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fish-gameI 

"CONSERVATION  OF  WILDUFE  THROUGH  EDUCATION" 


California  Fish  and  Game  is  a  journal  devoted  to  the  conservation  of  wild- 
life. If  its  contents  are  reproduced  elsewhere,  the  authors  and  the  California 
Department  of  Fish  and  Game  would  appreciate  being  acknowledged. 

Subscriptions  may  be  obtained  at  the  rate  of  $5  per  year  by  placing  an 
order  with  the  California  Department  of  Fish  and  Game,  1416  Ninth  Street, 
Sacramento,  California  95814.  Money  orders  and  checks  should  be  made  out 
to  California  Department  of  Fish  and  Game.  Inquiries  regarding  paid  sub- 
scriptions should  be  directed  to  the  Editor. 


Complimentary  subscriptions  are  granted,  on  a  limited  basis,  to  libraries, 
scientific  and  educational  institutions,  conservation  agencies,  and  on  exchange. 
Complimentary  subscriptions  must  be  renewed  annually  by  returning  the  post- 
card enclosed  with  each  October  issue. 


Please  direct  correspondence  to: 

Kenneth  A,  Hashagen,  Jr.,  Editor 
California  Fish  and  Game 
1416  Ninth  Street 
Sacramento,  California  95814 


u 


VOLUME  65 


JULY  1979 


NUMBER  3 


Published  Quarterly  by 

STATE  OF  CALIFORNIA 

THE  RESOURCES  AGENCY 

DEPARTMENT  OF  FISH  AND  GAME 

—LDA— 


STATE  OF  CALIFORNIA 
EDMUND  G.  BROWN  JR.,  Governor 


THE  RESOURCES  AGENCY 
HUEY  D.  JOHNSON,  Secretary  for  Resources 


FISH  AND  GAME  COMMISSION 

SHERMAN  CHICKERING,  President 
San  Francisco 

ELIZABETH  L.  VENRICK,  Vice  President  ABEL  GALLETTI,  Member 

Cardiff  Los  Angeles 

BERGER  0.  BENSON,  Member  RAYMOND  DASMANN,  Member 
San  Mateo  Nevada  City 


DEPARTMENT  OF  FISH  AND  GAME 

E.  C.  FULLERTON,  Director 

1416  9th  Street 

Sacramento  95814 


CALIFORNIA  FISH  AND  GAME 
Editorial  Staff 

KENNETH  A.  HASHAGEN,  JR.,  Editor-in-Chief Sacramento 

DARLENE  A.  OSBORNE,  Editor  for  Inland  Fisheries Sacramento 

RONALD  M.  JUREK,  Editor  for  Wildlife  Sacramento 

J.  R.  RAYMOND  ALLY.  Editor  for  Marine  Resources  Long  Beach 

DAVID  A.  HOOPAUGH,  Editor  for  Salmon  and  Steelhead Sacramento 

DONALD  E.  STEVENS,  Editor  for  Striped  Bass,  Sturgeon,  and  Shad Stockton 

KIM  McCLENEGHAN,  Editor  for  Environmental  Services Rancho  Cordova 


CONTENTS 


139 


Page 


Effects  of  a  305-mm  (12.0-Inch)  Minimum  Size  Limit  on 
Largemouth  Bass,  Micropterus  salmoides,  at  Merle  Collins 
Reservoir Ronald  J.  Pelzman     141 

The  Standing  Stock  and  Production  of  Eelgrass,  Zostera 
marina,  in  Humboldt  Bay,  California 
Lawrence  W.  Harding  and  James  H.  Butler     151 

Estimating  Fetus  Age  and  Breeding  and  Fawning  Periods  in  the 

North  Kings  River  Deer  Herd Hal  Salwasser  and  Stephen  A.  Holl     159 

Notes 

Hematological  Stress  Response  of  Rainbow  Trout,  Salmo 
gairdneri,  to  a  Simulated  Geothermal  Steam  Condensate 
Spill  James  A.  Steele  and  Louis  A.  Courtois     166 

Observations  of  Fingerling  Chinook  Salmon  in  the  Stomachs 
of  Yellow  Perch  from  the  Klamath  River,  California 
Trygve  F.  Dahle,  III     168 

An  Abnormally   Pigmented   Shortspine  Thornyhead,   Sebas- 

to/obus  a/ascanus  Qean William  H.  Barss     168 

A    Juvenile    Ocean     Triggerfish,     Canthidermis    maculatus 
(Bloch),  (Pisces,  Balistidae)  from  the  Gulf  of  California 
Robert  A.  Behrstock     169 

A  Pacu  (  Colossoma,  Family  Characidae)  Caught  in  the  Sacra- 
mento River  Martin  R.  Briltan  and  Gary  D.  Grossman     170 

Effect  of  First  Pectoral  Fin  Ray  Removal  on  Survival 
and  Estimated  Harvest  Rate  of  White  Sturgeon  in  the 
Sacramento-San  Joaquin  Estuary       David  W.  Kohlhorst     173 

Evidence  of  Successful  Reproduction  of  Steelhead  Rainbow 
Trout,  Salmo  gairdneri  gairdneri,  in  the  Ventura  River, 
California William  E.  Tippets     177 

Notes  on  a  Hybridization  Experiment  Between  Rainbow  and 

Golden  Trout  J.  R.  Gold,  R.  E.  Pipkin,  and  G.  A.  E.  Gall     179 

California  Condor  Survey,  1978 

Sanford  R.  Wilbur,  Robert  D.  Mallette,  and  John  C.  Borneman     183 

The  Relationship  Between  Megalopae  of  the  Dungeness  Crab, 
Cancer  magister,  and  the  Hydroid,  Velella  velella,  and 
Its  Influence  on  Abundance  Estimates  of  C.  magister 
Megalopae Daniel  E.  Wickham     184 

Winter  Food  Habits  of  Fishers,  Martes pennanti,  in  Northwest- 
ern California  William  E.  Grenfell  and  Maurice  Fasenfest     186 

An  Anti-roll  Beach  Seine     Range  D.  Bayer     189 

Term  Fetuses  From  A  Large  Common  Thresher  Shark,  Aloplas 

vulplnus Mark  A.  Hixon     191 


140  CALIFORNIA  FISH  AND  CAME 


IN  MEMORIAM 

John  E.  Skinner 

We  have  lost  a  close  friend  and  a  dedicated,  innovative  fishery  biolo- 
gist. John  E.  Skinner,  52,  died  in  a  tragic  home  fire  in  the  early  morning 
hours  of  December  19,  1978.  His  home  was  in  Rancho  Cordova,  near 
Sacramento,  where  he  lived  with  his  wife  Marjory  and  four  of  their  six 
children.  Although  hurt,  the  remainder  of  the  family  survived. 

John  was  employed  by  the  California  Department  of  Fish  and  Game 
for  nearly  25  years.  He  was  Coordinator  of  the  State  Water  Use  Planning 
Project  since  March  1976,  working  closely  with  the  California  Water 
Commission  and  the  Department  of  Water  Resources. 

A  native  of  Detroit,  Michigan,  he  was  a  graduate  of  Michigan  State 
University  with  a  degree  in  fisheries  and  wildlife.  He  served  as  a  machin- 
ist's mate  in  the  U.S.  Navy  at  the  close  of  World  War  II  and  worked  as 
a  journeyman  carpenter  and  in  aircraft  fabrication  and  metallurgy. 

John  joined  the  California  Department  of  Fish  and  Game  early  in  1954 
as  a  Junior  Aquatic  Biologist  assigned  to  the  Inland  Fisheries  Branch.  His 
assignments  over  the  years  included  3  years  as  a  researcher  on  statewide 
angling  statistics  and  on  the  fisheries  of  the  Sacramento-San  Joaquin 
Delta,  more  than  9  years  as  Water  Projects  Supervisor,  and  8  years  as 
Research  Supervisor  on  the  Bay-Delta  Study.  Among  John's  technical 
publications  is  the  classic  225  page  document,  "An  Historical  Review  of 
the  Fish  and  Wildlife  Resources  of  the  San  Francisco  Bay  Area". 

He  was  the  current  president  of  the  Western  Division  of  the  American 
Fisheries  Society  and  was  a  former  president,  vice-president,  and  secre- 
tary-treasurer of  the  California-Nevada  Chapter.  He  was  also  affiliated 
with  the  Pacific  Fishery  Biologists  and  the  Western  Section  of  the  Wildlife 
Society,  of  which  he  was  a  one-time  member  of  the  Executive  Board.  The 
various  professional  committees  he  worked  on  are  too  numerous  to 
mention. 

John  was  also  very  active  in  civic,  school,  and  church  affairs.  He  was 
a  member  of  the  California  Commonwealth  Club  and  the  philosophy  and 
goals  committee  of  Folsom-Cordova  Unified  School  District.  He  served 
as  president  of  the  St.  John  Vianney  parochial  school  board  and  was  past 
president  of  the  school's  Parents  Club. 

