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The seasonal and dirunal movements of some pacific salmon fry with particular reference to the sockeye,… McDonald, John George 1956

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THE SEASOHfcL AMD DIURHAL MOVEMIHTS OF SOME PACIFIC SALMON FRY WITH PARTICULAR REFERENCE TO THE SOCKETE (Onohorynchu* nerka).  JOHN GEORGE McDOIALD  A THESIS SUEMITTED U PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE <F MUSTER OF ARTS  Iii th© Department of Zoology  Me accept thie thesis as conforming to the standard required from candidates for the degree of MA.STER OF ARTS  Members of the Department of Zoology  THE UNIVERSITY OF BRITISH COLUMBIA April, 1956.  in ABSTRACT The seasonal and diurnal movements of sockeye, pink and coho salmon fry are described. For sockeye, at least, the time of the seasonal migration froa the spawning area is related to the temperature "budget" during their period of development i a the gravel. Their seasonal migration occurs earlier following an incubatory period in which above average temperature prevailed and later following relatively low temperatures. Emergence from the gravel appears to occur normally only after a certain stage of development is reached. The diurnal movements of all three species are precisely regulated by their response to light. The strong negative phototaxis exhibited by the fry at this time restricts their movement solely to the hours of darkness. The downstream movement of sockeye and coho and also apparently of pink fry is initiated within a three hour period following darkness. The presence of artificial light almost completely prevents this movement either throughout the night or until such time as the light is removed. The data Indicate that a period of night blindness occurs which is common to the three species and that their downstream movement is initially a result of a displacement by the current. Once entered into the stream the migration continues until evacuation of the stream is complete or until daylight approaches. The response of sockeye fry to current during this continued movement appears predominantly positive in fast currents and negative in relatively slew currents. The migration is considered to result from both a displacement by the current and a movement directed on the part of the fry.  ii ' ACKKOWIEDQEMENTS This study was carried out as part of an investigation conducted by the Fisheries Research Board of Canada at Lakelse Lake, B.C. Thanks are due to several fellow workers who helped in the field work. The writer is indebted to Dr. A . V . H . Reedier, Director of the Biological Station, Banaiao, B.C., for permission to use the material and to Dr. W.S. Hoar, University ©f British Columbia, under whose supervision this thesis was written.  TABLE CF CONTENTS  LIST OF TABLES AND ILLUSTRATIONS ACKNOWLEDGEMENTS ABSTRACT  i li i l l  INTRODUCTION  1  MATERIALS AND METHODS  2  RESULTS  5  Seasonal movements of fry  5  Emergence from the gravel  9  Soekeye fry Pink and coho fry Downstream movement and response to light Soekeye fry Pink and coho fry Downstream movement and response to current  9 12 12 12 21 23  Orientation of soekeye fry  25  Rate of downstream movement  27  Soekeye fry  27  Pink and coho fry  28  DISCUSSION AND SUMMARY. Seasonal movements  30 30  Diurnal movements  31  Response to current  32  LITERATURE CITED  31  LIST Cf TABLES AND lUUSTRATIOHS following P&ftff Table 1. The number of air thermal units and time in days required from egg deposition to the emergence of fry.  g  Table 2. The relation between the mean proportion of creek discharge and sockeye fry migrants in the three outlet channels of Williams Creek, 1954.  25  Fig. 1. Fry traps used at Williams Creek. Fig. 2. Seasonal movement of sockeye adults and fry at Scully Creek.  7  Fig. 3. Relative variation of weekly mean air temperatures at Terrace, B.C. from a five year average (1949 to 8  1954).  Fig. 4. Dally number of sockeye fry captured and creek levels, Williams Creek, 1954 and 1955.  11  Fig. 5. Proportion of sockeye fry captured in consecutive hours of the night for progressive periods throughout the season. Fig. 6,  14  The number of sockeye fry initiating movement during consecutive time intervals after dark.  17  Pig. 7.  Movement pattern of soekeye fry under natural illumination and when darkness was delayed.  Fig. 8.  20  Mean proportion of soekeye, pink and coho fry captured during consecutive hours of th® night for a seven day period during th© 1954 migration.  Fig. 9.  22  The proportions of soekeye fry and creek discharge measured daily in the east channel @f Williams Creek, 1954.  24  Fig. 10. Mean proportion of fry captured ia trap® located across the main channel of William® Creek, 1954.  26  Fig. 11. Percentage of soekeye fry and floats captured during consecutive intervals after release.  29  • 1 •»  Introduction Pacific salmon spawn in rivers or lakes and their tributaries during the late summer and fall of each year. The fertilized eggs which are deposited in the gravel develop throughout the winter and the young salmon or fry emerge from the gravel the following spring. Theee fry commonly move downstream te the sea in the ease of the piak (Oncorhvnchus gorbuscha) and chum (0. keta) and to lakes in the case ef the soekeye. The movements ef the eohe (§. kisutch) aad spring ((J. tsbawvtseha) are not as regular and they may live in streams, rivers or lakes for variable periods. The behaviour of Pacific salmon fry leading to their downstream movement has been investigated by Pritchard (1943), Hoar (1951, 1953), MacKinnon and Hoar (1953) and Heave (1955). Hoar (1951) described the movement as primarily a downstream displacement by the current resulting froa a loss of orientation is respect to position at the approach of darkness. The same author (Hoar, 1953) recognized that the migration was not an entirely passive one bat that the fish were capable of directing their movements to a considerable extent! "They are active fish and as they dart to and fro will move most easily and furthest with the current, and will at night go downstream rapidly until they can again see t© maintain position with respect to fixed objects' . 