﻿OYSTER 
  BOTTOMS 
  OF 
  LAVACA 
  BAY, 
  TEX. 
  39 
  

  

  GENERAL 
  PHYSICAL 
  AND 
  BIOLOGICAL 
  CONDITIONS. 
  

   TIDES 
  AND 
  CURRENTS. 
  

  

  Primarily 
  for 
  the 
  reduction 
  of 
  the 
  soundings 
  to 
  approximate 
  mean 
  

   low-water 
  level, 
  a 
  tide 
  gauge, 
  a 
  plain 
  staff 
  graduated 
  in 
  feet 
  and 
  

   tenths, 
  was 
  established 
  at 
  Port 
  Lavaca, 
  the 
  most 
  convenient 
  and 
  

   central 
  point 
  on 
  the 
  bay. 
  During 
  the 
  entire 
  period 
  of 
  the 
  survey 
  

   readings 
  were 
  made 
  every 
  two 
  hours 
  during 
  daylight. 
  The 
  highest 
  

   tide 
  recorded 
  was 
  on 
  April 
  23, 
  when 
  the 
  water 
  stood 
  at 
  4.7 
  feet 
  on 
  the 
  

   gauge 
  and 
  the 
  lowest 
  was 
  on 
  March 
  16, 
  when 
  it 
  fell 
  to 
  1.2 
  feet 
  on 
  the 
  

   staff, 
  a 
  maximum 
  range 
  of 
  3.5 
  feet. 
  The 
  daily 
  range 
  was 
  usually 
  from' 
  

   0.4 
  to 
  0.8 
  feet, 
  and 
  was 
  to 
  a 
  great 
  degree 
  affected 
  by 
  the 
  winds, 
  which 
  

   in 
  many 
  cases 
  obscured 
  or 
  obliterated 
  the 
  apparent 
  lunar 
  influences. 
  

  

  Although 
  the 
  normal 
  tidal 
  range 
  is 
  small, 
  the 
  currents 
  are 
  suffi- 
  

   ciently 
  strong 
  to 
  insure 
  ample 
  circulation 
  for 
  the 
  conveyance 
  of 
  oyster 
  

   food 
  and 
  the 
  renewal 
  of 
  water 
  for 
  respiratory 
  purposes. 
  

  

  SALINITY 
  AND 
  TEMPERATURE 
  OF 
  THE 
  WATER. 
  

  

  As 
  the 
  amount 
  of 
  salt 
  carried 
  by 
  the 
  waters 
  is 
  a 
  factor 
  important 
  

   to 
  oyster 
  growth 
  and 
  flavor, 
  as 
  well 
  as 
  conditioning 
  the 
  presence 
  or 
  

   absence 
  of 
  destructive 
  enemies, 
  a 
  series 
  of 
  observations 
  relating 
  to 
  the 
  

   salinity 
  and 
  water 
  temperature 
  were 
  continued 
  throughout 
  the 
  survey. 
  

   It 
  is 
  well 
  known 
  that 
  oysters 
  reach 
  their 
  maximum 
  development 
  and 
  

   finest 
  quality 
  in 
  waters 
  of 
  brackish 
  character, 
  having 
  a 
  specific 
  gravity 
  

   of 
  1.012 
  to 
  1.018, 
  about 
  midway 
  between 
  fresh 
  water 
  (specific 
  gravity 
  

   1.000) 
  and 
  open-sea 
  water 
  (specific 
  gravity 
  1.025). 
  Water 
  nearly 
  

   fresh, 
  on 
  the 
  one 
  hand, 
  or 
  very 
  salt, 
  on 
  the 
  other, 
  if 
  present 
  for 
  any 
  

   length 
  of 
  time 
  over 
  the 
  oyster 
  beds, 
  is 
  extremely 
  detrimental, 
  if 
  not 
  

   absolutely 
  prohibitive, 
  to 
  the 
  mollusks. 
  Certain 
  enemies 
  of 
  the 
  

   oysters 
  are 
  also 
  greatly 
  influenced 
  by 
  the 
  amount 
  of 
  salt 
  in 
  solution, 
  

   the 
  drill, 
  for 
  example, 
  avoiding 
  waters 
  of 
  low 
  salinity, 
  while 
  the 
  com- 
  

   mon 
  black 
  sea 
  mussel 
  thi'ives 
  in 
  them. 
  

  

  In 
  order 
  to 
  obtain 
  a 
  reasonably 
  accurate 
  or 
  reliable 
  estimate 
  of 
  the 
  

   proportion 
  of 
  salt 
  in 
  Lavaca 
  Bay, 
  two 
  separate 
  but 
  simidtaneous 
  

   series 
  of 
  observations 
  of 
  salinity 
  and 
  water 
  temperature 
  were 
  made. 
  

   From 
  the 
  Fish 
  Hawk, 
  anchored 
  in 
  the 
  vicinity 
  of 
  the 
  Middle 
  Ground 
  

   and 
  Sand 
  Point 
  Reefs, 
  observations 
  were 
  made 
  at 
  8 
  a. 
  m., 
  noon, 
  and 
  

   6 
  p. 
  m. 
  The 
  depth 
  of 
  water 
  varied 
  from 
  8 
  to 
  10 
  feet. 
  The 
  other 
  

   series 
  was 
  made 
  by 
  the 
  biological 
  party, 
  and 
  extended 
  over 
  the 
  

   greater 
  part 
  of 
  the 
  bay, 
  including 
  points 
  both 
  on 
  the 
  reefs 
  and 
  barren 
  

   grounds. 
  

  

  The 
  water 
  samples 
  in 
  both 
  series 
  of 
  observations 
  were 
  taken 
  a 
  few 
  

   inches 
  from 
  the 
  bottom 
  of 
  the 
  bay, 
  regardless 
  of 
  depth. 
  The 
  instru- 
  

   ment 
  or 
  apparatus 
  used 
  for 
  collecting 
  the 
  samples 
  is 
  illustrated 
  and 
  

  

  