nylon monofilament, wi th one bead tied onto one end, was sewn through the musculature at the front end of the dorsal fin using a sewing needle. The bead was secured onto the fish as described i n Kroon (1997). The fish was returned to the freshwater and allowed to recover. Five light-coloured beads were used: yellow, white, blue, green, and pink. These bead colours were chosen because they were i n sharp contrast to the dark surroundings (i.e., dark body colouration and sand). The presence of brightly coloured beads o n the fish apparently d id not change the motivational state of the neighbouring fish: there appeared to be no increase i n the frequency of agonistic acts directed towards beaded fish (pers. obs.). It was important to resolve this issue because body colour patterns are important i n the visual communication of cichlids and the pattern of colouration changes according to the motivational state of the fish (Billy, 1982; Nelissen, 1991). For a more detailed description of colour patterns i n tilapias see Bi l ly (1982). 11 Determination of Sex The sex of the fish was initially determined by the external examination of the genital papilla (Afonso and Leboute, 1993) and then verified later by the dissection of the gonads. The distinctive features of the genital papilla of the male and female tilapia are described by Maar et al. (1966). Briefly, the male has two orifices situated just forward of the anal fin. One is the anus, the other is the urogenital aperture which usually forms into a small papilla. The female, i n contrast, has three orifices, namely the anus, a transverse genital opening and a microscopic urinary orifice which is scarcely visible to the naked eye (Balarin and Hatton, 1979). The anaesthetized fish was placed belly-up on a moist sponge and a dye (potassium permanganate) was applied onto the genital papilla wi th a Q- tip, as suggested by L.O.B. Afonso (pers. comm.). This dye was used to highlight a slit (genital opening) present only i n the females (Afonso and Leboute, 1993). The anaesthetized fish was then placed under a dissecting microscope (magnification: 7-10X) to inspect the genital papilla. A fish was considered to be a female when the slit was observed. The sex determination procedure commenced on May 19th and was repeated and thereby verified during the monthly recordings of the weight and length measurements. Procedure for Recording Weight and Length Measurements Weight and length measurements were recorded monthly. The anaesthetized fish were placed on a wet Plexiglas surface alongside a metric ruler, and their standard length was recorded. The anaesthetized fish was then placed i n a large petri dish on a weight scale to record their weight. 12 Behavioural Measures Detailed descriptions of cichlid behaviour can be found i n Baerends and Baerends-van Roon (1950), Bi l ly (1982) and Fryer and lies (1972). For the purpose of this experiment, the activity was measured on the basis of the fol lowing twelve behaviours: Swimming Swimming is a movement of the fish i n any direction i n the water co lumn without any interactions wi th other fish; Resting A fish is considered to be resting when it stays i n the same position, either i n the water column or on the gravel bottom, long enough for the computer key used to encode resting behaviour to be pressed by the observer; Chasing/Escaping A fish swimming after another fish at a high velocity is described as chasing, while escape behaviour is carried out by the fish swimming away from the aggressor; Tail-beating Tail-beating occurs when a fish presents the lateral aspect of its body to an opponent, head to tail, and uses its caudal fin to beat the water sideways over the head of its opponent (Baerends and Baerends-van Rooh, 1950; Bi l ly , 1982; Fryer and lies, 1972). The tail-beating ind iv idua l does not actually touch the opponent. Tail-beating is used as a threat signal by a territorial male towards an in t ruding male (Billy, 1982); presumably, this act communicates the animal's strength 13 (Baerends and Baerends-van Roon, 1950). Tail-beating also serves as a courtship signal by a territorial male towards a female entering his territory (Billy, 1982); Nipping Biting directed towards a fin and/or the body of a neighbouring fish is referred to as nipping. Occasionally, nipping results i n fin amputation and body scarring (Billy, 1982); Confronting Confronting occurs between territorial males during boundary disputes. Opposing males rush at each other ending their charges at the c o m m o n boundary (nest rim). The males then oscillate back and forth i n synchrony, w i t h one male (fins collapsed) retreating while its opponent (fins raised) advances a few centimetres. This back and forth motion is completed several times i n rapid succession, after which the males separate or attack (e.g., jaw lock) (Billy, 1982); Jaw Lock A jaw lock is performed when the fish grip each others mouth, and start pushing and pul l ing each other to and fro (Fryer and lies, 1972); Opercular Flare Opercular flaring occurs when a fish erects the operculae and branchiostegal membrane, and reveals its dorsally-situated black opercular spots; Gulping The action of a fish swimming to the water surface and taking i n surface water wi th its mouth is termed gulping. This behaviour increases oxygen uptake, i.e., complements gi l l breathing (Weber and Kramer, 1983); 14 Feeding A fish is considered to be feeding when sand is picked up wi th its mouth, sifted (i.e., separates food particles from sand), and then dropped indiscriminately. Nesting A male fish establishes a territory by digging a nest pit i n the substrate. Nest ing occurs when a fish swims head down into the substrate, secures a mouthful of sand, swims a short distance from the centre of the pit, and spits out the substrate. In contrast to feeding, no sifting is performed. The displaced substrate is deposited on the edge of a territory, where it accumulates and forms a raised r i m around the nest. This raised r i m defines territorial boundaries. Localized digging produces a pit which a male occupies and defends from intruders whi le attempting to attract spawning partners. Nesting is used to maintain the nest r i m and to remove debris from the pit. Each male digs throughout its residency i n a territory, wi th the frequency of digging at a peak when the territory is being established. The female fish also nest, but only i n the later stages of courtship prior to spawning (Billy, 1982). The total duration of swimming and resting was recorded, while the number of bouts of chasing, escaping, tail-beating, nipping, confronting, jaw-locking, opercular flaring, gulping, feeding and nesting were recorded. The data o n locomotory and agonistic behaviours were then analysed using The Observer version 3.0 computer software (Noldus Information Technology, Wageningen, Netherlands). 15 Statistical Analyses Linear regression equations were used to test for significant differences i n the growth curves (weight and length). The Mann-Whitney U-test was used i n the comparison of independent measures of fish from the GIFT and control strain. These tests were one-tailed unless otherwise stated. The chi-square goodness of fit test was used to determine if there were significant differences between the actual number of fish from four experimental groups (i.e., female control, male control, female GIFT and male GIFT) that performed behavioural activities, and a theoretically even distribution. If the chi-square analysis detected significant departures from the even distribution, the chi-square analysis was subdivided to determine whether the significant difference between observed and expected frequencies was concentrated i n certain of the experimental groups, or whether the difference was due to the effects of the data i n al l of the four experimental groups (Zar, 1996). When the observed frequencies were small, the use of the two-tailed Fisher exact test was preferred over the chi-square analysis. The leve l of significance was set at a=0.05 for all statistical analyses. CHAPTER III 16 Experiment I: Growth, behavioural activity, and sexual maturation i n the control and GIFT strains of N i l e tilapia Introduction The examination of the relationship between maturity, size, and age i n fish has yielded conflicting results. A i m (1959) noted some cases i n which the slower growing forms matured earlier and at a smaller size than the faster-growing forms, and many more cases i n which the opposite was true. In tilapia, particularly i n N i l e tilapia, the female fish tend to have a lower growth rate than the male fish (Balarin and Hatton, 1979; Lowe-McConnell , . 1982). Furthermore, i n culture ponds, fish of the GIFT strain of Ni le tilapia grow faster than control fish (Pullin, 1998, and see p. 7). To examine these growth differences i n N i l e tilapia, the fol lowing questions were asked: Do the differences i n the growth rate of GIFT and control fish persist under controlled laboratory conditions? Does the difference apply to both male and female? Can any growth differences be related to a difference i n behavioural activity, and the onset of sexual maturity? To address the last question, nesting activity, a behaviour which is often the first indication of the sexual maturity of fish, was studied. This behaviour was used to examine the relationship between growth rate and the onset of sexual maturity i n both strains of N i l e tilapia. 17 Materials and Methods Small mixed sex groups (5 fish per tank) of GIFT and control strains were established i n 55 L aquaria on March 7th. A t this time, the mean weight and standard length of the mixed sex GIFT and control fish were 5.3 + 1.6 g and 5.3 + 0.6 cm, and 4.8 ± 1.8 g and 5.1 + 0.7 cm, respectively. Initially, the fish could not besexed, and hence the mixed sex design; however, as the experiment progressed and the fish grew, sex determination became possible. A t the start of the experiment (Apr i l 19th), each aquarium contained five fish. However, as the experiment progressed, some aquaria had less than five fish present as a result of mortality. The aquaria wi th four fish were retained i n the experiment. Groups wi th fewer than four fish were excluded. Prel iminary observations showed that the fish i n aquaria wi th four or five fish had s imi lar activity levels, while the surviving fish i n the tanks wi th less than four fish were very aggressive. This resulted, i n most cases, i n only one fish remaining i n the tank. O n day 1, the weight and standard length measurements were recorded. The Tocomotory and aggressive activities of the control and GIFT fish were videorecorded on day 10 and day 12 (trials #1 and 2, respectively) during a 300 second observation period. O n day 31, length and weight measurements were repeated. This experimental schedule was repeated three times over the three month study period (April-June). The mean growth and behavioural measurements of al l fish i n an experimental group were compared, instead of 18 ind iv idua l measures because growth and behaviour of ind iv idua l fish i n each aquarium were not independent of the behaviour of other members of the group. Due to my inability to identify ind iv idua l fish i n the videorecordings of the first trial i n A p r i l , only trial #2 could be used to compare activity levels between the female and male fish of each strain. Furthermore, size-specific mortality i n male and female fish could only be examined i n May and June because, i n A p r i l , the sex of the fish could be determined neither by the external examination of the genital papilla due to the small size of fish, nor by the dissection of the gonads, due to the cannibalistic practice of l ive tank mates towards dead fish. Results During the three mon th study period (April-June), the GIFT fish were observed to have significantly faster growth rates than the control fish (one-tailed comparison of simple linear regression equations; weight: P<0.05, length: P<0.005) (Figure 1 and 2). GIFT fish gained 4.9 g /month and increased i n length by 0.9 cm/month , while the values for the control fish were 3.2 g /month and 0.7 cm/month , respectively. Furthermore, the weight and length of the GIFT fish were found to be significantly greater than the control fish at each measurement (Figure 1 and 2). The GIFT fish also spent less time swimming and more time resting than the control fish (Table I). The differences i n swimming/ resting behaviours between the control and GIFT fish were significant i n A p r i l and May, but not i n June 19 Figure 1. Weight (mean ± SD) of fish from two strains of Nile tilapia (control and GIFT). A l l experimental aquaria had four or five fish present and the number of aquaria used during the study period is represented by the n-values (data from aquaria with less than four fish present were not used in the mean weight calculations). The Mann-Whitney U-test (one-tailed) was used to test for significant differences in the weight of fish of both strains. * P<0.05, ** P<0.01, *** P=0.005. 