﻿MANUAL 
  OF 
  FISH-CULTURE. 
  73 
  

  

  same 
  State, 
  where 
  the 
  water 
  becomes 
  moderately 
  warm 
  in 
  summer 
  

   and 
  food 
  is 
  plentiful, 
  they 
  reach 
  12 
  or 
  13 
  pounds, 
  fish 
  of 
  this 
  size 
  being 
  

   from 
  25 
  to 
  28 
  inches 
  long'. 
  In 
  the 
  Au 
  Sable 
  River, 
  in 
  Michigan, 
  they 
  

   attain 
  a 
  weight 
  of 
  5 
  to 
  7 
  pounds. 
  In 
  their 
  native 
  streams 
  of 
  California 
  

   they 
  are 
  often 
  caught 
  ranging 
  from 
  3 
  to 
  10 
  pounds, 
  but 
  average 
  from 
  

   1 
  to 
  2 
  pounds. 
  The 
  largest 
  specimen 
  ever 
  produced 
  in 
  the 
  ponds 
  at 
  

   Wytheville, 
  and 
  fed 
  artificially, 
  weighed 
  Oi 
  pounds, 
  but 
  many 
  others 
  in 
  

   the 
  same 
  ponds 
  weigh 
  from 
  1 
  to 
  3 
  pounds. 
  

  

  The 
  average 
  growth 
  of 
  the 
  rainbow 
  trout 
  under 
  favorable 
  artificial 
  

   circumstances 
  is 
  as 
  follows: 
  One 
  year 
  old, 
  from 
  f 
  to 
  1 
  ounce; 
  2 
  years 
  

   old, 
  from 
  8 
  to 
  10 
  ounces;- 
  3 
  years 
  old, 
  from 
  1 
  to 
  2 
  pounds; 
  4 
  years 
  old, 
  

   from 
  2 
  to 
  3 
  pounds. 
  They 
  grow 
  until 
  they 
  are 
  8 
  or 
  10 
  years 
  old, 
  the 
  

   rate 
  diminishing 
  with 
  age. 
  Some 
  grow 
  much 
  faster 
  than 
  others 
  under 
  

   the 
  same 
  circumstances, 
  but 
  the 
  rate 
  of 
  growth 
  is 
  largely 
  a 
  question 
  of 
  

   food, 
  temperature 
  of 
  water, 
  and 
  extent 
  of 
  the 
  range. 
  In 
  water 
  at 
  60°, 
  

   with 
  plenty 
  of 
  food, 
  fish 
  1 
  or 
  2 
  years 
  old 
  will 
  double 
  their 
  size 
  several 
  

   times 
  in 
  a 
  single 
  season; 
  while 
  in 
  water 
  at 
  40°, 
  with 
  limited 
  food, 
  the 
  

   growth 
  is 
  scarcely 
  perceptible. 
  

  

  The 
  rainbow, 
  like 
  the 
  brook 
  trout, 
  will 
  live 
  in 
  water 
  with 
  a 
  compara- 
  

   tively 
  high 
  temperature 
  if 
  it 
  is 
  plentiful 
  and 
  running 
  with 
  a 
  strong 
  

   current, 
  but 
  sluggish 
  and 
  shallow 
  water, 
  even 
  with 
  a 
  temperature 
  of 
  

   70° 
  F., 
  is 
  dangerous 
  for 
  brook 
  trout. 
  Eainbow 
  trout 
  will 
  live 
  in 
  warmer 
  

   water 
  than 
  brook 
  trout, 
  and 
  are 
  found 
  in 
  swift, 
  rapid 
  streams 
  at 
  85° 
  F., 
  

   especially 
  where 
  there 
  is 
  some 
  shade, 
  but 
  in 
  ponds 
  that 
  temperature 
  is 
  

   dangerous 
  even 
  with 
  shade 
  and 
  a 
  good 
  current. 
  In 
  its 
  natural 
  condi- 
  

   tion 
  this 
  trout 
  is 
  usually 
  found 
  in 
  water 
  varying 
  from 
  38° 
  F. 
  in 
  winter 
  

   to 
  70° 
  F. 
  in 
  summer, 
  and 
  in 
  selecting 
  a 
  site 
  for 
  a 
  trout 
  hatchery 
  spring 
  

   water 
  with 
  a 
  temperature 
  of 
  42° 
  to 
  58° 
  is 
  required. 
  

  

  The 
  rainbow 
  trout 
  is 
  a 
  superior 
  game 
  fish, 
  a 
  vigorous 
  biter, 
  and 
  fights 
  

   bravely 
  for 
  liberty, 
  though 
  in 
  the 
  East 
  it 
  is 
  somewhat 
  inferior 
  to 
  the 
  

   brook 
  trout 
  in 
  these 
  respects. 
  

  

  SPAWNING-PONDS. 
  

  

  In 
  constructing 
  ponds, 
  one 
  of 
  the 
  first 
  considerations 
  is 
  to 
  place 
  the 
  

   fish 
  absolutely 
  under 
  the 
  control 
  of 
  the 
  fish-culturist, 
  that 
  he 
  may 
  be 
  

   able 
  to 
  handle 
  them 
  without 
  delay 
  or 
  inconvenience. 
  At 
  Wytheville 
  

   they 
  are 
  constructed 
  entirely 
  of 
  wood, 
  about 
  15 
  by 
  50 
  feet 
  and 
  3 
  to 
  3^ 
  

   feet 
  deep, 
  and 
  shaped 
  as 
  shown 
  in 
  plate 
  22, 
  and 
  have 
  been 
  found 
  very 
  

   satisfactory. 
  Excellent 
  water 
  circulation 
  is 
  obtained 
  in 
  all 
  parts, 
  and 
  

   there 
  are 
  no 
  corners 
  for 
  refuse 
  to 
  lodge 
  in. 
  The 
  bottom 
  of 
  the 
  pond 
  is 
  

   built 
  with 
  a 
  gradual 
  elevation, 
  in 
  the 
  direction 
  of 
  the 
  upper 
  end, 
  of 
  2 
  

   inches 
  in 
  the 
  entire 
  length 
  of 
  the 
  pond. 
  This 
  makes 
  it 
  j)ractically 
  self- 
  

   cleaning; 
  nearly 
  all 
  of 
  the 
  foul 
  matter 
  will 
  pass 
  oft' 
  and 
  any 
  remainder 
  

   can 
  be 
  disposed 
  of 
  by 
  drawing 
  the 
  water 
  down 
  low 
  for 
  a 
  short 
  period 
  

   and 
  then 
  flushing 
  the 
  pond 
  with 
  fresh 
  water. 
  This 
  method 
  obviates 
  the 
  

   necessity 
  of 
  handling 
  the 
  fish, 
  which 
  is 
  very 
  important, 
  especially 
  when 
  

   near 
  the 
  spawning 
  time. 
  

  

  