The  foregoing  summarizes  his  impressive  accomplishments  and  con- 
tributions, yet  does  not  describe  John  as  a  person.  What  set  John  apart 
from  others  was  the  monumental  enthusiasm  and  dedication  with  which 
he  met  any  challenge,  whether  it  was  cooking  a  cioppino  dinner  for  400 
people  at  the  Western  Division  meeting  or  solving  some  major  resource 
protection  problem.  Because  of  his  strong  faith  in  people,  he  often  kin- 
dled in  them  these  same  attributes. — Almo  Cordone 


LARCEMOUTH  BASS  MINIMUM  SIZE  LIMITS  141 

Calif.  Fish  and  Came  65  ( 3 ):   1 4 1  - 1 50.     1 979. 

EFFECTS  OF  A  305-MM  (12.0-INCH)  MINIMUM  SIZE  LIMIT 

ON  LARCEMOUTH  BASS,  MICROPTERUS  SALMOIDES, 

AT  MERLE  COLLINS  RESERVOIR  ^ 

RONALD  J.  PELZMAN 

California  Department  of  Fish  and  Came 

Inland  Fisheries  Branch 

987  Jedsmith  Drive 
Sacramento,  CA  95819 

A  305-mm  minimum  size  limit  on  largemouth  bass,  Micropterus  sdlmoides,  im- 
posed in  1972  at  Merle  Collins  Reservoir,  Yuba  County,  was  evaluated  by  in  exten- 
sive creel  census.  Angler  harvest  of  largemouth  bass  was  reduced  over  50%,  with 
good  public  acceptance  and  without  reductions  in  game  fish  yields.  Combined 
annual  weights  of  largemouth  and  smallmouth  bass,  M.  dolomieui,  decreased  only 
about  3%.  The  size  limit  apparently  also  protected  smallmouth  and  spotted  bass,  M. 
punctulatus,  less  than  305  mm  total  length. 

INTRODUCTION 

Size  limits  have  been  used  by  other  states  to  control  overharvest  of 
largemouth  bass  and  to  attain  desirable  predator-prey  structure  by  protecting 
bass  large  enough  to  prey  on  slow-growing  panfish  and  other  fishes  which 
compete  with  smaller  bass  (Funk  1974).  Estimated  annual  exploitation  rates  as 
high  as  0.65  at  Merle  Collins  Reservoir  ( Rawstron  and  Hashagen  1 972 )  prompt- 
ed the  Fish  and  Game  Commission,  at  the  request  of  the  Department,  to  impose 
an  experimental  305-mm  size  limit  on  largemouth  bass  in  March  1972. 

A  continuing  creel  census  begun  in  1965  provided  a  means  to  follow  the 
effects  of  the  size  limit  on  the  fishery  and  to  assess  its  value  as  a  management 
tool.  Hashagen  (1973)  provides  detailed  information  on  the  census  through 
1972  and  a  description  of  Merle  Collins  Reservoir  and  its  fishery. 

METHODS  AND  MATERIALS 

A  creel  census,  modified  from  Best  and  Boles  (1956),  was  the  principal 
method  used  to  evaluate  the  size  limit.  From  June  1965  through  June  1977, 
departing  anglers  were  censused  at  the  only  point  of  exit  from  the  reservoir  on 
two  rotating  weekdays  per  week,  on  all  weekend  days,  and  on  all  national 
holidays.  All  anglers  were  interviewed  each  census  day  from  9:00  a.m.  to  dusk 
and  a  substantial  proportion  of  all  fish  were  weighed  and  measured. 

During  the  spring,  summer,  and  fall  of  1973  and  1974,  a  complete  census  was 
conducted  for  seven  continuous  days  and  nights  to  determine  how  many  anglers 
were  missed  by  the  9:00  a.m.  to  dusk  census.  The  complete  census  showed  that 
about  30%  of  the  anglers  were  not  censused  on  regular  census  days.  Missed 
anglers  included  those  who  stayed  in  the  campground  for  two  or  more  days 
before  passing  the  census  station,  and  anglers  who  fished  only  during  the  early 
morning  hours  or  at  night. 

Creel  census  data  were  expanded  to  give  estimates  of  total  catch  by  mutiply- 

'  This  work  was  performed  as  part  of  DIngell-johnson  Project  F-18-R,  "Coldwater  Reservoir  and  Special  Experi- 
mental Reservoir  Management  Program",  supported  by  Federal  Aid  to  Fish  Restoration  funds.  Accepted  for 
publication  January  1979. 


142  CALIFORNIA  FISH  AND  CAME 

ing  the  observed  monthly  weekday  catch  of  each  species  by  the  ratio  of  the  total 
number  of  weekdays  in  a  month  to  the  total  weekdays  censused  and  adding  the 
observed  catches  for  weekends  and  holidays.  Monthly  estimates  were  then 
summed  to  obtain  annual  estimates.  These  were  further  expanded  in  all  years 
by  30%  (as  determined  by  complete  creel  checks)  to  account  for  anglers  not 
censused.  Estimated  total  pounds  of  fish  caught  annually  were  calculated  by 
multiplying  the  estimated  total  monthly  catch  of  a  species  by  the  average  month- 
ly weight  for  that  species  and  summing  monthly  estimates.  Total  annual  pound- 
ages were  included  in  the  tables  in  addition  to  yield  values  since  mean  annual 
surface  acreage,  which  typically  fluctuates,  was  used  to  calculate  yield. 

An  interview  was  included  as  part  of  the  census  in  May  1973  to  gain  informa- 
tion on  the  number  of  bass  caught  and  released.  Anglers  were  questioned 
regarding  fish  preference,  whether  they  were  fishing  for  bass,  v. hether  they 
released  any  bass,  and  sizes  of  released  bass. 

Data  from  1 968  through  1 971  and  1 973  through  1 976  were  chosen  to  evaluate 
the  size  limit  since  they  appeared  most  representative.  Annual  weights  for 
largemouth  bass  for  1968  through  1970  were  nearly  identical  (Hashagen  1973), 
indicating  a  stabilization  of  the  fishery.  Data  for  years  1965  through  1967  were 
excluded  because  the  bass  fishery  was  dominated  by  an  extremely  large  1964 
year  class  which  grew  slowly  and  suppressed  bass  recruitment.  Data  for  1977 
were  not  included  because  drought  conditions  severely  reduced  angler  effort. 
Data  for  1965  through  1967  are  included  for  reference  only. 

Catch  and  effort  values  typically  fluctuate  from  year  to  year.  For  this  reason, 
pre-  and  post-size  limit  data  were  compared  by  averaging  values  for  the  two 
4-year  periods. 

RESULTS 
General 

Angler  use  pre-  and  post-imposition  of  the  size  limit  was  comparable.  Over 
the  period  1 968  through  1 971 ,  the  number  of  anglers  annually  using  the  reservoir 
averaged  17,316  and  the  number  of  hours  they  expended  averaged  76,242. 
Respective  values  for  the  period  1973  through  1976  were  19,256  and  82,482 
(Table  1  ).  The  average  number  of  hours  annually  expended  by  "bass  anglers", 
defined  by  Hashagen  (1973)  as  boat  anglers  fishing  during  March,  April,  May, 
and  June  using  lures,  minnows,  or  a  combination  of  these  methods,  increased 
from  9,571  before  1972  to  14,769  after  1972  (Table  2). 

Annual  weight  landed  and  yield  values  for  all  game  fishes  combined  and  for 
all  centrarchids  combined  before  and  after  the  size  limit  were  comparable. 
Pre-size  limit  annual  weight  for  all  game  fishes  averaged  4,823  kg  with  a  corre- 
sponding yield  value  of  13.5  kg/ha.  Respective  post-size  limit  values  were  4,664 
kg  and  13.6  kg/ha  (Table  1  ).  Pre-size  limit  annual  weight  for  all  centrarchids 
combined  averaged  2,453  kg  with  a  yield  value  of  6.8  kg/ha.  Post-size  limit 
values  were  2,500  kg  and  7.4  kg/ha.  Combined  annual  weights  of  largemouth 
and  smallmouth  bass  decreased  only  about  3%,  from  a  pre-size  limit  yearly 
average  of  1,786  kg  to  a  post-size  limit  average  of  1,731  kg  (Tables  2  and  3). 

Largemouth  Bass 
Pre-  and  post-size  limit  data  show  that  after  1972  anglers  caught  nearly  as 
many  largemouth  bass  as  before  but  retained  about  52%  fewer.  From  1968 


LARGEMOUTH  BASS  MINIMUM  SIZE  LIMITS 


143 


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LARCEMOUTH  BASS  MINIMUM  SIZE  LIMITS  145 

through  1971,  anglers  kept  a  total  of  14,649  fish  compared  to  6,957  retained  from 
1973  through  1976  (Table  2).  The  mean  total  weight  of  largemouth  bass  caught 
and  retained  annually  declined  from  1,454  kg  for  pre-size  limit  years  to  1,109  kg 
for  post-size  limit  years,  about  a  24%  decrease.  There  was  a  corresponding  22% 
decline  in  mean  yield  of  from  4.1  kg/ha  to  3.2  kg/ha.  As  could  be  expected,  the 
mean  length  and  mean  weight  of  creeled  fish  increased. 

