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The effect of trout predation on the abundance and production of stream insects Griffiths, Ronald W. 1981

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THE EFFECT OF TROUT PREDATION ON THE ABUNDANCE  AND PRODUCTION OF STREAM  INSECTS  by RONALD W. B. S c . , U n i v e r s i t y  GRIFFITHS  Of W e s t e r n O n t a r i o ,  London, O n t a r i o ,  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in  THE FACULTY OF GRADUATE STUDIES (Department o f Z o o l o g y ) We a c c e p t  this thesis required  as c o n f o r m i n g t o the standard  THE UNIVERSITY OF BRITISH COLUMBIA 30 J u l y 1981 R o n a l d W. G r i f f i t h s ,  1981  1978  In p r e s e n t i n g  this  thesis i n partial  f u l f i l m e n t of the  r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e of B r i t i s h Columbia, I agree that it  freely  the L i b r a r y  a v a i l a b l e f o r r e f e r e n c e and s t u d y .  agree that p e r m i s s i o n f o r extensive for  University  s c h o l a r l y p u r p o s e s may  for  financial  shall  of  The U n i v e r s i t y o f B r i t i s h 2075 W e s b r o o k P l a c e V a n c o u v e r , Canada V6T 1W5 Date  r>T?_<;  • to  /new  thesis  Columbia  my  It is thesis  n o t be a l l o w e d w i t h o u t my  permission.  Department  further  be g r a n t e d by t h e h e a d o f  copying or p u b l i c a t i o n of t h i s  gain  I  make  copying of t h i s  d e p a r t m e n t o r by h i s o r h e r r e p r e s e n t a t i v e s . understood that  shall  written  ii  ABSTRACT Trout  were  constructed  introduced  the the  and trout 9  crop  habits  populations  and  of  the  release  section.  stream  insect  and  of the i n s e c t The r o l e  communities  Production  estimates  of l o t i c  standing  crop  section. o r 9-10%  However,  trout  available  food  were supply.  Trout of  thought  of  these  insect  Competitive  i n the  in density  experimental  in  structuring  i n the  experimental  discussed. species  different  production to  stream  D a t a on t h e  section.  consumed o n l y  the  of  t r o u t p r e d a t i o n had  predation  s e c t i o n were n o t s i g n i f i c a n t l y  control  section.  populations  is briefly  3  experimental  f o r the increase  of t r o u t  of  experimental  crop  stream  as t h e r e a s o n  standing  t h e d e n s i t y and s t a n d i n g  i n the  standing  to  Following  crop  i n the  indicated that  the experimental  crop  stream  the  trout  density in  while  increased  stream  populations.  the c o n t r o l stream  the  was s u g g e s t e d  standing  stream  fishless  examined d e c r e a s e d  species  enclosure  on t h e d e n s i t y ,  insect  section (enclosure)  compared w i t h  reduced  of l o t i c  species  of 2 i n s e c t  food  small  i n t r o d u c t i o n , t h e d e n s i t y and s t a n d i n g  study  section  flow-through  of t r o u t p r e d a t i o n  production  insect  stream  a  i n the headwaters of a  examine t h e e f f e c t s crop  into  be  from  those  in  0.4 t i m e s  t h e mean  of  species.  prey  intensively  g r a z i n g the  iii  TABLE OF CONTENTS  ABSTRACT  i i  L I S T OF TABLES  v  L I S T OF. FIGURES  v i i  ACKNOWLEDGEMENTS  ix  Introduction Description Materials  1 o f Study  Area  3  a n d Methods  Experimental Sampling  7  Design  7  Methods  8  Benthos  8  Drift  9  Stomach C o n t e n t s Trout  10  Abundance  • •••  Methods o f A n a l y s i s  0  11  Benthos Life  1  11  Histories  of I n s e c t S p e c i e s  Insect  Density  Insect  Standing  Insect  Production  12 13  Crop  14 15  Drift  16  Trout  Abundance  17  Trout  Stomach C o n t e n t s  17  Food Sampling  C o n s u m p t i o n by T r o u t Variability  18 '.  20  iv  Life  Histories  of I n s e c t  Species  21  Stoneflies  21  Mayflies  31  .. ..  Caddisflies  41  Riffle  46  Beetles  Results Trout  52 Abundance  Food H a b i t s  52  of T r o u t  Food Consumption  56  by T r o u t  Insect  Density  Insect  Production  58  and S t a n d i n g  Crop  61 77  Drift  77  Discussion  84  Effect  of T r o u t  Predation  on  the  Abundance  of  Lotic  Populations Trout  84  Predation  and  Insect Production  P r e d a t i o n and Community Appendix  92 93  Density  Correction Factors  93  2  97  Relationship Aquatic Appendix  Structure  1  Insect Appendix  89  between  Head  Width  Insects  3  Insect Literature  and  Dry  Weight  of 97 98  Taxa L i s t Cited  f o r S p r i n g Creek  98 101  V  L I S T OF  Table  1. M o n t h l y minimum and  from June Table  t o December,  2.  Head-capsule  Glossosoma Table  3.  Head-capsule  4.  maximum  water  temperatures  1979  6  widths  of  larval  instars  of  peniturn from S p r i n g C r e e k  Heterlimnius Table  TABLES  widths  koebelei  D e n s i t y and  of  41  larval  instars  of  from S p r i n g C r e e k  51  s t a n d i n g c r o p of c u t t h r o a t t r o u t  in  S p r i n g C r e e k a t Road F-30 Table  5. Mean w e i g h t  stream Table  of  the  55 trout  in  the  experimental  section  6.  56  Occurrence  of  benthic  insects  in  the  trout  stomach c o n t e n t s Table  7. The  insects Table P. Table N.  8.  range  57 of  head-capsule  i n t h e b e n t h o s and  trout  Mean  dry  debilis  number  and C.  and  widths  weight  sp_.A p e r t r o u t  P. d e b i 1 i s  and  benthic  stomachs  59  of N.  cinctipes,  stomach  9. D i f f e r e n c e i n mean d e n s i t y and cinctipes,  of  C.  75  standing  sp_.A  crop  between  of  stream  sections Table  76  10. E s t i m a t e s  control  and  of p r o d u c t i o n o f l o t i c  experimental  stream  species in  sections  the  of S p r i n g  Creek Table G.  A1.1. peniturn  78 Number  of  collected  individuals in  each  of  H.  koebelei  collecting  net  and of a  double bag sampler Table  A1.2.  Density  93 correction  factors  for  Nemoura,  T r i z n a k a and P a r a l e p t o p h l e b i a Table A 2 . 1 . Values of r e g r e s s i o n c o n s t a n t s from  94 functional  r e g r e s s i o n s of dry weight on head-capsule width  97  L I S T OF FIGURES  Figure  1. Location  Figure  2. S i z e - f r e q u e n c y  and  Nemoura  of study  area  4  h i s t o g r a m s o f Nemoura  cinctipes  nymphs  from May,  1980 Figure  3. S i z e - f r e q u e n c y  Figure  from May,  4.  sg.A  Figure  1979 t o M a r c h ,  March,  sp_.B nymphs  from May, 7.  koebelei  nymphs from May,  h i s t o g r a m s of Cinygmula from May,  histograms  histogram  from S p r i n g  of f o r k  10.  Mean  densities  11.  Mean  Mean  peniturn 42  of  Heterlimnius 1980  lengths  47  of c u t t h r o a t  C r e e k a t Road F-30, A u g u s t  per t r o u t  1979  r a t e of prey  and the  standing  60 crops  T. d i v e r s a , P. sp.A and G. peniturn  P. d e b i l i s densities  53  stomach  and  densities  and  1980  9. R e l a t i o n s h i p between d r i f t  12.  1979  1980 ... 36  of Glossosoma  1979 t o M a r c h ,  from May,  sp_.A  1979 t o M a r c h ,  larva  N. c i n c t i p e s , Figure  debilis  histograms  N. c a l i f o r n i c a , Figure  26  Size-frequency  mean number o f p r e y Figure  1980  1979 t o M a r c h ,  8. F r e q u e n c y  trout  diversa  32  6. S i z e - f r e q u e n c y  Figure  Triznaka  1980  5. S i z e - f r e q u e n c y  larva  of  22  histograms of P a r a l e p t o p h l e b i a  and P a r a l e p t o p h l e b i a  Figure  Figure  histograms  Size-frequency  Cinygmula  Figure  1979 t o March  ,  nymphs  to  californica  and  standing  crops  of ... 62 of  and C. sp.A and  standing  68 crops  of  viii  H.  koebelei  Figure  13.  control  Total and  F i g u r e A1.1. 0.471  mm  and  C.  srj.B  number of  72 individuals  experimental stream  Proportion collecting  of  drifting  from  the  sections  individuals  80  retained  n e t of t h e d o u b l e bag  in  sampler  the 95  ix  ACKNOWLEDGEMENTS I wish t o thank my s u p e r v i s o r , Dr. committee  members  Walters and Mr. Linda Berg night  and  day.  Drs.  P.A.  G.G.E.  T.G.  Scudder,  Northcote and my  J.D.  McPhail, C.J.  Slaney f o r t h e i r h e l p and c r i t i c i s m .  provided  invaluable  field  assistance,  both  Personnel of the B i o s c i e n c e Data Centre were  extremely h e l p f u l and p a t i e n t , e s p e c i a l l y Dave Z i t t e n . Special  thanks  go  to  Tom  Johnston,  whose  ideas  and  comments c o n t r i b u t e d t o t h i s study. I  am  g r a t e f u l t o Dr.- G.B.  Wiggins  of the Royal O n t a r i o  Museum f o r c o n f i r m i n g the i d e n t i f i c a t i o n s of c a d d i s f l y Finally,  I  wish  to  thank  my  wife,  Beverly,  larva. f o r her  p a t i e n c e , understanding and v a l u a b l e a s s i s t a n c e throughout study.  this  1  INTRODUCTION Little abundance  i s known and  the  distribution  1977). Studies predation  about  in l e n t i c  and  of  and  competition  H a l l et a l . concerned  1970).  with  distribution  to  Minshall  1977;  s t r u c t u r e are  (Fox  systems  important  species  and  of  species  1974;  abiotic  Narver  in  1972;  the  1970;  factors  on  the  Rabeni  and  11). Thus the r e l a t i v e r o l e s  influencing  Elliott be  abundance of benthic  stream  stream then in adjacent  1967).  an  community  brown  Allan  1981; (1975)  mechanism  invertebrate  populations  insect  downstream areas  densities  i n h a b i t e d by c u t t h r o a t  S i m i l a r i l y , Straskraba  found that the amphipod, Rivulogammarus fossarum, was  (Allan  in the t r o u t - f r e e headwaters of a  (Salmo c l a r k i Richardson).  headwaters,  important  important  noted that benthic  to s i x times greater  i n h a b i t e d by  the 1980;  Connell  (Corkum et a l . 1977;  chapter  competition  in jLotic environments. He  the  found  Peacock  feeding s t u d i e s have shown t r o u t to be  1974;  determining  have  i n f l u e n c e s of  (Neill  Paine  suggested that t r o u t p r e d a t i o n may  trout  insect populations  of i n v e r t e b r a t e s in c o o l water streams  Griffith  were two  the  s t u d i e s though have been g e n e r a l l y  effect  lotic  determine  unclear.  Numerous predators  Stream  Hynes 1970,  of p r e d a t i o n and  be  Menge 1976;  the  of  lotic  that  intertidal  p o p u l a t i o n dynamics of aquatic Northcote et a l . 1978;  factors  (1965)  abundant  in  scarce in downstream reaches of a stream trout,  Salmo  trutta  Linnaeus.  However,  Waters  (1972) noted that i f t r o u t were to feed s o l e l y on  drift  or the  "excess  their  production  of . stream  invertebrates",  2  predation The  may  have l i t t l e  paucity  distinguish The  of  effect  experimental  between t h e s e  purpose  information  about  determining  the  of the  data  study  role  of  s t r u c t u r e of  production  of  density,  standing  species:  Nemoura  (Zapada)  cinctipes  SJD.A,  Heterlimnius in  the  sp_.A,  a  l a c k of  taxonomic  1966;  Hynes  elucidate the  the  study.  University described  the  and  The  SJD.B,  heretofore.  of  trout  production  by  of  and  life  the  histories Columbia  of  abundance  insect lotic  on  I the  9 common i n s e c t  diversa  Nemoura (Frison),  debilis  (Walker),  (Banks)  and  trout densities  Columbia  stream. hindered  knowledge the  species  (Wiggins  study  was  examined  insect species  Research Forest  and  study,  (Claassen),  o b j e c t i v e of  of  the  i n s e c t s have been  history  in  Specifically,  In  manipulating  lotic  experimental  predation  coastal British  h i s t o r y of  of B r i t i s h  to  interactions  G l o s s o s o m a peniturn  (Martin)  ecology  life  impossible  the  Tr iznaka  1970). Thus a s e c o n d life  on  californica  h e a d w a t e r s of a s m a l l on  populations.  