﻿MANUAL 
  OF 
  FISH-CULTURE. 
  63 
  

  

  all 
  weighed, 
  and 
  it 
  was 
  found 
  that 
  lot 
  c 
  had 
  made 
  a 
  slightly 
  better 
  

   growth 
  than 
  lot 
  a. 
  

  

  One 
  of 
  the 
  most 
  uncontrollable 
  diseases 
  attacks 
  salmon 
  fry 
  midway 
  

   in 
  the 
  sac 
  stage, 
  and 
  finishes 
  its 
  work 
  before 
  the 
  complete 
  absorption 
  

   of 
  the 
  sac. 
  The 
  most 
  evident 
  symptom 
  is 
  the 
  appearance 
  of 
  scattered 
  

   white 
  spots 
  in 
  the 
  sac; 
  the 
  fish 
  cease 
  to 
  try 
  to 
  hide, 
  but 
  lie 
  scattered 
  

   about 
  on 
  the 
  bottom 
  of 
  the 
  trough; 
  the 
  spots 
  increase 
  in 
  size, 
  coalesce, 
  

   and 
  finally 
  occupy 
  large 
  areas, 
  especially 
  in 
  the 
  tip 
  of 
  the 
  sac, 
  which 
  

   becomes 
  quite 
  white. 
  Soon 
  after 
  this 
  the 
  fish 
  dies. 
  The 
  attack 
  on 
  a 
  

   lot 
  makes 
  rapid 
  progress; 
  for 
  instance, 
  a 
  lot 
  of 
  2,000 
  in 
  which, 
  up 
  to 
  

   April 
  22, 
  the 
  losses 
  have 
  been 
  from 
  1 
  to 
  9 
  daily, 
  will 
  show 
  17 
  dead 
  on 
  

   the 
  23d, 
  and 
  five 
  days 
  later 
  360 
  die 
  in 
  a 
  single 
  day. 
  In 
  1890 
  this 
  epi- 
  

   demic 
  attacked 
  especially 
  the 
  fry 
  of 
  Atlantic 
  salmon, 
  destroying 
  about 
  

   a 
  third 
  of 
  them; 
  it 
  also 
  destroyed 
  many 
  landlocked 
  salmon, 
  and 
  some 
  

   other 
  species 
  suffered 
  heavily 
  about 
  the 
  same 
  time. 
  In 
  1891 
  there 
  was 
  

   not 
  a 
  trace 
  of 
  it. 
  In 
  1892 
  it 
  returned 
  again, 
  and 
  out 
  of 
  305,353 
  fry 
  of 
  

   Atlantic 
  salmon 
  it 
  left 
  but 
  3,874, 
  and 
  these 
  were 
  by 
  no 
  means 
  healthy; 
  

   but 
  it 
  attacked 
  only 
  Atlantic 
  salmon. 
  Salt 
  and 
  mud 
  were 
  tried 
  as 
  

   remedies, 
  but 
  though 
  the 
  progress 
  of 
  the 
  disease 
  appeared 
  in 
  some 
  

   instances 
  checked 
  thereby, 
  no 
  permanent 
  benefit 
  resulted 
  from 
  their 
  

   use. 
  

  

  In 
  1890 
  this 
  epidemic 
  appeared 
  to 
  run 
  in 
  families. 
  There 
  was 
  evi- 
  

   dence 
  tending 
  to 
  show 
  that 
  all 
  the 
  eggs 
  coming 
  from 
  a 
  particular 
  mother 
  

   would 
  have 
  a 
  common 
  degree 
  of 
  liability 
  to 
  the 
  disease 
  — 
  some 
  families 
  

   being 
  exterminated 
  by 
  it, 
  some 
  only 
  decimated, 
  and 
  others 
  able 
  to 
  resist 
  

   it 
  altogether. 
  It 
  did 
  not 
  appear 
  to 
  be 
  infectious, 
  as 
  several 
  lots 
  of 
  fry, 
  

   separated 
  by 
  screens, 
  would 
  occupy 
  a 
  single 
  trough, 
  and 
  in 
  some 
  cases 
  

   those 
  at 
  the 
  head 
  of 
  the 
  trough 
  would 
  be 
  totally 
  destroyed, 
  or 
  nearly 
  so, 
  

   and 
  those 
  below 
  them 
  escape 
  from 
  attack. 
  

  

  The 
  only 
  other 
  diseases 
  of 
  Atlantic 
  salmon 
  that 
  demand 
  notice 
  here 
  

   are 
  connected 
  with 
  the 
  so-called 
  fungus, 
  belonging 
  to 
  the 
  group 
  of 
  

   water 
  molds 
  called 
  SaproJegnicv, 
  and 
  probably 
  to 
  the 
  genus 
  Saproleguia, 
  

   one 
  species 
  of 
  which, 
  /S'./cTa.r, 
  is 
  noted 
  as 
  the 
  cause 
  of 
  very 
  destructive 
  

   epidemics 
  among 
  the 
  adult 
  salmon 
  of 
  Scotch 
  and 
  English 
  rivers. 
  The 
  

   species 
  that 
  attacks 
  fish 
  eggs 
  is 
  well 
  known 
  to 
  every 
  fish-culturist 
  as 
  

   a 
  fine 
  white 
  growth 
  of 
  a 
  cottony 
  or 
  woolly 
  appearance 
  that 
  forms 
  upon 
  

   dead 
  eggs, 
  and 
  when 
  neglected 
  spreads 
  out 
  so 
  as 
  to 
  envelop 
  in 
  its 
  

   threads 
  a 
  great 
  many 
  of 
  the 
  living 
  eggs 
  surrounding 
  it. 
  It 
  is 
  by 
  no 
  

   means 
  certain 
  that 
  all 
  such 
  growths 
  belong 
  to 
  one 
  species 
  or 
  even 
  to 
  

   one 
  genus, 
  but 
  they 
  are 
  much 
  alike 
  in 
  structure 
  and 
  growth 
  and 
  live 
  

   upon 
  animal 
  and 
  vegetable 
  matter, 
  either 
  as 
  parasites 
  attacking 
  living 
  

   matter 
  or 
  as 
  saprophytes 
  attacking 
  only 
  dead 
  and 
  decaying 
  matter. 
  

   There 
  has 
  never 
  been 
  serious 
  trouble 
  with 
  this 
  fungus 
  at 
  Craig 
  Brook 
  

   station, 
  and 
  great 
  loss 
  from 
  it 
  can 
  only 
  occur 
  in 
  consequence 
  of 
  neglect 
  

   of 
  the 
  duty 
  of 
  picking 
  out 
  the 
  dead 
  eggs. 
  An 
  instance 
  of 
  its 
  attacking 
  

   a 
  living 
  egg 
  except 
  by 
  reaching 
  out 
  from 
  a 
  dead 
  one 
  is 
  unknown. 
  Fish 
  

  

  