20 Figure 2. Length (mean ± SD) of fish from two strains of Nile tilapia (control and GIFT). A l l experimental aquaria had four or five fish present and the number of aquaria used during the study period is represented by the n-values (data from aquaria with less than four fish present were not used in the mean length calculations). The Mann-Whitney U-test (one-tailed) was used to test for significant differences in the length of fish of both strains. * P<0.025, ** P=0.005, *** P=0.0025. Months 21 M O N T H S STRAINS OF NILE TILAPIA T O T A L TIME (SEC) SPENT PERFORMING BEHAVIOURS PER 300 SECOND TRIAL (MEAN ± SD) Swimming Resting Apri l control (n=13) GIFT(n=10) 76.4 ± 81.0 * * * 19.3 ±33 .0 213.4 ± 85.3 * * * * 279.8 ± 33.2 May control (n=10) GIFT (n=9) . 51.9 ±45 .8 10.7 ± 12.6 233.3 ± 60.4 287.8 ± 15.3 June control (n=7) GIFT (n=9) 41.4 ±46 .1 19.1 ± 27.1 252.2 ± 57.7 280.1 ± 29.0 Table L Total time (mean ± SD) two strains of juvenile N i l e tilapia (control and GIFT) performed swimming and resting acts each m o n t h of the three month study. Each month two 300 second behavioural trials were recorded one day apart. A l l experimental aquaria had four or five fish present and the number of aquaria used is represented by the n-values (data from the aquaria wi th less than four fish present were not used). The Mann-Whitney U-test (one-tailed) was used to test for significant differences i n the total time the control and GIFT fish allotted to swimming and resting acts each month. * P<0.025, * * P<0.01, *** P<0.005, **** P=0.0025. 22 (Table I). The time the control fish spent swimming decreased by 46% during the three month period, while the level of swimming activity for the GIFT fish remained relatively constant (Table I). In contrast, the control fish increased the time spent resting by 18% during the study, while the resting values for the GIFT fish again remained relatively constant (Table I). Moreover, control fish performed more chasing and escaping behaviours than the GIFT fish (Table II). The differences were significant i n A p r i l and May, but not i n June (Table II). The frequency of chasing and escaping exhibited by control fish increased i n May by 23% and 10% of A p r i l values, respectively, and then declined i n June by 55% and 52%, respectively (Table II). In the GIFT fish, the frequency of chasing increased by 29% during the study, while escaping increased i n May by 20% of A p r i l values, and then declined i n June by 37% (Table II). A higher frequency of tail-beating was characteristic of the control fish compared to the GIFT fish; the differences were only significant i n A p r i l (Table II). Ta i l - beating frequency of control fish increased by 61% during the study while, i n GIFT fish, the frequency increased i n May by 327% of A p r i l values, and then declined by 70% i n June (Table II). Furthermore, nipping frequency was found to be significantly higher i n the control fish than the GIFT fish during the three month study period. The nipping frequency of control and GIFT fish increased i n May by 169% and 129% of A p r i l values, respectively, and then declined i n June by 73% and 94%, respectively (Table II). Confronting and jaw-locking behaviours were performed only by the control fish and the frequency of confronting declined by 73% during the study, while jaw-locking remained > < X w CQ U 2 O o < o o o u o P - , o o co PH o OH PH 2 3 co +i 2 < w ^ Si C -3 OJ 01 PH 3 5̂ o § o U or. c 'S. a (IS H oc c i u co W or. C • IH co i« u o +1 o o o +1 +1 CM r j o o ro +1 o CO o o +1 rH o o ro o +1 o ro T—i o o +1 * +1 ro rH O O 00 o o +1 * -H v£> T~H O O 00 I D r n ; O +1 * +1 ts * ro H O ro ^ * => +1 * +1 CM * CM rH O m o +1 eg o CO o o +1 rH o o o CO •A o +1 +1 •<* rH O - O CO LO +1 CO o o -H o o o o +1 o (N o +1 o vO CM o * o -H * +1 * (N O O O PH 2 d 2 g 1 / 5 2 ro O s- •s O 3 CD o O H CM +1 -H I D o o IS. 00 rH * O + i : +r O N * ro rH O I D rH O +1 * -H I D * CM rH O O !H •s o u O N II U 00 o +1 o o +1 ro o s o +1 ro o ro O +1 <N O CO o o +1 rH O O rH CO CM O +1 -H O rH rH O I D rH O +1 +1 O N CM O O o o +1 +1 K CM o o R ll c O N II c 0 l-H Ĥ  E o rj u T J cu T J RH o o a> S H a> cu co • R H RH c« at in C O C M TJ o o V PL, L O U T3 C CS "o RH H-> o o rC VH o > RS rC a> rQ TJ o u a> o o C O o CD o +1 ^ C r- 6 § S u w o > cs CU rQ _ ( J CD "•S rC CO •s O 6J0 RS TJ RS o H^ o 6 o o o o CA + H rJ o H O ai rQ s rJ d r Q n H t/5 RS C J • i—i o •a ll C H va  r—1 60 * i eft rC <u O H-» rC M—( C H—• -4—• eft o £ rQ •4-» o rC TJ H-» o o> RS TJ C U C O J 0> >-H CO o> o r-H o M - H pr  O H C| RS i cu C >H VH o> RS CO • R H CD RS aq  rC H C co ft R—1 o s ur  u o TJ ch  av i an  R3 <U eh  "o T3 R Q RH us e in g o o RS »RH TJ cu o> rC H—• >H CD RS aq u an d B o ) H W H [F T  is h O gu lp i M H TJ gu lp i C U rC H ^ RS * H o - Q M H o T 3 RH O H m e H ^ c cu u m e o X RH u cu o VH O eft CU <U O H J H •*-• nb e TJ cu a ct s nu i • R H RS H-> M H o CU RH o> on  cu rC o n R Q H 6 cu cu rC| H^ <*H o rCn H-> c o 6 rC u RS CU TJ CU a >H o "H-H CU H J O - T H .2 £ H P OH ™ Ql • r̂ CO cu 3 cu rCn H-> cu cu cu r Q L O C N o o o V ft * L O o o o V ft * * o o V ft * * 24 relatively constant (Table II). N o opercular flares were performed during the behavioural trials so this behaviour was excluded from analyses. Gulping was also found to be mostly performed by the control fish (Table II). A n increase (114%) i n the frequency of gulping was observed i n May, and then dropped to zero i n the behavioural sessions of June (Table II). Feeding behaviour was performed more often by control fish than GIFT fish especially i n May, but the differences were not significant (Table II). The feeding frequency of control fish increased i n May by 150% of A p r i l values while, i n the GIFT fish, the frequency remained relatively constant (Table II). In the behavioural sessions of June, no feeding behaviour was recorded by either control or GIFT fish (Table II). As the experiment progressed and the sex of each fish could be determined, the weight and length, and activity levels of male and female fish of both strains were compared. Dur ing the three month study period, the male GIFT were observed to have a faster growth rate than the female GIFT (Figure 3 and 4). The difference was significant only for growth i n length (one-tailed comparison of simple linear regression equations; P<0.05). The male GIFT fish gained 5.8 g /month and increased i n length by 1.0 cm/month , while the corresponding values for the female GIFT were 3.9 g /month and 0.9 cm/month , respectively. In contrast, the growth rates of the male and female control fish were s imi lar (Figure 3 and 4). The male control fish gained 3.1 g /month and increased i n length by 0.7 cm/month , and the values for the female control fish were 3.2 g /month and 0.7 cm/month , respectively. The growth rate i n weight of female 25 Figure 3. Weight (mean ± SD) of females and males from two strains of Nile tilapia (control and GIFT). The number of females and males from both strains used during the three month study is represented by the n-values. The Mann-Whitney U-test (one-tailed) was used to test for significant differences between the weight of females and males of same strain (GIFT: * P<0.025, ** P<0.01, *** P<0.0025), females or males of different strains (males: + P<0.01, ++ P<0.001, +++ P<0.0005), and females and males of different strains (GIFT male vs. control female: * P<0.025, # P<0.01, P<0.0025). *** 54 April May June Months 26 Figure 4. Length (mean + SD) of females and males from two strains of Nile tilapia (control and GIFT). The number of females and males from both strains used during the three month study is represented by the n-values. The Mann-Whitney U-test (one-tailed) was used to test for significant differences between the length of females and males of same strain (GIFT: * P<0.025/ ** P<0.0025), females or males of different strains (males: + P<0.01, ++ P<0.0025, +++ P<0.0005/, and females and males of different strains (GIFT male vs. control female: t P<0.025, t4 P<0.005/ t-t-t- P<0.0025). Months 27 however, i n the male GIFT, the growth rate i n weight was found to be significantly higher (one-tailed comparison of simple linear regression equations; comparison of female and male control to male GIFT fish: P<0.05, P<0.05, respectively). Furthermore, the growth rates i n length of the female and male GIFT were significantly different to the male and female control fish (one- tailed comparison of simple linear regression equations; comparison of female and male control to female GIFT fish: P<0.025, P<0.005, respectively; comparison of female and male control to male GIFT fish: P<0.025, P<0.025, respectively). The weight and length of the male GIFT were significantly higher than the female GIFT during the three month study period. In contrast, the weight of the male control was slightly lower than the female control during the study. The length of the male control also was slightly lower than the female control fish i n A p r i l , but then increased slightly above length values of female control i n May and June (Figure 3 and 4). Furthermore, the weight and length of male GIFT fish were significantly greater than either the male or female controls, while the measurements of the female GIFT fish were slightly higher than either the female or male controls (Figure 3 and 4). The only exception was i n A p r i l where the weight of the female GIFT fish was found to be slightly lower than i n the female controls. The male control fish also spent more time swimming and less time resting than the female control fish; however, a significant difference i n the allotment of t ime £ 3 0 0 C M * -S -S ,2 £ ^ SI c c ~ £ I . , en *-> . >• ^ -£ « / 1 - 1 -4-" r\ O) 0 » + cu 3 P x, o ^ 6 w r/1 S 3 - J •£ - G w S3 to +- ^ c •£ d" "x -S ° a> o <u o cn r- J J3 y a a» o _2i Mt, z p a ^ o S <u £ o u S H n n g * 2 6 •3 £ m al e G IF T  ( n= 23 ,2 2, 22 ) J un e 12 .8  ± 24 .6  25 .1  ± 27 .6  28 6. 0 ±2 8. 4 27 4. 6 ±2 8. 3 • 1 1 1 1 1 1 l 1 l 1 1 1 1 1 1 1 l 1 1 1 l ! m al e G IF T  ( n= 23 ,2 2, 22 ) M ay  10 .0  ± 18 .3  11 .5  ± 12 .7  28 8. 3 ±2 3. 7 28 7. 3 ±1 3. 9 1 1 1 1 1 1 1 l 1 1 1 1 1 1 1 l l 1 l l l 1 ) 1 . 1 m al e G IF T  ( n= 23 ,2 2, 22 ) A pr il 35 .3  ± 64 .3  35 .1  ± 55 .1  26 1. 2 ±6 5. 3 26 4. 0 ±5 5. 2 i l l 1 i 1 1 1 l 1 1 l 1 1 l l i m al e co nt ro l ( n= 39 ,3 1, 22 ) Ju ne  55 .5  ± 56 .7  25 .1  ± 27 .6  23 4. 8 ± 71 .4  27 4. 6 ±2 8. 3 55 .5  ± 56 .7  ** **  12 .8  ± 24 .6  23 4. 8 ±7 1. 4 ** **  28 6. 0 ±2 8. 4 j m al e co nt ro l ( n= 39 ,3 1, 22 ) M ay  62 .9  ± 51 .4  ** **  11 .5  ± 12 .7  21 8. 0 ±6 9. 7 ** **  28 7. 3 ±1 3. 9 62 .9  ± 51 .4  10 .0  ±  1 8.3  21 8. 0 ±6 9. 7 ** **  28 8. 3 ±2 3. 7 i m al e co nt ro l ( n= 39 ,3 1, 22 ) A pr il 84 .7  ± 99 .7  ** * 35 .1  ± 55 .1  20 2. 4 ±9 7. 6 26 4. 0 ±5 5. 2 84 .7  ± 99 .7  ** * 35 .3  ± 64 .3  20 2. 4 ±9 7. 6 26 1. 2 ±6 5. 3 1 1 l 1 1 1 1 1 fe m al e co nt ro l ( n= 18 ,1 4, 10 ) Ju ne  19 .2  ± 16 .5  25 .1  ± 27 .6  27 9. 7 ±1 8. 2 27 4. 6 ±2 8. 