to provide  Paraleptophlebia  Cinygmula  Studies by  drift  (Banks),  koebelei  it  populations?  impact  (Malenka)  Paraleptophlebia Cinyqmula  the  was  have  benthic  crop,  makes  stream communities.  does t r o u t p r e d a t i o n  examined  insect  predator-prey  what e f f e c t  experimentally  lotic  hypotheses.  this  stream  on  have  not  in  to in the  been  3  DESCRIPTION OF STUDY AREA The  study was conducted i n the headwaters  of S p r i n g Creek  in the U n i v e r s i t y of B r i t i s h Columbia Research F o r e s t , approximately Creek  is a  60 km east of Vancouver,  soft-water  alkaline  (pH  =  phophorus  < 0.01  (conductivity  7.5), mg/1)  B.C. =  nutrient-poor  40  s p r i n g - f e d stream. The  i s l a r g e l y g r a n i t i c , covers about 5.0  mild  and  with  an  average  1). Spring  uohms),  (nitrate  which  wet,  (Figure  <  located  slightly 0.1  mg/1;  drainage  basin,  km .  The c l i m a t e i s  2  annual p r e c i p i t a t i o n of 240  cm/yr. The study area c o n s i s t e d of a stream s e c t i o n 37 m long and approximately 3 m wide. The s i t e was  bounded by a small shallow  pond (area = 960 m ;  =  maximum  2  culvert  downstream.  and g r a v e l 15  cm  The  depth  stream bottom was  (few stones exceeded  thick,  laying  on  0.004  in  August  of  stream.bank Rubus  2°  C  and  a  composed of pebble  to  stream d i s c h a r g e  0.1  m /sec 3  temperature ranged from a maximum of 26.5° C minimum  upstream  5  to  a g r a n i t i c bedrock base. During the  to December 1979,  3  )  10 cm maximum d i a m e t e r ) ,  study from May m /sec  1m  in  varied  October. in  from Water  August  to  a  i n December (Table 1). V e g e t a t i o n along the  was composed  of  shrubs,  Gaultheria  shallon  and  s p e c t a b i l i s ; deciduous t r e e s , Alnus spp, S a l i x spp, Acer  macrophyllum  and Acer c i r c i n a t u m ; and c o n i f e r o u s  trees,  Tsuga  heterophylla. A  resident  population  of  cutthroat trout  lower p o r t i o n of Spring Creek. A s e r i e s of just  downstream  of  the  study  area  i n h a b i t e d the  waterfalls  prevented  located  the upstream  4  Figure  1.  L o c a t i o n of study  area.  STUDY SITE  metres  LOCATION  Table  1.  M o n t h l y maximum and minimum water t e m p e r a t u r e s a t t h e s t u d y s i t e from June t o December, 1979.  Temperature Month  Minimum  June July August September October November December  dispersal  of t r o u t  7.5 10.0 12.5 9.0 7.0 3.0 2.0  into  the study a r e a .  (°C) Maximum 23.5 26.0 26.5 24.5 16.0 10.0 5.0  7  MATERIALS AND METHODS  Experimental  Design  The stream was d i v i d e d l o n g i t u d i n a l l y an  experimental  approximately (4 1/2 m ), 2  (7  study  section.  Each  into a  control  s e c t i o n was  13 m long,  1 1/2 m wide, and c o n s i s t e d of an upstream  a shallow pool (7 1/2 m ) 2  1/2 m ). The stream 2  and a  s e c t i o n s were l o c a t e d  and  downstream  riffle riffle  12m downstream of  the pond and 12 m upstream of the c u l v e r t . In were  mid-July of 1979 the c o n t r o l and experimental  separated  by  an  aluminum  partition.  sections  A t r e n c h was dug  between the two s e c t i o n s and aluminum sheets (120 x 30 cm) were p l a c e d down the l e n g t h of the t r e n c h . Gaps between the aluminum sheets and the bedrock trench  was r e f i l l e d  the stream bed provide  and  support.  enclosed with metal size  of  of  with  plasticine,  fastened Each  end  to of  the the  aluminum  the  partition  to  experimental s e c t i o n  was  s c r e e n i n g (1.2.5 x 1.25 cm mesh).  The  mesh  to be small enough to r e t a i n  i n the enclosure while l a r g e enough not to  the  and  with s u b s t r a t e . Iron rods were d r i v e n i n t o  the s c r e e n i n g was chosen  the t r o u t with  were f i l l e d  interfere  movements of i n v e r t e b r a t e s i n t o or out from each end  the experimental stream  section.  The aluminum p a r t i t i o n prevented the l a t e r a l movements trout,  drift  and benthos between the c o n t r o l and experimental  stream s e c t i o n s . Thus a p a i r of streams, with  similar  study area.  of  f l o w i n g side by  side,  p h y s i c a l c h a r a c t e r i s t i c s were c r e a t e d w i t h i n the  8  Cutthroat  trout  from a downstream enclosure  in  experimental  cm  fork  screen  to  section  14.3  cm  fork  of S p r i n g C r e e k ,  mid-August  of  1979.  length),  density  until  l e n g t h ) were not  They were m a i n t a i n e d  mesh  was  not  t h e end  used  small  obtained  were p l a c e d i n t o  e n c l o s u r e a t a p p r o x i m a t e l y 3-4  downstream t r o u t 6.0  (8.7  in  enough  the  i n the  times the e s t i m a t e d  of November. F r y  (4.0  the  as  experiment  to  retain  them  to the  i n the  enclosure.  Sampling  Methods  Benthos Benthic (Merritt sampler  i n s e c t s were sampled  and was  substrata  Cummins  turned securely were  were s c r u b b e d  The  mm  into  and  debris  then were  a  had  a 0.471  plastic  mm  bottle  Hess-type  e n c l o s e d a 0.05 the  stream Stones,  removed  swept by  2  area.  The  and  the  g r e a t e r than  side  was  3  t h e sample  the c u r r e n t  mesh c o l l e c t i n g whose b o t t o m  m  sampler  bottom  from  n e t a t t a c h e d t o t h e downstream  sampler  removable  which  thoroughly s t i r r e d .  with a brush,  Invertebrates collecting  1978)  using  n e t which replaced  site.  into  of t h e  cm,  the  sampler. ended  in a  with  0.153  nitex. On  from  each  each  samples. downstream  sampling of  A  the  date, eight stream  sections,  habitat-stratified riffle)  random  bottom  samples  for  a total  (upstream  sampling  were  d e s i g n was  taken  of  sixteen  riffle,  pool,  used  to  locate  9  the  sampling s i t e s  within  each  stream  were drawn  from a random number  sites  the  and a  in  upstream  habitat  area  was  site  All  to  The number  of samples  samples  t h a n once  were p r e s e r v e d i n 80%  sampling  i n the pool taken  from  to the r a t i o  a r e a of t h e s t r e a m  more  of numbers 2  and 3 s a m p l i n g s i t e  to the t o t a l  was not u t i l i z e d  Pairs  locate  approximately proportional  of the h a b i t a t  sample  table  riffle  i n t h e downstream r i f f l e .  section.  of t h e  section.  every four  A  months.  ethanol.  Drift Drifting sampler  invertebrates  net which  with  i t s bottom  were  positioned  downstream received  water place  sampled  w i t h a 30 x 30 cm a p e r t u r e (McKone  mesh c o l l e c t i n g  while  were  end  replaced across of  the e n t i r e  the  ended  the  water  from  of samplers  filtered  iron  rods  the e n t i r e  On e a c h  driven  water  stream s e c t i o n  sunrise.  All  sampler.  samples water  the  Four  the  bottle samplers  stream  One p a i r  mm  at  the  of s a m p l e r s  control  section  the e n t i r e  f l o w of  The s a m p l e r s were h e l d  the stream bed. Each  in  sampler  column.  sampling date, hourly  from e a c h  and m i d - d e p t h  into  plastic  nitex.  received  from t h e e x p e r i m e n t a l s e c t i o n . by  of  stream s e c t i o n s .  flow of  second p a i r  width  mm  a Surber-type  1975) and a 0.471  i n a removable  w i t h 0.153  the  using  drift  samples  were  collected  f o r 5 hours, beginning 3 hours  before  were p r e s e r v e d i n 80% e t h a n o l . The d e p t h  velocity  were m e a s u r e d a t t h e mouth o f e a c h  10  Stomach Contents The c u t t h r o a t t r o u t were recovered from the e n c l o s u r e with a hand  net  collected each  immediately  after  the  drift  samples  had  been  ( i e 2-3 hours a f t e r s u n r i s e ) . The stomach contents of  t r o u t were removed with a stomach pump (Meeham and M i l l e r  1978). The tricaine  f i s h were a n e s t h e t i z e d methyl  sulfonate  during  the  procedure  with  (MS222), held i n f r e s h water  until  they had recovered from the e f f e c t s of the a n e s t h e t i c , and then r e l e a s e d back  i n t o the e n c l o s u r e . The stomach contents  removed  from each t r o u t were preserved i n 80% e t h a n o l . T h i s technique had the advantage of  each i n d i v i d u a l  experiment,  thus  experimental  f i s h c o u l d be sampled fish  stream  adapted  to  did  in  several  r e p e a t e d l y d u r i n g the  the  conditions  (1974)  observed  therefore  the  cutthroat  Idaho streams and noted that they g e n e r a l l y  not feed at n i g h t . The stomach contents  trout  in  s e c t i o n d i d not have to be s a c r i f i c e d f o r  stomach content a n a l y s i s . G r i f f i t h trout  that the stomach contents  were  assumed  to  be  removed  from  representative  the  of the  feeding h a b i t s of the t r o u t d u r i n g the day.  Trout Abundance To determine the minimum number and the of  trout  to be used i n the experiment, I censused a c u t t h r o a t  trout population week  prior  size-distribution  in a downstream s e c t i o n  o f ' Spring  Creek,  a  to the s t a r t of the experiment. B l o c k i n g nets were  p l a c e d above and below a 120 m s t r e t c h of  stream  so  that  no  11  t r o u t c o u l d enter of leave the area. The was  electrofished  three  times,  120m  s t r e t c h of stream  with about a 15 to 20 minute  r e s t p e r i o d between each e l e c t r o f i s h i n g p e r i o d . The fish  caught,  the  fork l e n g t h and wet and  number  weight, measured with a  s p r i n g balance,  of each f i s h  electrofishing  were recorded at the end  the  amount  of  time  spent  of each e l e c t r o f i s h i n g  p e r i o d . Since f r y c o u l d not be weighed a c c u r a t e l y in the a small number of them were taken  of  back to the l a b  and  field, weighed  on an t r i p l e - b e a m balance. S c a l e s were removed from a number of t r o u t to determine the age  s t r u c t u r e of the p o p u l a t i o n .  Methods of A n a l y s i s  Benthos Aquatic  i n s e c t s in each benthic  sample were separated  from  d e b r i s , i d e n t i f i e d and enumerated under a d i s s e c t i n g microscope (12  X  magnification).  which were abundant  Only  those benthic  insect  (10 or more i n d i v i d u a l s per  populations  sample),  were  examined f u r t h e r . One riffle,  benthic pool  experimental  and  was  lower  stream  head capsule width Nemoura  sample  riffle  sections across  californica,  randomly s e l e c t e d from the upper  the  Nemoura  from  both  eyes  of  each  c inctipes,  sp_.A,  Paraleptophlebia  Cinygmula  sp_.B,  Glossosoma  koebelei was  control  and  date and  the  individual  of  from each sampling  Paraleptophlebia SJD.A,  the  measured to the nearest  Triznaka debilis,  pen i turn  and  0.02  using  mm  diversa, Cinygmula  Heterlimnius an  ocular  1 2  micrometer. species  I f the t o t a l  was l e s s t h a n 50, t h a n a  selected  from  section  and  the the  Approximately collected  Life  life  analysis  of  of  the  riffle that  more  was  species  than  randomly  from t h a t  stream  measured.  30,000  individuals  recognize  head  species  capsule  Heterlimnius  i n the d r i f t ,  were benthic  study. A d d i t i o n a l adult  University)  koebelei,  made  Entomological  w i d t h was  of  but  from  or t r o u t  specimens  the  no  used  to  peniturn, and attempt  was  stomach  specimens  samples  (Biology  Department,  during were Simon  samples  c o l l e c t e d from  placed  in  J u l y , 1981.  