There  apparently  was  no  reduction  in  the  catch  per  hour  (bass  kept  and  bass 
released  in  combination)  for  "bass  anglers".  The  catch  per  hour  for  largemouth 
bass  retained  by  this  group  decreased  over  60%,  however  (Table  2). 

The  size  limit  was  favorably  accepted  by  the  majority  of  anglers.  Only  431 
sublegal  largemouth  bass  were  observed  by  the  census  clerks  from  1973  through 
1976.  During  this  period,  anglers  creeled  an  estimated  6,957  legal  fish  and 
reported  releasing  10,210  sublegal  and  1,953  legal  fish  (Table  2).  It  is  not  known 
how  many  of  the  released  fish  were  caught  more  than  once.  Also,  it  is  not  known 
how  many  of  the  released  largemouth  were  actually  smallmouth  bass  reported 
by  anglers  who  could  not  differentiate  between  the  two  species. 

Smallmouth  and  Spotted  Bass 
Anglers  caught  considerably  more  smallmouth  bass  after  imposition  of  the  size 
limit.  The  mean  annual  catch  from  1968  through  1971  was  928  compared  to 
1,352  for  the  4  years  after  1972,  an  increase  of  about  46%  (Table  3).  This  does 
not  reflect  the  3,294  smallmouth  bass  that  anglers  reported  releasing  from  1973 
through  1976.  The  mean  annual  weight  of  smallmouth  retained  increased  about 
88%  and  yield  values  doubled  after  1972.  Mean  length  and  mean  weight  in- 
creased substantially,  the  latter  by  50%.  Spotted  bass,  introduced  in  1970,  were 
not  observed  in  the  catch  until  1973.  Mean  total  length  was  greater  than  305  mm 
in  most  post-size  limit  years  (Table  4). 

TABLE  4.     Spotted  Bass  Catch  Statistics 

1970        1971        1972 

Estimated  annual  catch  tor  all  anglers _  _  _ 

Estimated  annual  weight  (kg) _  _  _ 

Mean  fork  length  (mm) _  _  _ 

Mean  weight  (g) _  _  - 

Yield  value  (kg/ha)  

Other  Centrarchids 
The  annual  catch  of  redear  sunfish  Lepomis  microlophus,  more  than  doubled 
after  1972  (Table  5).  Following  the  size  limit,  the  annual  weight  increased  by 
nearly  98%,  while  yield  values  doubled.  There  was,  however,  little  change  in  the 
mean  length  or  mean  weight  of  fish  observed  in  the  census.  Yield,  annual  catch, 
and  annual  weight  landed  for  bluegill,  L.  macrochirus,  declined  by  about  20% 
following  1972  (Table  6).  Mean  weight  increased  by  about  53%,  while  mean 
length  increased  slightly.  Annual  catch,  annual  weight,  and  yield  values  for  black 
crappie,  Pomoxis  nigromaculatus,  decreased  following  1972  (Table  7).  Mean 
length  and  mean  weight  increased,  however,  the  latter  by  about  69%.  Mean 
length  and  mean  weight  of  green  sunfish,  L.  cyanellus,  increased  after  1972 
(Table  8).  Declines  occurred,  however,  in  all  other  catch  figures. 


YEAR 

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148  CALIFORNIA  FISH  AND  CAME 

DISCUSSION 
Imposition  of  a  size  limit  on  largemouth  bass  carries  with  it  the  potential  for 
certain  negative  impacts: 

( 1  )    A  decline  in  the  growth  rate  of  largemouth  bass  resulting  in  the  stockpiling 
of  fish  at  lengths  below  the  size  limit. 

(2)  Overpredation  on  species  which  provide  angling  opportunity  as  well  as 
forage. 

(3)  High  mortality  of  angler  caught  undersized  bass  which  are  released. 

(4)  Low  angler  acceptance  with  a  subsequent  decline  in  fishing  effort. 
Creel  census  data  and  observations  made  during  electrofishing  operations 

provided  no  evidence  that  any  of  these  occurred  following  establishment  of  the 
size  limit  at  Merle  Collins  Reservoir. 

Following  reductions  in  the  take  of  largemouth  bass,  other  states  have  report- 
ed the  stockpiling  of  bass  at  lengths  just  under  a  size  limit  (Funk  1974).  Appar- 
ently this  did  not  occur.  Electrofishing  operations  conducted  from  1973  through 
1 977,  years  of  average  to  below  average  reproduction  ( R.  Rawstron,  Assoc.  Fish 
Biol.,  Dept.  Fish  and  Game,  pers.  commun.)  did  not  show  unusually  large 
numbers  of  bass  from  203  mm  (the  size  most  bass  entered  the  catch  in  the 
absence  of  a  size  limit)  to  304  mm  total  length  (tl).  It  is  reasonable  to  assume 
that  in  1972,  the  year  the  size  limit  was  instituted,  a  group  of  fish  in  this  range 
was  largely  protected  from  angling  mortality.  Most  of  these  fish,  however,  likely 
entered  the  catch  during  the  following  year  and  were  replaced  in  the  protected 
group  by  fish  produced  in  1971.  This  probably  occurred  each  year.  Stockpiling 
of  bass  just  under  the  size  limit  would  likely  occur  when  growth  rates  are 
seriously  retarded  (Funk  1974).  Preliminary  analysis  of  age  and  growth  data 
based  on  scale  measurements  indicates  that  a  decline  in  the  growth  rate  of 
largemouth  bass  at  Merle  Collins  Reservoir  did  not  occur  during  the  period  of 
this  study. 

Results  of  this  study  do  not  indicate  that  protected  largemouth  bass  effected 
a  substantial  reduction  in  the  panfish  forage  base.  Considerable  numbers  of 
panfish  less  than  102  mm  tl,  particularly  bluegill,  were  observed  during  electro- 
fishing work  in  years  following  1972. 

Because  hooking  mortality  will  diminish  the  effectiveness  of  size  restrictions, 
it  was  essential  that  the  magnitude  of  immediate  and  delayed  mortality  of 
sublegal  fish  be  determined.  Therefore,  a  companion  study  was  conducted  from 
January  through  March  1976  at  the  Department's  Field  Station  in  Sacramento  to 
assess  hooking  mortality  of  sublegal  largemouth  bass.  Results  of  this  study  sug- 
gest that  direct  mortality  due  to  hooking  is  not  a  factor  which  materially  reduces 
the  value  of  size  limit  regulations  (Pelzman  1978). 

Angler  acceptance  of  the  size  limit  was  good.  Most  anglers  interviewed  ex- 
pressed satisfaction  with  the  regulation  and  some  traveled  considerable  dis- 
tances to  fish  at  the  reservoir  because  of  the  size  limit.  Anglers  organized  into 
clubs  were  especially  supportive. 

Tagging  studies  of  largemouth  bass  conducted  before  and  after  the  size  limit 
provided  comparable  estimates  of  annual  exploitation  and  survival  rates.  Raw- 
stron and  FHashagen  (1972)  reported  an  exploitation  rate  of  0.65  and  survival 
rates  of  0.24  and  0.19  in  1968  and  1969,  respectively,  for  fish  >  203  mm  (8.0 
inches)  fork  length  (FL).  Exploitation  and  survival  rates  of  0.60  and  0.21,  respec- 


LARCEMOUTH  BASS  MINIMUM  SIZE  LIMITS  149 

lively,  for  fish  >305  mm  tl  were  recorded  in  1973  (Rawstron  and  Pelzman 
1978). 

Substantial  increases  in  the  annual  catch  of  smallmouth  bass  were  recorded 
following  establishment  of  the  size  limit.  While  the  size  limit  may  have  contribut- 
ed to  increases  in  the  smallmouth  take,  the  increasing  smallmouth  population 
played  a  substantial  role.  The  estimated  annual  take  of  smallmouth  steadily 
increased  to  a  high  of  1,500  fish  in  1971,  the  year  before  the  size  limit  was 
imposed.  During  the  4  years  following  1972,  the  annual  catch  averaged  1,352 
fish,  compared  to  928  for  the  4  years  prior.  A  tagging  study  of  smallmouth  bass 
>  203  mm  FL,  initiated  in  1976,  provided  a  weighted  estimate  of  mean  annual 
exploitation  rate  of  0.66  and  an  estimated  survival  rate  of  0.1 6  ( Pelzman,  Rapp, 
and  Rawstron,  in  prep.).  These  values  are  comparable  to  those  for  largemouth 
bass  at  Merle  Collins  Reservoir  (Rawstron  and  Hashagen  1972;  Rawstron  and 
Pelzman  1978). 