3 19 .2  ± 16 .5  **  12 .8  ± 24 .6  27 9. 7 ±1 8. 2 **  28 6. 0 ±2 8. 4 19 .2  ± 16 .5  55 .5  ± 56 .7  27 9. 7 ±1 8. 2 23 4. 8 ±7 1. 4 fe m al e co nt ro l ( n= 18 ,1 4, 10 ) M ay  35 .1  ± 43 .2  11 .5  ± 12 .7  25 6. 5 ±5 2. 3 * 28 7. 3 ±1 3. 9 35 .1  ± 43 .2  10 .0  ± 18 .3  25 6. 5 ±5 2. 3 ** • 28 8. 3 ±2 3. 7 35 .1  ± 43 .2  * 62 .9  ± 51 .4  25 6. 5 ±5 2. 3 * 21 8. 0 ±6 9. 7 fe m al e co nt ro l ( n= 18 ,1 4, 10 ) A p ril  70 .3  ± 79 .8  * 35 .1  ± 55 .1  22 1. 0 ±8 1. 1 * 26 4. 0 ±5 5. 2 70 .3  ± 79 .8  35 .3  ± 64 .3  22 1. 0 ±8 1. 1 26 1. 2 ±6 5. 3 70 .3  ±  7 9. 8 84 .7  ± 99 .7  22 1. 0 ±8 1. 1 20 2. 4 ±9 7. 6 SE XE S/ ST R AI N S  O F N IL E  T IL A P IA  S w im m in g  R es tin g S w im m in g  R es tin g S w im m in g  R es tin g SE XE S/ ST R AI N S  O F N IL E  T IL A P IA  fe m al e G IF T  (n =2 2, 23 ,2 3)  m ale  G IF T  (n =2 3, 22 ,2 2)  m al e co nt ro l (n =3 9, 31 /22 ) O N C N | 30 to swimming and resting was only found i n May (Table III). In contrast, the male GIFT fish spent less time swimming and more time resting than the female GIFT fish, except i n A p r i l (Table III). The differences i n swimming and resting behaviours were significant only i n June (Table III). Furthermore, the male control fish spent significantly more time swimming and less time resting than either female or male GIFT fish (Table III). The female control fish also spent more time swimming and less time resting than either female (except i n June) or male GIFT fish (Table III). The differences i n swimming and resting behaviours between the female control and male GIFT fish were significant throughout the three month study. The differences i n swimming behaviour between the female control and GIFT fish were only significant i n A p r i l , whi le the differences i n resting behaviours were significant i n both A p r i l and May (Table III). Dur ing the three month study, the total time male and female control fish spent swimming declined by 35% and 73% of starting (April) values, respectively, while the time spent resting increased by 16% and 27%, respectively (Table III). In contrast, the amount of time the male and female GIFT fish spent s w i m m i n g declined i n May by 72% and 67% of the A p r i l , values, respectively, but then increased i n June by 29% and 119%, respectively (Table III). Moreover, the total time male and female GIFT fish spent resting increased from A p r i l to May by 10% and 9%, respectively, but then declined slightly (i.e., by 1% and 4%, respectively) i n June (Table III). Male fish performed more agonistic behaviours than the female fish (except i n cu -Q Cl o res o co •3 ° CO £ X o bO cu CO U c > y — 1 / 1 £ -2 X5 CO 22 W S H o S H CU OH XS CO C at SS CU o bO CO cu r d CU XS S xs cu XS j 3 +- d 6 g o G <§ CO XS . cu co o co - s co -rj C CO * R - co 7£3 •I-H cu cu co CU RS s s cu 52 b 3 o S H H-» »rH CU M rC s ~ I ° & 6 x c cu o •° i CJ CO co cu o> ^ , CO TJ c co u O > to X cu H O CU > * S £ CU cu *CS P cu to H I B o o CO XS o c; - Q o u ° co 3 cu >" cu S H ca P H «s XS cu c o XS CU XS S H o u cu S H CU S H CU s * CO "co >rH J H co cu cu -5 z ~ cs ^ n > OH O CU rc cu u 3 CCS H^ -cl u ca cu o C • rH CO S H CO X CU co cu X cu CO cu S H P H CU S H CO cu 3 C CO o u co cu XS cu s S H o M H S H CU P H CO c CO S H -*-» co bo o 35 ^ bo o .5 * r* _g 0 - Q 1 3 £ 5 xi 1 ^ ca . bbii ^ • S -3 o . * H H - > •r, 6 "C © cu £ P H O CO _Q CU ^ S H CU cu * - C cu L O o o o M H O o V X ^ co * ^ * 13 rH xs S o R - H P H P - cu s CU co « 3 + + + S H CCS P H a CS efl CU L O M H CN O CU o •£ o V CO PH S H M 3 * • rH * X co « L O cu H — _Q O - -2 V O _• ^ P H CU . P H 1 £ >. CS ^ CU CJ - • CO 3 • OJ cl 3 a; 8 J b0r -H ' P H » H P H < •a c 6 0 CN • R H R— R—I CS cS r Q * ^ I * S H 3 C3 r C CO rS i s - a B <u « i ^ CU >H M H r 1 •S S » H ^ CO o o V P H & -S .2 • I—I JT 1 r-i s > CO « CCS rC U - Q XS cu H-* cu CO CU S H P H CU o ) H cu r C co CU XS C «S u co io •3 CN boo CO V M H ^ O + j2 io 3 q o o r Q V M H PH O * cu CO 0 ) _ S H _ » H P H J O ^ •rH S H H-> V H O S H . M 0> r- •2 r Q £ m al e G IF T  ( n= 23 ,2 2, 22 ) 0. 1 ± 0. 5 0. 04  ± 0. 13  0. 1 ± 0. 6 0. 2 ± 0. 6 ! ! ] j m al e G IF T  ( n= 23 ,2 2, 22 ) M ay  0. 3 ±1 .1  0. 1 ± 0. 1 0. 2 ± 0. 8 0. 4 ± 1.4  j ! j j m al e G IF T  ( n= 23 ,2 2, 22 ) A p ri l 0. 3 ± 0. 9 0. 03  ±  0 .0 9 0. 7 ±1 .6  0. 4 ± 1. 0 j | | m al e co nt ro l ( n= 39 ,3 1, 22 ) 0. 6 ± 1.6  0. 04  ±  0 .1 3 1.2  ± 2. 1 * 0. 2 ± 0. 6 0. 6 ±1 .6  0. 1 ± 0. 5 1.2  ± 2. 1 0. 1 ± 0. 6 j | m al e co nt ro l ( n= 39 ,3 1, 22 ) M ay  0. 9 ± 1. 4 0. 1 ± 0. 1 2. 1 ±3 .0  0. 4 ±1 .4  0. 9 ± 1. 4 0. 3 ±1 .1  2. 1 ±3 .0  * *  * * 0. 2 ±0 .8  j j m al e co nt ro l ( n= 39 ,3 1, 22 ) A p ri l 0. 5 ± 1. 4 * 0. 03  ± 0. 09  2. 2 ± 3. 9 0. 4 ± 1. 0 0. 5 ± 1.4  0. 3 ± 0. 9 2. 2 ± 3. 9 0. 7 ±1 .6  j fe m al e co nt ro l ( n= 18 ,1 4, 10 ) 0. 2 ± 0. 6 0. 04  ±  0 .1 3 0. 6 ± 1. 0 0. 2 ± 0. 6 0. 2 ± 0. 6 0. 1 ± 0. 5 0. 6 ±1 .0  0. 1 ± 0. 6 0. 2 ± 0. 6 0. 6 ± 1. 6 0. 6 ± 1. 0 1.2  ± 2. 1 fe m al e co nt ro l ( n= 18 ,1 4, 10 ) M ay  0. 1 ± 0. 3 0. 1 ± 0. 1 1.6  ± 1. 9 0. 4 ±1 .4  0. 1 ± 0. 3 0. 3 ±1 .1  1.6  ± 1. 9 0. 2 ± 0. 8 0. 1 ± 0. 3 0. 9 ±1 .4  1.6  ± 1. 9 2. 1 ± 3. 0 fe m al e co nt ro l ( n= 18 ,1 4, 10 ) A p ri l 0. 1 ± 0. 1 0. 03  ±  0 .0 9 I N p CO ^ rH +1 * +1 O * T}H ro O 0. 1 ± 0. 1 0. 3 ± 0. 9 3. 0 ± 3. 7 * *  0. 7 ±1 .5 8 0. 1 ±0 .1  0. 5 ±1 .4  3. 0 ± 3. 7 2. 2 ± 3. 9 S E X E S /S TR A IN S  O F  N IL E  T IL A P IA  A go ni st ic  E sc ap in g A go ni st ic  E sc ap in g A go ni st ic  E sc ap in g S E X E S /S TR A IN S  O F  N IL E  T IL A P IA  fe m al e G IF T  (n =2 2, 23 ,2 3)  m al e G IF T  (n =2 3, 22 ,2 2)  m al e co nt ro l (n =3 9, 31 ,2 2)  33 June between male GIFT and female control); however, only the differences between the male control and female GIFT fish were significant (Table IV). When males of both fish strain were compared, the male control performed more agonistic behaviour than the male GIFT fish (Table IV). The differences were significant i n May and June, but not i n A p r i l . W h e n the females were compared, the control also performed more agonistic behaviour than the GIFT fish, but the differences were not significant (Table IV). The frequency of agonistic behaviour exhibited by male control, and female and male GIFT fish increased i n May by 65%, 100% and 4% of the A p r i l values, respectively, then declined i n June by 27%, 33% and 48%, respectively, while the frequency of agonistic behaviour exhibited by female control increased by 243% during the study. The number of male control fish performing agonistic behaviours was significantly greater than the number of female control, and male and female GIFT fish combined (corrected chi-square analyses: A p r i l , P<0.01; May, P<0.001; June, P<0.005). Escape behaviour was performed by both female and male fish (Table IV). Bo th the male and female control fish performed more escape behaviour than the male and female GIFT fish (Table IV). The differences i n escape behaviour between the female control and GIFT fish were only significant i n A p r i l , wh i l e the differences between female control and male GIFT were significant i n both A p r i l and May (Table IV). In the comparison of the male control to the female and male GIFT, significant differences were found i n A p r i l and June, and May and June, respectively (Table TV). When female and male control fish were 34 compared, male fish exhibited less escape behaviour i n A p r i l than female fish, but i n May and June, male fish performed more escape behaviour than female fish. In contrast, male GIFT fish exhibited more escape behaviour i n A p r i l , but performed less escape behaviour than female GIFT fish i n May and lune. N o significant difference i n escape behaviour was found between female and male of either the control or GIFT strain. The frequency of escape behaviour exhibited by the female and male control, and the female and male GIFT fish declined dur ing the study by 82%, 47%, 42%, and 80% of the A p r i l values, respectively. The number of male control fish performing escape behaviour was significantly greater than the number of female control, and male and female GIFT fish combined (corrected chi-square analyses: A p r i l , P<0.025; May, P<0.001; lune, P<0.025). Gulping was mostly performed by the male control fish; however, i n May, the female control fish also performed gulping behaviour (Table V) . A slight increase i n the gulping frequency of male control and GIFT fish was observed i n May, but it dropped to zero i n lune. The number of male control fish gulping was greater than either the number of female control, male GIFT or female GIFT fish; however, the differences were not significant. A greater number of feeding bouts was performed by the male control and GIFT fish than the female fish; however, i n May, the feeding frequency of the female control was higher than male GIFT. The feeding frequency of male control fish also was greater than male GIFT fish; the difference was significant only i n May 35 M O N T H S SEXES/STRAINS OF NUMBER OF BOUTS OF LOCOMOTORY NILE TILAPIA BEHAVIOURS ( M E A N ± SD) Gulping Feeding Nesting female control (n=18) 0 0 0 male control (n=39) 2.7 + 13.4 0.5 ± 1.9 0 Apri l female GIFT (n=22) 0 0.1 ± 0.5 0 male GIFT (n=23) 0 0.3 ± 1 . 1 0 female control (n=14) 1.3 + 4.7 0.2 ± 0.8 0 male control (n=31) 2.8 ± 9 . 7 r 0.4 ± 1 . 2 0.3 ± 1 . 3 May female GIFT (n=23) 0 * 0.1 ± 0.2 0 male GIFT (n=22) 0.02 ± 0.11 _ 0.1 ± 0 . 5 0.02 + 0.11 female control (n=10) 0 0 0 male control (n=22) 0 0 0.4 ± 1.7 June female GIFT (n=23) 0 0 0 male GIFT (n=22) 0 0 0.1 ± 0.3 Table V. Number of bouts of locomotory behaviours (mean + SD) performed by the female and male juvenile N i l e tilapia (control and GIFT strains) each m o n t h of the three month study. Each month two 300 second behavioural trials were recorded one day apart. Due to unforeseen circumstances, only data from the behavioural trial #2 i n A p r i l were tabulated. The number of female and male fish of both strains used each month is represented by the n-values. The M a n n - Whitney U-test (two-tailed test, except for nesting behaviour) was employed to test for significant differences between the number of acts performed by the female and male fish from the control and GIFT aquaria for each month . * P<0.05. 