each  Museum.  adults  from t h e s t u d y a r e a  from emergence t r a p  1980 u n t i l  Specimens  from  w i d t h - f r e q u e n c y d a t a from t h e  t o me by K. F r a n k e n h u y z e n  September,  was e l u c i d a t e d  the i n s t a r s of the s t o n e f l i e s or m a y f l i e s .  identifications  collected  Spec i e s  i n s t a r s of the c a d d i s f l y , Glossosoma  to  Fraser  sample  of t h e s t r e a m . Head c a p s u l e  beetle,  supplied  of  the  h i s t o r y of each  riffle  Species  the  lower  individuals  11,000  section  discriminate  made  and  second  were m e a s u r e d .  The  the  pool  H i s t o r i e s of I n s e c t  control  number o f i n d i v i d u a l s measured o f any  species  were  the  UBC  13  Insect Density The width  abundance  of i n d i v i d u a l s with a maximum head or body  l e s s than 0.471 mm was underrepresented  samples  due  to  collecting  head  net  proportion capsule  collected  benthic  placed  i n March, 1980 with a 0.116 over  the o r i g i n a l  c o l l e c t i n g net (double bag sampler). From actual  the  the mesh s i z e of the c o l l e c t i n g n e t . A set of  samples t h e r e f o r e was c o l l e c t e d mesh  in  of  width  with  the  individuals  size  these  mm  0.471 mm mesh samples,  the  of each s p e c i e s i n 0.04 mm  classes  (from  0.16  to  0.52  mm)  o r i g i n a l 0.471 mm mesh c o l l e c t i n g net was  estimated. C o r r e c t i o n f a c t o r s were c a l c u l a t e d f o r each 0.04 head  mm  capsule width s i z e c l a s s f o r each s p e c i e s and the d e n s i t y  estimates of each s p e c i e s were a d j u s t e d a p p r o p r i a t e l y  (Appendix  1). Each benthic i n s e c t p o p u l a t i o n had dispersion  ( i e . v a r i a n c e > mean) ( E l l i o t t  a r e s u l t , the data were transformed 1),  where  a  In  contagious  spatial  1977; Resh 1979). As  with the  function  ln(x +  i s the n a t u r a l l o g a r i t h m and x i s the number of  i n d i v i d u a l s of a s p e c i e s i n a sample. A three-way f a c t o r i a l (sample stream  date), section  h a b i t a t (upper  trout  of  riffle,  ( c o n t r o l , experimental)  used to determine species  analysis  variance,  introduction.  between stream  time  p o o l , lower  r i f f l e ) and  as treatment  l e v e l s , was  whether the mean p o p u l a t i o n  differed  with  densities  of  a  s e c t i o n s before and a f t e r the  14  Insect Standing Crop In September and October unpreserved benthic samples collected were  from  the  measured,  preweighed  stream.  killed  in  were  L i v e i n d i v i d u a l s of each s p e c i e s hot  water  and  placed  in  small  aluminum weighing pans. These samples were d r i e d at  60° C f o r 24 h r , cooled to room temperature i n a d e s s i c a t o r and then weighed groups  to the nearest 0.001 mg.  small  of up to four i n d i v i d u a l s were weighed  mean weight recorded. L i v e organisms avoid  For  possible  (Howmiller  changes  in  dry  were  weight  individuals,  together and the  used  in  order  to  due to p r e s e r v a t i v e s  1972; Standford 1972). The l o g - l i n e a r analogue of  a  power curve,  log(W) = log(a) + b log(HW)  where, a and b are c o n s t a n t s , was  used  to  estimate  (HW) (see Appendix  dry weight  (W) from head c a p s u l e width  2 ) . T h i s f u n c t i o n has been  found to p r o v i d e  the best f i t f o r weight-length data of i n s e c t s This  relationship  capsule  width-frequency  species  in  not  measured,  head  s p e c i e s was assumed to analyzed sample A  data  (see s e c t i o n  capsule,  be  the  above)  of  head each  i n t o a standing crop e s t i m a t e .  i n which the i n d i v i d u a l s of  the  1980).  was used t o convert the c o r r e c t e d  each benthic sample  For those samples  (Smock  width  same  as  a  species  distribution that  found  were of the  i n the  i n the same h a b i t a t on the same date.  three-way  factorial  analysis  of  v a r i a n c e , with time  15  (sample d a t e s ) , h a b i t a t (upper r i f f l e ,  p o o l , lower r i f f l e )  stream s e c t i o n ( c o n t r o l , experimental)  as treatment  used  and  l e v e l s , was  to determine whether the mean standing crops of a s p e c i e s  d i f f e r e d between stream s e c t i o n s before introduction.  The  standing  crop  and  data  of  transformed  to uncouple the v a r i a n c e from  power  (Elliott  law  1977)  indicated  after  the  trout  each s p e c i e s were  the  that  mean.  the  Taylor's  square  root  1946;  Allen  t r a n s f o r m a t i o n was a p p r o p r i a t e f o r the data.  Insect Product ion The 1949)  instantaneous  was  used  to estimate  the upper r i f f l e , section  during  estimates capsule  growth rate method (Ricker  the p r o d u c t i o n of each s p e c i e s i n  pool and lower r i f f l e the  experiment.  h a b i t a t s i n each stream  Since  the  standing  of a s p e c i e s were determined i n d i r e c t l y width  production  distribution  f o r each  species  data, in  only each  from the head  a s i n g l e estimate of habitat  could  calculated. T h i s method c a l c u l a t e s p r o d u c t i o n as:  P = G x B  where,  P  i s the  production  f o r a given p e r i o d of  t ime, G i s the  instantaneous  growth  rate  crop  f o r the  time  p e r i o d and B i s the mean standing crop d u r i n g the time p e r i o d .  be  16  The  instantaneous  growth  rates  were  calculated  for periods  between sampling as the n a t u r a l l o g a r i t h m of the r a t i o mean  individual  weight  at  the end of the time p e r i o d to the  mean i n d i v i d u a l weight at the species  were  hatching  weight  of  standing  the  crop  calculated  date,  10 l a r g e s t of  as  a  the  beginning.  during  i n d i v i d u a l weight on each  If  have  species  other  methods  that  for  eggs  of  a  experiment, then the mean  was  calculated  as  the  mean  i n d i v i d u a l s i n the sample. The mean between  arithmetic  shown  the  the  sampling  periods  was  mean of adjacent standing crop  estimates (Chapman 1968). Waters and Crawford (1977)  of the  (1973)  and  Resh  t h i s method gives s i m i l a r r e s u l t s as  calculating  production  for  benthic  invertebrates. A  two-way a n a l y s i s of v a r i a n c e  with h a b i t a t section  (upper r i f f l e ,  (control,  pool,  (randomized block d e s i g n ) , lower  experimental)  as  riffle)  factors,  and was  used  determine whether the p r o d u c t i o n of a species d i f f e r e d stream s e c t i o n s a f t e r the t r o u t  stream to  between  introduction.  Drift Aquatic debris,  insects  i n each d r i f t  i d e n t i f i e d and enumerated  (12 X m a g n i f i c a t i o n ) . Because  sample were separated from  under a d i s s e c t i n g microscope  of the low hourly d r i f t  each  s p e c i e s , the f i v e hourly samples  were  pooled.  determine drifting  A  whether  paired-sample  the  of  from each stream  section  of  from each stream s e c t i o n  Wilcoxon  number  rates  test  individuals differed  was of  after  used  to  a species the  trout  17  introduction.  Trout Abundance Delury's  method  (Ricker  1975)  was  used to estimate  the  d e n s i t y of the t r o u t i n the downstream s e c t i o n of Spring Creek. Since  fry  could  electofishing  is  not  be  less  used  in  effective  1961), the d e n s i t y of the f r y was  the with  experiment small  estimated  and  fish  as  (McFadden  s e p a r a t e l y from the  r e s t of the p o p u l a t i o n . The  l o g - l i n e a r analogue of the power  estimate  wet  weight  from  measured when c o l l e c t e d , length-density  data  fork  i t was  into  curve  was  used  to  l e n g t h . Since a l l t r o u t were  p o s s i b l e to  convert  a standing crop estimate  the  fork  using  this  relationship.  Trout Stomach Contents Prey  organisms  separated  from  removed  debris,  from  the  identified  trout  and  enumerated  d i s s e c t i n g microscope (12 X m a g n i f i c a t i o n ) . width  across  the  californica,  Nemoura  Paraleptophlebia sjo.A,  Cinygmula  koebelei  was  micrometer.  eyes  sp.A, SJD.B,  measured  of  each  The  pen i turn  to the nearest  0.02  mm  a  of  Nemoura diversa,  debilis, and  under  capsule  Triznaka  Paraleptophlebia  were  head  individual  cinctipes,  Glossosoma  stomachs  Cinygmula  Heterlimnius  using an o c u l a r  18  Food Consumption by Trout Following E l l i o t t  and  Persson  (1978),  I  estimated  d a i l y mean number of i n d i v i d u a l s consumed per t r o u t  the  (C) a s :  C= (24) (S) (R)  where, the  S  i s the d a i l y mean number of i n d i v i d u a l s i n  stomach and  R i s the hourly r a t e of g a s t r i c  evacuation.  Since the stomach contents of the t r o u t were sampled in  the  morning (2-3 hours a f t e r s u n r i s e ) , S was assumed to be  equal to the mean number of i n d i v i d u a l s i n the at t h i s time. Data from A l l a n feeding  activity  Mitchill)  indicated  stomach  from  approximated Griffith similar per  in that  samples the  (1974) feeding  stomach  brook  mean that  (Salvelinus  number  collected  observed habits,  trout  the mean  daily  2  of  to  stomachs  number  fontonalis  individuals  4 hours a f t e r  of  prey  per  brook and c u t t h r o a t  and found that  per  sunrise stomach.  t r o u t had  the mean number of  trout  i n streams  prey  inhabited  was s i m i l a r . Thus my assumption seems reasonable.  I was unable to f i n d any p u b l i s h e d data evacuation  data presented evacuation  trout  (1981) on the temporal p a t t e r n of  of brook and c u t t h r o a t  sympatrically  gastric  only  by  for cutthroat Elliott  f o r brown  (1972)  trout.  on  the  rate  of  t r o u t . T h e r e f o r e I used the on  Elliott  the  rate  of  gastric  (1972) found that  water  temperature and the s p e c i e s of prey had a s i g n i f i c a n t e f f e c t on  19  the r a t e of g a s t r i c evacuation while t r o u t s i z e , prey s i z e feeding  r a t e had l i t t l e  e f f e c t . Thus R was  and  assumed to be equal  to the time f o r 95% g a s t r i c . e v a c u a t i o n  of  rhodani  t r o u t at the mean water  from  temperature  the  stomach  of  brown  a  meal  of  Baetis  that occurred on each sampling date ( E l l i o t t  1972,  F i g u r e 7). The  number  of  individuals  (N)  consumed  i n t e r v a l around each sampling date was  over  a  time  estimated as:  N = (C) (D) (I)  where, D i s the d e n s i t y of t r o u t  i n the e n c l o s u r e and  I i s the d u r a t i o n of the time i n t e r v a l Since each time i n t e r v a l began consecutive  sampling  dates,  and the  i n days.  stopped  half-way  t o t a l number of  consumed by the t r o u t during the experiment  individuals  i s equal to the  of the number of i n d i v i d u a l s consumed i n each time  2  the  t r o u t d u r i n g the experiment  was  the stomach contents was  weight on head capsule width  consumed  c a l c u l a t e d by the same  proceedure as o u t l i n e d above. The dry weight of in  sum  interval.  An estimate of the standing crop (mg dry-wt./m ) by  between  an  individual  estimated from a r e g r e s s i o n of dry (see Appendix  2).  