9  Pritchard (1943), on the other hand, when observing piak fry recorded that the fry make "a swift and vigorous migration", leave (1955) substantiated Pritchard*s view and described the pink fry, at the time of their downstream movement, as showing a strong negativ© response to both light and current. The speed of their movement was sufficient to cause a "bow-wave". Neav© pointed out that th© result of this behaviour is th© evacuation of a stream only during th© hours of darkness and in the shortest possible time.  This report describes how seasonal and diurnal changes in temperature, light and current effect the activities and movements of sockeye fry. In addition, the presence of two other species, namely, pink and coho, afforded a comparative study of th© behaviour of all three species. Observations were made at an Identical stage in their life histories and under at least similar stream conditions. This approach permitted evaluation of the basic similarities and differences in the behaviour of the fry which lead to their migration from the spawning area. Materials and Methods The data were obtained during the course of an investigation of the freshwater production of sockeye carried out by the Fisheries Research Board of Canada at Lakelse Lake, B.C. Here, there are two tributaries, Scully and Williams Creeks, in which almost the total Lakelse escapement spawns. Scully Creek is the smaller and least important of the two. This creek averages about 25 feet in width. The spawning area extends from the mouth to a point approximately 5,000 feet upstream. In recent years the escapement has ranged from 400 to 1,200 sockeye. Daily records of the number of adults ascending the creek to spawn and of the number of resulting fry which migrate to the lake in the following spring have been obtained by the operation of a counting weir. This weir has been operated annually since 1949 and complete counts of the migrants have been obtained. Williams Creek is the largest salmon producer of the Lakelse area and usually between 5 and 10 thousand sockeye spawn here each year. Suitable gravel for spawning extends from its mouth to over 1 1/2 miles upstream. This creek has three outlet channels. The two small side channels (termed the east and west channels) break away from the main channel 200 yards from its mouth.  Counts and estimates of th© escapements to Williams Greek have been obtained by the operation of an adult weir, by tagging, and stream survey procedures. The numbers and movements of fry have been assessed by a method of sampling carried on at th© creek mouth. A series or "string" of small traps were placed at intervals across th© outlets. Six traps were operated across the main channel while two and one were operated in the west and east channels respectively. The essential features of the traps are shown in Figure 1. Each trap consisted of a long rectangular funnel leading downstream to a floating pen. Th© funnel was framed of wood and covered with hardware cloth (6 meshes to the inch). It was 3 f t . deep and 1.3 f t . wide at the mouth and tapered down to A in. by U i n . where it joined the pen. Th© pen, roughly 3 f t . by 2 ft., was buoyed up by cedar floats. A screened bottom ensured a constant level of water in the pen. The traps were held in position by attaching them to a steal cable stretched from  bank t© bank. The traps were operated continuously throughout the migratory periods of 1954 and 1955. A count was made of the number of each species captured each hour In each trap. Some pink and coho also spawn in both Scully and Williams Creeks. A l though the operations wer© carried out primarily to record th© numbers and movements ef the soekeye, some additional information on pinks and coho was obtained. Further details on th© behaviour of fry wer© obtained by conducting experiments in which th© fish were observed under both natural and controlled light conditions. The movement of fry in relation to changes in light intensity were recorded "by observing fry placed in a long trough. This trough was "set up" to simulate the essential features of gravel cover and water flow encountered by the fry in the stream. The trough was 16 ft, long, 14 in. wide and 8 in. deep. The ends were covered with wire screening thus allowing a flow of water through the trough when it was partially submerged in the creek. The current through the trough was measured by timing the displacement of small wooden floats. It was found to be approximately 0.3 f t . per second. The bottom of the upper two feet  - u-  P i g . 1. Pry traps used at Williams Creek. Photo also shows operator measuring flow i n the main channel with a current meter.  ef the trough was covered with coarse gravel. A snug removable tray was placed at the downstream end to collect fry present in that portion of the trough. Pry were placed in the gravel portion of the trough in mid afternoon. Counts of the fry which had moved from the upstream end of the trough to the downstream end were made at 10 minute Intervals. At these same intervals, the light intensity was measured by using a model 210 photovolt lightmeter. In addition to the above, the rate of downstream movement of sockeye was compared to the movement of small floats (household toothpicks). Large numbers of fry and floats were released simultaneously in a small side channel of Williams Creek. Recoveries were made 355 feet downstream and the time of recovery was recorded. Results Seasonal movements of fry The fry emerge from the gravel and move downstream after a prolonged period of development in the gravel. The rate of development in salmonolds is dependent upon temperature (Wallrich, 1900} Battle, 1944.) and variation from year to year in the period spent In the gravel and thus in the time at which emergence occurs will therefor© most probably reflect variation in temperature from one year to th© other. Records obtained at Scully Creek have provided a means of assessing the length of time spent in the gravel and of describing the influence of both temperature and water level on the time of migration. Sockeye adults at Scully Creek were found to be consistently in the final stages of maturity at the time of passing through the weir. Females, which presumably had partially spawned in the stream below the weir, were often recorded. Frequent observations over th© complete length of the spawning grounds were mad© each year and i t was noted that spawning activity began  within on® or two days after entering the creek. These observations indicate that the time at which adults moved into the creek provided a good index of the time of egg deposition. The interval of time spent i n the gravel is therefore closely approximated by that between th® movement of adults onto the spawning ground and the emmigration of their progeny, as fry, from the creek.  