The  size  limit  apparently  protected  smallmouth  bass  less  than  305  mm  tl  in 
that  they  were  released  by  anglers  unable  to  distinguish  them  from  largemouth. 
Angler  interviews  revealed  that  species  identification  was  a  common  problem 
among  anglers.  An  increase  of  over  25.4  mm  in  the  mean  length  of  smallmouth 
in  the  catch  following  imposition  of  the  size  limit  suggests  that  anglers  selected 
for  fish  that  met  the  largemouth  size  requirement.  In  no  year  after  the  size  limit 
was  in  effect  was  the  mean  total  length  for  smallmouth  bass  less  than  305  mm 
(Table  3). 

Spotted  bass  constituted  only  a  minor  portion  of  the  Merle  Collins  Reservoir 
fishery.  It  is  probable,  however,  that  the  size  limit  served  to  protect  spotted  bass 
since  very  few  anglers  could  differentiate  them  from  largemouth  bass.  Twenty- 
three  of  the  38  spotted  bass  measured  in  the  census  from  1973  through  1976 
were  305  mm  or  greater  tl.  Considerable  increases  in  the  spotted  bass  popula- 
tion were  noted  during  electrofishing  operations  in  1975,  1976,  and  1977.  Most 
fish  observed  were  less  than  305  mm  in  length. 

The  annual  catch  of  redear  sunfish  more  than  doubled  (118%)  after  1972, 
while  bluegill  catches  decreased  by  about  20%.  These  changes  are  more  likely 
related  to  population  shifts  that  began  before  1972  than  to  an  influence  of  the 
size  limit.  Pre-size  limit  census  data  showed  that  redear  were  steadily  increasing 
in  the  catch.  Observations  made  during  electrofishing  operations  conducted 
prior  to  1972  suggested  that  redear  were  replacing  bluegill  as  the  dominant 
panfish.  Large  numbers  of  bluegill  less  than  102  mm  tl,  however,  were  observed 
during  electrofishing  work  in  1976  and  1977.  It  is  not  known  if  changes  in  catch 
data  for  black  crappie  or  green  sunfish  were  related  to  the  size  limit. 

Several  events  occurred  at  Merle  Collins  Reservoir  following  1972  which 
altered  the  fishery  and  may  have  affected  the  impact  of  the  size  limit: 

(1 )  Threadfin  shad,  Dorosoma  petenense,  which  had  been  present  in  large 
numbers  and  provided  an  important  food  item  for  bass  since  1967,  unex- 
pectedly declined  in  numbers  beginning  in  1974;  only  a  few  were  ob- 
served during  electrofishing  operations  in  1 975  ( 6  fish )  and  1 976  ( 3  fish ) . 

(2)  The  number  of  catchable  trout  planted  at  the  reservoir  annually  was 
increased  considerably. 

(3)  A  severe  drought,  which  affected  much  of  California,  reduced  water 
levels  in  late  1975  and  in  1976. 

2—78.025 


150  CALIFORNIA  FISH  AND  GAME 

(4)  Largemouth  bass  reproduction  was  below  average  during  most  years 
following  1972;  a  phenomenon  which  may  have  been  related  to  water 
level  manipulations. 

It  is  difficult  to  relate  certain  changes  in  the  fishery  of  Merle  Collins  Reservoir 
after  1972  to  the  size  limit  because  of  the  complexity  of  the  reservoir  environ- 
ment and  because  of  the  abnormal  events  listed  above.  Similarly,  detection  of 
changes  in  predator-prey  structure  is  difficult.  Census  data  and  observations 
made  during  electrofishing  operations  do  not  suggest  that  intermediate-sized 
panfish  were  substantially  reduced  in  number.  This  study  has  shown,  however, 
that  the  size  limit  reduced  angler  harvest  of  largemouth  bass,  a  desired  result  of 
minimum  size  limits  (Funk  1974).  This  was  accomplished  with  good  public 
acceptance  and  without  reductions  in  angler  effort  or  total  yield  of  game  fish. 
Evidence  was  gathered  to  indicate  that  the  size  limit  also  protected  smallmouth 
and  spotted  bass  less  than  305  mm  long.  As  these  findings  became  apparent,  size 
limits  were  applied  to  all  black  bass  at  Merle  Collins  Reservoir  and  26  other 
California  waters. 

ACKNOWLEDGMENTS 
Robert  R.   Rawstron  initiated  and  administered  the  creel  census  at  Merle 
Collins  Reservoir  until  1975.  Many  seasonal  aids,  too  numerous  to  list,  ably 
served  as  census  clerks  during  the  study  period.  Charles  E.  von  Geldern,  Jr.  made 
helpful  editorial  suggestions. 

REFERENCES 

Best,  E.  A  ,  and  H    D   Boles.     1956.     An  evaluation  of  creel  census  methods.  Calif.  Fish  Came,  42(2):  109-115. 

Funk,  J.  L.,  ed.  1974.  Largemouth  bass  harvest  in  the  midwest,  an  overview.  Symposium  on  overharvest  and 
management  of  largemouth  bass  in  small  impoundments.  North  Cent.  Div.,  Amer.  Fish.  Soc,  Spec.  Pub.  No. 
3,  )ulv  1974.  116  pp. 

Hashagen,  K.  A.,  Jr.  1973  Population  structure  changes  and  yields  of  fishes  during  the  initial  eight  years  of 
impoundment  of  a  warmwater  reservoir.  Calif   Fish  Came,  59(4):  221-244. 

Pelzman,  R.  ].  1978.  Hooking  mortality  of  juvenile  largemouth  bass  (Micropterus  salmoides).  Calif  Fish  Came, 
64(3):  49-52. 

Rawstron,  R.  R.,  and  K.  A.  Hashagen,  )r.  1972.  Mortality  and  survival  rates  of  tagged  largemouth  bass  (Microp- 
terus salmoides)  at  Merle  Collins  Reservoir.  Calif.  Fish  Came,  58(3):  221-230 

Rawstron,  R.  R.,  and  R.  J.  Pelzman.  1978.  Comparison  of  floy  internal  anchor  and  disk-dangler  tags  on 
largemouth  bass  (Micropterus  salmoides)  at  Merle  Collins  Reservoir   Calif   Fish  Game,  Mil):  121-123. 


HUMBOLDT  BAY  EELCRASS  STOCKS  151 

Calif.  Fish  and  Came  hS(l).   151-158.      1979. 

THE  STANDING  STOCK  AND  PRODUCTION  OF 
EELCRASS,  ZOSTER  A  MARINA,  IN 
HUMBOLDT  BAY,  CALIFORNIA  ^ 

LAWRENCE  W.  HARDING,  JR.^ 

Hopkins  Marine  Station  of 

Stanford  LJniversity 

Pacific  Grove,  California  93950 

and 

JAMES  H.  BUTLER 

Department  of  Oceanography 

Humboldt  State  University 

Areata,  California  95521 

Measurements  of  the  eelgrass,  Zostera  marina,  standing  stock  in  Humboldt  Bay, 
California,  were  conducted  on  seven  occasions  from  June  1971  through  August  1972. 
The  distribution  of  eelgrass  in  the  Bay  was  initially  determined  by  mapping  the 
Zostera  beds  in  extensive  surveys  using  light  aircraft,  automobiles,  and  small  boats. 
Following  these  preliminary  studies,  eelgrass  samples  were  periodically  taken  from 
representative  sites  in  the  eelgrass  beds.  These  studies  were  performed  in  an  effort 
to  determine  the  contribution  of  eelgrass  to  primary  production  in  Humboldt  Bay 
relative  to  that  of  the  phytoplankton,  and  to  estimate  the  annual  production  of 
eelgrass  by  repeated  collection  of  samples  throughout  the  year.  Values  ranged  from 
1.4  X  10*  kg  dry  wt  in  April  1972  to  6.9  X  lO*-  kg  dry  wt  in  )uly  1972.  South  Humboldt 
Bay  eelgrass  accounted  for  78  to  95%  of  the  total  stock.  The  area  supporting  Z. 
marina  growth  was  12.2  x  lO*"  m^.  Densities  of  plant  biomass  ranged  from  0.03  to 
0.73  kg  dry  wt/m^,  with  highest  values  recorded  for  south  Humboldt  Bay  beds.  A 
minimum  value  for  eelgrass  production  was  estimated  from  the  seasonal  increase  in 
standing  stock  and  published  values  for  carbon  content.  Production  for  the  April- 
July  interval  was  1.48  g  C/m^/day.  Minimum  eelgrass  production  for  Humboldt  Bay 
was  18.1  X  lO*"  g  C/day.  The  value  for  eelgrass  production  for  this  interval  in  Hum- 
boldt Bay  was  similar  to  that  reported  for  phytoplankton  production  measured  over 
the  same  period.  This  level  of  primary  production  is  comparable  in  magnitude  on  an 
areal  basis  to  those  of  highly  productive  cultivated  systems  and  rich  coastal  and 
estuarine  regions. 

