﻿8 
  WATEK-POWER 
  DEVELOPMENT 
  IN 
  THE 
  MISSISSIPPI. 
  

  

  from 
  the 
  parent 
  bed 
  or 
  perhaps 
  in 
  some 
  tributary 
  stream 
  that 
  the 
  

   fish 
  host 
  may 
  have 
  entered. 
  

  

  Investigations 
  carried 
  on 
  by 
  the 
  Bureau 
  during 
  recent 
  years 
  have 
  

   shown 
  that 
  mussels 
  do 
  not 
  necessarily 
  attach 
  to 
  fish 
  indiscriminately, 
  

   but 
  that 
  a 
  given 
  species 
  of 
  mussel 
  may 
  make 
  use 
  of 
  only 
  certain 
  species 
  

   of 
  fish, 
  as 
  the 
  piraple-back 
  mussel 
  (Q. 
  pustulosa) 
  seems 
  to 
  be 
  generally 
  

   restricted 
  in 
  parasitism 
  to 
  certain 
  species 
  of 
  catfishes, 
  and, 
  a 
  more 
  

   striking 
  instance, 
  the 
  niggerhead 
  mussel 
  (Q. 
  ehena) 
  restricts 
  itself 
  

   so 
  far 
  as 
  is 
  known 
  to 
  the 
  river 
  herring, 
  or 
  blue 
  herring, 
  Pomolohus 
  

   chrysocliloris.°' 
  Conditions, 
  therefore, 
  which 
  affect 
  the 
  movements 
  of 
  

   the 
  river 
  herring 
  or 
  the 
  catfish 
  may 
  vitally 
  affect 
  the 
  welfar(> 
  of 
  these 
  

   important 
  mussels. 
  

  

  It 
  is 
  not 
  here 
  simply 
  a 
  question 
  of 
  v/hethcr 
  mussels 
  will 
  be 
  trans- 
  

   ported 
  from 
  below 
  the 
  dam 
  to 
  the 
  waters 
  abc^ve, 
  })ut, 
  if 
  the 
  river 
  herring 
  

   is 
  a 
  truly 
  migratory 
  fish, 
  going 
  down 
  the 
  river 
  in 
  the 
  fall 
  and 
  ascending 
  

   again 
  in 
  the 
  spring, 
  and, 
  if 
  its 
  course 
  is 
  so 
  checked 
  by 
  the 
  inter- 
  

   position 
  of 
  a 
  dam 
  that 
  comparatively 
  few 
  find 
  the 
  way 
  into 
  the 
  

   upper 
  river, 
  two 
  results 
  wdll 
  follow: 
  The 
  fish 
  wiU 
  become 
  a 
  rare 
  species 
  

   in 
  the 
  upper 
  river, 
  and 
  the 
  future 
  generations 
  of 
  niggerhead 
  mussels 
  

   wall 
  so 
  generally 
  fail 
  of 
  finding 
  attachment 
  to 
  the 
  only 
  suitable 
  fish, 
  

   that 
  successive 
  broods 
  will 
  perish, 
  until, 
  with 
  the 
  ultimate 
  death 
  or 
  

   capture 
  of 
  the 
  old 
  mussels, 
  the 
  species 
  wiU 
  become 
  extinct 
  in 
  that 
  

   portion 
  of 
  the 
  river 
  l}nng 
  above 
  Keokuk; 
  that 
  is 
  to 
  say, 
  in 
  practically 
  

   the 
  entire 
  Mississippi, 
  for 
  the 
  mussel 
  resources 
  of 
  the 
  Mississippi 
  

   proper 
  (tributaries 
  excluded) 
  are 
  exceedingly 
  limited 
  south 
  of 
  Keokuk. 
  

  

  On 
  the 
  other 
  hand, 
  it 
  is 
  not 
  to 
  be 
  lost 
  sight 
  of 
  that 
  the 
  flood 
  region 
  

   of 
  the 
  repressed 
  water 
  will 
  make 
  available 
  new 
  bottoms 
  for 
  clam 
  

   beds. 
  The 
  future 
  condition 
  is 
  not 
  to 
  be 
  predicted. 
  None 
  of 
  the 
  

   existing 
  bottom 
  of 
  the 
  new 
  lake 
  is 
  definitive. 
  Bottoms 
  now 
  covered 
  

   with 
  former 
  land 
  vegetation 
  will 
  acquire 
  a 
  new 
  character 
  in 
  time 
  

   as 
  they 
  are 
  covered 
  with 
  silt 
  or 
  stream-washed 
  sand. 
  The 
  old 
  

   channel 
  itself, 
  no 
  longer 
  washed 
  as 
  before 
  by 
  active 
  stream 
  action, 
  

   will 
  undergo 
  changes. 
  The 
  Des 
  Moines 
  Rapids 
  was 
  formerly 
  the 
  

   home 
  of 
  abundant 
  niggerhead 
  shells 
  of 
  particularly 
  good 
  quahty, 
  

   which 
  could 
  readily 
  be 
  taken 
  from 
  among 
  the 
  rocks. 
  Deeply 
  sub- 
  

   merged 
  as 
  these 
  beds 
  now 
  are, 
  it 
  will 
  be 
  scarcely 
  possible 
  to 
  obtain 
  

   the 
  mussels. 
  The 
  gradual 
  accumulation 
  of 
  silt 
  over 
  and 
  among 
  

   these 
  rocks 
  will 
  probably 
  make 
  conditions 
  unfavorable 
  for 
  this 
  species, 
  

   although 
  other 
  beds 
  of 
  diiferent 
  species 
  may 
  be 
  expected 
  to 
  be 
  formed 
  

  

  o 
  In 
  some 
  publications 
  the 
  name 
  "skipjack" 
  is 
  applied 
  to 
  this 
  species. 
  Except 
  as 
  derived 
  indirectly 
  

   from 
  books, 
  that 
  common 
  name 
  does 
  not 
  seem 
  to 
  be 
  applied 
  to 
  this 
  sp(-cies 
  by 
  local 
  fishermen. 
  The 
  name 
  

   "skipjack," 
  in 
  fact, 
  seems 
  generally 
  to 
  be 
  appropriately 
  applied 
  to 
  the 
  (;izzard 
  shad, 
  while 
  the 
  Pomolohus 
  

   is 
  Kcnerally 
  and 
  very 
  appropriately 
  designated 
  as 
  the 
  "river 
  herring," 
  local 
  fishermen 
  havmg 
  correctly 
  

   recognized 
  its 
  close 
  relationship 
  to 
  the 
  true 
  herruxgs. 
  It 
  has 
  l)een 
  learned, 
  however, 
  that 
  the 
  Ohio 
  shad 
  

   (Alnxa 
  i'hunsis) 
  is 
  not 
  regularly 
  distinguished 
  by 
  fishermen 
  from 
  the 
  river 
  herring. 
  To 
  avoid 
  further 
  

   confusion 
  the 
  use 
  of 
  the 
  term 
  "skipjack 
  " 
  as 
  applied 
  to 
  Pomolobus 
  should 
  be 
  discouraged. 
  

  

  