20  Samplinq V a r i a b i l i t y A number of procedures were undertaken during to  increase  the  estimates: F i r s t ,  precision the  of  l o s s of  the  by:  the  b) e s t i m a t i n g  the  l o s s of  collecting  nets;  and  field;  fine  mesh  magnification.  included  sampling  fourth,  the  not  each  design  the in  was  sample.  Third,  at  a  the  enumerating  component  used to l o c a t e  t r a n s i t i o n areas between the  was  through  s o r t i n g and  hyporheic  the  density  sample  individuals c)  study  c o l l e c t i n g nets i n  samples under a stereoscope  Second,  random  were  in  a) using f i n e mesh (0.471 mm)  i n d i v i d u a l s from the  p o p u l a t i o n was  insect population  individuals  minimized  this  12  times  of  stratified  sampling s i t e s  riffles  and  each  the  and pool  sampled; i n s e c t p o p u l a t i o n d e n s i t i e s were assumed to  vary monotonically from one  habitat  to the  other.  21  LIFE HISTORIES OF INSECT SPECIES  Stoneflies Three p o p u l a t i o n s of s t o n e f l i e s were examined study:  Nemoura  (Zapada)  (Malenka)  cinctipes  c a l i fornica  (Banks)  (Claassen),  Triznaka  diversa  Nemoura  californica  per year  ( F i g u r e 2) while T r i z n a k a d i v e r s a had a  cycle  and  and  Nemoura (Frison).  Nemoura c i n c t i p e s had one generation  eggs  of  2  year  life  Nemoura c a l i f o r n i c a began to hatch i n e a r l y  autumn and continued probably Young  nymphs  throughout  (HW)  between  and  0.14  the  and  0.16  mm  of  these  were  summer  months.  instars  (other s p e c i e s of Nemoura r e p o r t e d l y go  They  i n s t a r s , Harper  developed  1973; B r i t t a i n pads  appeared  through  on  nymphs  through  the  instars  spring  and  an unknown number of through  12-16  with a HW > 0.70  developed  wing  pads  mm; and  ready to emerge. Emergence of a d u l t s occurred  l a t e summer. A d u l t s were present  September  measured  1973), to reach m a t u r i t y i n l a t e  nymphs with a HW > 0.96 mm had w e l l considered  October  probably f i r s t  1973). The nymphs grew r a p i d l y d u r i n g  Wing  months.  nymphs  (Harper  summer.  winter  l a c k i n g c e r v i c a l g i l l s were present from  through March. The head width  in  the  (Figure 3). The  were  during  November.  Kerst  on  the  and  study  site  from  Anderson (1974;1975)  reported a s i m i l a r l i f e h i s t o r y p a t t e r n f o r Nemoura  californica  in Oregon. The eggs  of  Nemoura  cinctipes  hatched  throughout  the  s p r i n g months. Young nymphs l a c k i n g c e r v i c a l g i l l s were present  22  F i g u r e 2. Size-frequency histograms of Nemoura c a l i f o r n i c a and Nemoura c i n c t i p e s nymphs from May, 1979 to March 1980 . Shaded histograms represent i n d i v i d u a l s of Nemoura c i n c t i p e s . M i n d i c a t e s mature nymphs (wingpads well-developed) p r e s e n t . A1 i n d i c a t e s a d u l t s of Nemoura c a l i f o r n i c a p r e s e n t . A2 i n d i c a t e s a d u l t s of Nemoura c i n c t ipes present, (next 3 pages)  rO- INDIVIDUALS PER 0-06 SO- M-  N3- INDIVIDUALS PER O-CS SO- MK  !  K  S  2  9  !  l  t  l  l  t  i  IS-  6  . in  S  B  S  1237  6  I  ffitr  5?  rO- INDIVIDUALS PER 0-CS SO- M-  N3- INDIVIDUALS PER 0-05 SO- MB  K  8  5!  ffl  W  W  S  ! a "  S  2  ffl  in  ! 96,6  "*  I  ID  75.4  tn  co  rO- IrCIVICLIALS PER O-CS SO- M*  NO- INDIVIDUALS PER O-CS SO- M-  M>  f .  I^IVIOUALS PER 0-05 SO- M-  ^  K .  S .  l  ' .  f  f .  ND- INDIVIOJALS PER 0-C6 SO- M-  l  W .  W .  f  e .  o o*  * •  m  IS  R  8  ro Ul  26  Figure  3. S i z e - f r e q u e n c y h i s t o g r a m s of T r i z n a k a d i v e r s a nymphs f r o m May, 1979 t o M a r c h , 1980 . M indicates m a t u r e nymphs ( w i n g - p a d s w e l l - d e v e l o p e d ) p r e s e n t . A indicates that adults are present, (next 3 pages)  27  MAY H3  1379  JULY 12  1379  2  2. 2  •IB  0.24  0-40  Him 0.56  0.72  0-BB  1.04  n 1-20 n  1-3E  o-  0-15  to-  0-24  Q-rfl li-n  0-40  HEAD CAPSULE WIOTH CIvW)  JUNE 14  O-SS  0-72  0-68  1.04  1.20  1.36  1-20  1-3G  HEAD C A P S L L E WIDTH ((*()  1379  AUGUST , 9  1979  2  0.12-0*24  0*40  11  O-SS  0-72  O-SB  1-04  K > 0 CAPSULE WIDTH (KM)  1-20  1-3G  J-12  0*24  0*40  0-56  HH>0  0-72  CVaLE  O-fcti  1-04  WIDTH (MJJ  SEPTEMBER S  • 12  0-24.  0.40  OCTOBER 4 1379  1379  r r i l l l l h n O-SS  0-72  m i  o-  0-88  1-04  1.20  1.36  0-12  0-24  0-40  SEPTEMBER B3 1979  1.04  1-20  1-36  1-20  1.3S  N3VEM3ER 1 1379  - nQ.4Q . ^ / rQ.So T l r T T T h0 -H6 8  0-S4  r-e/a opsixe  O-BB  r O O CAPSULE WIDTH (M*)  l£AO CAPSULE WIDTH tkW)  •IE  n i ri0 - 7 2 0-56  WIDTH  1-04  0*0  1-50  1-36  0-12  0.24  h  :TiTK>n  •• rri>  0.40  O.SS  0-73  O.BU  1-04  HEAD CAPSULE WIDTH Cr*t)  NJVEM3ER 29  0-12  0.54  1979  n..rrimnnn  0.40  0-SE  0-72  0.88  1-04  1-20  1-3S  HEAD C A P S U L E WIDTH CIA(1  MARCH SB  e t a  0*12 0*24  1SS0  0-40  0-36  HEAD  xtm. 0-(  0-72  r/fcji r  WIDTH  r n , l~h 1.04 (MJJ  i.pO  1-3G  30  from  April  through  July.  Nymphs  with  a  HW  < 0.30  mm  were  m o r p h o l o g i c a l l y i n d i s t i n g u i s h a b l e from s i m i l a r s i z e d nymphs Nemoura 0.14 mm  californica.  and 0.16  mm  Nymphs of both s p e c i e s with a HW  had no c e r v i c a l g i l l s ;  had one p a i r of unbranched  and 0.28  mm  gills  nymphs  with  a HW  > 0.30  and thus c o u l d be d i s t i n g u i s h e d  nymphs  which  had  unbranched  Nemoura c i n c t i p e s nymphs was the  cervical gills;  had two p a i r of unbranched  californica  possibility  Hynes  1970;  between 0.16  and  cervical  Nemoura  gills.  0.20  Nemoura  had branched  from  0.20  and between  cervical cinctipes  Growth of the  slow d u r i n g the summer, suggesting  that the nymphs undergo a diapause  Harper  between  cervical g i l l s . mm  of  (Harper  and  1973). The nymphs grew r a p i d l y through the  autumn and reached m a t u r i t y i n November. Wing pads appeared nymphs  with  a HW  > 0.70  mm;  nymphs with a HW  > 1.0 mm  on  in late  November had w e l l developed wing pads and were c o n s i d e r e d ready to  emerge. Emergence of  autumn site  through  early  adults spring.  probably  cinctipes  was  life  described  by  (1974;1975) i n Oregon and by Radford and in  southwestern The  eggs  summer and may Young,  late  history Kerst  pattern and  for  Anderson  Hartland-Rowe  (1971)  Alberta. of  Triznaka  diversa  began  to hatch i n e a r l y  have continued throughout the r e s t of the  colourless  nymphs  with  a HW  between 0.14  were present from J u l y through March. The during  from  A d u l t s were found on the study  i n March and A p r i l . A s i m i l a r  Nemoura  occurred  nymphs  year.  and 0.16 grew  mm  slowly  the summer and autumn and r e q u i r e d two years to mature.  Nymphs of age  1+ were found with P a r a l e p t o p h l e b i a sjo.A  nymphs,  31  chironomid ingested, T. d i v e r s a  and  ceratopogonid  suggesting are  that  larvae  at  least  and the  nematodes older  nymphs  of  c a r n i v o r o u s . The nymphs matured i n the s p r i n g .  Wing pads were found on nymphs with a HW > 1.0 mm. a d u l t s occurred  partly  Emergence of  i n the l a t e s p r i n g .  Mayf1ies Four p o p u l a t i o n s  of  mayflies  were  sjo.A,  examined  study:  Paraleptophlebia  (Walker),  Cinygmula sp_.A and Cinygmula sjo.B. A l l  during  Paraleptophlebia  the  debilis  four  species  had a u n i v o l t i n e l i f e h i s t o r y (Figure 4 and 5 ) . The  eggs  of P a r a l e p t o p h l e b i a  sjo.A hatched throughout the  summer. Young c o l o u r l e s s nymphs with a head width (HW) 0.14  and  0.16  mm  were present  nymphs were not f i r s t  from J u l y to September. These  i n s t a r s s i n c e nymphs with a HW of 0.10 mm  were o c c a s s i o n a l l y c o l l e c t e d . Growth of during  between  the  nymphs  was  the autumn but a p e r i o d of r a p i d growth occurred  s p r i n g . Wing pads were present  on nymphs with a HW >  slow i n the  0.70  mm;  nymphs with a HW > 1.0 mm had w e l l developed wing pads and were considered  ready  to emerge. Adult emergence probably  from l a t e s p r i n g through mid-summer. The l i f e  occurred  history  pattern  of t h i s s p e c i e s i s very s i m i l a r to P a r a l e p t o p h l e b i a q r e q a l i s i n Oregon  (Lehmkuhl  Paraleptophlebia  and sjo.A  using the key provided  Anderson key  out  1971). as  The  mature nymphs of  Paraleptophlebia  gregalis  by Lehmkuhl and Anderson.  The eggs of P a r a l e p t o p h l e b i a d e b i l i s began to hatch the winter  and probably  continued  until  during  l a t e s p r i n g s i n c e young  32  F i g u r e 4. Size-frequency histograms of P a r a l e p t o p h l e b i a sp,A and P a r a l e p t o p h l e b i a d e b i l i s nymphs from May, 1979 t o March, 1980 . Shaded histograms represent i n d i v i d u a l s of P a r a l e p t o p h l e b i a d e b i l i s . M i n d i c a t e s mature nymphs (wing-pads well-developed) p r e s e n t . A indicates adults of P a r a l e p t o p h l e b i a d e b i l i s present, (next 3 pages)  33  MAY 23  2  BB-  SS 8  24.  1S79  JULY 12  2  1379  2B-  Si  M  0-12  0.24  n rfl , • nTh-n m  0-40  0-56  0-72  O-SS  1-04  1.20  1-32  0.12  0.24  HEAD CAPSULE WIDTH CMM1  JUNE 14  0-40  O-SS  0-72  O-BB  1-04  1-20  1.3  1-04  l-PO  l»3E  HEAD CAPSULE WIDTH CKWI  1979  ALGLST 9  1379  S  2  28.  s 8  24.  2  • IM 0-12  0.24  0.40  0-S6  0-72  0-88  HEAD CAPSULE WIDTH Ch.M)  1-04  1.2J  1-32  2B.  0-13  0-24  0-4O  0-56  0-75  OtU  HEAD C A P S l.E WIDTH CKM)  34  SEFTENfiER S 1379  2  aa.  OCTOBER A 1379  1  0-12  0-24  0.40  O-SG  0-72  0-B8  1-04  1-20 1-32  S  28-  8  24.  0-12  0-24  HEAD CAPSULE WIOTH (KM)  0-56  0«72  4=3-  0-86  1-04  1-20 1-32  1-04  1-20 l v  HEAD CAPSULE WIDTH CKM)  SEPTEMBER 50 1379  2  0.40  NDVEM3ER 1 1379  28-  a  8  24.  A  pi 0*12  0*24  0-40  0-S6  0*72  0-E3B  HtAO CAPSULE WIDTH (KM)  1*04  1.20 1-32  0-12  0-24  0.40  0-56  0-72  M  &3-  O-ftJ  HEAD CAPSULE WIDTH (KWI  N3VEM3ER 2 3  1379  M  0-12  0-24  0-40  0-SG  0-72  . ~0-88 l T h P1-04h  m  1-20  1.32  1>2U  1-32  HEAD CAPSULE WIDTH (MM)  MARCH 2 8  0.12  0-24  1SS0  irrfnrn  0-40  0.56  0.72  M  0-66m - i 1>04  HEAD CAPSULE WIDTH (MM)  36  F i g u r e 5. S i z e - f r e q u e n c y histograms of Cinygmula S J D . A and Cinygmula sp_.B nymphs from May, 1979 t o March, 1980 . Shaded histograms represent i n i d i v i d u a l s of Cinygmula sjo.A. M i n d i c a t e s mature nymphs (wing-pads w e l l developed.) present, (next 3 pages)  37  MAY S3 1379  JULY 12 1379  >  2  0-12  tu  C 3 5  0.12  0-36  HEAD CAPSULE WIDTH CM*)  HEAD CAPSULE WIDTH (MMJ  JUNC 14 1979  AUGUST 9 1379  5  8  6-  0.12  0-35  0-12  HEAD CAPSULE WIDTH (KM)  C 3 S  HEAD CAPSLLE WIDTH CMJ)  38  SEPTEM3ER S  OCTOBER A  1379  1979  6  > 2  2 s  IL 0-12  I—I—1  0.36  0-GB  1.00  0.12  J J  0-3S  HEAD CAPSULE WIDTH (MM)  SEPTEMBER E C  tL  0.66  1.00  X X  1-32  HEAD CAPSULE WIDTH tKWJ  rOVE^SER 1  1379  1979  6  > 2  0-12  0.3S  0-66  1.00  HEAD CAPSULE WIDTH  1.32  Cf*l)  111 0-12  n  0-3S  J=L 0.6B  l.OO  HEAD CAPSULE WIDTH ().*»  1-32  1-64  N3VEK6ER 59  0-12  1379  0.3S  0-6B  1-00  1-32  1-64  HEAD CAPSULE WIDTH CMM)  MARCH 2S  0-12  0-36  1SB0  -H  O.SB  r~ l-OO  HEAD CAPSULE WIDTH  1-32 0*4)  1-64  40  nymphs  with a head width between 0.14 and 0.16 mm were present  from March through May. The nymphs grew s t e a d i l y throughout the year and were mature by mid-autumn. Wing pads were nymphs with a HW > 0.70 mm; developed  wing  pads  present  nymphs with a HW > 0.94 mm had w e l l  and were c o n s i d e r e d ready to emerge. The  emergence of a d u l t s probably o c c u r r e d from mid-October November. debilis  A  similar  The eggs of Cinygmula sjo.A, a f t e r hatched  (1971) i n Oregon.  