INTRODUCTION 

Eelgrass,  Zostera  marina,  grows  on  broad  expanses  of  intertidal  mudflats  in  the 
two  major  regions  of  Humboldt  Bay,  California  (Figure  1 ).  The  biomass  density 
and  area  of  coverage  are  so  large  as  to  render  the  Zostera  beds  one  of  the  most 
prominent  features  of  the  Humboldt  Bay  estuary.  This  study  is  an  examination 
of  the  eelgrass  standing  stock  and  production  in  Humboldt  Bay.  Our  preliminary 
studies  indicated  that  changes  had  occurred  both  in  the  density  of  biomass  and 
the  distribution  of  eelgrass  during  the  10-year  interval  since  earlier  studies  were 
completed  (Keller  1963;  Keller  and  Harris  1966).  The  importance  of  Z  marina 
to  primary  production  in  the  Bay  prompted  further  quantitative  investigation  for 
comparison  with  previous  studies  and  for  evaluation  of  the  status  of  the  Hum- 
boldt Bay  eelgrass  population. 

Zostera  marina  is  an  important  primary  producer  in  the  temperate  waters  of 
northern  hemisphere  estuaries  and  sheltered  embayments.  This  seagrass  com- 

'  Performed  under  the  auspices  of  the  United  States  Energy  Research  and  Developme-^'  Administration.  Accepted 

for  publication  February  1979. 
^  Current  address:  University  of  California,  Santa  Barbara,  DeparJnent  of  Biological  Sciences,  Santa  Barbara 

California  93106. 


152 


CALIFORNIA  FISH  AND  CAME 


ARCATA 


w9; 


PACIFIC  OCEAN 


^. 


NORTH  BAY 


EUREKA 


CENTRAL 
BAY 


SCALE 
0   1 


MILES 
■  I 
3   4 


SOUTH 
BAY 


Figure  1.     Eelgrass  beds  and  sampling  locations  in  Humboldt  Bay,  California. 

prises  the  base  of  a  complex  food  web  and  provides  habitat  for  a  diverse 
assemblage  of  associated  organisms.  Various  aspects  of  eelgrass  biology  have 
been  discussed  before  (Peterson  and  Boysen-Jensen  1911;  MacGinitie  1935; 
Cottam  and  Munro  1954;  Thayer,  Wolfe,  and  Williams  1975).  For  a  complete 
literature  survey  on  Z  marina,  consult  Phillips  (1964)  and  McRoy  and  Phillips 
(1968). 


HUMBOLDT  BAY  EELCRASS  STOCKS  153 

Before  1931,  very  little  attention  was  given  to  the  populations  of  this  aquatic 
angiosperm.  A  sudden  decline  in  eelgrass  standing  stocks,  and  the  subsequent 
reduction  in  commercial  fish  yields  along  the  eastern  seaboard  of  North  Ameri- 
ca, prompted  numerous  investigations  of  community  interrelations  of  Zostera 
(Cottam  1934;  Stauffer  1937;  Moffitt  and  Cottam  1941;  Dexter  1944,  1953). 
Peterson  (1918)  recognized  early  the  economic  importance  of  Z  marina  as  he 
traced  the  diet  of  cod  and  other  commercially  important  species  and  suggested 
that  eelgrass  formed  the  autotrophic  base  of  those  food  chains.  Later  studies 
associated  with  the  eelgrass  blight  emphasized  the  importance  of  Zostera  to  the 
production  of  mollusks,  crustaceans,  annelids,  and  other  animal  forms.  Recent 
investigations  have  confirmed  the  importance  of  eelgrass  as  both  substratum  and 
habitat  for  a  diverse  estuarine  flora  and  fauna  (Marsh  1973;  Rasmussen  1973). 

Aside  from  its  direct  participation  in  marine  and  estuarine  food  webs,  eelgrass 
assumes  an  important  role  in  the  cycling  of  nutrients.  Organic  materials  from 
natural  decomposition  processes  or  sewage  effluent  are  filtered  and  collected  by 
eelgrass  leaves  and  turions  (Milne  and  Milne  1951),  providing  an  additional 
nutrient  source  for  the  Zostera  community.  Nutrients  that  otherwise  would  be 
accumulated  in  sediments  or  flushed  out  to  sea  may  thereby  be  retained  by 
eelgrass  and  recycled  within  the  estuarine  system.  The  functional  significance  of 
eelgrass  in  nutrient  cycling  and  biogeochemistry  has  been  discussed  further  by 
McRoy  and  Barsdate  (1970)  and  McRoy  and  Goering  (1974). 

Measurements  of  eelgrass  standing  stocks  have  been  conducted  throughout 
the  northern  hemisphere  (McRoy  1970);  several  of  these  studies  involved  eel- 
grass populations  from  the  west  coast  of  North  America.  Keller  (1963)  and 
Keller  and  Harris  (1966)  estimated  the  distribution  and  biomass  of  Z  marina '\n 
Humboldt  Bay.  Waddell  (1964)  studied  the  effects  of  oyster  dredging  on  eel- 
grass standing  stocks  in  Humboldt  Bay.  McRoy  (1966,  1968,  1970)  examined  the 
distribution  of  eelgrass  along  the  coast  of  Alaska  and  performed  biomass  meas- 
urements at  10  locations. 

Our  general  approaches  in  this  study  involved  collecting  a  temporal  series  of 
samples  from  representative  sites  in  the  Humboldt  Bay  eelgrass  beds  and  deter- 
mining the  areal  distribution  and  density  of  biomass  of  eelgrass  in  the  entire  Bay. 
From  these  data,  gathered  throughout  the  year,  we  hoped  to  infer  the  seasonal 
pattern  of  growth  and  decline  of  the  Humboldt  Bay  eelgrass  beds,  and  to 
estimate  the  proportion  of  primary  production  attributable  to  eelgrass  in  relation 
to  that  of  the  phytoplankton  in  this  estuary. 

MATERIALS  AND  METHODS 

Estimation  of  the  total  biomass  of  eelgrass  in  Humboldt  Bay  required  a  twofold 
approach:  (1  )  determination  of  the  total  acreage  that  supports  eelgrass  growth 
in  Humboldt  Bay,  and  ( 2 )  measurement  of  eelgrass  density  at  various  locations. 
The  product  of  the  area  and  density  of  biomass  values  for  each  eelgrass  bed 
yielded  the  total  quantity  of  eelgrass  present.  Summing  these  products  provided 
an  estimate  of  the  standing  stock  of  Humboldt  Bay. 

The  total  area  supporting  eelgrass  was  determined  during  1971  and  1972. 
Mapping  was  conducted  on  foot  and  from  small  boats,  automobile,  and  light 
aircraft.  The  boundaries  of  the  eelgrass  beds  were  mapped  on  a  U.S.  Geological 
Survey  Chart  (No.  5832)  of  Humboldt  Bay.  The  areas  supporting  eelgrass 
growth  were  determined  with  a  plane  planimeter. 


154  (  ALIFORNIA  FISH  AND  CiAME 

Eelgrass  beds  were  subjectively  classified  according  to  biomass  density  as 
supporting  light,  medium,  or  heavy  growth.  The  area  supporting  eelgrass  growth 
of  each  density  classification  was  determined  and  representative  sample  sites 
were  selected.  Five  stations  in  south  Humboldt  Bay  and  three  in  northern  Hum- 
boldt Bay  were  chosen  for  sampling  (Figure  1 ). 

Samples  were  collected  over  a  2-day  period,  with  north  and  south  Humboldt 
Bay  measurements  made  on  successive  days.  Similar  procedures  were  em- 
ployed on  seven  separate  occasions  from  June  1971  through  August  1972.  Sam- 
pling procedures  for  the  eight  representative  areas  were  standardized  to 
eliminate  bias  in  the  collection  of  eelgrass.  A  1-m  ring  thrown  in  a  direction 
determined  by  two  successive  coin  tosses  defined  the  area  to  be  sampled;  for 
consistency,  the  northeast  quadrant  of  the  ring  was  always  sampled.  Four  of  the 
samples  (each  0.25  m^)  were  collected  from  each  of  the  eight  sites.  All  plant 
material  within  each  quadrant  was  removed,  including  underground  portions, 
which  were  carefully  collected.  The  samples  were  stored  in  plastic  bags  and 
labeled,  returned  to  the  laboratory,  and  kept  in  a  cold  room  (6  C)  prior  to 
processing. 

In  the  laboratory,  eelgrass  samples  were  washed  to  remove  sediment  from  the 
plant  material.  Individual  samples  were  subsequently  shredded  with  a  knife, 
placed  in  tared  800-ml  beakers,  and  weighed  (for  fresh  weight).  Samples  were 
then  dried  at  60  C  to  constant  weight  and  dry  weights  determined. 

