﻿206 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  density 
  of 
  the 
  water, 
  the 
  softness 
  of 
  the 
  bottom, 
  the 
  suspension 
  of 
  silt 
  

   in 
  deep 
  water, 
  and 
  changes 
  in 
  the 
  composition 
  of 
  the 
  water 
  of 
  03^ster 
  

   beds. 
  Dean**, 
  who 
  carefully 
  studied 
  the 
  problem, 
  concluded 
  that 
  the 
  

   slime-covered 
  bottom 
  probabl}^ 
  prevented 
  tixation, 
  and 
  that 
  silt 
  sus- 
  

   pended 
  in 
  the 
  water 
  made 
  it 
  impossible 
  for 
  the 
  oyster 
  to 
  live, 
  these 
  

   being 
  the 
  chief 
  factors 
  of 
  the 
  distribution. 
  

  

  The 
  habits 
  of 
  the 
  young 
  oyster 
  and 
  of 
  the 
  young 
  clam 
  are 
  very 
  dif- 
  

   ferent 
  in 
  many 
  respects, 
  but 
  the 
  segregation 
  in 
  both 
  cases 
  to 
  definite 
  

   and 
  limited 
  localities 
  is 
  probably 
  from 
  the 
  same 
  cause. 
  Over 
  any 
  area 
  

   a 
  greater 
  number 
  settle 
  to 
  the 
  bottom 
  where 
  currents 
  are 
  swift. 
  At 
  

   the 
  same 
  time, 
  many 
  sink 
  on 
  other 
  parts 
  of 
  the 
  bottom. 
  Wherever 
  

   silt 
  is 
  absent 
  either 
  may 
  become 
  established; 
  in 
  a 
  silt 
  deposit 
  neither 
  

   can 
  live. 
  The 
  favorable 
  localities 
  may 
  be 
  near 
  the 
  shore 
  or 
  in 
  deep 
  

   water, 
  as 
  the 
  case 
  ma}'^ 
  be. 
  In 
  some 
  places 
  the 
  presence 
  of 
  enemies 
  

   must 
  also 
  be 
  considered. 
  

  

  We 
  may 
  conclude 
  that 
  on 
  a 
  clam 
  beach 
  or 
  flat, 
  embryos 
  settle 
  to 
  the 
  

   bottom 
  both 
  above 
  and 
  below 
  the 
  low-water 
  mark. 
  Fewer 
  embryos 
  

   lodge 
  above 
  the 
  low 
  tide 
  line 
  than 
  just 
  below 
  it, 
  because 
  of 
  the 
  reces- 
  

   sion 
  of 
  the 
  water. 
  Where 
  definite 
  currents 
  are 
  present 
  we 
  find 
  the 
  

   greater 
  number 
  of 
  the 
  young. 
  Where 
  currents 
  keep 
  the 
  bottom 
  clean 
  

   but 
  do 
  not 
  erode, 
  clams 
  are 
  for 
  a 
  time 
  able 
  to 
  establish 
  themselves. 
  

   In 
  distributions 
  like 
  this 
  one 
  at 
  West 
  Falmouth 
  it 
  may 
  be 
  asked 
  what 
  

   is 
  the 
  relation 
  between 
  the 
  two 
  separated 
  beds 
  of 
  clams. 
  The 
  answer 
  

   may 
  be 
  given 
  with 
  some 
  certainty 
  that 
  there 
  is 
  none. 
  It 
  seems 
  prob- 
  

   able 
  that 
  the 
  mature 
  clams 
  between 
  tide 
  lines 
  are 
  recruited 
  only 
  slightl}', 
  

   if 
  at 
  all, 
  from 
  the 
  beds 
  lower 
  down, 
  and 
  that 
  their 
  number 
  is 
  added 
  to 
  

   by 
  the 
  small 
  clams 
  which, 
  in 
  the 
  beginning, 
  settled 
  between 
  the 
  tide 
  

   lines 
  and 
  were 
  able 
  to 
  establish 
  themselves. 
  The 
  multitude 
  constitut- 
  

   ing 
  the 
  lower 
  bed 
  seems 
  ultimately 
  to 
  perish. 
  

  

  The 
  bed 
  of 
  young 
  clams 
  was 
  first 
  found 
  at 
  West 
  Falmouth 
  on 
  July 
  

   10, 
  1899, 
  and 
  during 
  the 
  remainder 
  of 
  the 
  summer 
  was 
  examined 
  often. 
  

   On 
  this 
  date 
  clams 
  were 
  very 
  thickly 
  set. 
  Numbers 
  of 
  them 
  were 
  

   small, 
  many 
  being 
  about 
  1 
  mm. 
  long, 
  while 
  the 
  maximum 
  length 
  was 
  

   about 
  11 
  mm. 
  The 
  clams 
  shown 
  in 
  figure 
  3 
  were 
  selected 
  from 
  a 
  large 
  

   number 
  to 
  represent 
  the 
  minimum 
  and 
  maximum 
  sizes 
  of 
  those 
  on 
  the 
  

   bed, 
  and 
  also, 
  as 
  nearly 
  as 
  possible, 
  the 
  relative 
  number 
  of 
  intermediate 
  

   sizes. 
  No 
  doubt 
  many 
  smaller 
  than 
  those 
  represented 
  were 
  lost 
  through 
  

   the 
  meshes 
  of 
  the 
  sieve. 
  

  

  The 
  ages 
  of 
  these 
  clams 
  can 
  only 
  be 
  conjectured. 
  The 
  larger 
  are 
  

   probably 
  from 
  5 
  to 
  7 
  weeks 
  old; 
  the 
  smaller 
  may 
  have 
  lived 
  1 
  or 
  2 
  

   weeks. 
  The 
  breeding 
  season 
  in 
  Buzzards 
  Baj' 
  extends 
  from 
  the 
  latter 
  

   part 
  of 
  May 
  to 
  the 
  earlj^ 
  part 
  of 
  August, 
  reaching 
  its 
  height 
  in 
  late 
  

   June 
  and 
  early 
  July. 
  Here 
  and 
  there 
  very 
  small 
  clams 
  are 
  found 
  as 
  

  

  aThe 
  Physical 
  and 
  Biological 
  Characteristics 
  of 
  the 
  Natural 
  Oyster 
  Grounds 
  of 
  South 
  Carolina. 
  

   By 
  Bashford 
  Dean. 
  Bulletin 
  of 
  the 
  U. 
  S. 
  Fish 
  Commission 
  for 
  1890. 
  

  

  