r e s t i n g over the  with a HW < 0.22 mm.  the summer  and  matured  in  early  autumn.  on nymphs with a HW of 0.88 mm;  mm  well  developed  Wing  through  pads  first  wing pads and were c o n s i d e r e d ready to late  September  October.  The  eggs of Cinygmula sjo.B hatched  i n the l a t e summer and  e a r l y autumn. Young nymphs (HW between 0.24 and 0.32 present  from  September  mm)  pads  were  present on nymphs with a HW > 0.88 mm;  with a HW > 1.36 mm developed emergence  i n March and 1.2 mm  spring. nymphs  i n May or June had well  wing pads and were c o n s i d e r e d ready of  were  to November. The nymphs grew s t e a d i l y  through the autumn and winter and matured i n the e a r l y Wing  were  nymphs with a HW > 1.4  emerge. Adult emergence probably o c c u r r e d from through  nymphs  The nymphs grew r a p i d l y  appeared had  winter  i n the s p r i n g . Young nymphs with a HW between  0.24 and 0.32 mm were present i n May and June. No collected  through  l i f e history pattern for Paraleptophlebia  i s d e s c r i b e d by Lehmkuhl and Anderson  months,  on  to  emerge.  The  a d u l t s probably o c c u r r e d i n the l a t e s p r i n g . The  l i f e h i s t o r y of Cinygmula sjo.B i s s i m i l a r to that d e s c r i b e d  by  Lehmkuhl  in  and  Anderson  (1970)  for  Cinygmula  reticulata  41  Oregon.  Caddisflies A s i n g l e c a d d i s f l y p o p u l a t i o n , Glossosoma was examined from  the  during the study.  head  Table 2.  Five  instars  penitum (Banks), were  identified  capsule width data (Table 2 ) . These data agree  Head-capsule widths of l a r v a l i n s t a r s of Glossosoma penitum from Spring Creek,  Instar  Head-capsule width  1 2 3 4 5  0.16 0. 18 - 0.20 0.26 - 0.30 0.36 - 0.42 0.50 - 0.58  w e l l with  the  Glossosoma  penitum i n Oregon  Glossosoma  (mm)  instar-head  width  relationship  (Anderson and Bourne  reported 1974).  penitum had a b i v o l t i n e l i f e - c y c l e  The eggs of the summer generation of Glossosoma  for  (Figure 6 ) .  penitum  began  to hatch i n June and probably c o n t i n u e d though J u l y . The l a r v a e grew  very  stadium.  rapidly Emergence  and of  by  July  adults  l a r v a e were present i n each  probably  began  in  July  and  continued through August. The  eggs  l a i d by the summer generation probably began to  42  F i g u r e 6. Size-frequency histograms of Glossosoma peniturn l a r v a from May, 1979 to March, 1980 . A indicates a d u l t s of Glossosoma peniturn present, (next 3 pages)  NO- IhCrviCUALS PER 0-05 SQ- M*  NO-  IhOIVIDUALS PER 0-CS SQ- M-  NO- INDIVIDUALS PER 0-05 SQ- M-  NO- INDIVIDUALS PER 0-05 SQ- M-  44  SEPTEMBER G  SEPTEMBER S 3  CCTCBER 4  1379  1379  NOVEMBER 1  INSTAR  1979  1979  INSTAR  NO- INDIVIDUALS PER 0-05 SO- M-  NO-  INDIVIDUALS PER 0 - 0 5 SO- M-  Ol  46  hatch i n August and continued i n t o were  present  from  August  October  as  first  u n t i l October. Growth of the l a r v a e  proceeded s t e a d i l y through the autumn. The l a r v a e winter  predominently  as  instars  third  entered  and f o u r t h i n s t a r s . Pupa were  present from the end of March through June. The a d u l t s in  late  s p r i n g . Anderson  bivoltine l i f e history  f o r Glossosoma  penitum  i n Oregon.  Beetles  beetle population,  examined  emerged  and Bourne (1974) reported a s i m i l a r  Riffle A single r i f f l e  the  during  the  Heterlimnius  koebelei  (Martin),  was  study. Four i n s t a r s were  identified  from the head width data (Table 3 ) . I n d i v i d u a l s with  a head width (HW) between 0.16 and 0.18 mm were assumed first  instars  never  because  individuals  with  collected.  complete  though  i t s l i f e history  could  not  second and t h i r d the  be  a HW < 0.16 mm were  H e t e r l i m n i u s koebelei appeared to r e q u i r e at l e a s t to  to  year.  First  be  (Figure  recognized  7).  from  Individual  2 years cohorts  the data s i n c e  i n s t a r l a r v a were present at a l l times i n s t a r l a r v a e were most abundant  during  i n the l a t e  summer and autumn; t h i r d  i n s t a r l a r v a e were  the  summer ; and f o u r t h i n s t a r l a r v a e were  spring  most abundant the  and . e a r l y  most  first,  i n the e a r l y autumn. T h i s p a t t e r n  abundant  suggests  in  that  l a r v a e r e q u i r e one year to develop from an egg to the t h i r d  instar  and  a f u r t h e r year to develop from the t h i r d  i n s t a r to  an a d u l t . A d u l t s began to emerge i n the s p r i n g and were present in  the stream u n t i l November. Pupae were not c o l l e c t e d as  they  47  F i g u r e 7. S i z e - f r e q u e n c y histograms of H e t e r l i m n i u s k o e b e l e i l a r v a from May, 1979 to March, 1980 .  NO-  INDIVIDUALS PER 0 - 0 5 S 3 - M-  NO-  INDIVIDUALS PER 0 - O S SO-  M-  NO-  INDIVIDUALS PER 0 - C 6 SO- M-  NO-  INDIVIDUALS PER 0 - 0 5 SO- M-  49  SEPTEMBER S  SEPTEMBER 2 0  1379  OCTOBER 4  1379  NOVEMBER 1  INSTAR  1373  1379  INSTAR  NO- INDIVIDUALS PER O-CS SO- M-  NO- INDIVIDUALS PER 0-CS SO- KI-  o  r  u  *  in  to  o  9  I  1  £  7  1  ?  9  51  Table 3.  Head-capsule widths of l a r v a l i n s t a r s of H e t e r l i m n i u s k o e b e l e i from Spring Creek.  Instar  Head-capsule width  1 2 3 4  are  terrestrial  previous  (mm)  0.16-0.18 0.20 - 0.26 0.30 - 0.38 0.40 - 0.46  (Brown  1972).  s t u d i e s have provided  Qualitative  little  s e r i a l data from  information on  h i s t o r y of Elmidae b e e t l e s p e c i e s (Hynes  1970).  the  life  52  RESULTS  Trout Abundance The  August  density  of c u t t h r o a t t r o u t  s e c t i o n of S p r i n g Creek was 0.18 f i s h / m 4).  The  trout  population  2  or  o l d p a r r , ranging  1.17  g  8).  to  14.3  2  in  (Table  weight;  1+  from 8.2 to 9.2 cm i n l e n g t h and 4.0 to  6.0 g i n weight; and 2+ and 3+ year o l d a d u l t s , 9.5  g/m  c o n s i s t e d of f r y (age 0+), ranging  from 4.0 t o 6.0 cm i n l e n g t h and 0.5 t o 1.5 year  i n the downstream  ranging  from  cm i n l e n g t h and 8.0 to 28.0 g i n weight (Figure  The r e l a t i o n between wet weight  cm) was determined  (W gm) and fork  length  (L  to be:  In W = -5.08 + 3.15 In L  based on 18 t r o u t  from 5.0 t o 14.3 cm fork l e n g t h ( r = 0.97). 2  In mid-August t h e r e f o r e , I p l a c e d s i x t r o u t fork  length)  fish/m  2  or  into 4.1  the  g/m ). 2  experimental But  trout  (8.7 - 13.2 cm  enclosure  ( d e n s i t y = 0.3  "disappeared"  from  the  enclosure at a rate of one to two per week. E l e c t r o - f i s h i n g the area  upstream and downstream of the enclosure f a i l e d  the missing f i s h . escaping  from  Although  the  Beginning  i s possible  the  trout  were  e n c l o s u r e and d i s p e r s i n g f a r downstream, I  suspect that predators removing t r o u t  it  to locate  (eg. raccoons,  Procyon l o t o r ) a l s o  were  from the e n c l o s u r e . in  enclosure with e i g h t  mid-September  therefore  trout.  were  Trout  added  I  stocked  the  approximately  53  Figure  8. F r e q u e n c y h i s t o g r a m of f o r k l e n g t h s of c u t t h r o a t t r o u t from S p r i n g C r e e k a t Road F-30, A u g u s t 1979. T r o u t were c o l l e c t e d by e l e c t r o f i s h i n g a 360 m stretch of s t r e a m . 2  54  CUTThRDAT TROUT  SPRING  CJ^EK  IS- „  >  10.  i  B-  1  6-  1  4-  1  2-  1  E-5  J  4.0  6-0  I  I  i  8-0  10.0  FGRK LEMJTH  12-0  CCM)  14.0  +H—I 16-0  55  Table  4.  D e n s i t y and s t a n d i n g c r o p of c u t t h r o a t t r o u t i n S p r i n g C r e e k a t Road F-30, A u g u s t 1979.  Density (no. / s q . m) Fry (0+) P a r r and A d u l t s  (1+  Total  Population  every  two  to  14.7  used cm  in  and  mean abundance of was  0.28  that  estimated The  Only the  3+)  fish/m  from  0.07 1.10  0.18  1.17  or  2  i n the  October  available maintenance  trout 11 food  to  t h a t had  experiment  6.0  trout  trout lost  two  the  to  i n the  4.4  28.5  disappeared.  ranged gm  2  during  30„ supply  requirements  during  weight  time was of  the  during  period. not the  length  the  T h i s abundance was  downstream s e c t i o n of  gained  in fork  i n w e i g h t . The  enclosure  g/m .  weight  Standing Crop wet-wt/ s q . m)  0.10 0.08  weeks t o r e p l a c e any  Trout 8.7  -  (gm  experiment  This  sufficient trout during  suggests  the  times  (Table  interval,  t o meet  4  Creek.  experiment a time  estimated  3 to  Spring  from  both  that the  5). in the  minimum  experiment.  56  Table 5.  Mean weight of the t r o u t i n the experimental stream s e c t i o n that s u r v i v e d u n t i l the end of each time p e r i o d .  Mean weight of t r o u t Time P e r i o d  n  Aug 22 - Sept 1 1 Sept 11 - Sept 25 Sept 25 - Oct 11 Oct 11 - Oct 30 Oct 30 - Nov 20  2 5 7 4 5  (gm wet-wt)  Beginning  End  12.8 16.0 15.7 13.8 12.5  12.3 14.6 14.6 14.0 12.1  Food H a b i t s of Trout A n a l y s i s of the stomach contents c inctipes,  Paraleptophlebia d e b i l i s  important prey s p e c i e s of  the  Paraleptophlebia  was  throughout they  debilis  c i n c t ipes was  from  the  and  trout  stream  sjo.A  in  Nemoura sjo.A were  experiment.  was  present and  until Nemoura  present from l a t e September u n t i l the end of  (Table  6).  At  least  one  species  of  accounted  for  42%  in the t r o u t stomachs.  were  the  mid-October  stomachs.  taxa  Cinygmula  during  occurred i n 88% of the t r o u t  present  that  present i n the d i e t of the t r o u t  the experiment; Cinygmula  emerged  experiment  suggested  chironomids  of these three s p e c i e s Together  the  next  most  consumed by the t r o u t .  three  organisms abundant  (20%) and ceratoponogids (18%), Nemoura  c i n c t ipes, P a r a l e p t o p h l e b i a d e b i l i s and Cinygmula accounted f o r at l e a s t a  these  the t o t a l number of  Since  the  similar  proportion  of  sjo.A probably the  biomass  57  Table  6.  Occurrence of benthic i n s e c t s in the t r o u t stomach c o n t e n t s .  Sampling Sept n= Nemoura cinctipes californica Triznaka diversa 0+ cohort 1+ cohort Paraleptophlebia sp. A debilis Cinygmula sp. A sp. B Glossosoma penitum Heterlimnius koebelei n= P= 0= -=  11  Sept 25  Date  Oct 11  Oct 30  4  5  7  4  5  P  P 0  P  P  P  -  -  -  P  P  P  P  P P  P P  P  P  P  0  0 P  -  -  -  P  .-  -  number of t r o u t sampled presence of s p e c i e s i n stomach contents absence of s p e c i e s from the benthos and stomach absence of s p e c i e s i n stomach contents  The numerical  remaining  p r o p o r t i o n of the d i e t . Heter1imnius k o e b e l e i , the 0+  californica  autumn-hatching  sjo.B  and  cohort  of  apparently were not u t i l i z e d by the t r o u t  while Glossosoma penitum, the 1+ cohort Cinygmula  contents  i n s e c t p o p u l a t i o n s c o n s t i t u t e d only a small  cohort of T r i z n a k a d i v e r s a and the Nemoura  Nov 20  Paraleptophlebia  o c c a s i o n a l l y d u r i n g the experiment  of  Triznaka  SJD.A  (Table  diversa,  were u t i l i z e d only  6).  