36 (Table V) . In contrast, female GIFT performed more feeding bouts than female control i n A p r i l , while female control performed more feeding bouts than female GIFT i n May. The feeding frequency of male control, and female and male GIFT fish declined i n May by 4%, 50%, and 63% of A p r i l values, and then dropped to zero i n June. The number of male control fish feeding during the behavioural trials was significantly greater than the number of female control, and male and female GIFT fish combined (corrected chi-square analyses: May, P<0.01). To assess the sexual maturity of fish, nesting behaviour, and the number of bowers present i n both the control and GIFT aquaria were recorded during the three month study period. Nests were first observed on A p r i l 1st i n three of the control tanks; and by the eve of the first behavioural trial i n A p r i l , bowers were present i n 11 of the 13 control tanks compared to only 1 GIFT tank out of a total of 10. Dur ing the three month study period/nesting behaviour was performed more frequently by the control fish than the GIFT fish, but the differences were not significant (Table II). A large increase (236%) i n nesting frequency of control fish, was observed during the study, while the nesting frequency of GIFT fish increased slightly (Table II). Only males of both the GIFT and control strains were observed to perform nesting behaviour. The nesting frequency of male control increased from May to June by 45%, while the frequency of male GIFT increased slightly (Table V) . The number of male control fish nesting was greater than either the number of female control, male GIFT or female GIFT fish; however, the differences were not significant. Furthermore, significantly more Figure 5. Number of nests (mean ± SD) present in the experimental aquaria (control and GIFT strain of Nile tilapia). A l l experimental aquaria had four or five fish present and the number of aquaria used during the three month study is represented by the n-values (data from aquaria with less than four fish present were not employed in the mean calculations). The Mann-Whitney U-test (one-tailed) was used to test for significant differences between the number of nests present in the control and GIFT aquaria for each month. * P=0.05, ** P<0.005, ***P<0.0005. Apri l May June Months 38 bowers were present i n the control aquaria than GIFT aquaria during the three month study (Figure 5). Control fish also built more bowers earlier i n study (i.e., Apr i l ) than GIFT fish; it took the GIFT fish t i l l June to reach the number of bowers found i n the control aquaria i n A p r i l (Figure 5). Size-specific mortality was observed i n both strains (Table VI). The dead control fish had lower weights and lengths than the l ive fish present i n the same experimental aquaria; the differences were significant i n May and June, but not i n A p r i l (Table VI). The dead GIFT fish also had smaller weight and length measurements than the l ive fish i n the same experimental aquaria; however, no rigorous analyses could be performed due to the low number of dead fish (Table VI). The weight and length of dead and live male control fish were significantly different i n both May and June, while the dead and live female fish were s imi lar (Table VII). Therefore, size-specific mortality occurred i n only male fish. ON CO O 2 w 6 0 o I—I w ô oo 3 NO CN l - 1 in m 3 00 .a O N ^ O rH •Hli* H C ô —' +1 CN m O N +1 CM O ^ 00 NO +1 CM O N O N O ^ N O CM rH CO in -zr- CN C CO w in rH C O <c Tj5 O N in 3 * fi NO ^ 9 § S 5 o a c o u CM CO 5? o 3 r H rH II r H C cu <u cu cu r d r H . bOTS co cu 1/3 03 T j X LO CN to . O N1H cu 0 5 / — N - H +-J cu cu rJ _ r H OH CU i—i r H u . a T S C O r ^ ^ l O S ' § 2 u •s - s ; l fS . 05 05 T3 * --3 <u a> cu 3 ~ -3 -C| o £ w C O ^ M H a> C O r—I ^n C O CU u C cu >H cu ST 2 Ti OT 05 s3 O r-H - > ! H-> +-> CJ CU S rC o 2 • w cu -9 £ 05 CJZJ S •2 H o boH £ ^rC • cu * T S C r 2 8 •S-g ° H TH CO CU -TH O H * to Cl XS cd O <- S 2 5 m a> « cu cu .y co c M H _^T>rS "2 « * • H B A C O , H-» H * 6 0 M H H-3 - H *- .52 a C O *3 3 cu cS T S H-» -4-» co xJ 3 ffi O U l H ^ 05 H-> V S 3 O ^ » H 2 .a P *o C J T - J C O 0H.2 * io m h 2^ OHW .9 > w . 3 g -2 £ 2 ^ cl o cj cu rC - H o 2 o TS cu • r H CO I CU 5fi to d. r ^ co i ~* CU Q) ' ^ - r H 3 g 05 O 0> TJ > o b J £ CH ••rH CS ^ TS ' -2 • • g TS cu LO- 05 O o o d cu "§P CU rji -C S -H H r * H ' > H cu ^ * ^ H TS * 40 CONTROL STRAIN NILE TILAPIA female dead (n=4,3) male dead (n=7,4) May June May June Weight (g) 9.2 8.9 female live 8.9 9.6 (n=2,l) Length (cm) 6.6 65 6.6 6.7 male live Weight (g) 6.8 *** 144 10.8 * 21.6 (n=7,4) Length (cm) 5.9 ** 7.6 7.1 * 9.0 Table VII. Size-specific mortality i n the male and female fish of the control strain Nile tilapia. Due to unforeseen circumstances, only data from May and June were tabulated. The results of GIFT fish were not tabulated due to zero mortality observed during May and June. The number of dead and live fish of both sexes used each month is represented by the n-values (e.g., # of fish in May , and June, respectively). In each table cell, the top values represent sex/state (dead or live) of Ni le tilapia of the column heading, while the bottom values represent the sex/ state of Nile tilapia of the row. The Mann- Whitney U-test (one-tailed) was used to test for significant differences i n weight and length of dead and live fish of both sexes. * P<0.025, ** P<0.01, *** P<0.005. CHAPTER I V 41 Experiment II: Aggressive behaviour of males from the control and GIFT strains of Ni le tilapia i n response to a mirror image Introduction In juvenile coho and chinook salmon, the reactions to mirror images have been correlated wi th the reactions to conspecifics (Rosenau, 1984; Taylor and Larkin , 1986; Rosenau and McPhai l , 1987; Taylor, 1988; Swain and Holtby, 1989). F i sh that spend more time performing mirror-elicited agonistic behaviours were also found to be more aggressive i n social interactions under more natural circumstances. In my first experiment, male control fish were observed to perform more agonistic behaviours than male GIFT fish (see Chapter III). However, the effect that social interactions i n mixed sexed groups have o n behavioural measures (see Toguyeni et al., 1997) may have complicated the results of my first experimental study. Therefore, offensive aggression was quantified using the mirror image stimulation (MIS) tests (Gallup, 1968). These tests have the advantage that individuals are tested against 'opponents' of exactly the same size and motivational state and that adequate replication is practical (Swain and Riddel l , 1990). Male fish were only examined i n this MIS test because female fish were observed to perform relatively little agonistic behaviour i n mixed sexed groups (Experiment I), and i n all-female stock aquaria (pers. obs.). 42 Materials and Methods Biting and tail-beating behaviours were distinguished i n the MIS tests. These two behaviours are similar to the nipping and tail-beating behaviours previously mentioned (see Behavioural Measures), except that they are directed towards a mirror instead of a conspecific. Small populations (5 fish per tank) of mixed sex GIFT and control strains were re-established i n ind iv idua l 55 L aquaria i n mid-November (Nov. 15th). These fish had been previously used i n the growth experiment approximately four and a half months earlier. O n day 1 (Nov. 19th), the weight and standard length measurements of al l male fish were recorded; during the two week study period, the mean weight and standard length of the male control and GIFT fish were 26.2 ± 9.8 g and 9.5 ± 1.3 cm, and 34.0 ± 10.6 g and 10.2 ± 1.2 cm, respectively. O n day 3, one day prior to the start of behavioural observations, male control and GIFT fish were indiv idual ly placed i n 55 L aquaria; the mean water temperature of the experimental aquaria was 23.7 + 0.3°C during the two week study period. Each experimental aquarium was divided i n two by an opaque partition; the fish was placed on the left side wi th a boxed filter, while the mirror was positioned on the right side behind the partition. O n day 4, at the start of each behavioural session, the partition was lifted exposing the mirror to the fish. A 300 second observation period began when the male fish was observed, on the video monitor, swimming towards the mi r ro r and performing either biting or tail-beating behaviours. A t the end of the day 43 when al l behavioural sessions were recorded, the fish were returned to their appropriate stock tanks and new fish were transferred to the experimental aquaria for the next day. Each male was tested twice about a week apart between the two trials, so the data provided is a mean of the two trials. Results During the two week study period, the male control fish performed a higher number of bouts of mirror-directed biting and tail-beating than the male GIFT fish (Figure 6). Only the differences i n mirror-directed biting was significant (Figure 6). 44 Figure 6. Number of mirror-directed biting and tail-beating (mean ± SD) performed by the male fish from two strains of Nile tilapia (control and GIFT) during the two behavioural trials. Each behavioural trial was five minutes in duration and the two trials were spread out over a one week period. The Mann-Whitney U-test (one-tailed) was used to test for significant differences between the number of mirror-directed acts performed by the male control and GIFT fish during the behavioural trials. * P<0.001. biting tail-beating Mirror-directed behaviours CHAPTER V 45 Experiment III: Nest bui lding i n male fish of the control and GIFT strains of N i l e tilapia Introduction The time(s) of day nests are built, the total time required to bui ld nests and size of completed nests have rarely been studied i n fish. Fryer and lies (1972), and Balarin and Hatton (1979) have described the nest shapes and sizes of some tilapia species; however, the details of fish nesting activity were not documented. In this third experiment, the nesting behaviour of the two strains of N i l e tilapia was closely examined. More specifically, the total time required for males to complete a nest, the size of the nest at completion, and the number of nests built per fish were recorded. The time of day nests are built was also noted i n both strains of N i l e tilapia to see if nesting behaviour is a diurnal and/or nocturnal activity. Materials and Methods Eleven days before observations began, the weight and standard length were recorded; the mean weight and standard length of the male control and GIFT fish were 31.6 ± 12.5 g and 10.0 + 1.5 cm, and 46.1 + 12.1 g and 11.2 ± 1.0 cm, respectively. 46 A t the start of each recording session, a male control and a GIFT fish were individual ly placed i n one of two 55 L aquaria wi th a mean water temperature of 25.5 ± 1.1°C. Each experimental aquaria was divided i n two by a clear partition; the fish was placed on the left side of the partition, while the boxed filter was o n the right side. This partition was used to l imit the amount of space occupied by each fish, so two fish i n separate aquaria could be monitored simultaneously by one videocamera. Also , the clear partition allowed for sufficient light to enter the test area of aquarium and no shadows to be present. In my preliminary experiment, nesting activity occurred during both the day and night, so round-the-clock recordings were undertaken i n this study. However, it was not possible to view fish under complete darkness. Complete darkness was replaced by low light sufficient to allow videorecordings. One light strip, positioned upwards and mounted 2 m above the row of experiment aquaria, was used to i l luminate the laboratory. This d i m light level was sufficiently dark to signal to the fish that it was night time (i.e., the fish positioned themselves lower i n the water column), and thus still maintained fish under a 12-h photoperiod. A Sanyo monochrome videocamera was positioned approximately 42 cm on top of the r i m of the two experimental aquaria and was connected to a V C R wi th a 24-h recording potential. Nesting behaviour was recorded from 17:30 to 17:00 o n the next day. In some cases, the behavioural sessions were extended to a 48 hour period when no nests were present at 17:00. The videorecordings of nesting activity was then examined (see Behavioural Measures) to determine the time of 47 day nests are built, the total time required to bui ld nests and the size of nests at completion. The start point of nest bui lding behaviour was demarcated by the fish performing nesting behaviour and a black spot gradually being seen on the videomonitor (i.e., indicating that the fish had removed enough sand, exposing the glass bottom of the aquarium), while the nest was considered complete w h e n the size of the nest d id not increase during the rest of the recording session. The size of nest was determined by attaching a grid (each square is approximately 1 cm x 1 cm) to the screen of a Panasonic videomonitor and recording the number of squares comprising the nest. The conversion factor of 5.2 cm on screen of the videomonitor equals to 7 cm on the aquarium was used to determine the 'actual' area of nest present i n each experimental aquaria (i.e., 'actual' nest size = 1.81 x screen nest size). To control for fish size (i.e., male GIFT larger than control fish), the ratio of nest diameter relative to fish length was calculated. The nest diameter was calculated using the following formulas: area = rt x r 2 , where rt = 3.14 and V is the radius, and diameter = r x 2. Results The weights and lengths of the nesting fish were higher than those of the non- nesting fish of the same strain (differences significant only i n fish from the control strain) (Figure 7 and 8). Furthermore, the