In Figure 2 the movement of sookey®  adults  and fry recorded at the  weir are described. The total number of adults each year ranged from 400 to  1,200 while the number of fry denote  ranged  from 35,000 to 250,000. The arrows  the dates on which 5, 50 and 95 percent of the run® were recorded.  The interval between the runs using th® % point of each, varied from 248 days in 1952-53 to 270 days in 1950-51 and 1951-52. The temperatures prevailing during thee® periods i n the gravel were apparently the chief ef  this variation.  Continuous  records  able. However, air temperatures  of stream  recorded  temperatures  at Terrace,  cans®  were not avail-  B.C., 15 miles distant,  provided a reasonable basis for comparing from year to year the temperature  •budgot" during incubation. Meteorological Division ©f  These air temperatures were recorded by  the  the Department ef Transport (Canada). The rslativ©  variation ef weekly mean air temperature® from a five year average (1949 to 1954) The  i s shown  in Figure 3. Variation above tho averag®  i s shown  month® of December through to February were not included  tures  in black.  as mean tempera-  were considerably below freezing in these months and would hav® littl®  or no effect on water temperatures. The weekly mean dominantly above average in  1949-50, 1952-53  temperatures  and 1953-54 when th© shortest  periods in the gravel (248, 249 and 260 days) wer® recorded. temperatures prevailed  days occurred.  wer® pre-  Below averag©  in the remaining two years when an interval of 270  ~7~  r i  g. 2. Seasonal movement of sockeye adults and fry at Scully  Creek*  Arrows represent the time at which  95% of the runs were completed.  5, 50 and  - 3-  AUG,  NOV.  MARCH  JUNE  I  Fig. 3. Relative variation of weekly mean air temperature at Terrace, B.C. froa a five year average (1949 to 1954). Above average values are shown in black. Arrows represent the 5, 50 and 9555 points of the adult and fry runs..  . 9 -  Only p a r t i a l counts of pink and  was  However, s u f f i c i e n t i n f o r m a t i o n  coho vera obtained i n most y e a r s .  gathered  to  show  that both  adult  the  and  f r y runs were l a t e r than those o f the sockeye. A oomplete account o f the  and fry were  movements o f p i n k a d u l t s spawners were  recorded  t o pass through  obtained i n 1950-51.  the  from  weir  Seventy-two  September 9 t o September  2 3 , 1950 and n e a r l y 2,400 fry were recorded from May 11 t o June 8, 1951.  An  This is a  i n t e r v a l o f 252 days occurred between the 5% p o i n t s o f the r u n s .  c o n s i d e r a b l y s h o r t e r p e r i o d than the 270 days taken by the sockeye i n t h a t  S i n c e development o f the young salmon is a f u n c t i o n of both temperature and t i m e , the age o f the embryo i s o f t e n designated i n terms o f thermal u n i t s .  W a l l i c h (1901) d e f i n e d one thermal u n i t as 1 ° f a h r e n h e i t  above 32® f o r one day.  The  emergence o f both sockeye  number o f air  and  p i n k f r y and the number  development are g i v e n i n Table I. ranged from 2,296 t o 2,507 and years  studied. In  thermal u n i t s  a  of days spent in  the number of days from 248 t o 270 i n t h e f i v e  1950-51 the p i n k s  considerably  up t o the  The number o f u n i t s r e q u i r e d by sockeye  required only 1,862  2,403 f o r sockeye and the p e r i o d spent i n the This indicates  recorded  greater rat© of  gravel  units  compared  to  was 18 days s h o r t e r .  development  for p i n k s than f o r  sockeye under i d e n t i c a l stream c o n d i t i o n s .  Emergence from t h e g r a v e l  Sockeye fry The emergence  and  c h a r a c t e r i s t i c p a t t e r n each i n d i v i d u a l s per Th© m i g r a t i o n  day  took  r u n progressed  downstream movement  year  (Fig. 2).  t o a peak o f thousands  place  ther©  over  occurred  a  period of  of  sockeye f r y  followed a  Th© r u n b u i l t up from  and  then p r o g r e s s i v e l y  a  few  declined.  approximately s i x weeks.  As  the  a change in th© appearance of th© fry. Th© fry  I 1 U The number ef a i r thermal units aad time i n days required from egg deposition to the emergence of f r y  Tear  A i r Thermal Units Sockeye Pink  Kumber of Days Sockeye  1949-50  2379  -  260  1950-51  2403  1862  270  1951-52  2302  1952-53  2507  1953-54  2296  -  270 248 249  Pink  252  - 10 » migrating at the  first  of  the migratory period generally showed prominent  yolk sacs while i a those that followed the yolk sac diminished i n size and eventually  disappeared.  The  seasonal pattern  of  emergence, as reflected by the  downstream  movement of fry, did not appear to be influenced, at least primarily, by water temperature  level. Throughout th®  or  period of emergence there occurred  considerable variation ia temperature but i n general an upward trend was noted. Soekeye migrant® were recorded  in  some years  week® of March at temperatures as low as 1.5^0.  as  as  and  temperatures up t® 8.0*6. The emergence cf fry from the such a wide temperature range and over such an  ©arly  as  late as  the  two  last  June at  gravel throughout  extended period  of  time seems  to show clearly that this aetivity does not depend on the existence of a "critical" temperature or variation in temperature. The corresponding  number days  of  soekeye  during  the  fry captured  1954  and  and  the  water level recorded  1955 migration at Williams Creek is  shown in Figure 4.  