Together  these  58  populations organisms  accounted  i n t h e stomach  Immature a q u a t i c organisms insects,  present chiefly  including sp_.A  of  i n v e r t e b r a t e s accounted  adult  dipterans  and  a fraction  i n d i v i d u a l s of each s p e c i e s p r e s e n t that  vulnerability  95%  of  the  o f t h e t r o u t . Winged but  also  d e b i 1 i s and C i n y g m u l a  of the t o t a l  size  i n the benthos  to trout predation  range  (Table  is a  7)  function  size.  Nemoura  Paraleptophlebia Heterlimnius organisms  and  trout  were The  contents crop  penitum  than  the  of  d e b i 1 i s and C i n y g m u l a  debilis  Nemoura sp_.A  7%  trout,  of only  and the the  cinctipes,  consumed  sampling' of  sp_.A p e r  d a t e a r e shown i n T a b l e  individuals  by t h e d r i f t  prey  (mg) o f Nemoura  and C i n y g m u l a  per  by  the  (r=0.98;  stomach  cinctipes,  trout  stomach  8 . The v a r i a t i o n i n may  be  partially  r a t e . A p o s i t i v e r e l a t i o n s h i p was  between t h e mean number o f p r e y the  less  of  mean number and d r y w e i g h t  number  explained  for  diversa,  estimated.  Paraleptophlebia each  stomach  Triznaka  sp_.B, G l o s s o s o m a  accounted  standing  Paraleptophlebia  by T r o u t  c a l i fornica,  sp_.A, C i n y g m u l a  koebelei  i n the  density  of  for  the r e s t .  Since  the  number o f  hemipterans  of P a r a l e p t o p h l e b i a  Food C o n s u m p t i o n  on  7% o f t h e t o t a l  contents.  t r o u t consumed o n l y  suggesting of  than  i n t h e stomach c o n t e n t s  subimagos  composed The  for less  p e r stomach and t h e d r i f t  found rate  P<0.01), which s u g g e s t s a dependence of  59  Table  7.  The range of head-capsule widths of benthic i n s e c t s i n the benthos and t r o u t stomachs between September 6 and November 29.  Taxa  Head-capsule width t r o u t stomach  (mm) benthos  minimum  maximum  minimum  maximum  0..48 0.,60 0..50 0..88 0..42  1 .02 , 0,.96 1 .00 , 1 .60 , 0,.42  0. 1 6 0. 1 6 0. 1 6 0.28 0. 1 4 0. 18  1 .20 . 1 .,1 6 1 .,1 4 1 .90 , 0,.56 0,.44  Nemoura Triznaka . Paraleptophlebia Cinygmula Glossosoma Heterlimnius  --  --  the feeding r a t e on the abundance of prey  i n the d r i f t  (Figure  9) . The  total  d e n s i t y of Nemoura c i n c t i p e s ,  d e b i l i s and Cinygmula sjo.A consumed by experiment total  was  estimated  the  Paraleptophlebia  trout  during  to be 198 i n d i v i d u a l s per m  2  the  and the  standing crop to be 42 mg dry-weight per m . 2  Insect Density Figures population  to  12  densities  experimental examined.  stream Prior  experimental densities  10  and Standing  display  and  standing  sections to  the  the  of  Crop  changes  crops the  introduction  in  standing  crops  of  mean  i n the c o n t r o l and  nine of  benthic trout  stream s e c t i o n i n mid-August, the mean  and  the  species into  the  population  a l l s p e c i e s except Nemoura  60  Figure  9. R e l a t i o n s h i p between d r i f t r a t e of prey and the mean number of prey per t r o u t stomach. Prey s p e c i e s c o n s i s t e d of N. c i n c t i p e s , P. d e b i l i s and C. sp.A. D r i f t was sampled f o r 5 hours beginning 3 hours before sunrise. Trout stomach contents were sampled 2-3 hours after sunrise. r = .98 , P<.01.  61  EOIS-  1 4 . ..  G-  1 + +  + 50-  GO-  ISO'.  100.  140-  IfsOIVILXJALS IN CRIFT  •41B0-  500-  62  Figure  10. Mean d e n s i t i e s and s t a n d i n g crops of N. c a l i f o r n i c a , T. d i v e r s a , P. sp.A and G. penitum i n the c o n t r o l C x - x T and experimental (*-•*) stream sections. V e r t i c a l l i n e s r e p r e s e n t 1 SE. Cutthroat t r o u t p l a c e d i n t o the experimental stream s e c t i o n i n mid-August. (next 5 pages)  DENSITY OF INEM3JRA DVLIFORWICA 500-  1979  OATE  DENSITY OF TRIZNAKA • I VERSA CO rjD-TJRT) E D O -  1979  OATE  STAfSOIIVE CROP O F TRI2NAKA D I V E R S A 4-0 _  3*5 .. '  a  3  - ° -  6  2-5..-  7  2-0..  1979  •ATE  (0+  CQHGRT)  64  65 DENSITY  DF  TRIZNAKA  DIVERSA  (1+  COHORT)  100-  B 6 10.1  > Q  JU  EE 1979  AU  DC  NO  DE  DATE  STANDING  S5  8  4.0  T  3.5  1  3  '°  5-5 ..  7  2-0 ..  Q  DF  TRIZNAKA  DIVERSA  C1+  COHDRT)  T  ^  13  CROP  1-5..  1-0 1  itn  0.5  0-0 AU  SE  1979 • A T E  CC  NO  DE  66 •EJNGITY C F P A R A L E P T O R - L S I A  SP-A  GOO-  1979 •ATE  S T A N D I N G CROP C F PARALEP1 G P K . E B I A 10.  9.  T  1  1979  •ATE:  SP-A  DENSITY DF GLDSSOSDMA PENITUM 100 •  JM  JU  AU  SE  1979 •ATE  DC  NO  DE  68  Figure  11. Mean d e n s i t i e s and'standing crops of N. c i n c t i p e s , C. sp_.A and P. d e b i l i s i n the c o n t r o l (xx) and experimental T ± - * ) stream s e c t i o n s . Vertical l i n e s represent 1 SE. C u t t h r o a t t r o u t p l a c e d i n t o the experimental stream s e c t i o n i n mid-August, (next 3 pages)  1379  •ATE  70  DENSITY OF CINYLMJ_A SP-A 100-  2  1379  DATE  5TANDING CROP CF CINYGMJLA SP-A 4-0  2  3-5 . .  JN  JU  All  SE 1979  DATE  DC  NO  OE  STANDING L-T?DP CF PARALEPTOPHLEBIA DEBILIS T  10. 3-  1  1  JU  1  AU  1  SE •ATE  oc  1  1  NO  OE  72  Figure  12. Mean d e n s i t i e s and standing crops of H. k o e b e l e i and C. S J D . B i n the c o n t r o l (x-x) and experimental (>-A ) stream s e c t i o n s . V e r t i c a l l i n e s represent 1 SE. Cutthroat t r o u t p l a c e d i n t o the experimental stream s e c t i o n i n mid-August, (next 2 pages)  DENSITY DF CINYGMULA SP-B 100'  DATE  STANDING CROP CF CINYQAJLA SP-B 1-0  DATE  74  75  Table 8.  Mean number and dry weight of Nemoura c i n c t i p e s , P a r a l e p t o p h l e b i a d e b i l i s and Cinygmula sp A per t r o u t stomach. Stomach contents were removed with a stomach pump 2-3 hr a f t e r s u n r i s e on each date.  mean number per stomach  Date  September 1 1 September 25 October 11 October 30 November 20  mean dry weight per stomach  3 0 0 8 1 0 1 2,3 2 ,4  0.73 0.26 0.50 1 .83 0.53  c i n c t i p e s , were not s i g n i f i c a n t l y stream  sections.  While  c i n c t i p e s were not stream  sections,  significantly section  the  different  mean  significantly  (P>0.05)  standing different  between  crops of Nemoura (P>0.05)  between  the mean d e n s i t i e s of Nemoura c i n c t i p e s were  higher  (P<0.05)  in  the  experimental  stream  ( F i g u r e 11).  The section  introduction had  little  californica,  of  trout  effect  population  densities  and  not s i g n i f i c a n t l y d i f f e r e n t The  on  Paraleptophlebia  0+ or 1+ c o h o r t s of T r i z n a k a  the  (mg)  trout  i n t o the experimental the  abundance  of  stream Nemoura  sp_.A, Glossosoma penitum or the  diversa  (Figure  10).  The  mean  standing crops of these s p e c i e s were (P>0.05) between stream s e c t i o n s .  i n t r o d u c t i o n however had a  negative  impact  on  p o p u l a t i o n dynamics of Nemoura c i n c t i p e s , P a r a l e p t o p h l e b i a  d e b i l i s and Cinygmula densities  and  SJD.A  (Figure  standing  crops  11). of  The these  mean  population  species  were  76  significantly  lower  (P<0.01) i n the experimental  stream s e c t i o n  compared to the c o n t r o l s e c t i o n . The d i f f e r e n c e i n mean d e n s i t y and  standing crop between stream s e c t i o n s f o r each  shown  in  Table  of  stream  each  sections  Together, stream  population from  between  mid-August  densities control  to  the  and  and end  standing  experimental of  November.  the d e n s i t y of the three s p e c i e s i n the experimental  section  standing  is  9. These values were c a l c u l a t e d by i n t e g r a t i n g  the d i f f e r e n c e i n the mean p o p u l a t i o n crops  species  crop  decreased decreased  270  individuals  per  53 mg dry weight per m  2  m  2  and  the  more than i n  the c o n t r o l s e c t i o n during, the experiment.  Table 9.  D i f f e r e n c e i n mean d e n s i t y and standing crop of N. c i n c t i p e s , P. d e b i l i s and C. sp.A between stream s e c t i o n s during the experiment  Density (no./sq. m) Nemoura cinctipes  Standing Crop (mg dry-wt/sq. m)  142  12.8  Paraleptophlebia debilis  98  24.2  Cinygmula sp.A  30  16.0  Finally, the  the t r o u t i n t r o d u c t i o n had a p o s i t i v e  p o p u l a t i o n dynamics of H e t e r l i m n i u s  effect  on  koebelei and Cinygmula  77  sjo.B (Figure 12). The mean p o p u l a t i o n crops  of  Heterlimnius  (P<0.001)  in  the  densities  of  Cinygmula  (P<0.05) i n standing  the  crops  koebelei  experimental sjo.B  experimental  densities  were  standing  significantly  stream were  and  section;  higher  the  also s i g n i f i c a n t l y  stream  section  but  were not s i g n i f i c a n t l y d i f f e r e n t  mean higher  the  mean  (0.06>P>0.05)  between stream s e c t i o n s .  Insect Product ion The  trout  production  of  each l o t i c between  i n t r o d u c t i o n had no  measurable  effect  on  the  any i n s e c t p o p u l a t i o n . Production estimates f o r  s p e c i e s were not  stream  sections  significantly  different  (P>0.05)  (Table 10). Production estimates f o r  H e t e r l i m n i u s k o e b e l e i c o u l d not be c a l c u l a t e d  as  the  cohorts  c o u l d not be d i s t i n g u i s h e d .  Drift More  than  80%  of  the  collected  i n the f i r s t  sunrise),  indicating  drifters.  Small i n d i v i d u a l s  mm)  of each s p e c i e s  experiment. drift (Table  As  i n d i v i d u a l s of each s p e c i e s were  2 hours of d r i f t that  were  these  sampling  species  in  the  they  nocturnal  l e s s than  drift  during  these i n d i v i d u a l s were underrepresented  samples and were g e n e r a l l y not preyed 7),  were  (head capsule width  present  (3-1 hr before  were  on  by  the  0.48 the  i n the trout  removed from the data before the d r i f t  r a t e s of each s p e c i e s were compared  between  stream  sections.  78  Table  10.  Estimates of production (mg dry-wt. / sq. m) of l o t i c s p e c i e s from August to December, 1979 in the c o n t r o l and experimental stream s e c t i o n s of Spring Creek. UR = upstream r i f f l e ; P = p o o l ; DR = downstream r i f f l e .  Control  Nemoura c inctipes californica Triznaka diversa 0+ cohort 1+ cohort Paraleptophlebia sp. A debilis Cinygmula sp. A sp. B Glossosoma penitum  Variation  in  discharge the d r i f t the  stream five,  rate  P  DR  UR  P  DR  1 70 5  80 4  204 <2  1 60 3  38 10  146 6  <2 32  <2 32  <2 24  <2 28  <2 38  <2 36  370 208  266 1 58  316 1 96  268 192  250 1 24  348 1 20  54 13  68 4  90 8  54 4  48 5  54 10  10  12  12  12  16  12  1  r a t e s observed for each species  partially  due  of the stream  to  sections  because at l e a s t on one  was  Nemoura between  in  the only  between  sampling date in r a t e between  the  zero which reduced the sample s i z e below  the minimum sample s i z e necessary  (P>0.05)  variation  during  (Figure 13). U n f o r t u n a t e l y ,  s p e c i e s the d i f f e r e n c e i n the d r i f t  sections  r a t e of  the  r a t e s of Nemoura c i n c t i p e s could be compared  stream  the other  UR  the d r i f t  the experiment was  Experimental  c i n c t ipes  was  not  stream s e c t i o n s . The  f o r the t e s t . The significantly  drift  different  t r o u t i n t r o d u c t i o n thus  79  had  no observable e f f e c t on the d r i f t  (head capsule (Figure  13).  width The  greater relatively  than low  rate of l a r g e i n d i v i d u a l s  0.48  mm)  drift  r a t e of these  though, made the d e t e c t i o n of a d i f f e r e n c e  of  any  difficult.  