weights and lengths of the nesting GIFT fish were significantly greater than the nesting control fish (Figure 7 and 8). This result was not surprising because GIFT fish were bigger than Figure 7. Weight (mean + SD) of the nesting and non-nesting male fish from two strains of Nile tilapia (control and GIFT). The number of nesting and non-nesting control and GIFT fish used during the study is represented by the n-values (i.e., # of control fish, # of GIFT fish). The Mann-Whitney U-test (one-tailed) was used to test for significant differences between the weight of the nesting and non-nesting male fish of the same strain (control fish: * P<0.05), and the nesting or non-nesting male fish of different strains (nesting males: ** P<0.025.). strains of Nile tilapia 49 Figure 8. Length (mean + SD) of the nesting and non-nesting male fish from two strains of Ni le tilapia (control and GIFT). The number of nesting and non-nesting control and GIFT fish used during the study is represented by the n-values (i.e., # of control fish, # of GIFT fish). The Mann-Whitney U-test (one-tailed) was used to test for significant differences between the length of the nesting and non-nesting male fish of the same strain (control fish: * P=0.025), and the nesting or non-nesting male fish of different strains (nesting males: ** P<0.05). strains of Nile tilapia 50 control fish at the start of the study. The measurements of the non-nesting GIFT fish were not significantly greater than the non-nesting control fish (Figure 7 and 8). There were no significant differences i n the nesting behaviour of the control and GIFT strains; however, there were a number of suggestive differences i n various measures of nesting activity. The male GIFT fish required more time to complete nest(s) compared to the control male (Table VIII). The total nest size (i.e., the addition of al l nest sizes present i n the experimental aquarium) and the mean nest size (i.e., the total nest size/the number of nests present i n the experimental aquarium) were also higher i n male GIFT than control fish (Table VIII). However, the mean ratio of nest diameter relative to fish length for both male control and GIFT fish was similar (Table VIII). Furthermore, the number of nests built by the male control fish was greater than the GIFT fish (Table VIII). Lastly, it was noted that the control and GIFT fish nested during both the low light and day portions of the recording period; however, the fish often started and completed its nest(s) during the day time. 51 NESTING CHARACTERISTICS STRAINS OF NILE TILAPIA control (n=14) GIFT(n=7) Total time (hour) required to complete nest 8.1 ±6 .3 11.2 ±7 .6 Total nest area (cm2) 74.3 ±54.1 92.9 ±60.0 Mean nest area (cm2) 56.9 ±58 .3 74.2 ±65.4 Ratio of nest diameter relative to fish length . 0.8 ±0 .3 0.8 ±0 .4 Number of nest(s) built / fish 1.6 ± 0.7 1.4 ±0 .5 Table VIII. Total time required to bu i ld a nest, the size of the nest at completion, nest diameter relative to fish length, and the number of nests built per fish (mean ± SD) were examined i n the male fish of two strains of Ni le tilapia (control and GIFT). The number of male control and GIFT fish used during the study is represented by the n-values. Each fish was videorecorded from 17:30 to 17:00 on the next day. In some cases, the recording sessions were extended to a 48 hour period when no nests were present at 17:00. The total nest area was calculated by the addit ion of a l l nest sizes present in the experimental aquarium, while the mean nest area was calculated by the divis ion of the total nest area value by the number of nests present in the experimental aquarium. The nest diameter was calculated using the following formulas: area = n x r 2, where re = 3.14 and V is the radius, and diameter = r x 2. The Mann-Whitney U-test (two-tailed) was employed to test for significant differences i n various measures of nesting activity of the control and GIFT fish; no significant differences were found. CHAPTER VI 52 Discussion Under laboratory conditions, the GIFT fish grew faster than the fish from the control strain. It was not surprising that growth performance was higher i n the GIFT than control fish, as the former had been subjected to intentional selection for that trait (Pull in, 1998, and see p. 7). The results from my behavioural experiment on Ni l e tilapia suggest that behavioural activity may contribute to this effect on growth. In the following paragraphs, behavioural effects o n growth, possible hormonal causes i n relation to sex, and other confirmatory findings as wel l as nest bui lding w i l l be discussed. The fast growth of GIFT fish was associated wi th a lower activity level compared to control fish. GIFT fish performed less swimming and more resting behaviour than control fish. These findings are similar to the study by Koebele (1985) o n juvenile Tilapia zillii, which suggested that an increase i n activity such as swimming may have resulted i n a slight decrease i n their mean growth. The fast-growing GIFT fish also exhibited a lower frequency of agonistic behaviour than the slow-growing control fish. This connection between growth and aggression has been previously documented. Ruzzante and Doyle (1991) observed i n the medaka, Oryzias latipes, that fish "indifferent' to other neighbouring fish (i.e., not involved i n aggressive behaviour) grew the fastest. In addition, a negative correlation between aggression and growth was found i n 53 the tilapia hybrid, Oreochromis mossambicus x O. hornorum (Robinson and Doyle, 1990) and Atlantic salmon (Holm and Ferno, 1986). Swimming activity, and especially agonistic interactions are energetically costly, and thus passive (i.e., GIFT) fish, wi th a relatively lower metabolic expenditure, should gain a growth advantage over active (i.e., control) fish. Increased demand for energy during exercise has been confirmed i n several studies on oxygen consumption, w h i c h reflect behavioural activities i n fish (Beamish, 1980; Nahhas et al., 1982; Butler, 1985). The fact that the more active control fish are compromised i n their growth performance suggest that the amount of energy generated i n the control fish is l imited. The l imitat ion of energy output can be attributed to many factors. A hypothesis to explain various features of fish growth i n terms of growth l imitation by oxygen supply was proposed by Pauly (1981; see also Pauly, 1984, 1994). He proposed that i n addition to food, oxygen plays an important role i n l imi t ing fish growth as they derive the energy for the synthesis of body substances exclusively from the oxidation of energy-rich assimilates (Pauly, 1981). It has been observed by Stewart et al. (1967) that largemouth bass held i n hypoxic waters usually had a lower percent dry weight than fish held at concentrations near the air-saturation level. Balarin and Hatton (1979) also found, i n tilapia, that at low oxygen levels, growth decreased. This decrease i n growth is due chiefly to the inability of fish to store but small quantities of oxygen for later use (Pauly, 1981); most fish die wi th in a short period of time when kept i n anoxic water. Thus, anything, i n a given population, that causes a higher metabolic 54 expenditure (e.g., high activity level), w i l l result i n a reduced fish size. It is thought that the h igh activity level of the control fish, which l imited amount of oxygen allocated to growth, may have resulted i n their reduced size. Gulping was mostly performed by the active, slow-growing control fish. It has been observed that aquatic surface respiration (i.e., gulping) is initiated at higher oxygen concentrations than absolutely necessary for survival , and thus this behaviour can provide an energetic advantage to fish (Weber and Kramer, 1983). The fish approaching the water surface and aerating their gills wi th more oxygen-saturated water increase oxygen uptake rate and /o r decrease the work required for ventilation, as compared to subsurface respiration (Weber and Kramer, 1983). A n increase i n the oxygen uptake rate of fish would permit greater food intake (Weber and Kramer, 1983). The control fish was also observed to perform more feeding behaviour than the GIFT fish. Intraspecific comparisons between w i l d and hatchery-reared Atlantic salmon have shown that w i l d fish generally feed more than hatchery fish (Fenderson et al., 1968; Sosiak et al, 1979). A possible explanation for the higher gulping of control fish i n A p r i l and May could be due to the higher oxygen requirement due to high activity and feeding frequency compared to GIFT strain. However, i n June, no gulping was performed by the control fish during the behavioural recordings, which may be the result of a decline i n locomotory and agonistic activity of control fish. Furthermore, it has been noted that as fish increase i n size, more energy is 55 needed to maintain bodily functions (i.e., higher standard metabolic rate) (Wootton, 1990). It is thought that as the active control fish became larger i n size, less energy was available for performing behavioural activity because it was being re-directed into standard metabolism and growth. Thus, this change i n the allocation of energy resulted i n the observed decline i n the activity level of control fish. However, i n the case of the passive GIFT fish, as they increased i n size, sufficient amount of energy was still available for the higher standard metabolic rate, so the low activity level of GIFT fish remained relatively unchanged. The divergence i n locomotory and agonistic behaviour of the GIFT and control fish is not surprising, because behavioural traits are among the first traits to respond to domestication; it is usually the frequency or intensity wi th which a particular behaviour is expressed that is affected by domestication (Price, 1984). In the Phil ippines, both fish strains tested were reared under similar hatchery conditions (e.g., p H , salinity, temperature). Thus, the difference i n activity l eve l between GIFT and control fish must have been due to a genetic difference between the two types or to prefertilization environmental differences (environmental maternal effects) rather than a phenoty pic /environmental effect (Swain and Riddel l , 1990). A genetic basis has been demonstrated for behavioural differences among families (Bakker, 1986), populations (Rosenau and McPhai l , 1987), and closely-related species of fish (Ferguson and Noakes, 1982, 1983), but no scientific studies have indicated an effect of the prefertilization, maternal environment on behaviour (Swain and Riddel l , 1990). 