Generally a rapid and more or less continuous rise i n  creek level, from  winter  fry  run.  Such wa®  a  low,  the case  number of migrants occurred i t wa®  with  the greater part  when Increases i n both  after May  level  part of  the water level remained the  relatively  constant  the  and the  i n water level as  well as  seasonal pattern  throughout the greatest  run. Mergence therefore must be considered  independent of variation  of  3. In the following year, however,  noted that the migration followed its characteristic  although  this  was associated  la 1954  on  to be  temperature.  primarily Most probably  activity occurs only after a certain stage of development is reached by  the young salmon. Th© early and represent the  extremes  late  of this stag©.  running fry described earlier probably  - 11 -  M A Y  J U N E  g» u* Daily number ©f soekeye fry captured and ereek levels Williams Greek, 1954 and 1955.  - 12 -  Pink and coho fry A partial account of th© coho fry run was obtained each year. The run usually began in April and continued with a gradual increase in the number migrating each day until operation of the weir and traps was discontinued for the season (usually during the first week in June). The movement of pink fry was recorded within thie same period. A complete account of the migration of thes© fry was obtained at Scully Creek in 1951 and at  William© Creek in 1954. In 1951 the run began oa Hay 11. By the 26 ©f May 50% of the run was completed, fhe last fry was recorded on June 8. The dates recorded in 1954 et Williams Creek for comparable stages of the migration were May 1, May 24 and June 7. The evidence indicates that the pink and coho follow the same general pattern as was shown for th© sockeye. The number of migrants per day generally increased until a peak was reached and then steadily declined until the run was terminated. It is most probable that the emergence of pink and coho occurs in essentially the same manner as for th© sockeye. Downstream movements and response to light Sockeye fry Throughout th© total period of weir and trap operation sockeye fry were observed to follow a consistent pattern in their movement in respect to day and night. This pattern is shown in Figure 5 where the total night's run captured at Williams Creek in consecutive hours is given for different periods throughout the 1954 and 1955 season. A diurnal periodicity may be said to be th© main character of the run.  On any on© night the first fry were captured  shortly after darkness set in. Th© number migrating per time interval increased steadily until a "peak was reached which generally occurred 3 to 5 9  13 hours after dark. Following th© peak, the rat© of movement progressively decreased and ceased completely with the coming of daylight. On only one occasion were the fry observed to deviate from this pattern. In early April, 1951, immediately prior to th© usual seasonal migratory period, a number ©f young soekeye were carried into the weir in the daytime during a severe freshet* These fish had very prominent yolk sacs and were far less advanced in development thaa "normal8 migrants.  There  was  little doubt that the appearance ef these individuals during the day was a direct result ef the abnormally high water velocity which eccurred  at that  time. The alevins were "displaced" frea the gravel by the current and because ©f their immaturity and limited swimming ability wer® carried downstream. The broken lines shown in Figure 5 designate the shift in the time ©f sunset and sunrise with the advance ef the season (source Brown's lautical Almanac, 1955). The arrows denote the mid point of th© runs. Th© advance ia the length of the day restricted the movement ©f fry to progressively shorter periods of time. At the first of the season, the migration continued for 10 hours of each 24. This interval wa® decreased to about 8 hours by the end of April and to approximately 7 hours in the latter part ©f the season. Accompanying the shift in the advent of darkness there occurred a shift in the time of the peak. This was clearly evident in 1954 but not the following year (Fig. 5). The arrow® in the figur® designate the peak, i.e. the time at which 50% of th© night'® run wa® captured. Th© 5056 point occurred between 11 to 12 P.M. during mid April and from 12 to 1 A.M. during th© latter part of th© run In early June. All times reported are Pacific Standard Time.  14 -  Fig. 5. Proportion of sockeye fry captured in consecutive hours of the night for progressive periods throughout the season. Arrows represent the mean time at which 50% of the run was completed.  The rate at which fry were captured after the night1a peak changed progressively with the season. During aid April there was a gradual decrease ia the proportion of fry captured in the hours before daylight. As the season progressed this became more abrupt until at the end of the season a very abrupt cessation of movement occurred. This trend indicated that th© period of darkness early in the season was sufficient to allow a complete or nearly complete evacuation of the creek in one night. Later, however, the period of darkness decreased and the run was terminated, abruptly, by th© coming of daylight. The changing pattern in the movements ef the sockeye fry with the advance of the season was not as evident in 1955. The effects of the advancing length of day were partially masked by more variable conditions of cloud cover and natural illumination in 1955 than in 1954.  