species species  80  Figure  13. T o t a l number of i n d i v i d u a l s d r i f t i n g from the c o n t r o l and experimental stream s e c t i o n s . Shaded histograms represent d r i f t from the c o n t r o l stream section. D r i f t was sampled f o r 5 hours beginning 3 hours before s u n r i s e on each date. Stream d i s c h a r g e on each date was 4.2, 51.5, 11.6, 9.8, 117.7, and 55.4 1/sec respectively, (next 3 pages)  ^£M•JRA  81  CALIFCRSIICA  25.  B z n If]  33.  15- 1  i  i i i i i i i i i i i i i i i i i  NEM3JRA CINCTIFE5  t  B  ao.|  z Lfl  H >  15-  io- J,  ^—H-  TRIZNAKA  DIVERSA  25.  1  20-  1  15-  I  10. I  I  AUG  I  I  I  I  I  SEPT  11  I  I  I  I  SEPT 25  |  [  |  OCT  •ATE  11  1 |  i  OCT 30  FT1 NOV 20  i  NOo *  INDIVIDUALS IN DRIFT ^ •  S  K •  S •  Q «  i .  NO- INOIVIUDUALS IN DRIFT o  '«  «  •  8 •  K •  8 «  111 .  NO- INDIVIDUALS IN DRIFT oi  o •  ' B •  K •  S »  W .  .  03  ro  NO-  ND« INDIVIDUALS IN DRIFT  o  w  6  K  S  (H  4  1  1  1  1  1  o • 4  INDIVIDUALS IN DRIFT  u,  S  E  8  N  1  1  1  1  1  03 CO  84  DISCUSSION  E f f e c t of Trout  Predation  S e l e c t i v e predation important  component  invertebrates  of  (Northcote  on the Abundance of L o t i c by the  fish  has  been  population  et a l . 1978;  Populations  shown  to  be  dynamics  of  lentic  H a l l et a l .  1970;  1966). While s t u d i e s have i n d i c a t e d stream-dwelling selective  predators  (Elliott  none of these have considered lotic  1967;  Griffith  of  this  study  feeding a c t i v i t y , can a f f e c t populations.  The  experimental  predation  on  density  suggest that t r o u t , through t h e i r the  abundance  and  standing  the  and  trout  were introduced  50%  of  the  predation  the  crop  of  insect Nemoura  Cinygmula sjo.A  in  the  (Figure 11). At the s t a r t of individuals  individuals  of  as prey  for  found  in  the  by  debilis  a s p e c i e s to be v u l n e r a b l e  to  individual  the t r o u t stomach contents  September,  i n d i v i d u a l s of these  Cinygmula  I  While i n d i v i d u a l s of Nemoura c i n c t 1 p e s were not until  of  trout.  i f they were l a r g e r than the s m a l l e s t  species  predation  lotic  i n d i v i d u a l s of P a r a l e p t o p h l e b i a  were l a r g e enough to be c o n s i d e r e d considered  of  stream s e c t i o n decreased, compared to the c o n t r o l ,  the experiment more than 90% of the  that  t r o u t to be A l l e n 1981),  the e f f e c t of t h i s  c i n c t ipes, P a r a l e p t o p h l e b i a d e b i l i s and  sjo.A  Macan  populations. Results  after  1974;  an  the end  three p o p u l a t i o n s  had  of  (Table 8).  vulnerable  to  of the experiment a l l been  vulnerable  to  predation. The  drift  data  indicated  that  l a r g e i n d i v i d u a l s (head  85  capsule width greater  than  0.48  mm)  of  Nemoura  cinctipes,  P a r a l e p t o p h l e b i a d e b i l i s and Cinygmula sp_.A were present drift. had the  In f a c t , P a r a l e p t o p h l e b i a d e b i l i s and Nemoura c i n c t i p e s  the highest d r i f t species  (Griffith the  As  cutthroat  would  species  was  not  measurably  observed  (Wilcoxon  without  Recruitment  Thus  young  loss  of  the  individuals  compensated by the recruitment  in  the  diet  density  and  standing  crop  sections  during  of  77% these  of  each  experiment to  (Figures  predation  these  not  be  individuals. species  74% of the observed  were  of  the  three  observed species  difference in  difference between  i n the d e n s i t y  prey p o p u l a t i o n s  i n mean  the  the experiment. Thus t r o u t p r e d a t i o n  of  from  2,4,5).  could  t h a t these three  was a major cause of the decrease crop  individuals  of the t r o u t . Trout were estimated to  have consumed approximately mean  large  species.  of new  Stomach a n a l y s i s suggested important  section  i n t o each of these p o p u l a t i o n s had  before the s t a r t of  the  stream  drift  p a i r e d sample t e s t , w=1; P<0.05), which  differentiating of  between  r e d u c t i o n i n the combined  that the t r o u t were removing  the d r i f t  in  the d r i f t  different  rate of these three s p e c i e s i n the experimental  stopped  of  t r o u t are d r i f t - f e e d e r s  be a v a i l a b l e to the them. Although  sections, a significant  suggests  hours)  1974; Brocksen et a l . 1968), only s p e c i e s present  drift  stream  r a t e s (number c o l l e c t e d per 5  examined.  rate of each  was  i n the  and  stream probably  standing  i n the experimental  stream s e c t i o n . The  t r o u t i n t r o d u c t i o n had l i t t l e  affect  on  the  density  86  and  standing  californica, winter  crop  the  autumn-hatching cohort  the 0 + and 1+ c o h o r t s  cohort  of  Triznaka  relatively  diversa,  the  stream s e c t i o n (Figure 1 0 ) . I n d i v i d u a l s  c a l i f o r n i c a and the 0 + cohort  Nemoura  of Nemoura  of Glossosoma penitum and P a r a l e p t o p h l e b i a sp.A  in the experimental  to  of  of T r i z n a k a d i v e r s a were  small throughout the experiment and  predation.  Stomach  analysis  of  confirmed  not  vulnerable  that these  species  were not part of the d i e t of the t r o u t . I n d i v i d u a l s of Glossosoma penitum were not predation  until  vulnerable  to  October and at the end of the experiment  less  than 5 0 % of the p o p u l a t i o n was l a r g e enough to be considered as prey,  9 0 % of the i n d i v i d u a l s  whereas approximately  cohort  of  Triznaka  diversa  throughout the experiment. though  were  not  were  vulnerable  Individuals  available  predation populations  (Figure  13).  Only  when  and i n d i v i d u a l s of both s p e c i e s found i n the  stomach contents. Individuals  of  Paraleptophlebia  v u l n e r a b l e to p r e d a t i o n of  these  1+  was high, were i n d i v i d u a l s of T r i z n a k a d i v e r s a  found i n the d r i f t trout  to  the  to the t r o u t as l a r g e i n d i v i d u a l s  were g e n e r a l l y absent from the d r i f t stream discharge  of  of  the  population  available  was  i n the d r i f t  experiment  (Figure  t r o u t during t h i s significant experiment.  13) time  i n l a t e September and by vulnerable. from  October  and (Table  were 6 ) .  marked  decrease  first  became  November 5 0 %  Large  individuals  until  the  present  e f f e c t on t h i s p o p u l a t i o n The  SJD.A  Trout  end  of  were the  i n the d i e t of the predation  had  no  u n t i l near the end of the  in  standing  crop  i n the  87  experimental trout,  stream s e c t i o n i n l a t e November suggests  by  the c l o s e of the experiment Trout  predation  and  also  standing  was  not  had  crop  of  little  present  direct  in  the  stomach  The  koebelei  i n the d i e t of the t r o u t , probably  contents  of  Cinygmula  sjo.B  the t r o u t only had  just  was  in late become  ( F i g u r e 5) and a v a i l a b l e (Figure 13).  d e n s i t y and standing crop of H e t e r l i m n i u s  Cinygmula  and  stream s e c t i o n . H e t e r l i m n i u s  November, when i n d i v i d u a l s of the p o p u l a t i o n vulnerable  at  impact on the  Heterlimnius  because of the small s i z e of the s p e c i e s . present  species  ( F i g u r e 10).  Cinygmula sjo.B i n the experimental koebelei  the  feeding on the l a r g e r i n s t a r s from t h i s p o p u l a t i o n ,  may have begun to reduce the standing crop of t h i s  density  that  sjo.B  in  the experimental  stream s e c t i o n i n c r e a s e d ,  compared to the c o n t r o l s e c t i o n , a f t e r the t r o u t Recruitment  of  approximately  new  individuals  k o e b e l e i and  into  each  at the same time as the s t a r t of  introduction.  p o p u l a t i o n began the  experiment  (Figures 5 and 7 ) . The i n c r e a s e i n d e n s i t y and standing crop of each  p o p u l a t i o n , due e i t h e r tp i n c r e a s e d s u r v i v o r s h i p of young  or to reduced of  e m i g r a t i o n , may have been a r e s u l t of the removal  competitors  Heter1imnius  by  the  koebelei,  trout  ( i e . competitive  Cinygmula  spp., Nemoura c i n c t i p e s and  P a r a l e p t o p h l e b i a d e b i l i s are a l l d e t r i t i v o r e s Chapman  and  Heterlimnius from  the  Demory  1963;  Merritt  k o e b e l e i and Cinygmula  reduced  abundance  of  release).  and sjo.B  (Brittain  Cummins may  1978). Thus  have  their potential  1973;  benefited  competitors:  Nemoura c i n c t i p e s , P a r a l e p t o p h l e b i a d e b i l i s and Cinygmula sp.A.  88  A l t e r n a t i v e l y , the i n c r e a s e in d e n s i t y and of to  Heterlimnius  k o e b e l e i and Cinygmula sp_.A may  g r e a t e r egg-deposition  Unfortunately,  was  a f f e c t e d the species. of  s p e c i e s were  deposition  The d r i f t  13).  of  probably  data  eggs  section.  deposited  before  the  This  the  adults  of  either  suggests  in  both  stream  sections  that d e p o s i t i o n of eggs f o r t h i s i n each stream s e c t i o n . can  affect  the  abundance  of  i n s e c t p o p u l a t i o n s . S e l e c t i v e p r e d a t i o n upon the l a r g e r instars  standing  of  crop  lotic  species  decreased  the  density  and  of prey p o p u l a t i o n s through i n c r e a s e d m o r t a l i t y  and may have i n d i r e c t l y of  by  k o e b e l e i was s i m i l a r  Trout p r e d a t i o n t h e r e f o r e  late  stream  i n d i c a t e d that the abundance of a d u l t s  s p e c i e s may have been s i m i l a r  stream  have been due  c o n s t r u c t e d . Thus the enclosure should not have  Heterlimnius  (Figure  i n the experimental  crop  I have no data on egg d e n s i t i e s of any s p e c i e s .  The eggs of both enclosure  standing  i n c r e a s e d the d e n s i t y and standing  crop  non-prey p o p u l a t i o n s through competitive r e l e a s e . S i z e - s e l e c t i v e p r e d a t i o n of stream-dwelling  demonstrated i n the l a b o r a t o r y occur drift switch  in  nature  (Allen  (Ringler  p r i m a r i l y on the b a s i s of s i z e then they would (Murdock  1969) from one prey  shown  from the passively  species to another  s p e c i e s i n the  drift  to  as the changed  the year. T h i s c o u l d account f o r the seasonal change i n  the d i e t of trout•observed 1972;  and  1981). If t r o u t s e l e c t prey  r e l a t i v e abundance of l a r g e prey during  1979)  t r o u t has been  Allen  1981).  Thus  abundance of numerous l o t i c  here and reported by others trout  (Narver  c o u l d p o t e n t i a l l y a f f e c t the  p o p u l a t i o n s throughout the year.  89  H a l l et a l . (1970) found that fewer  emergent  ponds  with  fish"  i n s e c t s than ponds without f i s h . Whether t r o u t  p r e d a t i o n a c t u a l l y decreased the number of emerging Cinygmula  sjo.A, which emerged from the stream  Paraleptophlebia  debilis,  which  and the end of the experiment, from  each  produced  stream  section  is  was  adults  of  i n mid-October  or  emerged between l a t e unknown not  as  emergence  collected.  the  presence of emerging  data  However  decreased d e n s i t y of nymphs i n the experimental stream and  October  the  section  subimagos of both s p e c i e s i n the  stomach contents of the t r o u t suggests that t r o u t p r e d a t i o n may have decreased the number of emerging This  suggests  a d u l t s of  both  that t r o u t p r e d a t i o n c o u l d reduce the number of  eggs d e p o s i t e d by a s p e c i e s , p o t e n t i a l l y reducing of  species.  