56 Thus, it is l ikely that the behavioural differences reported between GIFT and control fish are the result of the selection program described by P u l l i n (1998). In the comparison of female and male GIFT fish, the growth performance of males was higher than females. The growth advantage experienced by male GIFT fish was connected wi th a lower activity level. Male GIFT performed less swimming and escaping, and more resting behaviour than female GIFT. E v e n though a higher frequency of agonistic behaviour (excluding escape behaviour) was exhibited by the fast-growing male GIFT fish, the difference i n male and female frequencies was not significant, and the number of bouts of agonistic behaviour performed by the male GIFT fish was up to 4.5 times less than male control values. The mirror image stimulation tests supported the finding that male control fish are more aggressive than male GIFT fish. W h e n female and male fish of the GIFT and control strains were compared, the connection between growth and activity level was still observed, suggesting that differences i n growth between sexes may be to some extent mediated by behavioural differences. However, i n the control fish, the growth rates, and size of male and female fish were similar even though the male control fish performed more swimming and escaping behaviour, and less resting than the female control fish. The male controls also exhibited a higher frequency of agonistic activity than the female controls. In the comparison of female and male fish, low growth of fish was also associated wi th a high activity level; however, a few experimental observations 57 seemed to deviate from this relationship. For example, the fast-growing male GIFT exhibited a higher frequency of agonistic activity (excluding escape behaviour) compared to slow-growing female GIFT, and i n the control fish, growth of male and female fish was relatively similar even though, the male control fish performed more locomotory and agonistic acts than the female control fish. Physiological differences between sexes, such as due to different hormone levels, may be the underlying cause of this observed deviation f rom the relationship between growth and behavioural activity. Higher growth i n males has been attributed to androgens or male sex hormones (Donaldson et al, 1979; Ufodike and Madu , 1986). The anabolism-enhancing effect of androgens has been observed i n Ni l e tilapia (Ufodike and Madu , 1986), goldfish (Yamazaki, 1976), and all salmonids (see Donaldson et al., 1979). Varadaraj and Pandian (1988) suggested, i n normal ' (phenofypic and genetic), and phenofypic males Oreochromis mossambicus, that androgens stimulated growth by increasing food intake or food conversion efficiency. Thyroid hormones (T 3 and T 4 ) are also involved i n controlling growth and development of fish (see Donaldson et al, 1979). Toguyeni et al. (1996, 1997) observed, i n the Ni l e tilapia, that plasma T 3 levels were higher i n males than females, and thus could account for the males' growth advantage over females. It was suggested that T 3 increases the efficiency of food utilisation by males, and thus their growth as wel l (Toguyeni et al., 1997). Eales and Shostak (1985) also observed, i n a population of Arctic charr, that plasma T 3 levels are strongly 58 correlated wi th both food ration and growth, which supports the notion that increased T 3 production induced by food intake may exert some role i n promoting growth. In this study, male GIFT fish, even wi th a higher agonistic activity than female GIFT, could still have a growth advantage because of both the growth-promoting effects of androgens and thyroid hormones, and their relative low level of locomotory activity. In the case of the male controls, the growth-promoting effects of androgens and thyroid hormones could balance out the inhibitory effects of high levels of locomotory and agonistic activity on growth. Therefore, the male controls would be able to maintain growth rates similar to female control fish, even though males expend more energy i n behavioural activity than females. To test this hypothesis, further experimentation is necessary to examine the relationship between growth, behavioural activity, and hormone levels i n male and female fish. Nesting behaviour, which is often the first indication of the sexual maturity of fish, was observed only i n males. Bi l ly (1982) observed, i n Oreochromis mossambicus, a species closely related to Ni l e tilapia, that both female and male fish performed nesting behaviour, but female fish only performed nesting behaviour immediately prior to spawning. Male controls performed more nesting behaviour than male GIFT fish. A significantly higher number of nests also was present i n the control than GIFT aquaria. Aggression, as observed mostly i n the male control fish, appears to be the prevalent mechanism of 59 establishing and maintaining nesting sites (Fenderson et al., 1968; Mabaye, 1971; Koebele, 1985), and thus attracting mates (Oliveira et al., 1996). The control fish also built more nests earlier i n the study (i.e., Apr i l ) than the GIFT fish; it took the GIFT fish t i l l lune to reach the level of nesting activity observed i n the control aquaria i n A p r i l . These findings indicate, at least i n males, that the slow- growing control fish became sexually mature sooner, and at a smaller size than the fast-growing GIFT fish. Siddiqui et al. (1997) also observed that i n male and female hybrid tilapia, Oreochromis niloticus x O. aureus, fast-growing fish matured at larger sizes, whereas slow-growing fish matured at smaller sizes. In contrast, A i m (1959) summarized, i n his review of the connection between maturity, size, and age i n fish, that larger specimens wi th in a certain age group would mature sooner than smaller specimens. He suggested that this circumstance could be considered the rule', since a connection of this k ind was found to exist for al l species of fish that had been examined (e.g., salmonids, coregonids, perch) (A im, 1959). However, most of the data about w h i c h generalisations were made came from temperate fish species. Therefore, the connection between growth and sexual maturation needs to be further examined i n tropical fish species to ascertain if it is similar or different to that of temperate fish species. From the results of my study, the relationship between growth and sexual maturation seems to differ i n tropical and temperate fish species; this difference may be associated wi th their different environmental conditions. 60 Size-related mortality was found i n both strains of N i l e tilapia: dead fish were smaller than the survivors (i.e., l ive fish). O n examination of the bodies of the dead fish, many fish had frayed fins (i.e., pectoral, tail). Christiansen and Jobling (1990), Christiansen et al. (1991), and Siikavuopio et al. (1996) used the incidence of caudal fin damage as an indirect indication of aggressive interactions. If this interpretation is correct, most fish seem to have died from an aggressive encounter wi th a tank mate or the consequence of the aggression rather than from natural causes. It was suggested that high mortality i n small fish may result from starvation as a consequence of the aggression of a few large individuals (Saclauso, 1985). This behaviour could have elicited inhibitory effects (e.g., small fish become less mobile) which denied the smaller conspecifics access to the food even if it was given i n excess (Saclauso, 1985). In the control strain, it was observed that only male control fish experienced size- related mortality. The male control fish could have experienced size-related mortality because they performed more agonistic behaviour than females, and the subordinate males, as suggested by Saclauso (1985), were probably unable to evade damaging and potentially lethal attacks of the dominant fish i n closely confined aquaria. Furthermore, control fish suffered a higher mortality than GIFT fish. The higher mortality of control fish could be correlated wi th their higher bouts of agonistic behaviour compared to GIFT fish; high mortality rates have been attributed to increase aggressiveness of fish (Saclauso, 1985). Si ikavuopio et al. (1996) 61 observed a h igh mortality and incidence of caudal fin damage amongst w i l d - caught Arctic charr, while amongst hatchery-reared fish, mortalities were low and little evidence of fin damage was found. In contrast, Vincent (1960), and Flick and Webster (1964) observed a higher mortality rate i n the larger and faster growing individuals of the domestic strains of brook trout. This higher mortality rate observed i n fast-growing domestic brook trout could be due to them performing more agonistic behaviour, but aggression was not examined. E i n u m and Fleming (1997) found the farmed Atlantic salmon, wi th a higher growth rate, tend to be more aggressive. Aggressive behaviour, i n the form of nipping, also was reported to be more frequent among fast-growing domesticated brook trout (Moyle, 1969). In all , these results add further support to the conclusion that the slow-growing control fish were more aggressive than the fast-growing GIFT fish during the three month study period. The weight and length of nesting male fish were higher than non-nesting male fish of the same strain. This finding agrees wi th the results of previous studies on the sand goby, Pomatoschistus minutus (Magnhagen and Kvarnemo, 1989; Kvarnemo, 1995), and the cichlid fish, Oreochromis mossambicus (Oliveira et al, 1996) which showed that territorial fish were larger i n size than non-territorial fish. It has been suggested that larger males are more successful i n defending territories (Downhower and Brown, 1980; DeMart ini , 1987; Goto, 1987; Hastings, 1988; Cote and Hunte, 1989, Magnhagen and Kvarnemo, 1989; Oliveira et al, 1996), bui lding nests, and obtaining mates (Magnhagen and Kvarnemo, 1989). In my study, even though small males were isolated i n the experimental aquaria 62 wi th no male-male interactions, they still had a lower nest bui lding rate than the larger males. Thus, it seems that small fish may not have the physical ability or be at the motivational state to bui ld nests (see Pauly, 1994). The fast-growing male GIFT fish required more time to complete their nest(s), and built fewer nests than the slow-growing male control fish. Even though the nest diameter to fish length ratios of control and GIFT fish were similar, the total and mean nest areas were higher i n the larger male GIFT than control fish. This connection between large males and larger-sized nests has also been observed i n the blenny, Istiblennius enosimae (Sunobe et al., 1995). However, i n mouthbrooding cichlids, size does not appear to be a major consideration i n mate choice (McKaye, 1983, 1984). Only nest size is k n o w n to be an important correlate of male reproductive success and social status i n other lek-breeding cichlids (McKaye et al., 1990; McKaye, 1991). It was observed that a large nest size is preferred by females (Bisazza et al, 1989; McKaye et al., 1990; Sunobe et al., 1995), thus males who bui ld large nest(s) should experience a higher mating success. It was noted that males wi th larger nests expended more time and energy i n defending the nest from other breeding males. They also spent more time and energy defending the nest territory against nonbreeding coloured conspecifics, including "sneakers' (McKaye, 1983). It was suggested that male's nest size may signal to the female his ability to defend the nest from egg eaters, which are specialized i n stealing eggs before the female can put them into her mouth (McKaye, 1984). Thus, nest size probably plays a role i n inducing the female to lay eggs wi th a given male (McKaye et al, 1990). In all , more research 63 on mouthbrooding cichlids is needed to confirm the importance of body and/or nest size i n the breeding success of males. Nesting activity was recorded during both low light and day portions of the observation period; however, the fish often started and completed its nest(s) during the day. To my knowledge, this is the first study that examined the t ime of day nesting is performed i n fish. More work is needed to discover why the nest is mostly started and completed during the day. Brett (1979) suggested that light stimulates the brain-pituitary responses which radiate through the endocrine and sympathetic systems; this induces the production of growth hormone (GH) and anabolic steroids, and can influence locomotory activity i n association wi th thyroid stimulation. Therefore, light may play a role i n regulating nesting activity of fish. Concluding Remarks 64 The rearing of cultured fish has become an increasingly important industry. F i sh culturists seek fish strains that possess high growth rates and reach harvestable size before attaining sexual maturation. Sexual maturation of fish can complicate production operations and /or affect product quality. This is especially important for the tilapia which, when they mature precociously, can overpopulate waters wi th small, stunted fish. Aggressiveness i n the form of attacking and fin-nipping, also associated wi th breeding behaviour, is an undesirable habit for farmed fish (Balarin and Hatton, 1979) and one for important consideration when choosing a tilapiine strain for culture practices. It has been argued that i n competitive environments, artificial selection for fast growth may lead to higher levels of overall aggression, and therefore w o u l d result i n no net gain i n assimilation efficiency or growth i n the populations (Kinghorn, 1983). By considering the energy budgets' of fish under domestication, such as N i l e tilapia, the information could be used i n selective breeding of this and other fish species. For example, the fast-growing, passive GIFT fish wi th a delayed maturation would be ideal i n fish rearing programs, while the slow-growing, aggressive control fish wi th a precocious maturat ion would not be selected. The results of behavioural studies are likely to be of more direct utility to breeders than most physiological and biochemical measures such as food conversion efficiency, and protein, l ip id and water contents of body tissues. 