RESULTS  AND  DISCUSSION 

Standing  Stock 

The  total  eelgrass  standing  stock  in  Humboldt  Bay  ranged  from  1.4  X  10^  kg 
dry  wt  in  April  1972  to  6.9  X  10^  kg  dry  wt  in  July  1972;  south  Humboldt  Bay 
eelgrass  beds  constituted  78  to  95%  of  the  total  dry  weight  (Table  1).  The 
density  of  plant  biomass  was  consistently  higher  in  south  Humboldt  Bay  than 
in  north  Humboldt  Bay. 

The  total  eelgrass  standing  stock  for  south  Humboldt  Bay,  as  determined  by 
Keller  and  Harris  (1966),  was  lower  than  the  value  obtained  in  this  study  (Table 
2).  The  difference  is  partially  attributable  to  the  area  of  coverage  considered. 
Keller  and  Harris  (1966)  examined  only  those  mudflats  above  the  —1.5  foot 
tidal  level.  Since  a  considerable  portion  of  the  eelgrass  population  lies  below  that 
level,  the  additional  area  (about  2.75  X  10*'  m^)  should  have  been  included  in 
their  calculations.  They  also  neglected  a  significant  portion  of  the  plant  material, 
collecting  and  drying  only  the  eelgrass  turions,  thereby  underestimating  the  total 
eelgrass  standing  stock  based  on  density  of  biomass  measurements.  Therefore, 
our  higher  values  do  not  necessarily  indicate  increases  in  the  number  or  size  of 
eelgrass  beds  from  1960  to  1972,  but  may  be  the  result  of  more  complete 
mapping  of  subtidal  and  intertidal  areas  supporting  the  growth  of  Zostera,  and 
a  more  complete  sampling  of  the  plant  material. 

Results  obtained  by  Keller  (1963)  on  the  relative  biomass  per  unit  area  of 
north  and  south  Humboldt  Bay  eelgrass  were  similar  to  ours.  He  attributed  the 
differences  between  the  regions  to  sediment  composition,  tidal  flushing,  and  the 
commercial  dredging  for  oysters  in  north  Humboldt  Bay.  Most  mudflats  in  north 
Humboldt  Bay  are  lower  with  respect  to  tidal  height  than  those  in  south  Hum- 
boldt Bay,  but  it  is  doubtful  that  the  relationship  between  tidal  height  and 


HUMBOLDT  BAY  EELCRASS  STOCKS 


155 


TABLE  1 


Date 


)une 

Dec 

Apr 

May 

)une 

luly 

Aug 


)une 

Dec 

Apr 

May 

June 

luly 

Aug 


The  Densities  of  Biomass  and  Standing  Stocks  of  Eelgrass  in  North  and  South 
Humboldt  Bay,  June  1971  Through  August  1972 

Density  of  Density  of  Percent 

biomass  biomass  total 

(T±s.e.)  (7±  s.e.)  eelgrass 

No.  of     (kg  fresh  I  kg  dry                Total  Total  in  Bay 

samples      wt/m')  wt/m')          (kg  fresh  wt)  (kg  dry  wt)  (dry) 

South  Humboldt  Bay  (area  of  eelgrass  cover  =  7.86  x  10*  m^) 

1971 12         2.8+1.4  0.2110.11         22.0X10''  1.65X10*  88.3 

1971 20        2.1  +  1.1  0.32  +  0.09         16.5x10*  2.52x10*  95.1 

1972 19         1.110.3  0.14  10.12           8.6x10*  1.10x10*  78.3 

1972 18        1.9  10.5  0.29  10.06         14.9x10*  2.28x10*  82.6 

1972 20         4.7  12.6  0.61+0.40         36.9x10*  4.79x10*  90.2 

1972 20         6.9  13.9  0.73  10.45         54.2x10*  5.74X10*  83.1 

1972 20         5.4  +  3.9  0.60  10.54         42.4x10*  4.72x10*  82.5 

North  Humboldt  Bay  (area  of  eelgrass  cover  =  4.35  x  10*  m^) 

1971 12     0.70  10.40  0.05  10.03         3.05x10*  0.218X10*  11.7 

1971 12     0.33  10.20  0.03  10.02         1.44x10*  0.131X10*  4.9 

1972 12     0.45  10.16  0.07  10.04         1.96x10*  0.305x10*  21.7 

1972 12     0.7110.09  0.1110.02         3.09x10*  0.479X10*  17.4 

1972 12         1.0+1.2  0.12  +  0.11         4.35x10*  0.522x10*  9.8 

1972 12         2.5  12.3  0.27  10.22         10.9x10*  1.17x10*  16.9 

1972 12         1.4  11.1  0.23  10.11         6.09x10*  1.00x10*  17.5 


TABLE  2.     Eelgrass  Standing  Stocks  and  Mean  Biomass  Densities  from  Selected  Studies 
Conducted  Along  the  Western  Coast  of  North  America 

Mean 
biomass 
Total  area         Total  standing  stock         density 
Location  tm^)  (kg  dry  wt)         (kg  dry  wt/m') 

Izembek  Lagoon,  Alaska  170  X  10*  256  X  10*  1.52 

(McRoy  1970) 
Kinzaroff  Lagoon,  Alaska 8,71  X  10*  17.0x10*  1.96 

(McRoy  1970) 
Red  Head  Lagoon,  Alaska 0.45x10*  0.1x10*  0.22 

(McRoy  1970) 
Humboldt  Bay 12.2  X  10*  1.4-6.9  X  10*°         0.12-0.57° 

(Present  study) 
South  Humboldt  Bay 8.86  X  10*  1.1-5.7  x  10*°         0.14-0.73° 

(Present  study) 
South  Humboldt  Bay 5.55  X  10*  0.9  X  10*  0.16 

(Keller  and  Harris  1966) 

Range  of  values  for  the  seven  sampling  periods  in  this  study 

eelgrass  biomass  density,  as  proposed  by  Keller  and  Harris  (1966),  contributed 
much  to  this  difference.  The  hypothesis  does  not  account  for  the  low  eelgrass 
densities  at  the  —1.0  and  —1.5  foot  tidal  levels.  Their  results  did  show  that  the 
eelgrass  biomass  may  be  more  dense  at  or  below  the  —1.0  foot  level  at  a 
particular  sampling  site,  but  such  differences  cannot  be  applied  to  a  comparison 
of  two  different  locations. 


156  CALIFORNIA  FISH  AND  CAME 

Our  values  (Table  2)  indicate  that  both  the  eelgrass  standing  stock  and 
biomass  density  in  Humboldt  Bay  are  of  similar  magnitude  to  those  in  the  Gulf 
of  Alaska  lagoons.  Previous  determinations  of  standing  stock  for  west  coast 
eelgrass  (Keller  and  Harris  1966;  McRoy  1970),  hov^ever,  did  not  cover  a 
sufficient  period  of  time  to  permit  complete  assessment  of  the  populations. 
Significant  fluctuations  in  standing  stock  resulting  from  seasonal  influences  ne- 
cessitate the  gathering  of  temporal  data.  Since  samples  from  the  Gulf  of  Alaska 
lagoons  and  the  earlier  south  Humboldt  Bay  study  were  taken  during  the  sum- 
mer months,  standing  stock  values  were  probably  near  the  annual  maxima  for 
the  particular  study  areas.  These  values  can  therefore  be  compared  to  the  higher 
values  obtained  in  this  study. 

Eelgrass  Production 

A  minimum  value  for  eelgrass  production  during  the  spring  and  early  summer 
was  estimated  from  the  increase  in  standing  stock  from  April  through  July  1972. 
Because  losses  attributable  to  herbivore  grazing  and  the  physical  removal  of 
broken  turions  were  not  considered,  the  estimate  is  a  minimum  value  for  net 
production;  it  should  not  be  construed  to  represent  gross  production  of  eelgrass 
in  Humboldt  Bay. 

The  difference  in  total  standing  stock  between  April  and  July  was  5.5  X  10^ 
kg  dry  wt,  representing  a  mean  daily  increase  of  6.1  X  10'*  kg  dry  wt/day. 
McRoy  (1970)  used  a  value  of  0.296  g  C/g  dry  wt  for  estimates  of  eelgrass 
production  in  Alaska,  a  number  which  corresponds  closely  to  data  gathered  by 
Udell,  Zarudsky,  and  Dohney  (1969)  in  Hempstead  estuary  on  Long  Island. 
With  this  conversion  factor,  the  change  in  standing  stock  and  the  area  of  eelgrass 
coverage,  a  value  of  1.48  g  C/mVday  was  calculated  for  eelgrass  production  in 
Humboldt  Bay.  This  is  less  than  McRoy's  (1970)  value  of  8  g  C/mVday  for 
Izembek  Lagoon  eelgrass  in  Alaska,  but  McRoy's  measurements  were  based  on 
oxygen  evolution,  not  changes  in  biomass. 