In  th© latter  year, the sky was generally overcast throughout April and May while in 1955 ther© occurred alternate periods of dear and cloudy weather. It became apparent early in th© season that on cloudy days followed by cloudy nights th© fry migrated at an earlier hour than on clear days and nights. The data presented above shows the degree to which th© movements of the fry throughout tho season and from day to day are influenced by light. In order to obtain a more detailed account of their response to light and their resulting behaviour the fry were observed under varying intensities of both natural and artificial light. The observations were mad© in the trough described on page 3. Two hundred sockey© fry, which had been captured the night previous and which had been  kept under subdued light, were placed in the gravel portion of the  trough in mid afternoon. These fry with only a few exceptions remained in this portion of the trough either under cover of the gravel or maintaining  16  their position directly over the gravel. Counts of th© number of fry which had moved from the upstream end of the trough to the downstream end were mad© at ten minute At these  intervale beginning approximately oh© hour before dark.  same intervals, th© light intensity was measured with a model 210  photovolt lightmeter. Precautions were taken during these procedures to avoid alarming the fish either by the movements of th© observer or by th© ua© of artificial light. fhe  observations were carried out for s i x nights. On each night  a "fresh" group ef fry were used, fhe number of fry which moved downstream during each ten minute interval is shown in figure 6. fhe arrows denote the time that light intensity registered 0 f t . candles on the photometer. Downstream movement  was  Initiated in the same general way in all  tests.  It began between 9i20 and 9*30 P.M. and only after the light intensity had reached the "0" f t . candle level. The few individuals recorded in the downstream end of the trough before that time were those which had moved into that area shortly after being introduced into the trough. The number of individuals which initiated movement during each progressive time interval increased until a peak was reached  60  to 90 minutes later  (10i20 to 11$00 9  P.M.). The rate of initial movement then declined steadily and movement ceased entirely between 150 and 190 minutes (Hi50 PJ*. to 12:40 A.M.) after th© light intensity reached "0 M . Hot all the fry moved downstream in each test. Observations were made by using very brief flashes of light from a hand torch. They revealed that the fry which had not moved downstream were oriented positively to the current and maintained their position in the upstream end of the trough. Periodic observations showed that their behaviour remained the same throughout  - 17 -  Fig. 6. The number of soekeye fry initiating movement in consecutive time intervals for six nights. Arrows represent the time at which the light intensity reached "0" f t . candles.  - l i -  the rest of the night. The proportion net Initiating movement varied from 6 to 4.0^. There appeared to be a tendency for the largest proportion to remain In the upper portion of the trough on cloudy nights than on clear nights. On two cloudy evenings 38 and lp% did not migrate. This may be compared to 2256 on a partly cloudy night and 6 and ll& on two dear nights. The manner in which the fry moved down the length of the trough could not be observed in all its details as the use of light was restricted to the brief flashes mentioned earlier. It was noted that at the time the light intensity reached "0" the fry were confined te the head end of the trough and appeared to be distributed almost randomly over this area. A l l were oriented positively t® the current but there occurred no net movement upstream. As time progressed the fry tended to spread downstream and to lie over the whole of the upper half ef the trough rather than in the extreme upstream portion as formerly. Their behaviour was the same, however, they responded positively to the current and maintained their position. After 12t30 A.M. when movement to the downstream end of the trough ceased, the remaining fry were all in the upstream end of the trough. Three tests were made following those described above in which the trough was kept under illumination for varying lengths of time after darkness normally occurred. At approximately 8s30 P.M. or one hour before dark, two gasoline lanterns were placed above and alongside the trough. The illumination from these varied somewhat due to variation in air pressure within th® lantern but averaged about 3 f t . candles at the surfac® of the water in the trough. On the first test the trough was illuminated until 11*30 P.M. or two hours after darkness normally occurred. On the second night the lamps were removed after three hours and th® last night th® trough wa® illuminated throughout  - 19 the whole night. A record was kept of the number of fry which had initiated movement from the time the lamps were first placed into position until th© following morning. The proportion of the fry which initiated movement in cone©cutiv© units of time on the first two nights is shown i n Figure 7. The movement pattern during a night when the fry were subjected only to natural illumination is shown for comparison. Th© presence of artificial light can be seen to have almost completely prevented the movement of the fry at their normal time. Upon removal of the lamps, movement was initiated in a similar manner to that which occurred tinder normal light conditions. On th© third night, when th© trough was kept under continued illumination, only two of the 200 fry in the trough were found in the downstream end. Movement was initiated In a somewhat more abrupt manner on the nights when darkness was delayed compared te nights of natural light conditions (Fig. 7). Th© period in which the movement occurred was also considerably less  (90-100 min.  compared to 150-190 min.). Again not all of the fry  initiated movement. Th© proportions remaining in the upper end of the trough on thes© nights were 22 and 32 percent. This is comparable to the percentages recorded on cloudy "control" nights. The strong negative response to light on the part of the sockeye was evident during the course of their movement. The migrants, regardless of their orientation in respect to current responded in a well defined manner when subjected to direot light from a lantern or hand torch. Fry oriented negatively to the current were seen to reverse their direction, sound i.e. swim for the bottom, and either seek cover in the gravel or attempt t© remain in a fixed position over th® gravel. In instances where the fry entered the beam of light oriented positively to the current their direction remained unchanged but sounding and a cover reaction occurred as before.  