﻿MANUAL 
  OF 
  FISH-CULTURE. 
  201 
  

  

  but 
  they 
  can 
  rarely 
  be 
  induced 
  to 
  eat. 
  A 
  certain 
  percentage 
  of 
  the 
  

   penned 
  fish 
  die 
  and 
  are 
  removed 
  at 
  once 
  from 
  the 
  cars. 
  The 
  develop- 
  

   ment 
  of 
  the 
  sexual 
  organs 
  is 
  noted 
  when 
  the 
  dead 
  fish 
  are 
  takeu 
  out. 
  

   Fish 
  about 
  ready 
  to 
  spawn 
  are 
  placed 
  in 
  a 
  separate 
  car 
  aud 
  carefully 
  

   watched. 
  They 
  are 
  examined 
  two 
  or 
  three 
  times 
  a 
  week 
  and 
  any 
  ripe 
  

   eggs 
  are 
  taken. 
  

  

  In 
  taking 
  and 
  fertilizing 
  the 
  eggs 
  of 
  brood 
  cod 
  the 
  same 
  general 
  

   methods 
  are 
  followed 
  as 
  are 
  adopted 
  on 
  the 
  fishing 
  vessels 
  in 
  Ipswich 
  

   Bay. 
  The 
  spawn-taker 
  grasps 
  the 
  ripe 
  fish 
  near 
  the 
  tail 
  with 
  his 
  left 
  

   hand 
  and 
  holds 
  the 
  fish's 
  head 
  cither 
  between 
  his 
  body 
  and 
  left 
  arm 
  or 
  

   between 
  his 
  thighs, 
  using 
  his 
  right 
  hand 
  to 
  strip 
  the 
  fish. 
  The 
  eggs 
  

   are 
  usually 
  taken 
  in 
  a 
  bucket. 
  Both 
  the 
  dry 
  and 
  wet 
  methods 
  of 
  fertil- 
  

   ization 
  are 
  used 
  at 
  Woods 
  Hole. 
  Usually 
  about 
  80 
  per 
  cent 
  of 
  the 
  eggs 
  

   taken 
  are 
  fertilized. 
  Unlike 
  many 
  other 
  fishes 
  artificially 
  propagated, 
  

   the 
  cod 
  does 
  not 
  yield 
  all 
  of 
  its 
  eggs 
  at 
  one 
  time. 
  After 
  expressing 
  all 
  

   the 
  eggs 
  possible 
  from 
  a 
  given 
  fish, 
  it 
  is 
  retuined 
  to 
  the 
  live-car, 
  and 
  in 
  

   a 
  few 
  days 
  will 
  have 
  nmtured 
  more 
  eggs, 
  which 
  are 
  then 
  taken. 
  When 
  

   the 
  ovaries 
  have 
  discharged 
  all 
  their 
  eggs, 
  the 
  fish 
  is 
  released. 
  

  

  In 
  recent 
  years 
  from 
  1,600 
  to 
  9,000 
  cod 
  have 
  been 
  penned 
  annually 
  

   in 
  the 
  protected 
  basin 
  at 
  Woods 
  Hole. 
  Only 
  from 
  one 
  ninth 
  to 
  one- 
  

   third 
  of 
  these, 
  according 
  to 
  the 
  season, 
  yield 
  good 
  eggs. 
  

  

  CHARACTERISTICS 
  OF 
  COD 
  EGGS. 
  

  

  Cod 
  eggs 
  are 
  nearly 
  transparent, 
  and 
  float 
  at 
  the 
  surface 
  of 
  the 
  water 
  

   when 
  first 
  taken. 
  They 
  vary 
  in 
  color 
  from 
  a 
  pale 
  green 
  to 
  a 
  deep 
  red, 
  

   those 
  having 
  the 
  green 
  color 
  being 
  the 
  best. 
  Good 
  results 
  are 
  seldom 
  

   obtained 
  from 
  the 
  red 
  eggs, 
  aud 
  those 
  of 
  a 
  deep 
  red 
  color 
  almost 
  invari- 
  

   ably 
  die 
  in 
  three 
  or 
  four 
  days 
  after 
  being 
  received. 
  Unless 
  the 
  density" 
  

   of 
  the 
  water 
  is 
  low, 
  the 
  eggs 
  normally 
  float 
  during 
  the 
  entire 
  hatching 
  

   period. 
  However, 
  it 
  frequently 
  happens 
  that, 
  owing 
  probably 
  to 
  the 
  

   accumulation 
  of 
  sediment, 
  the 
  eggs 
  gradually 
  sink 
  duringthelast 
  third 
  

   of 
  the 
  incubation 
  period, 
  and 
  finally 
  mass 
  together 
  on 
  the 
  bottom 
  jf 
  the 
  

   hatching-box; 
  here 
  they 
  would 
  quickly 
  smother 
  but 
  for 
  the 
  current. 
  

  

  Floating 
  eggs 
  are 
  not 
  necessarily 
  good 
  ones, 
  for 
  mifertilized 
  and 
  

   injured 
  eggs 
  usually 
  float 
  18 
  to 
  36 
  hours 
  before 
  going 
  to 
  the 
  bottom. 
  

   Unfertilized 
  eggs 
  may 
  be 
  readily 
  detected, 
  as 
  they 
  have 
  no 
  disc 
  which 
  

   marks 
  fertilization 
  and 
  have 
  a 
  milky 
  appearance. 
  Th'e 
  dead 
  eggs 
  

   quickly 
  sink, 
  and 
  are 
  easily 
  distinguished 
  from 
  the 
  sound 
  eg^s 
  by 
  a 
  

   white 
  spot 
  in 
  the 
  center. 
  

  

  Figgs 
  received 
  at 
  the 
  hatchery 
  are 
  transferred 
  from 
  the 
  vessels 
  in 
  

   which 
  they 
  came 
  to 
  Chester 
  jars 
  partly 
  filled 
  with 
  water, 
  and 
  in 
  10 
  

   or 
  15 
  minutes 
  they 
  rise 
  to 
  the 
  surface 
  in 
  a 
  dense 
  mass. 
  Tl>e 
  eggs 
  are 
  

   put 
  in 
  each 
  jar 
  to 
  the 
  depth 
  of 
  an 
  iuch, 
  a 
  (juantity 
  representing 
  approx- 
  

   imately 
  379,000 
  eggs. 
  If 
  the 
  hatchery 
  is 
  full, 
  abour. 
  a 
  filth 
  more 
  eggs 
  

   may 
  be 
  put 
  in 
  a 
  box, 
  the 
  raa.ximum 
  number 
  that 
  may 
  be 
  safely 
  carried 
  

   being 
  450,000. 
  The 
  first 
  measurements 
  are 
  carefully 
  made, 
  as 
  they 
  form 
  

   the 
  basis 
  for 
  subsequent 
  estimates. 
  As 
  soon 
  as 
  the 
  eggs 
  ai"e 
  measured 
  

   they 
  are 
  transferred 
  to 
  the 
  hatching-boxes 
  with 
  dippers. 
  

  

  