Our  estimate  for  eelgrass  production  is  similar  to  the  mean  phytoplankton 
production  rate  determined  for  the  same  period  in  Humboldt  Bay  (Table  3), 
values  which  are  comparable  in  magnitude  to  primary  production  levels  in 
highly  productive  coastal  upwelling  (Anderson  1964;  Ryther  1969)  and  estuarine 
systems  (Williams  1966;  Taylor  and  Hughes  1967)  which  have  been  studied. 
These  values  are  also  comparable  to  production  figures  for  Z  marina  presented 
by  Thayer  et  al.  ( 1 975 )  and  indicate  that  eelgrass  primary  production  on  an  areal 
basis  is  similar  to  that  of  highly  productive  cultivated  crop  plants  such  as  corn, 
rice,  and  hay  (Odum  1959). 

TABLE  3.     Comparison    of    Eelgrass    and    Phytoplankton    Production    in    Humboldt    Bay, 
April  Through  |uly  1972 

Mean  daily  Mean  total 

Area               production  production 

(m^  X  W")        (gC/m^/day)  (gC  X  lO^/day) 

Phytoplankton  30.3-65.6            1.05-1.50°  32.3-53.4° 

Eelgrass 12.2                    1.48  18.1 

^  Values  given  are  for  lower  low  and  higher  high  water  surface  areas,  respectively  (Harding.  Cox.  and  Pequegnat  1978) 


HUMBOLDT  BAY  EELCRASS  STOCKS  157 

The  mean  daily  production  of  eelgrass  in  Humboldt  Bay  was  18.1  X  10^  g 
C/day,  and  the  mean  phytoplankton  production  for  Humboldt  Bay  from  April 
to  July  1972  was  32.3  X  10^  g  C/day  for  low  tide,  and  53.4  X  10^  g  C/day  for 
high  tide  (Harding,  et  al.  1978).  Because  the  estimate  for  eelgrass  production 
is  a  minimum  value,  the  data  indicate  that  total  production  by  eelgrass  was  of 
comparable  magnitude  to  that  of  the  phytoplankton  in  Humboldt  Bay  during  the 
spring  and  early  summer  of  1972.  These  data  support  the  conclusion  of  Williams 
(1973)  that  production  by  seagrasses  may  equal  or  exceed  that  of  phytoplank- 
ton and  contribute  substantially  to  overall  production  in  these  rich  marine  sys- 
tems. 

REFERENCES 

Anderson,  C.  C.     1 964.     The  seasonal  and  geographic  distribution  of  primary  productivity  off  the  Washington  and 

Oregon  coasts.  Limnol.  Oceanogr.  9:  284-302. 
Cottam,  C.     1934.     The  eelgrass  shortage  in  relation  to  waterfowl.  Am.  Came  Conf.,  Trans.  20:  272-279. 
Cottam,  C,  and  D.  A.  Munro.     1954.     Eelgrass  status  and  environmental  relations.  ).  Wild).  Manage.  18:  449^60. 
Dexter,  R.  W.     1944.     Ecological  significance  of  the  disappearance  of  eelgrass  at  Cape  Ann,  Massachusetts.  ). 

Wildl.  Manage.  8:  173-176. 

1953.     Recession  of  eelgrass  at  Cape  Ann,  Massachusetts.  Ecology  34:  229. 

Harding,  L.  W.,  Jr.,  J.  L.  Cox,  and  ).  E.  Pequegnat.     1978.     Spring-summer  phytoplankton  production  in  Humboldt 

Bay,  California.  Calif.  Fish  Came  64:  53-59. 
Keller,  M      1963.     Growth  and  distribution  of  eelgrass  (Zostera  marina)  in  Humboldt  Bay,  California.  M.S.  Thesis. 

Humboldt  State  College.  Areata,  California.  53  pp. 
Keller,  M.,  and  S.  W.  Harris.     1966.     The  growth  of  eelgrass  in  relation  to  tidal  depth.  ).  Wildl.  Manage.  30: 

280-285. 
MacCinitie,  C.  E.     1935.     Ecological  aspects  of  a  California  marine  estuary.  Am.  Midi.  Nat.  16:  629-765. 
McRoy,  C.  P.     1966.     The  standing  stock  and  ecology  of  eelgrass  Zostera  marina  L.  in  Izembek  Lagoon,  Alaska. 

M.S.  Thesis.  University  of  Washington.  Seattle.  138  pp. 

1968.     The  distribution  and  biogeography  of  Zostera  marina  (eelgrass)  in  Alaska.  Pac.  Sci.  22:  507-513. 

1970.     Standing  stocks  and  other  features  of  eelgrass  (Zostera  marina)  populations  on  the  coast  of 

Alaska.  Fish.  Res.  Bd.  Canada,  ).  27:  1811-1821. 
McRoy,  C.  P.,  and  R.  ).  Barsdate.     1970.     Phosphate  adsorption  in  eelgrass.  Limnol.  Oceanogr.  15:  6-13. 
McRoy,  C.  P.,  and  |.  ).  Coering.     1974.     Nutrient  transfer  between  seagrass  Zostera  marina  and  its  epiphytes. 

Nature  248:  173-174. 
McRoy,  C.  P.,  and  R.  C.  Phillips.     1968.     Supplementary  bibliography  on  eelgrass  Zostera  marina.  U.S.  Fish,  and 

Wildl.  Serv.,  Spec.  Sci.  Rep.  Wildl.  114.  14  pp 
Marsh,  C.  A.     1973.     Zostera  epifaunal  community  in  the  York  River,  Virginia.  Chesapeake  Sci.  14:  87-91. 
Milne,  L.  J  ,  and  M.  ).  Milne.     1951.     The  eelgrass  catastrophe.  Sci.  Am.  184:  52-55. 
Moffitt,  ).,  and  C.  Cottam.     1941.     Eelgrass  depletion  on  the  Pacific  coast  and  its  effect  on  the  black  brant.  U.S. 

Dep.  Inter.  Fish.  Wildl.  Serv.  Leaflet  204.  26  pp. 
Odum,  E.  P.     1959.     Fundamentals  of  ecology.  2nd  ed.  W.  B.  Saunders.  Philadelphia    546  pp. 
Peterson,  C.  C.  ).     1918.     The  sea  bottom  and  its  production  of  sea  food.  Rep.  Dan.  Biol.  Sta.  25:  1-62. 
Peterson,  C.  G.  ).,  and  P.  Boysen-Jensen.     1911.     Valuation  of  the  sea.  I.  Animal  life  of  the  sea  bottom,  its  food 

and  quantity.  Rep.  Dan.  Biol.  Sta.  20:  1-81. 
Phillips,  R.  C.     1964.     Comprehensive  bibliography  o\  Zostera  marina.  U.S.  Fish.  Wildl.  Serv.  Spec.  Sci.  Rep  Wildl. 

79.  35  pp. 

Rasmussen,  E.     1973.     Systematics  and  ecology  of  the  Isefjord  marine  fauna  (Denmark)  with  a  survey  of  the 

eelgrass  (Zostera)  vegetation  and  its  communities.  Ophelia  11:  1-507. 
Ryther,  ).  H.     1969.     Photosynthesis  and  fish  production  in  the  sea.  Science  166:  72-76. 
Stauffer,  R.  C.     1937.     Changes  in  the  invertebrate  community  of  a  lagoon  after  disappearance  of  the  eelgrass. 

Ecology  18:  427-431. 
Taylor,  W.  R.,  and  ).  E.  Hughes.     1967.     Primary  productivity  in  the  Chesapeake  Bay  during  the  summer  of  1964. 

Chesapeake  Bay  Inst.,  Tech.  Rep.  34.  31  pp. 
Thayer,  G.  W.,  D.  A.  Wolfe,  and  R   B.  Williams.     1975.     The  impact  of  man  on  seagrass  systems.  Am.  Sci.  63: 

288-296. 


158  CALIFORNIA  FISH  AND  CAME 

Udell,  H.  P.,  ).  Zarudsky,  and  T.  E.  Dohney.     1969.     Productivity  and  nutrient  values  of  plants  growing  in  the  salt 
marshes  of  the  town  of  Hempstead,  Long  Island.  Torrey  Bot.  Club,  Bull.  96:  42-51. 

Waddell,  ).  E.     19M.     The  effect  of  oyster  culture  on  eelgrass  (Zostera  marina)  growth.  M   S  Thesis.  Humboldt 

Stale  College.  Areata,  California.  48  pp 
Williams,  R.  B      1966      Annual  phytopiankton  production  in  a  system  of  shallow  temperate  estuaries.  Pages 

619-716  in  H    Barnes,  ed.  Some  contemporary  studies  in  marine  science.  Hafner  Publishing  Co.,  New  York. 

1973.     Nutrient  levels  and  phyloplankton  productivity  in  the  estuary.  Pages  59-89  in  R.  H.  Chabreck, 

ed.  Proc.  Coastal  Marsh  and  Estuary  Manag.  Symp    Baton  Rouge   Louisiana  State  Univ.  Div.  Cont.  Educ. 


