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  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  Change 
  of 
  density 
  lias 
  an 
  important 
  effect 
  upon 
  the 
  spawning 
  of 
  

   oysters. 
  At 
  St. 
  Jerome 
  Creek, 
  Dr. 
  Ryder 
  found 
  that 
  the 
  eggs 
  could 
  

   not 
  be 
  impregnated 
  in 
  a 
  density 
  much 
  exceeding 
  that 
  in 
  which 
  the 
  

   parent 
  animals 
  live. 
  With 
  oysters 
  raised 
  in 
  water 
  ranging 
  from 
  1.007 
  

   to 
  1.0095 
  it 
  was 
  found 
  that 
  the 
  milt 
  was 
  killed 
  by 
  a 
  density 
  greater 
  

   than 
  1.Q13, 
  the 
  individual 
  spermatozoa 
  losing 
  their 
  mobility 
  in 
  a 
  few 
  

   momeuts 
  when 
  exposed 
  to 
  the 
  greater 
  density. 
  The 
  frequent 
  failure 
  

   of 
  oysters 
  to 
  spawn 
  in 
  the 
  season 
  in 
  which 
  they 
  are 
  trans'planted 
  is 
  

   perhaps 
  in 
  a 
  measure 
  owing 
  to 
  this 
  cause. 
  In 
  Chesapeake 
  Bay 
  they 
  

   are 
  usually 
  transplanted 
  from 
  deeper, 
  denser 
  water 
  to 
  more 
  shallow 
  

   and 
  less 
  dense, 
  and 
  when 
  taken 
  from 
  the 
  Chesapeake 
  to 
  Long 
  Island 
  

   Sound 
  they 
  go 
  through 
  a 
  similar 
  experience. 
  There 
  is 
  at 
  the 
  same 
  

   time, 
  however, 
  usually 
  a 
  change 
  in 
  temperature, 
  and 
  doubtless 
  both 
  

   factors 
  combine 
  to 
  produce 
  the 
  eflect 
  noticed. 
  

  

  It 
  has 
  been 
  suggested 
  by 
  Lieutenant 
  Piatt 
  that 
  the 
  density 
  of 
  the 
  

   water 
  has 
  an 
  effect 
  on 
  the 
  distribution 
  of 
  the 
  set; 
  that 
  is, 
  the 
  specific 
  

   gravity 
  of 
  the 
  swimming 
  embryo 
  is 
  such 
  that 
  it 
  can 
  not 
  sink 
  in 
  

   dense 
  water 
  and 
  therefore 
  must 
  become 
  attached 
  in 
  marginal 
  beds 
  

   between 
  tide 
  marks, 
  as 
  is 
  seen 
  on 
  the 
  "raccoon" 
  oyster-beds 
  of 
  South 
  

   Carolina. 
  

  

  In 
  some 
  places 
  it 
  has 
  been 
  found 
  that 
  the 
  best 
  results 
  in 
  oyster- 
  

   culture 
  are 
  to 
  be 
  had 
  in 
  brackish 
  water, 
  and 
  Dr. 
  Uyder 
  suggests 
  that 
  

   this 
  may 
  be 
  largely 
  due 
  to 
  the 
  fact 
  that 
  water 
  of 
  the 
  lower 
  densities 
  

   is 
  usually 
  shallower, 
  and 
  consequently 
  warmer 
  and 
  better 
  adapted 
  to 
  

   the 
  production 
  of 
  an 
  abundant 
  supply 
  of 
  the 
  minute 
  organisms 
  which 
  

   constitute 
  the 
  principal 
  source 
  of 
  the 
  oyster's 
  food. 
  There 
  can 
  be 
  no 
  

   doubt, 
  however, 
  that 
  the 
  eastern 
  oyster 
  is 
  distinctively 
  a 
  brackish- 
  

   water 
  form. 
  It 
  has 
  been 
  found 
  that 
  it 
  will 
  not 
  thrive 
  in 
  French 
  waters 
  

   perfectly 
  adapted 
  to 
  the 
  culture 
  of 
  the 
  European 
  species, 
  and 
  there 
  is 
  

   reason 
  to 
  believe 
  that 
  it 
  will 
  reproduce 
  itself 
  in 
  a 
  lower 
  density 
  than 
  is 
  

   necessary 
  for 
  the 
  native 
  oyster 
  of 
  California. 
  

  

  For 
  determining 
  the 
  temperature 
  and 
  the 
  density 
  of 
  sea 
  waters 
  the 
  

   apparatus 
  shown 
  in 
  plate 
  ii 
  is 
  used. 
  It 
  consists 
  of 
  a 
  glass 
  float 
  with 
  a 
  

   long 
  stem 
  and 
  a 
  large 
  bulb, 
  weighted 
  so 
  as 
  to 
  sink 
  in 
  fresh 
  water 
  to 
  a 
  

   point 
  near 
  the 
  top 
  of 
  the 
  stem. 
  The 
  stem 
  is 
  graduated 
  to 
  read 
  between 
  

   1.000 
  and 
  1.031, 
  the 
  figures 
  representing 
  the 
  specific 
  gravity; 
  that 
  is, 
  

   they 
  show 
  the 
  weight 
  of 
  the 
  salt 
  water, 
  an 
  equal 
  body 
  of 
  fresh 
  water 
  

   being 
  supposed 
  to 
  weigh 
  1.000. 
  

  

  In 
  practice 
  a 
  scale 
  having 
  the 
  entire 
  range 
  would 
  be 
  too 
  long 
  for 
  

   safety 
  and 
  convenience, 
  and 
  therefore 
  the 
  saliuometers 
  are 
  made 
  in 
  

   sets 
  of 
  three, 
  reading 
  from 
  1.000 
  to 
  1.011, 
  from 
  1.010 
  to 
  1.021, 
  and 
  from 
  

   1.020 
  to 
  1.031, 
  respectively. 
  

  

  There 
  is 
  also 
  provided 
  with 
  them 
  a 
  deep 
  copper 
  cup 
  or 
  cylinder, 
  

   at 
  one 
  side 
  of 
  which 
  a 
  thermometer 
  is 
  attached 
  (plate 
  ii). 
  The 
  method 
  

   of 
  using 
  the 
  salinometer 
  is 
  as 
  follows: 
  The 
  cup 
  is 
  filled 
  with 
  the 
  water 
  

   to 
  be 
  tested, 
  the 
  appropriate 
  float 
  is 
  placed 
  in 
  the 
  water, 
  the 
  density 
  of 
  

  

  