20 -  Fig. 7. Movement pattern of soekeye fry under natural illumination (curve Ro. 1) and when darkness delayed until 11*30 P.M. and 12:30 A.M. (curves No. 2 and 3 respectively). The top most curve designates the general level of natural light intensity during the three tests.  21 Weave (1955) describes a similar response by pink fry. He points out the similarity between the behaviour of fry at the coming of day resulting in complete cessation of movement and their behaviour when subjected to artificial light. The evidence Indicates that the responses of the pink and soekeye in this regard are essentially the same. Pink and coho Data describing the movements of these fry are much less detailed than those for soekeye. However, there is sufficient information available to demonstrate the general movement pattern of these fry and its relation to light. As was the case for soekeye, the movements of pink and coho were also almost solely restricted to the hours of darkness. In Figure 8 the proportion of these fry captured in consecutive hours of the night are shown for a seven day period in 1954. The movements of coho followed almost exactly those of the soekeye. Th© night's run began at dark, built up to a peak and then progressively declined up to dawn. The  pink  fry wer© captured  in  relatively  large proportions during the earlier part of the evening. On numerous occasions some pinks were found to enter the traps before th© light intensity reached th© level required for the movement of the other two species* The time at which these fry wer© captured was a function of the time movement began, distance to travel aad the rate of movement. The variation recorded in the time of captur© of the soekeye and coho ©n one hand and the pinks on the other was, at least in part, due to variation in the distance between the spawning area and th© traps. Typically th© pink salmon spawn in the lower areas of this stream while the soekeye and coho tend to be concentrated in the middle and upper areas.  - 22  8.  Mean proportion of soekeye, pink and coho fry captured during consecutive hours of the night for a seven day period during the 1954 migration.  ~ S3 I n two o f t h e t e s t s made i n the trough t o determine  the  manner  i n -which doTmstreem movement began a number o f coho  were i n t r o d u c e d i n t o t h e f r y were not mailable make a s i m i l a r  trough  w i t h the oocheye.  alonp  pinfc  i n s u f f i c i e n t numbers a t t h i s time t o  test*  Under n a t u r a l l i g h t c o n d i t i o n s the coho i n i t i a t e d movement I n a manner s i m i l a r t o t h a t shown f o r ©ocjscye  (Fie..  6).  She coho w r e k e p t under a r t i f i c i a l l i g h t i n g throughout the . n i g h t o f the second t e s t * completely  AB v l t h  the s o c k e y e , the l i f h t  prevented movement, d o w n the  trou|$u  Only 6fj  almost  of the •  coho f r y were found i n the d o t m e i r e a © end o f tlie trough compared to  6 2 ^ i n the t e s t under n o r m a l c o n d i t i o n s ,  DrnnxstxetM  movement  end r e s p o n s e  to current  ' s h o r t l y sifter oT-erettioo commenced a t W l l l i e m o Creek, i t bee m e a p p a r e n t t h a t t h e number o f ooclceye f r y moving through each o f the t h r e e o u t l e t c h a n n e l s _ \?aa prop ort l o a d t o the d i s charge through each* c h a n n e l . s h i p water T e l o c i t y m&  I n o r d e r t o measure t h i s r e l a t i o n -  d i s c h a r g e was d e t e r m i n e d almost d a i l y  throughout the t & o l e • o f the m i g r r t o i y p e r i o d of 1954. measurement®  Thane  were umde "by u s i n g ' a h r y c e c u r r e n t meter r-nd hy  f o l l o w i n g ' a standard  metering proeeedure.  The p r o p o r t i o n o f  fry  end d i s c h a r g e c a r r i e d "by the? east channel i s shown I n f i g u r e  9.  The east c l e n n e l d u r i n p A p r i l c a r r i e d a. c o n s i d e r a b l e p r o -  p o r t i o n o f b o t h water s a d f r y .  A sudden r i s e i n ereeh l e v e l .  end t o t e l d i s c h a r g e which occurred ebout Hay 5 g r e a t l y changed this, p i c t u r e ,  f h e r e o c c u r r e d a sudden decrease i n th© pro- .  p o r t i o n © ! d i s c h a r g e through t h e c h a n n e l ? h l c h -was accompanied by fry.  a s i m i l a r hut l e e s d r a s t i c decrease i n the p r o p o r t i o n o f 'He r e m a i n i n g two c h a n n e l s ,  on the  other  fig. 9. The proportion of sockeye fry and creek discharge measured daily in th© east channel of Williams Greek, 1954«  - 25 -  hand, showed corresponding Increases. This relationship was found to be statistically significant. In Table 2, the number and mean proportion ef fry captured in each channel, the mean proportional discharge and the calculated n r n values are given. Within the mitt channel the fry followed a fairly consistent pattern of distribution throughout the ran (Fig. 10). The distribution in the case ef the sockeye aad pink was related to water velocity. Consistently less of these species was captured in the traps located near the banks where the current was slow, than in those located midstream and in relatively fast currents. The coefficients of correlation ealculated froa the proportion of fry captured in each trap and the relative water velocities at each trap site equalled 0.94 and 0.96 for sockeye and pink respectively. Both values are significant at the .01 level of confidence. The distribution of coho fry, on the other hand, did not appear to be related to water velocities ( « 0.65, Pa .05). The proportion captured by each trap was similar as i f these fry were moving unrelated to currents. Orientation of sockeye fry Th© behaviour of the sockeye which led to th© distribution reported above was frequently observed. In all instances, the us© of artificial light was required. It has already been shown that sockeye react in a characteristic manner to direct light during their downstream movement. However, the observations reported here were mad® under conditions in which a change in behaviour du© t© th© light was improbable. Th© fry wer© observed as they abruptly entered into a dimly l i t area. Their degree of activity and orientation in respect to the current was noted immediately.  