the  density  that  stream-  the f o l l o w i n g g e n e r a t i o n .  Trout Predation and Insect P r o d u c t i o n Allen  (1951)  and  Horton  (1961)  reported  d w e l l i n g t r o u t consumed 9 to 150 times the mean of  their  prey.  As  the  annual  standing turnover  crop ratio  (production/biomass) of most b e n t h i c i n v e r t e b r a t e s l i e s between 3 and 7 (Waters  1977),  these e s t i m a t e s of prey  consumption  to  prey abundance are c l e a r l y wrong. My  results  show  that  t r o u t consumed only 0.4  mean standing crop or 9 - 10% of Nemoura  combined  production  c i n c t i p e s , P a r a l e p t o p h l e b i a d e b i l i s and Cinygmula  d u r i n g the experiment. The small  the  times the  fraction  of  the  trout  therefore  consumed  of sp.A  only  a  t o t a l p r o d u c t i o n of t h e i r prey i n the  90  experimental stream s e c t i o n . The  l o s s of weight by  suggests meet  that  the  the  the  available  minimum  trout food  maintenance  Although food was apparently  during  supply  the  experiment  was i n s u f f i c i e n t to  requirements  of  the  trout.  abundant, i t appears that the food  was not a v a i l a b l e to the t r o u t . As  noted  previously,  a v a i l a b l e to the c u t t h r o a t feeders. will  Thus  any  drifting  trout since  the  discharge  1969;  Elliott  study  were  discharge  the  drift-  rate of prey  drift  1967). The d r i f t observed  (Figure  rate  of  invertebrates  is  to  r a t e of  prey  species  in  this  be p o s i t i v e l y c o r r e l a t e d with stream  13). The low stream discharge  during most  of  study t h e r e f o r e , may have reduced the a v a i l a b i l i t y of prey  dependent  upon  the d r i f t  r a t e of  the  rate of prey  trout  rate  were  been  to  discharge  reported  maintenance  requirements.  and  to be both s u f f i c i e n t  Hynes 1969; Warren et a l . 1964) and  Drift  measurements were studies.  made,  effected  drift well rates  (Mundie 1974; Bishop  insufficient  (Jenkins  a l . 1970; A l l e n 1981) to support the t r o u t p o p u l a t i o n s streams. P o s s i b l y , the discharge  be  during  high, were the t r o u t able to feed s u f f i c i e n t l y  to meet t h e i r minimum have  seemed  (Figure 9 ) . Only  the l a s t h a l f of October when the stream  in  are  (Pearson and Kramer 1972; Chapman and Bjourn  to the t r o u t as the feeding  et  trout  a f f e c t the a v a i l a b i l i t y of prey to the t r o u t . An important  stream  and  i n v e r t e b r a t e s were  f a c t o r that e f f e c t s the d r i f t  f a c t o r found to e f f e c t  the  only  found  r a t e at the time the d r i f t the  conclusions  of  these  91  The  behavior  of the prey i s another f a c t o r that may have  reduced t h e i r a v a i l a b i l i t y prey  species  reported  to the t r o u t . Large i n s t a r s  here  drifted  primarily  tendency f o r stream i n v e r t e b r a t e s to d r i f t increase (Allen  in  size  1978;  suggested  has  Steine  that  been 1972;  this  s i n c e the r i s k of  Thus,  drifting  availability  at  was  a  predator  increases  estimated  invertebrates true  and  that  only  10-20%  to  the  present  If t h i s  the a v a i l a b l e food supply  9-10%  production  the  production  of  c inct ipes,  Paraleptophlebia  lower i n control  the  each  (Table  significant  their  the  experimental  section  statistically  of  of 3  stream but  (P>0.05).  since  main  main  debilis  10),  with  size.  reduce t h e i r  Hynes  is  (1969) of l o t i c  generally  study then the t r o u t were  heavily grazing of  (1978) avoidance  of the production  i s a v a i l a b l e i n the d r i f t .  applies  they  predators.  Waters and Hokenstrom (1980) and Bishop and have  Allen  l a r g e i n s t a r s may  to v i s u a l l y - f e e d i n g  night. A  n o c t u r n a l l y as  1980).  predation  night,  at  the  i n a number of s t u d i e s  Fjellheim  tendency  adaptation by  reported  of  prey and  section  they  consumed  prey s p e c i e s . Mean species,  Nemoura  Cinygmula sjo.A, compared  to  was the  these d i f f e r e n c e s were not  92  P r e d a t i o n and Community S t r u c t u r e Connell  (1975) suggested  importance  in  intertidal  and  experiments  determining lentic  and  that  predation  community  ecosystems,  comparisons  of  i s of  structure. utilizing  primary  Studies  of  manipulation  n a t u r a l communities with and  without  the presence of c e r t a i n s p e c i e s , support t h i s view (see  Connell  1975 f o r examples).  insect  communities  While  with and without  t r o u t p r e d a t i o n may be important communities  (Allan  experiments  have  studies  in  comparing  stream  t r o u t have suggested structuring  lotic  that  insect  1975; S t r a s k r a b a 1965), stream manipulation not  been  conducted  to  verify  these  observations. Results important  in  communities. Paine  this  study  determining Trout  suggest  the  appear  that t r o u t p r e d a t i o n i s  structure  to  of  lotic  i n r o c k y - i n t e r t i d a l communities  in  lentic  communities  (Hall  T r o u t , by feeding on the l a r g e r drift,  reduced  the  of  large  available  investigation (sensu spec i e s .  Paine  interactions  i s c l e a r l y needed 1980)  of  as  i n the  individuals  the complementary response  t r o u t p r e d a t i o n may have suppressed competitive  way  et a l . 1970; Macan 1966).  smaller s p e c i e s ( H e t e r l i m n i u s k o e b e l e i , Cinygmula  strong  (sensu  (Paine 1966, 1974) and  individuals  abundance  benthos which may have caused  insect  be "strong i n t e r a c t o r s "  1980) w i t h i n stream communities i n much the same  starfish fish  of  sjo.B) .  i n the of the Thus  the e x p r e s s i o n of otherwise between the s p e c i e s . F u r t h e r  to  competitive  establish linkages  the  "strength"  between  lotic  93  APPENDIX 1  Insect Density C o r r e c t i o n F a c t o r s Unfortunately, c o r r e c t i o n factors width  for  each  head-capsule  s i z e c l a s s could only be c a l c u l a t e d f o r three of the s i x  genera s i n c e small i n s t a r s of Cinygmula and Glossosoma were not present and  the  penitum  i n the benthos when the samples were c o l l e c t e d  number  of  individuals  of H e t e r l i m n i u s  koebelei  insufficient  to c a l c u l a t e r e l i a b l e values  Table  Number of i n d i v i d u a l s i n each i n s t a r of H e t e r l i m n i u s koebelei and Glossosoma penitum c o l l e c t e d i n each c o l l e c t i n g net of a double bag sampler from Spring Creek, March, 1980.  A1.1  Heterlimnius  koebelei:  C o l l e c t i n g Net 0.471 mm 0.116 mm total Glossosoma  Instar 2 3  4  5 3 8  2 0 2  1 0 1  1  Instar 2 3 . 4  5  -  -  1 1 0 1 1  penitum:  C o l l e c t i n g Net 0.471 mm 0.116 mm total  A linear head  (Table A1.1).  1  2 0 2  was  5 1 6  27 0 27  r e l a t i o n s h i p was assumed f o r each  genus  capsule width and the p r o p o r t i o n of i n d i v i d u a l s  between collected  94  in the 0.471 mm c o l l e c t i n g net ( F i g u r e A1.1). of  Nemoura  All  individuals  with a head capsule width equal to or g r e a t e r than  0.50 mm and a l l i n d i v i d u a l s of T. d i v e r s a and  Paraleptophlebia  with a head capsule width equal to or g r e a t e r than 0.54 mm were retained  in  the  0.471  mm  collecting  n e t . The abundance of  i n d i v i d u a l s of Nemoura with a head capsule width mm  and  the  abundance  Paraleptophlebia  Table A1.2.  with  of a  individuals  of  head capsule width  l e s s than  T. d i v e r s a  0.16 and  l e s s than 0.20 mm  Density c o r r e c t i o n f a c t o r s f o r each head-capsule width s i z e c l a s s of Nemoura, T r i z n a k a and Paraleptophlebia.  Taxa Size c l a s s (mm) 0.16 0.20 0.24 0.28 0.32 0.36 0.40 0.44 0.48 0.52  -  0.20 0.24 0.28 0.32 0.36 0.40 0.44 0.48 0.52  Nemoura  Triznaka  16.7 4.9 2.8 2.0 1 .5 1 .3 1. 1 1 .0 1 .0 1 .0  were not c o r r e c t e d . The d e n s i t y  Paraleptophlebia  30.0 6.3 3.4 2.4 1 .8 1 .5 1 .2 . 1 .0  correction  20.0 5.9 3.4 2.4 1 .9 1 .6 1 .3 1. 1 1 .0  factors  for  each  head capsule width s i z e c l a s s f o r each genus are given i n Table A1 .2.  95  F i g u r e A1.1. P r o p o r t i o n of i n d i v i d u a l s of Nemoura, T r i z n a k a and P a r a l e p t o p h l e b i a r e t a i n e d i n the 0.471 mm c o l l e c t i n g net of the double bag sampler. A l l i n d i v i d u a l s of Nemoura with a head-capsule width > 0.48 mm and a l l i n d i v i d u a l s of Triznaka and P a r a l e p t o p h l e b i a with a head-capsule width > 0.52 mm were r e t a i n e d i n the 0.471 mm c o l l e c t i n g net.  96 NEKOLRA  5  ,0.  B  °- S  0-1 . CO .  HEAD CAPSLLE WIDTH lO-CWIvM S I Z E CLASSES)  T R I Z N A K A  1  S W  1.0 0-S  I  0-7  2  3 °'  5  j  i  0,3  s *—  0-1  jij  0-0  HEAD CAPSULE WIDTH CO-CMMM S I Z E CLASSES)  PARALEPTOPHLEBIA  •S  i-o 0-9  3 Z B  °-  S  i 5 h-  0.1  ^  0-0  HEAD CAPSULE WIDTH CO-CWKW S I Z E CLASSES)  97  APPENDIX 2  R e l a t i o n s h i p between Head Width and Dry Weight of Aquatic Insects With the exception of H e t e r l i m n i u s k o e b e l e i , the slopes of the  functional  regressions  (P>0.05) between taxa  were  not s i g n i f i c a n t l y  (Table A2.1). I n d i v i d u a l s of H e t e r l i m n i u s  koebelei weighed s i g n i f i c a n t l y more then taxa  at  all  sizes.  koebelei l a r v a e was on the exoskeleton  Table A2.1.  different  The  probably  increased a result  of the l a r v a  individuals  weight  of  of mineral  of  other  Heterlimnius accumulations  (Brown 1970).  Values of the r e g r e s s i o n constants l o g a and b, with 95% confidence i n t e r v a l s , from f u n c t i o n a l r e g r e s s i o n s of dry weight (mg) on head-capsule width (mm). n i s the number of i n d i v i d u a l s ; r i s the c o r r e l a t i o n c o e f f i c i e n t . A l l correlation c o e f f i c i e n t s were s i g n i f i c a n t at 0.1% l e v e l .  Nemoura Tr iznaka Paraleptophlebia Cinygmula Glossosoma Heterlimnius  n  log a  b  23 19 20 16 16 13  -0. 35 -0. 31 -0. 35 -0. 72 0. 21 1 .09  2..76 2,.75 2..84 2,.69 2,.75 3,.92  95% CI 0. 19 0. 1 5 0. 1 7 0. 19 0. 26 0. 37  I  0..98 0..99 0..99 0..99 0..97 0..97  APPENDIX 3  Insect Taxa L i s t  f o r Spring Creek  Order  Family  Spec i e s  Stoneflies  Nemouridae  Nemoura  californica  N. c i n c t i p e s  Chloroper1idae  N.  oregonensis  N.  frigida  N.  producta  N.  cataractae  Sweltsa  coloradensis  Triznaka diversa Perlodidae  Skwala  parallel  Isoperla Leuctridae  Despaxia augusta Moselia  infuscata  Peltoperlidae  Yoraperla  Perlidae  Calineuria  brevis  Claassenia  Mayflies  Capni idae  Capnia  Pteronarcyidae  Pteronarcys  Leptophlebiidae  Paraleptophlebia  debil  Paraleptophlebia  sp A  Heptageniidae  Cinygmula  sp A  Cinygmula  sp B  Rhithrogena Epeorus Cinygma  Caddisflies  Baetidae  Baetis  (2 s p e c i e s )  Siphlonuridae  Ameletus  Ephemerellidae  Ephemerella  Glossosomatidae  Glossosoma  Hydropsychidae  Hydropsyche  Lepidostomatidae  Lepidostoma  Hydroptilidae  Hydroptila  (2 s p e c i e s )  penitum  Oxyethr i a Rhyacophilidae  Rhyacophila  Polycentropodidae  Polycentropus  Brachycentridae  Microsema  Philopotamidae  Wormaldia  Limnephi1idae  Neophylax Apatania Cryptochia Onocosmoecus Ecclisomyia  Beetles  Elmidae  Heterlimnius Narpus Lara  koebelei  100  101  LITERATURE CITED  A l l a n , J.D. 1975. 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