﻿REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  CXXIII 
  

  

  animals 
  suitable 
  for 
  bass 
  food, 
  and 
  also 
  in 
  small 
  vegetable 
  and 
  animal 
  

   organisms 
  on 
  wliicli 
  the 
  fish 
  food 
  subsists. 
  The 
  more 
  abundant 
  forms 
  

   included 
  species 
  of 
  Cyclops^ 
  Baphnia, 
  Alona, 
  Scapholeheris, 
  Amoeba^ 
  

   Hydra, 
  Bothrimonus, 
  several 
  genera 
  of 
  infusoria, 
  nematodes, 
  Volvox, 
  

   Spirogyra, 
  Micr 
  aster 
  ias, 
  Euglena, 
  and 
  some 
  other 
  alga». 
  The 
  stomach 
  

   contents 
  of 
  the 
  young 
  bass 
  from 
  the 
  same 
  ponds 
  showed 
  that 
  cladocera 
  

   were 
  being 
  principally 
  consumed. 
  One 
  small-mouth 
  bass 
  4 
  days 
  old 
  

   contained 
  10 
  specimens 
  of 
  Cyclops, 
  Daphnia, 
  and 
  other 
  cladocera; 
  one 
  2 
  

   days 
  old 
  had 
  8 
  specimens 
  of 
  the 
  same 
  animals 
  ; 
  three 
  large-mouth 
  bass 
  

   a 
  few 
  days 
  old 
  had 
  been 
  subsisting 
  on 
  Daphnia. 
  

  

  The 
  possible 
  use 
  of 
  finely 
  powdered 
  cereals 
  as 
  food 
  for 
  young 
  white- 
  

   fish 
  has 
  from 
  time 
  to 
  time 
  been 
  suggested. 
  At 
  Putin 
  Bay, 
  Ohio, 
  station 
  

   in 
  1897 
  Superintendent 
  Stranahan 
  fed 
  wheat 
  shorts 
  to 
  about 
  2,000,000 
  

   whitetish 
  fry 
  contained 
  in 
  tanks. 
  They 
  at 
  first 
  appeared 
  to 
  thrive, 
  but 
  

   by 
  May 
  7 
  had 
  all 
  died, 
  and 
  specimens 
  were 
  forwarded 
  to 
  Washington 
  

   for 
  examination. 
  In 
  nearly 
  every 
  case 
  the 
  alimentary 
  tract 
  was 
  well 
  

   filled 
  with 
  granules 
  of 
  wheat 
  starch, 
  and 
  it 
  was 
  apparent 
  that 
  the 
  fry 
  

   readily 
  took 
  the 
  food. 
  The 
  nutritive 
  value 
  to 
  fish, 
  however, 
  of 
  such 
  a 
  

   substance 
  is 
  doubtful, 
  and 
  an 
  examination 
  of 
  the 
  condition 
  of 
  the 
  gran- 
  

   ules 
  in 
  the 
  hind 
  gut, 
  as 
  compared 
  with 
  those 
  in 
  the 
  anterior 
  part 
  of 
  the 
  

   alimentary 
  canal, 
  showed 
  no 
  evidence 
  that 
  they 
  had 
  undergone 
  diges- 
  

   tion 
  to 
  the 
  slightest 
  degree. 
  The 
  assimilative 
  jiowers 
  of 
  the 
  very 
  short 
  

   intestinal 
  canal 
  of 
  the 
  whitefish 
  fry 
  are 
  not 
  sufficiently 
  active 
  to 
  utilize 
  

   raw 
  vegetable 
  material 
  of 
  this 
  nature. 
  It 
  is 
  possible, 
  however, 
  that 
  by 
  

   cooking 
  the 
  shorts 
  and 
  diluting 
  them 
  with 
  other 
  food 
  they 
  may 
  prove 
  

   of 
  service 
  in 
  rearing 
  young 
  whitefish. 
  

  

  Study 
  of 
  rainhoiv 
  trout 
  and 
  steelhead 
  trout 
  in 
  aquaria. 
  — 
  In 
  the 
  month 
  

   of 
  April, 
  1897, 
  the 
  aquaria 
  at 
  Washington 
  contained 
  a 
  large 
  number 
  of 
  

   artificially 
  hatched 
  rainbow 
  trout 
  [Salmo 
  irideus) 
  and 
  steelhead 
  trout 
  

   {Salmo 
  gairdneri). 
  The 
  fish 
  were 
  4 
  inches 
  in 
  length 
  and 
  12 
  months 
  old, 
  

   the 
  rainbow 
  trout 
  having 
  been 
  hatched 
  from 
  eggs 
  of 
  domesticated 
  fish 
  

   at 
  the 
  Wytheville 
  (Va.) 
  station, 
  and 
  the 
  steelheads 
  from 
  eggs 
  of 
  wild 
  

   fish 
  obtained 
  at 
  Fort 
  Gaston 
  (Cal.) 
  station. 
  Comparing 
  the 
  fish 
  as 
  

   they 
  appeared 
  in 
  the 
  aquaria, 
  the 
  rainbow 
  trout 
  were 
  relatively 
  shorter 
  

   and 
  deeper, 
  darker 
  in 
  coloration, 
  with 
  more 
  numerous 
  spots, 
  especially 
  

   on 
  the 
  caudal 
  fin 
  ; 
  the 
  under 
  parts 
  were 
  darker, 
  the 
  middle 
  of 
  the 
  side 
  

   more 
  rosy; 
  the 
  pectoral, 
  ventral, 
  and 
  anal 
  fins 
  were 
  darker, 
  the 
  white 
  

   edges 
  being 
  made 
  prominent 
  by 
  contrast. 
  The 
  rainbow 
  trout 
  have 
  the 
  

   spots 
  on 
  the 
  back 
  larger 
  and 
  more 
  numerous. 
  In 
  the 
  steelhead 
  the 
  

   spots 
  on 
  the 
  top 
  of 
  head 
  are 
  very 
  much 
  smaller 
  and 
  more 
  numerous. 
  

   Comparative 
  measurements 
  showed 
  no 
  differences 
  except 
  that 
  the 
  

   rainbow 
  is 
  somewhat 
  deeper 
  than 
  the 
  steelhead 
  (depth 
  4|^ 
  in 
  rainbow, 
  

   4i 
  in 
  steelhead). 
  The 
  scales 
  in 
  the 
  lateral 
  line 
  are 
  rather 
  larger 
  in 
  the 
  

   rainbow 
  and 
  the 
  origins 
  of 
  the 
  dorsal 
  and 
  anal 
  fins 
  are 
  more 
  anterior. 
  

  

  Fish 
  parasites 
  and 
  diseases. 
  — 
  About 
  May 
  15, 
  1897, 
  a 
  very 
  destructive 
  

   disease 
  appeared 
  among 
  fresh-water 
  fishes 
  in 
  the 
  aquaria 
  at 
  Washing- 
  

   ton. 
  The 
  onset 
  of 
  the 
  attack 
  was 
  very 
  rapid, 
  and 
  in 
  a 
  short 
  time 
  spread 
  

  

  