65 The main focus of many breeders is on genetic improvement of farmed fish. If indeed quiet, low energy' behaviour reflects an underlying genetic variation and thus amenable to selection (as the GIFT fish seem to demonstrate), then it could be incorporated into or even become a primary basis of fish breeding programs. 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Prentice H a l l , Upper Saddle River, N e w Jersey. 662pp. MO " r - X ^ .2 S ^ > CU » H KS CU CCS RS C J •J3 T3 ^ 3 cr, CU cu C O 5 E ° cu H J m 5" » 5 -s e l r CJ cu u CO « r—I — —< to f o x i '«9 Jr}-1 & t N C N o & o V CO 4=1 CD 2 § O N CN 06 ON C N C N | O N O N C N 1̂ N O O N C N M I N O O N C N N O I"* O N C N O o o cn > u N O in C N irj C N C N ho CO o N O co t N o C N C 42 •a g to C c/i ^ co| <3_ '3 fc 3 1 fc i—i i 2 . fc i—i o CO 1 ^ TS 3 CD 3 H § S e s CO B s CM r H O o 0 w r H CM r H CM Vi be ha vi ou  S S CN CO be ha vi ou  P S L O CM s s r H CN 5 s r H CO r H R E  (se c)  28 4. 1 30 0. 0 30 0. 0 30 0. 0 30 0. 0 29 8. 2 30 0. 0 30 0. 0 30 0. 0 30 0. 0 29 4. 0 28 9. 3 29 5. 6 28 1. 9 29 1. 2 28 6. 1 25 4. 2 26 7. 8 25 9. 5 27 8. 3 49 .9  63 .8  68 .8  52 .3  82 .8  30 0. 0 30 0. 0 30 0. 0 SW  (se c)  15 .9  0 0 r H o L O 10 .7  18 .1  oo 0 0 13 .9  45 .8  32 .3  40 .5  21 .8  23 3. 8 22 8. 2 21 3. 4 23 6. 1 21 4. 0 st ra in / nu m be r N © r H v© r H \ © r H r H 0 0 r H 0 0 r H 0 0 r H 0 0 r H 0 0 r H CN CN CN CN CN N © CN \ © CN \o CN N © CN N © CN fis h ta nk  G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / G IF T / r H B I/ID  r H B CT /1  C T /1  CO B CO B CT /3  ON T 5 iH c be ha vi ou rs  I-H I-H be ha vi ou rs  E g be ha vi ou rs  t N be ha vi ou rs  be ha vi ou rs  O s- be ha vi ou rs  S g be ha vi ou rs  £ g t N N O be ha vi ou rs  8 g CN T—t t—1 t N CO be ha vi ou rs  5 g 0 0 CO I-H be ha vi ou rs  R E  (s ec ) o o o CO O N 0 0 O N CN o o o CO o o o CO o o o CO CN N O O N CN o o o CO o o o CO o o o CO o O N CN CO CN q o o CO q o o CO C N CO 0 0 CN q o o CO CN $ I-H 0 0 N O CN CN CO CN m O N I-H CN N O CN N O CN 0 0 I-H CO CN o 0 0 I-H CN N O ' CN CN O N CN N O l-H I-H t N o CN 0 0 I-H m be ha vi ou rs  SW  (se c)  H oo CO N O O N I N N O CN *# N O I-H oo CO m I-H N O CN CO 0 0 in N O m o 0 0 TJH I-H CN CO CN o I-H I-H O N t N in in 0 0 CO t N K in N O CN CO c© CO CN fi sh  s tr ai n/  ta nk  n um be r CO B CO B I N B I N B I N B t N B t N B O N B O N B O N B O N B I-H I-H B I-H I-H B I-H I-H B l-H I-H B CO I-H B CO I-H B CO I-H B cr/ 13  CO I-H B m I-H B m I-H B in I-H B C T/ 15  in I-H B t N l-H B t N l-H B t N I-H B o a> J O e s sag m cj P H to co CN C O CO ( N No io LO CN LO C N CO CO ho 0 0 o\ CN CO o I N ! 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LO LO Pi CU cu LO |LH cu o S CO CD T 3 .5 o o rt H C cu OH cu 6 cu C/3 CO cu X cu *fc e g rjg U *«: 5 I? fc P H LO CN n cu C U fc o O N O N c cu cu >H , O N fc O O N CN C O N O P H CN CN CU cu CN N O £jfc P H c cu cu Ml LO CN 3 LO CN LO fc o .̂ IN CN CO P H t N CN S C U t N CN t N O NU . 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CJ CJ CJ CJ CJ CJ CJ CJ CJ CJ CJ CJ CJ CJ CJ o V rs X cu JO O ff- P £ g 5g rV ND P H c/j In wi CN CO CN N £ > co CN CO LO 0 0 LO CO LO oo LO 0\ O N 0 0 LO CO CN CM oo CO cu =s .s c, o cj cu cu CO CU 6 bo 53 - co K O N O N CN CU CO 01 H T J G cu OH P H P H P H P H P H P H P H P H P H P H P H ^ *H p cu •ii « 5 o c j TS c3 cu H O CO c cu CO OH! CO O 1=1 s cu o cu H O N s ^ . 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C N O N o S CS X CU eg *fc u p g £g LLl CJ P5 to > u > CO In co C O T h CS CO ON CO m CO in C N l NO ON I 3 3 in C O co C O cd ON CM ON T h in I N en cS CU a £ 1 oo od NO X cu <=n CM T h T h C O CO C O CO I CO CN |co T h CN ON T h I N T h CU P H P H P H P H P H P H P H P H o !=l CU H CM E H H o cu cu CN E H H o I T h CH CU cu T h E H H o T h E o cu H NO E c cu cu NO E o NO ;E H H o H x CH Ol CU oo E o 0 0 E r—I O O CU EH CU cu , cl 1 fe1 H H , O , 4-» IB T h r H E H H O CH cu cu be | T h H H u H H o o V a cu eg 8 g P H cn CN CN CN coj | N O CN o o o CO o o o C O 0 0 0 0 co CN CN O N CN 55 <» oo oo O N t N CO O N CN 0 0 L O c CJ s CU CO c3 CD 0 0 C O o N O 0 0 oo 0 0 4H cu v 2 q fc CO L O CN o O N 0 0 C O CN t N CO CO H ICN CN CN O N CO X cu CO P H P H P H P H P H P H P H P H P H P H P H P H | P H | P H fc o N O N O C cu cu. N O fc N O 0 0 0 0 cu W oo 0 0 fc o N CN cu NV . 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I 1 I I I I i i i i i i i i i i i ! i i . i i i i i i i i i i i i i i i i i i i i i i i i i i i i t i i i i » i i i i i i i i i i i i i i i i i i I 1 I I I I I I I 1 I I 1 1 1 1 1 1 i i i i i i i i i i i be ha vi ou rs  @g i i i i i I I I i i i i t i i i i i i t i i i i t i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i t i t i i i i I I 1 I I I I I I I 1 1 1 1 1 i i i i i i i be ha vi ou rs  i i i i i i i i i i i i i i i » i i i i t i i i t i i i i t i i i i i i i • i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i t I I I t t t I I 1 I I I 1 1 j 1 1 i i i i i i i i i be ha vi ou rs  0 & i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i t ! i i i i i » i i i i i i r i i i i I I 1 I I I I I I I I I 1 1 1 1 I t i i i i t i i i i » be ha vi ou rs  § g i i j i i i i i i i i i i i i i i i i » i i i t t i j i i i i i i i i j i i i i i i i i i i i i i ! i i i i i i i i i i i i i t I 1 I I t t i I t l I 1 1 ! 1 1 i i i i i i i i i be ha vi ou rs  £g LO i i i i i i i i i i i i i i i i 1 i i i i i i i j i i i i i i i i i i i i i i i i i i i i i i i i i t i i i i i i i » i i i i i i i i i ! i i j I I I I I I 1 1 1 1 1 ( i i i i • t i i i i i i be ha vi ou rs  8 g C N CO i i i i i i i i i i i i i i i t i i i » i i i i i » i i i i i » i i i i i i ! i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i t i t i i I I j I I 1 1 1 1 1 1 i i i i i i i i i i i be ha vi ou rs  5g LO r H i i i i i i i i i i i i i i i i i i i i ! i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i t i i i t i t i t i i i i i i i i i i i i i i i i i i i i I I I I I I 1 1 1 1 1 1 i i i i i • i i i i i be ha vi ou rs  tN CO r H 0 0 oo CN r H N O r H i i i i i i i i 1 1 1 1 i i i i i i i i i i i • i i i i i i i i i i i i i i i i t ! 1 1 . 1 1 t i i i i i t i i i ! i i i i i i i i i i i i i i i i i i i i 1 i i i i i i i i i i i i i i i i o o o CO o o o CO o o o CO o o o CO i i i i i i i I t I 1 1 I I I t i i i j i i i i i i i be ha vi ou rs  CO O S OO LO CO LO r H CN r H t i i i i i i 1 1 1 1 1 1 1 i i i i i i i i i i i i i i i i i i i i j i i i i i i i i 1 1 . 1 1 1 1 1 i i i i i i i i i i i i i i i i i i i i i i i i i i t i i i t t i i »• i i i i i i i i i i i i i i I I I I I I I I 1 1 1 1 1 1 1 1 i i i i i i i i i i i i i i i i m ea su re m en ts  CU ' t N 0 0 C N LO N O i i i i i i i 1 1 1 1 1 ( t t i i i • i t i t i i i i i i t i i i i i \ t t i i i i ( < 1 1 1 j 1 1 i i i i j i i i i i i i i i i i . i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i » i i i i C N C N N O LO K CN 0 0 i i i i i i i i I I I I 1 I I I 1 1 1 1 1 1 1 1 i i i i i i i i * » i i i i m ea su re m en ts  • I f ® fc 0 0 r H CM C N r H r H r H cd t i i i i i i 1 1 1 1 1 1 1 1 ! i i i i i i ! i i i i j 1 1 1 1 1 1 1 i i i i j i i i i i i i i i i i i i i i . i i i i i i i i i t t i » i i i »• i i i i i i i i i i i i i i i i i i i CN CN r H CN O N CO CN r H CN C N r H I I I I I I I 1 1 1 1 1 1 1 t i i i i i i i i i i i i i se x P H i i i i i i 1 i 1 1 1 i i i i i i i i i i i i i i i i i i i i 1 1 1 1 1 1 i i i t • t i i t i t t i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i P H i j i 1 l 1 t t I 1 I 1 r i i • t ! 1 1 t i i i i i i fi sh  s tr ai n/  ta nk  n um be r/  be ad  c ol ou r cu C N r H B s CU SH be C N r H B u C N r H B CT /1 9/ ye llo w  <u -t-» 1 r H B cu J3 X > O N r H B s cu SH be O N r H B U O N r H B fc o U H 1 CU r H CN B CU -4—» 1 r H CN B cu J3 r H CN B S cu SH be r H CN B u r H CN B fc o =1 cu > N LO CN B cu 1 LO CN B cu LO CN B c cu cu ?H be LO CN B % a LO CN 6 fc o !=l cu C N CN B CU -t-» C N CN B CU 3 C N CN B 1 CT /2 7/ gr ee n 1 C T /2 9/ ye llo w  CU 1 O N CN B CU X > O N CN B C cu cu SH be O N CN B % 0- O N CN 6 o S CO X cu eg u [2 S g : m C J P H CO 05 C T \ 0 0 O N O N oo fN L O N O O N C N C N L O O N L O C O CO C U . 6 cu CO C3 cu £ 1 bp cu - N O IN C N T h C O C O C O O N T h T h X cu CO P H P H P H P H P H P H P H P H P H o H C N C cu cu & C N E HH o o ^. 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I 1 I 1 I I i i i i i i i i i i be ha vi ou rs  Bg 1 I 1 1 1 I i i i i i i I I I I I i i i i i i i i i i be ha vi ou rs  t ig 1 1 1 1 j i i i i i I I 1 I t t i i i t t i i i be ha vi ou rs  O rrr- 1 1 1 1 1 t t i i i i i i i i i i i i i be ha vi ou rs  § g r H 1 1 1 1 i i i i j I I I I I I i i i » i i i i t be ha vi ou rs  P g 1 1 1 1 1 1 » i i i t t I 1 I I I i i i i i i i be ha vi ou rs  S g 1 1 1 1 i i i i i i i I I j ! i i i i i i i i be ha vi ou rs  5g i i i i i i i i i i i i i i j i i i i i i i i i i i i r H be ha vi ou rs  RE  (s ec ) 29 6. 5 30 0. 0 30 0. 0 30 0. 0 30 0. 0 28 5. 0 27 9. 7 27 9. 2 26 4. 6 28 4. 7 28 8. 6 29 9. 6 29 6. 9 30 0. 0 29 6. 8 30 0. 0 30 0. 0 28 7.1  30 0. 0 30 0. 0 30 0. 0 i i i i | j i i i i i i i i i i i i t i i i i i t i i i i i i i i i i 2 37 .5  30 0. 0 be ha vi ou rs  SW  (s ec ) L O C O 15 .0  20 .3  20 .8  35 .4  15 .3  11 .4  T h o r H C O C N C O 12 .9  i i i i i i i i t t t i i i i t • i i i i i i i i i i i i i i i i i i i i 61 .8  m ea su re m en ts  le ng th  (c m ) C O CTN' C O O N o O N L O K I N C O C N O N ' C O CjS o o C O K v O K I N K T h K T h K V O v O o K C O oo 0 0 I N 0 0 C O 10 .3  v O 0 0 t i t i i l i t i i i i i i i i i i i i i i i i i i i i i i C O 0 0 T h m ea su re m en ts  w ei gh t (g ) 23 .1  26 .3  21 .3  14 .3  23 .0  26 .5  30 .2  21 .2  15 .8  16 .4  13 .7  13 .1  12 .5  13 .0  o O N 11 .0  23 .8  13 .7  21 .3  33 .5  22 .7  i l i i i i t i 19 .4  13 .4  se x F /M  P H P H P H P H P H P H P H P H P H P H P H P H P H P H I i i t i i i i i i i i i i i j i i i i i i i i i i j fi sh  s tr ai n/  ta nk  n um be r/  be ad  c ol ou r G IF T /1 4/ pi nk  G IF T /1 6/ ye U ow  G IF T /1 6/ w hi te  G IF T /1 6/ bl ue  G IF T /1 6/ gr ee n 1 G IF T /1 6/ pi nk  G IF T /1 8/ ye U ow  G IF T /1 8/ w hi te  G IF T /1 8/ bl ue  G IF T /1 8/ gr ee n 1 G IF T /1 8/ pi nk  G IF T /2 4/ ye llo w  1  G IF T /2 4/ w hi te  G IF T /2 4/ bl ue  G IF T /2 4/ gr ee n | ' C H T h C N E r—I a G IF T /2 6/ ye U ow  G IF T /2 6/ w hi te  G IF T /2 6/ bl ue  G IF T /2 6/ gr ee n 'o. v O C N E o C T /1 /y el lo w  C T /1 /w hi te  i — i r Q r H 6 c cu cu r H B CT /l /p in k C T /3 /y eU ow  C T /3 /w hi te  o V cs cu X> e s i—1 O s g g 8 g 5g UJ CJ P S cn OO CN LO Ov OO CN CO oo oo CN CO CN LO 0 0 vO O LO > CJ 55 2̂, CO Ov C O vO oo vO LO 00 o cu B cu cn cci cu B 0 0 t N oo vO vO LO od cu -^1 fc oo vo LO 0 0 oo cu cn P H P H P H P H P H P H P H P H P H P H c cu & . aj CO &1 CO fc 1 cu cu I N 0 | L N fc O Ov g cu. a* Ov >ix> s cu *H . 04 fc o cu . H CO C cu cu CO fc I* CO LO s cu |LO jbbbbbbbbbbbbbbbbbbbbbbbbbbb o V CO CD e g C N u sg r j j CJ P H co 05 <£ L O C O C N C N O N Os C N O N 9 C N | C O C O O I N T3 cu 3 O CJ H I1 CU I OH O. < cu CO ra cu 00 I N N O C N 00 C O C N CN K cu CO P H 6 cu cu o 4 1 . >N| ; O N 2 O N O N o d . O J > N O N O N C N C N C N C N O v . >A L O C N s cu B I N C N I N C N o cu cu o CU H | O N C N O N C N c cu cu *H bO ! ION C N jbbbbbbbbbbbbbbbbbbbbbb b b b b bo a *H — O ^3 73 ai O) CO 0> >H CL, cS tn CO H H CJ 73 C TH 0 1 > »H o »H o co Ol • CO c ca .