The relation between the mean proportion of creek discharge and soekeye fry migrants in the three outlet channels of Williams Creek, 1954.  Channel  Mean proportion of discharge carried  Mean proportion migrants carried  Main  67.1  78.6  East  20.5  West  18.7  19.4 5.6  "J* • 0.58 .01 • 0.85 .01 • 0.55 .02  - 26 -  SOCKEYE PINK COHO  20  RIGHT BANK  LEFT BANK  10.  Mean proportion of fry captured la traps located at different points across the main channel of Williams Creek during th© 1954 migrations.  - 27 -  Tha fry were found to be variously oriented to the current and in all stages of activity. Some wer® seen actively swimming against the current but with a net movement downstream while others, similarly oriented, appeared to be carried passively. Sot infrequently fry were found either swimming or drifting at various angles to the ourrent, la relatively slow moving water their behaviour appeared quite different. The fry exhibited a predominant negative rhootaxi®. The fry were seen to swim in the general direction ef the current throughout the whole of the illuminated area. Their swimming movement® were irregular and what might be described as a "thrust and drift" method was followed. They were observed to accelerate often by a single thrust of the body and then drift passively for a distance of several feet before reaceelerating. It seemed apparent that this movement was a directed one and not merely random movements while being displaced by th© current. Rate of downstream movement Soekeye fry The net rate at which th® soekeye move downstream was estimated by timing the movement of fry released in a side channel of the ereek. In order to compare this rat® to water flow a number of floats (toothpicks) were released simultaneously. In addition the mean rate of flow at midstream was determined from a number of measurements made with a current meter. Two tests were mad® on consecutive nights in which approximately 500 fry and 250 float® were released. In both instances the fry used had been captured in the main channel trap® two to three hours previous. Recoveries wer© made in a trap located 355 f t . downstream from th® point ©f release. As this trap spanned only a small proportion of the channel only a small number of the fry and floats were recovered.  28 On both nights the first fry were recovered  between 5 and 7 minutes  after release. The first float was recovered in the same interval on the first night and after 7 minutes on the second. No further recoveries of fry were made after 13 minutes in both tests and only a few floats were recorded after this time although many were seen "hung up* ia eddies and along  the  banks of the channel. The floats recovered within the first 13 minute period were those which had not been delayed to any extent during the journey. The  both  mean proportion of fry and floats which entered  nights in  th© trap  on  consecutive two minute intervals is shown in Figure 11,  Although the number recovered was small, particularly on the second night, the results clearly shew the similarity between the net rate of  movement for  fry and the unimpeded floats. Their rate ranged from 0.4 '/• to 1,0 >/s and averaged approximately 0.8 '/s. The current in midstream was found to range from 0.8 greater  to 1.6 •/» and  rate than  averaged  1.3  '/s. This is  that found for the fry and floats and  a considerably  indicates  that  both  were subjected to meandering of the current thus greatly Increasing the distance covered. The  results  suggest that the movement of th© fry was  primarily a displacement by th© current. However, the fact  that  all the fry  moved through the channel after a short time while the majority of the floats were "hung up"  along the way reveals that th© fry were capable of regaining  entry into the main current after being carried or led into eddies or pools. Pink and coho fry A comparison of the time of arrival at the trapping site of these species with that of the  soekeye  (Fig. 8) affords a relative measure of  their rate of downstream movement. Th© odho and soekeye which wer© spawned in approximately the same area apparently travelled downstream at the same  - 29 -  FRY* FLOATS 6Cf  TIME AFTER RELEASE (MIN.)  Fig. 11. Percentage ef soekeye fry and floats captured during consecutive time intervals after release.  - 30 -  rate as the runs reached the traps in nearly equal proportions at the same time. The pink fry, on the other hand, reached the traps at a much earlier time. As was pointed out earlier, this may be attributed at least partly to the relatively short distance between the traps and their spawning area. The observations by Heave (1955), however, suggest that the pink® ar® relatively more active. The time at which the pink fry were recorded by Neave at the mouth of th® streams in relation to the length of the spawning areas indicates that these fry swim downstream at a considerably .greater rate than the soekeye. Discussion and summary Th® activities of sockey®, coho and pink fry are largely determined by their response to temperature, light and current. These factor® rather precisely regulate both seasonal and diurnal movements. Seasonal movement® Temperature was shown to determine th® length of the period which soekeye spent in the gravel and hence the time of ©mergence and downstream migration. This activity occurred earlier in year® in which air temperatures were above average and later in relatively cold years. A range of 22 day® in their timing occurred during the fiv® year® studied. Comparable data was not available for coho aad piak® but it is not unreasonable to assume that their activities ar® similarly affected by the temperature "budget". The actual act of emergence from the gravel was apparently not "triggered" by water temperature er any variation in temperature and only secondarily influenced by water level. It was concluded that emergence normally occurred only after a certain stage of development was reached. The alevin® probably react to internal stimuli or to external stimuli (e.g. water flow through the gravel) which are more or less continuously present.  