£3 73 2 73 n5 • i H >H ns & ns H H c 0 ) 6 Ol CL, X 0 1 0 1 0 ) CO 3 o ^ ns ns ^ ns Ol * 73 Ol — CL, ^ X s Ol 3 <! 0 1 3 o Ol >H Ol fc Ol CO Ol CL,-< - - H Ol S Ol H - L H CL, 73 co O 'C JH 0 1 3 CL O 5 x CO H - * CO CD c < J H o 0 1 1. 7 * i« H 2 4 H x 6-1 a Ol > C U 4T, JH ns 3 < cu 6 •a cu a x pa ns Q C on tro l O N C N T-H T-H T-H C O C N C N C O C N C O C O L O C N C O v O V O C on tro l t N C N C N T-H C on tro l L O C N T-H T-H T-H T-H T-H T-H T-H C N C N C N C N C N C N C on tro l i — i C N C N T-H T-H T-H T-H C N C N C N C N C N L O C N T-H C N L O C N C on tro l a\ T-H T-H T-H T-H T-H T-H T-H T-H C on tro l t N T-H T-H T-H C N T-H C N C O C N L O L O C N V O C N v O C O C O C O "tf. V O r H C on tro l L O T-H C N C N L O C N C N C N C N C N r H C on tro l C O T-H T-H C O C O C N C on tro l T-H T-H C on tro l as T-H T-H C N C N C N C N T-H T-H C N C on tro l C N T-H T-H C on tro l C O C N C N T-H T-H C N C N C N L O C O T-H r H r H C N C N C N C on tro l T-H C N C N T-H T-H T-H G IF T v O C N T-H G IF T *̂ C N G IF T 00 T-H G IF T V O T-H r-H G IF T T-H G IF T o T-H G IF T 00 r H r H T-H G IF T V O G IF T C O G IF T C N A pr il 1 A pr il 2 C O t < A pr il 5 A pr il 7 A pr il 8 A pr il 9 A pr il 10  A pr il 11  A pr il 12  A pr il 13  A pr il 14  A pr il 15  A pr il 17  A pr il 18  A pr il 20  A pr il 21  A pr il 22  A pr il 23  A pr il 24  A pr il 25  A pr il 26  A pr il 28  A pr il 29  T3 Ol .5 H-> C O cj C Ol CH cs •c cS c r cx X cu ta P F Io O N CN r H vO T h in CN CO m T h r H CO ON m m CM m I N CN r H r H r H I N CO CN I N T h T h CM r H CO LO CN 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 r H CN CO T h m CO T h T h LO m m CO in m T h m LO CO o\ r H 1 1 1 1 1 1 1 1 1 ! 1 1 1 1 1 1 1 1 1 1 1 I N T-H LO CO CO CO CO m m T h vO CM vO vO v© CM r H CO T h T h NO in LO r H CN CN CN CN r H CO T H T h m CO T h CO CM m CN T h T h T h CO r H r H r H CO T h r H vO m m I N CO CM I N r H I N I N I N I N vO r H r H r H o\ LO LO CN LO LO T h CN CN CN r H CM CO CO r H CM CM r H r H r H I N CO CN T h CN CM CO CO T h T h CO CM CM CM m T h CO CO CN CN CN CN CN CO r H r H CN r H r H CM I N r H CM CM in CO r H 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 vO CN r H r H T h T h CN 00 r H r H CN r H r H r H CM CO r H r H r H T h r H o r H CO r H 00 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 vO r H m T h r H CO CO CO CN m T h m CO T h CN CN T h T h T h CO CO CO r H v© I N T h I N I N CN r H r H >•> CO £ CN £ CO £ T h £ in £ vO £ I N £ OO > N CO £ o r H CS £ r H r H > l CS £ T h r H CS £ m r H CS £ vO r H C3 £ I N r H CS £ 00 r H CS £ Ov r H >, CS £ CN1 £ I N CM £ 00 CM £ o CO CS £ r H CO JS- CS £ CN 1 1 1 1 1 1 1 1 1 1 1 1 t N CN CN r H CN SO LO CN LO CN 1 1 1 1 1 1 1 1 1 1 1 1 r H CN 1 1 1 1 1 1 1 1 1 1 1 1 Os r-H 1 1 1 1 1 1 1 1 1 1 1 1 C N T-H LO LO CO LO r H CN co co CO C on tri  LO T-H CN CO r H CO SO CO LO CO •<* C on tri  CO T-H SO CO 0 0 r H sO LO t N SO LO r-H r-H CN ar ia  Os CN r H r H CN r H r H r H CO CO A qu  t N 1 1 1 1 1 1 1 1 1 1 1 1 en ta l CO SO CN r H r H T-H r H CN SO er ir n r-H 1 1 1 1 1 1 1 1 1 1 1 1 Ex p sO CN CN r H LO LO r H CN CN oo r H CO SO r H r H FT  r H r H CO G I o r H r H CN CO 0 0 1 1 1 1 1 1 1 1 1 1 1 1 SO LO CO CN CO CO CO CN r H rJH t N SO LO sO SO CO LO CO LO CN CN LO CO D at e CN CU 1 J un e 6 1 J un e 9 CN r H CU 1 J un e 15  t N r H CU 1 J un e 24  LO CN CU sO CN 1 J un e 27  O CO CU CN 3 T* O T"J co O J O ^ 3 T-f O TS CD •2 ° B -5 <% - g TS 0 ) co •rH CO (H H-> 1/1 o TS CB r H o J D 6 CD X CD 05 o co X CD to T3 CD H H CCS T3 S r 5 r > CCS OJO v ~ H *H O § <« r H H-> r H O H H . 2 CJ oo £ a * N • T-H C O ca CD £ c3 C O CH g CH CH < °i cj 0 5 • r H W CD 5rf o CM CD - r H — CD w * C M ^ CD C O CD co rC <- X TS c CD CH _ C 3 QJ TH ^ TS 5 C r S R S TS cfl I X C O I T S bo CH ' rC SPbrJ I T S ' g ccS .2 a> H H ITS cf i T J ' a; IrC bOCr\ 53 -55Jco P H I T S CO CD T S CD > rS CO co v© K in ho ho O N 0 0 CO T h T h C N v© O N o T S CO cu T S T S CO CU T S cu > to i-S cu > rH" 1̂ cu > rS CU CO K C N v d v d T h \ d v© 0 0 T h in m od m v d N O 0 0 v d I N Os" T h T h T h 0 0 C O r H C N T h C O co| I N 0 0 Ov v d i-S cu > T S CO CD T S i-S cu L O CO T h I N vO Os in" T h oo o T h CO C N in" I N in" co I N ON V O CO T h I N 0 0 v d P H P H £1 P H P H P H P H o r=l CU co cu oo oo cu cu loo oo ta g r CU ! o to cu fe P H -IH I H CU 4-» ta I I N CU r CU ! I I N ~ t o to vD . H ION" ,2" ta Ov CJN c C D cu r H . ION o CU | C N C N d cu cu SH bo C N j v j t j b b b b b v j b b b j b b b b b b b 0) de ad / liv e l 1 l l I 1 1 l I I I 1 I I I de ad  I I I I 1 I I I i i i i i i i i i i i i I I I 1 i i I I I I 1 I I I I I i 1 I I I cu > de ad  de ad  de ad  de ad  le ng th  (c m ) l l 1 1 l i I I I I I 1 I I I N O O N C N N O I i t I 1 • i i i i i i i i i i i i i . i i i I I I I 1 I I I I I I I j I I I I I 1 I I l I I I I 1 I I C N 0 0 r - H I N C O N O C N I N •«* L N w ei gh t (g ) l l l i i i i I I I I I I I I • H H N O C N O N 0 0 i i i i i i ! i i i i i i I I I I 1 I I I I I I I 1 I I I I I I I 1 I I I I I I I 1 I I N O L O r - H r H O r H 0 0 L N o r - H O N r H r H M ay  de ad / H ve  de ad  i t I I I I I I & de ad  i i i i i I I I i i i i I I I I 1 I I I I I I I 1 i t I I I I I 1 t I I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ( 1 l 1 1 1 1 M ay  le ng th  (c m ) C O L O I I I 1 I I I L O 0 0 N O N O C O L O i i i . i > i i i i i ) i i » i i i t i i i t I I I I I I I I I I I I I I I I I I I I I I I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ! i i 1 1 1 1 1 1 1 1 M ay  w ei gh t (g ) 0 0 I I I I 1 I I I O N T - H r-H O N L O i i i i i i i i i i i i i i i i i i i i I I I I I I I I I 1 i • I I I I 1 i i i 1 1 1 1 1 1 ) 1 1 I I ) 1 1 1 1 1 1 1 I 1 1 1 i i i i i i i ( 1 1 1 1 1 1 A pr il de ad / liv e de ad  Si % % de ad  •x cu > •X cu > de ad  t 1 1 1 j 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i i i i i i i i 1 1 1 1 1 1 1 A pr il le ng th  (c m ) o L O C N C N L N K O N L O N O L O N O N O L O o N O C N N O oo N O 1 1 1 1 1 i ( 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 i i i i i i t i t 1 1 1 1 1 j A pr il w ei gh t (g ) C N N O T - H T - H L O T - H N O N O C O C O o 0 0 L O N O N O I N K C N O N 0 0 C N 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I i i i i 1 ! 1 1 1 1 1 1 1 1 X o> cn F /M  s C > - P H C N - P H C N . P H P H s ~>H •H cn •̂ a <d § 1 C T /2 1/ pi nk  fc o !=l CD >> L O C N 6 cu fc B CT /2 5/ bl ue  C cu CL) ?H br. L O C N B •i-H a L O C N B 1 C T /2 7/ ye llo w  1 C T /2 7/ w hi te  C T /2 7/ bl ue  1 C T /2 7/ gr ee n 1 C T /2 7/ pi nk  1 C T /2 9/ ye llo w  CU H—» $ O N C N B 1 C T /2 9/ bl ue  c cu CD * H 60 O N C N B • i H 0- O N C N B 106 A p p e n d i x I V . Number of mirror-directed bi t ing (BI) and tail-beating (TB) performed by the male fish of the control (CT) and GIFT strains of N i l e tilapia during the two behavioural trials. Each behavioural trial was five minutes i n duration and the two trials were spread out over a one week period. The table cell was left blank if fish did not perform behaviour. fish strain/ tank number/ bead colour trial #1 trial #2 weight length (cm) BI (#) TB (#) weight length (cm) BI (#) TB (#) GIFT/2/yellow 40.7 11.3 42.4 11.3 GIFT/2/blue 40.6 11.0 42.9 11.0 4 2 GIFT/2/green 33.0 10.3 34.0 10.4 2 . 25 GIFT/2/pink 19.7 8.8 48 16 20.3 8.9 31 20 GIFT/6/yellow 24.3 9.1 6 25.6 9.3 GIFT/6/blue 47.1 11.6 41 50.9 11.5 19 GIFT/6/green 14.3 7.6 14.8 7.7 11 18 GIFT/8/pink 33.7 10.3 33.8 10.2 19 16 GIFT/14/white 26.8 10.0 27.0 9.9 42 37 GIFT/14/blue 35.3 10.3 10 35.9 10.3 21 GIFT/14/pink 40.0 11.2 42 31 40.7 11.2 GIFT/16/blue 22.8 9.0 26.0 9.2 GIFT/16/green 34.8 10.5 37.6 10.4 35 54 GIFT/18/yellow 47.7 11.5 50.7 11.7 37 39 GIFT/18/green 24.0 9.0 24.9 9.2 3 3 GIFT/26/green 46.6 11.6 48.2 11.5 4 CT/1/pink 22.9 9.6 50 39 24.2 9.7 31 29 CT/3/yellow 21.7 9.1 22.3 9.3 14 CT/3/white 19.9 8.8 21.3 8.8 21 12 CT/3/green 15.8 8.2 16.2 8.2 94 37 CT/3/pink 10.6 7.2 11.0 7.3 CT/5/white 19.6 9.2 19 20.1 9.1 78 14 CT/7/yellow 28.9 10.2 36 19 29.5 10.4 20 8 CT/9/white 36.5 10.7 39.3 11.0 51 91 CT/9/green 17.4 8.4 44 5 18.1 8.5 31 18 CT/11/pink 5.7 6.1 6.0 6.0 20 13 CT/13/white 32.4 10.3 35 20 34.5 10.4 6 58 CT/13/blue 10.5 7.2 81 14 11.1 7.2 64 17 CT/13/green 38.8 10.6 15 71 41.4 10.8 6 62 CT/13/pink 22.0 9.1 1 16 22.9 9.3 CT/15/pink 31.3 10.3 120 14 33.8 10.5 87 22 CT/17/yeUow 18.0 8.5 2 101 20.5 8.7 6 65 CT/17/white 29.8 10.0 69 3 32.5 10.1 44 4 CT/17/blue 27.1 9.8 85 16 28.6 9.8 119" 19 CT/17/green 18.8 8.7 62 67 20.8 8.9 54 118 CT/17/pink 16.1 8.3 34 14 17.4 8.4 46 8 CT/19/white 44.3 11.2 44.4 11.3 65 68 CT/21/yellow 34.9 10.7 62 1 35.5 10.8 43 28 CT/23/white 38.3 11.0 55 10 39.0 11.2 51 19 CT/27/yeUow 28.7 9.9 30.6 10.1 CT/27/blue 25.2 9.3 10 18 26.0 9.3 3 107 Appendix IV. continued. fish strain/ tank number/ bead colour trial #1 trial #2 weight <K) length (cm) BI (#) TB (#) weight te> length (cm) BI (#) TB (#) CT/27/green 31.1 10.3 25 13 31.4 10.0 6 CT/29/yellow 28.5 10.2 22 73 29.1 10.3 44 54 CT/30/yellow 19.7 9.0 58 3 19.8 9.1 CT/30/white 16.9 8.3 41.6 11.1 28 7 CT/30/blue 40.0 11.0 17.2 8.3 8 97 CT/30/green 27.0 9.8 38 35 28.2 9.7 CT/30/pink 41.1 11.4 95 2 41.9 11.3 55 1 108 Appendix V . Weight and length of nesting and non-nesting ( N / N ) male fish of the control (CT) and GIFT strains of Ni le tilapia. For the nesting male fish, the total time required to bui ld a nest (start and stop times included), the size of the nest at completion, and the nest diameter relative to fish length were tabulated. The number of nests built per fish is given by the number of nesting (i.e., start/stop) times recorded i n the table cell of individual male fish. fish strain/ measurements time of day at total time nest area nest tank number/ start / completion to build (cm2) diameter bead colour of nesting nest(s) relative fliour) to fish length weight length start stop 05) (cm) GIFT/2/yellow 55.3 11.9 N / N N / N N / N N / N N / N GIFT/2/blue 50.4 11.5 23:34 9:53 10.3 45.3 0.7 15:39 16:17 0.6 25.4 0.5 GIFT/2/green 44.3 11.4 18:20 15:22 21.0 52.6 0.7 GIFT/2/pink 23.5 9.1 N / N N / N N / N N / N N / N GIFT/6/blue 62.9 12.5 7:49 15:43 7.9 99.7 0.9 GIFT/14/white 28.8 10.1 1:44 13:38 11.9 58.0 0.9 3:23 15:44 12.4 23.6 0.5 GIFT/14/blue 44.4 11.0 13:39 14:32 0.9 23.6 0.5 GIFT/14/pink 52.2 12.0 18:11 15:05 20.9 212.0 1.4 GIFT/16/green 44.9 11.0 N / N N / N N / N N / N N / N GIFT/18/yellow 54.5 11.8 21:04 16:01 19.0 54.4 0.7 15:38 16:29 0.9 56.2 0.7 CT/1/pink 33.6 10.5 9:56 16:14 6.3 32.6 0.6 13:03 13:10 0.1 16.3 0.4 CT/3/yellow 27.3 9.7 N / N N / N N / N N / N N / N CT/3/white 29.7 9.7 N / N N / N N / N N / N N / N 0.8CT/3/green 20.3 8.7 N / N N / N N / N N / N N / N CT/3/pink 13.3 7.7 9:36 10:31 0.9 30.8 0.8 CT/5/white 22.9 9.3 15:01 16:36 1.6 67.1 1.0 16:40 17:20 0.7 16.3 0.5 CT/7/yellow 30.5 10.5 2:32 11:03 8.5 63.4 0.9 CT/9/white 47.4 11.7 5:43 13:15 7.5 52.6 0.7 CT/9/green 22.2 9.0 13:34 18:31 5.0 235.6 1.9 C T / l l / p i n k 10.1 6.9 N / N N / N N / N N / N N / N CT/13/white 45.4 11.5 9:38 9:53 0.3 10.9 0.3 CT/13/blue 10.7 7.2 N / N N / N N / N N / N N / N CT/13/green 46.1 11.3 18:18 16:27 22.2 123.2 1.1 18:33 21.9 CT/13/pink 27.1 9.8 17:53 14:28 20.6 39.9 0.7 15:31 16:35 1.1 27.2 0.6 CT/17/white 42.1 11.1 18:35 14:15 19.7 29.0 0.5 12:57 15:31 2.6 25.4 0.5 CT/19/white 47.3 11.6 19:39 14:19 18.7 21.8 0.5 7:10 14:19 7.2 39.9 0.6 CT/23/white 41.6 11.3 17:53 13:12 19.3 14.5 0.4 9:36 10:35 1.0 18.1 0.4 10:38 13:36 3.0 18.1 0.4 Appendix V . continued. 109 fish strain/ tank number/ bead colour measurements time of day at start / completion of nesting total time to build nest(s) (hour) nest area (cm2) nest diameter relative to fish length weight fe> length (cm) start stop CT/27/yellow 40.1 11.0 21:25 14:30 17.1 54.4 0.8 CT/27/blue 29.9 9.9 N / N N / N N / N N / N N / N CT/27/green 36.6 11.0 9:24 11:19 14:54 16:42 5.5 5.4 41.7 61.6 0.7 0.8 CT/30/white 19.5 8.6 N / N N / N N / N N / N . N / N CT/30/blue 50.6 12.0 N / N N / N N / N N / N N / N

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