31 -  Diurnal movements Soekeye Soekeye fry responded  to & considerable degree to changes in light  intensity. Variation from day to day in the amount of natural illumination was reflected in the timing of the nightly runs. The seasonal shift in the time of dark and dawn was found to restrict their movements to a decreasing interval ef darkness. Emergence or entry into the current occurred only after the light intensity reached a low level and continued in a characteristic manner up to three hours  after dark. The evidence indicates that this movement into the  current is dependent upon a change in intensity from a "day" to "night" level rather than the absence of light. When darkness was delayed by artificial means,  movement was initiated at a time when under normal light conditions,  the fry no longer ©merged into the current and were capable of maintaining position In the stream. This suggests that, at least Initially, the movement results from a displacement by the current, i.e. the fry fail to orient themselves after darkness and are carried downstream. Th© lose of orientation is probably du© te a failure of the eye to dark adapt at a rate equal to the decrease in light intensity. Pink  and coho Their negative response to light also lead to migration only during  the night. Coho fry, under experimental conditions, were seen to begin migration within th© first tare© hours after dark. Observations by leave (1955) indioat© that the activity of pink fry is the same in this respect. He states "th© data suggests....that emergence into the stream tends to take plaee during the first half of the night." The evidence indicates that a  emmon p e r i o d of n i | 3 i t "blindness exist© In a l l three s p e c i e s . Apparently the I n i t i a l movement of p i n k and coho eo v e i l aa t h a t of the soekeye i n due t o a displacement mechanism. Eerpoonc to c u r r e n t Soekeye f r y Once entered i n t o the c u r r e n t the M i g r a t i o n continued u n t i l t i e s i r e n s , tree e v a l u a t e d or u n t i l the approach of day* D u r i n g thi© continued movement the f r y were observed, t o .exhibit "both negative oriel p o s i t i v e r h o o t e x l B ,  21?ey r cop ended p r e -  d e r d n a n t l y p o s i t i v e t o c u r r e n t -while present i n s w i f t l y moving water raid p-redominrntly n e g a t i v e i n r e l a t i v e l y o l o v c u r r e n t s , !Jhe mi p r a t i o n , t h e r e f o r e , mey  he regarded ee a r e s u l t of both  a d i o p l c c e n e n t a d ra e c t l v e downstream movement on the v e r t o f the f r y , Socl-eye. d u r i n g t h e i r m i g r a t i o n were d i s t r i b u t e d i n t h e etroeaa r e l a t i v e t o c u r r e n t s .  She number of f r y i n car/ p a r t  of a c r o s s s e c t i o n of the creek was d i r e c t l y proportioned, to the speed of the c u r r e n t to t h a t s e c t i o n . SS\eir net r a t e of movement» however* was  found t o be c o n s i d e r a b l y l e e s than  would he expected under the above c o n d i t i o n s . The  evidence  i n d i c a t e s t h a t the fry d u r i n g t h e i r journey ere c a r r i e d "by or tend t o f o l l o w c u r r e n t s which s&eandcr from one s i d e of the creek to the other aasd enter i n t o innumerable eddies a i d pool©.  The  t o t a l dluttmee covered d u r i n g the m i g r a t i o n v o u l d he g r e a t l y lengthened by t h i s a c t i o n .  S n t r y i n t o eddies end poolo w t x l d  not r e s u l t i n exceonive d e l a y , however, as the n e g a t i v e r h e o t o x i s e x h i b i t e d by the soekeye under tkeoe c o n d i t i o n s serves t o "bring the f r y once again i n t o the c u r r e n t . 3?in!: end coho f r y D i r e c t observations responses fry*  of  however,  pink were  and  were  coho  found  to  fry he  not to  made  on  the  current.  distributed  rink in  th®  33  stream relative to currents as were the soekeye. This suggests that th® mechanism underlying the migration of the pinks is similar. leave's (1955) observations, however, indicate that a displacement is not involved, at least after emergence into the current has occurred. Pink fry wer© observed responding negatively to the current and swimming at a greater rate of speed. This activity i® similar to that ef th© soekeye in relatively slow current®.  It Is possible that pink fry, in currents faster than those in which the observations were made, exhibit a positive rheotaxis. Should their response be solely negative i t would b© expected that evacuation of th© streams reported by leave would be complete in a much shorter period ©f the night than he recorded.  Coho fry apparently respond to current differently than do the others. They were found to migrate downstream unrelated to currents. Further observations are required on coho in order to describe their behaviour at this time.  34  LITERATURE CITED Battle, H.I. 1944* The embryology of the Atlantic salmon (Salroo salar Linnaeus). Can. Jour. Res., D. 22* 105-125. Hoar, M.S.  1951. The behaviour of chum, pink and coho salmon in relation to their seaward migration. J . Fish. Res. Bd. Canada, 8* 241-263.  Hoar, W.S.  1953. Control and timing of fish migration. Biol. Rev., 28t 437-452.  MacKinnon, D., and ¥,3. Hoar. 1953. The responses of coho and chum salmon fry to current.  leave, F.  J . Fish. Res. Bd. Canada, 10* 523-538.  1955. Notes on the seaward migration of pink and chum salmon fry.  J.  Fish. Res. Bd. Canada, 12*  369-374.  Pritchard, A.L. 1944. Physical characteristics and behaviour of pink salmon fry at McClinton Creek, B.C. J . Fish. Res. Bd. Canada, 6* 217-227. Wallich, C. 1900. Rept. U.S. Comm. Fisheries, 26* 185-194.  


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