NORTH  KINGS  RIVER  DEER  HERD  159 

Calif.  Fish  and  Came  65  ( 3 ):  1 59-1 65.     1 979. 

ESTIMATING  FETUS  AGE  AND  BREEDING  AND  FAWNING 
PERIODS  IN  THE  NORTH  KINGS  RIVER  DEER  HERD  ^ 

HAL  SALWASSER  ^  and  STEPHEN  A.  HOLE  ' 

California  State  University,  Fresno 

Fresno,  CA     93710 

Hindfoot  length  was  selected  as  the  best  parameter  for  aging  late  term  California 
mule  deer,  Odocoileus  hemionus  californicus,  fetuses.  Regression  analysis  indicated 
that  litter  size  has  a  bearing  on  fetal  growth.  Therefore,  aging  models  were  devel- 
oped for  both  single  and  twin  fetuses.  Estimation  of  breeding  and  fawning  periods 
based  on  fetuses  aged  by  the  hindfoot  length  model  showed  a  3  week  peak  of 
breeding  centered  on  1  December,  and  a  3  week  fawning  period  centered  on  22  June. 
The  methods  described  are  applicable  to  any  wild  deer  herd. 

INTRODUCTION 

Knowledge  of  the  breeding  and  fawning  periods  of  deer  herds  is  important  to 
management  and  research.  The  purpose  of  this  study  was  to  determine  breeding 
and  fawning  periods  of  the  North  Kings  River  deer  herd.  In  the  course  of  this 
work  we  needed  to  develop  a  method  for  estimating  the  age  of  late  term  fetuses. 

The  North  Kings  River  deer  herd  is  located  in  Fresno  County,  California.  Other 
recent  studies  on  this  herd  have  dealt  with  fawn  production  and  survival  (Sal- 
wasser,  Holl,  and  Ashcraft  1978)  and  diets  and  nutrition  during  pregnancy  ( Holl, 
Salwasser,  and  Browning  1979). 

Breeding  and  fawning  period  estimates  are  often  based  on  the  ages  of  fetuses 
acquired  through  special  hunts,  road  kills,  and  scientific  collections  (Chattin 
1 948;  Robinette  and  Gashwiler  1 950;  Lassen,  Ferrel,  and  Leach  1 952;  Taber  1 953; 
Bischoff  1 957 ) .  Most  fetal  aging  studies  have  relied  upon  morphological  changes 
during  fetal  development.  Armstrong's  (1950)  and  Hudson  and  Browman's 
(1959)  keys  for  whitetailed,  Odocoileus  virginlanus,  and  mule  deer,  O.  hem- 
ionus, are  the  basis  for  this  approach.  However,  as  the  fetus  enters  the  last 
trimester  of  gestation,  external  changes  other  than  growth  are  not  easily  discerni- 
ble. 

Chattin  (1948)  presented  a  fetal  growth  curve  based  on  hindfoot  length  for 
fetuses  up  to  170  days  old.  Hudson  and  Browman  (1959)  provided  growth 
curves  for  four  physical  parameters.  These  were  based  on  five  known-age  and 
numerous  calculated-age  fetuses.  Their  data  terminated  at  180  days  of  fetal  age. 
Short  (1970)  developed  linear  regression  models  for  mule  deer  fetuses  from 
Hudson  and  Browman's  data.  Nellis  ( 1 966 )  explored  the  use  of  eye  lens  weights 
for  aging  mule  deer  fetuses.  He  found  the  technique  useful  but  pointed  out  that 
lens  weight  was  positively  correlated  with  body  weight.  Only  Short  (1970) 
worked  with  data  from  fetuses  (a  sample  of  three  mule  deer  fetuses)  in  the  last 
month  of  prenatal  growth.  Since  much  of  our  work  was  done  during  this  period 
we  needed  to  extend  aging  curves  to  full-term. 

An  ideal  parameter  for  aging  deer  fetuses  would  have  the  following  character- 

'  Assistance  to  this  investigation  was  provided  by  Federal  Aid  in  Wildlife  Restoration  Projects  W-51-R  "Big  Came 
Studies"  and  W-52-R  "Wildlife  Investigations  Laboratory,  '  and  by  the  Union  Foundation  Fund,  University  of 
California,  Berkeley.  Accepted  for  publication  January  1979 

^  Current  address:  Tahoe  National  Forest,  Nevada  City,  California  95959. 

^  Current  address:  San  Bernardino  National  Forest,  Cajon  Ranger  District,  Star  Route  Box  100,  Fontana,  California 
92335. 


160  CALIFORNIA  FISH  AND  GAME 

istics:  1  )  it  would  change  in  a  predictable  and  accurately  measurable  way  as  the 
fetus  gets  older,  2)  it  would  be  relatively  insensitive  to  environmental  variables, 
3)  it  could  be  easily  and  precisely  measured  by  field  biologists  and  researchers 
alike,  and  4)  it  would  require  a  minimum  of  laboratory  and  analytical  treatment 
to  derive  the  age  estimate. 

Unfortunately,  as  Verme  (1963,  1977)  has  shown,  maternal  nutrition  affects  all 
easily  measured  growth  parameters  of  deer  fetuses.  Thus,  while  it  is  conceivable 
that  criteria  1,  3,  and  4  could  be  met,  the  need  for  a  parameter  that  is  insensitive 
to  environmental  conditions  is  not  likely  to  be  met  exactly.  We  thus  explored 
the  use  of  three  parameters  that  we  suspected  of  being  the  least  influenced  by 
maternal  nutrition:  1 )  hindfoot  length,  2)  contour  length,  and  3)  eye  lens  weight. 
Since  the  eye  lens  technique  requires  extra  laboratory  work,  we  felt  it  would 
have  to  be  far  superior  to  the  skeletal  growth  methods  to  warrant  its  use. 

METHODS 

Deer  collections  were  made  during  the  springs  of  1971-1975,  as  described  by 
Salwasseret  al.  (1978).  Fetuses  from  each  doe  were  sexed,  tagged  for  identifica- 
tion, and  stored  in  10%  formalin.  They  were  removed  from  the  preservative  in 
the  laboratory,  rinsed  with  tap  water,  and  measured. 

Contour  length  was  measured  with  a  cloth  metric  tape  to  the  nearest  millime- 
ter. It  is  the  dorsal  length  of  the  fetus  from  the  distal  edge  of  the  brown  nasal 
patch,  along  the  contour  of  the  head,  shoulders  and  spine  to  the  center  point 
on  a  line  drawn  across  the  ischial  tuberosities  (see  Armstrong  1950).  In  our 
attempts  to  measure  crown-rump  and  forehead-rump  lengths  of  near-term 
fetuses,  we  encountered  variation  due  to  how  the  preserved  fetus  was  contorted. 
This  problem  could  have  been  avoided  by  measuring  fetuses  prior  to  preserva- 
tion. We  used  the  contour  length  because  it  is  less  subject  to  errors  that  result 
from  deformation  of  the  fetus  than  are  the  crown-rump  and  forehead-rump 
lengths. 

Hindfoot  length  (HFL)  was  measured  on  an  "L"  shaped  device  containing  a 
metric  ruler  on  the  base.  The  ankle  was  placed  in  the  angle  of  the  measuring 
board,  and  the  length  of  the  hindfoot,  to  the  nearest  millimeter,  was  read  at  the 
tip  of  the  hoof.  The  left  hindfoot  was  measured  for  standardization.  We  compen- 
sated for  hooves  damaged  during  preservation  by  estimating  the  length  of  hoof 
tips  missing. 

Eye  lenses  were  removed  and  rinsed  in  tap  water.  (If  the  fetus  has  not  been 
in  preservative  storage,  the  eyeball  should  be  removed  intact  and  stored  in 
fixative  prior  to  removing  the  lens.)  Lenses  were  oven  dried  at  80  C  until  a 
constant  weight  was  achieved.  Lenses  were  removed  from  the  oven,  allowed 
to  cool  for  3-5  minutes,  and  weighed  on  a  Mettler  automatic  balance  to  the 
nearest  0.01  milligram.  Weighing  was  done  within  10  minutes  of  removal  from 
the  oven.  Drying  time  averaged  12  days.  Larger  lenses  required  more  time  than 
smaller  ones.  The  heavier  eye  lens  was  used  as  the  datum  for  each  fetus. 

The  estimated  average  size  of  fawns  at  birth  was  calculated  from  measure- 
ments of  captured  fawns  and  all  fetuses  that  exceeded  the  smallest  captured 
fawn  in  size.  We  thus  assumed  that  any  fetus  equal  to  or  larger  than  the  smallest 
captured  fawn  was  a  full-term  fetus. 

Fetal  parameters  were  regressed  on  the  number  of  days  since  1  November  to 
find  the  best  fit.  We  had  known  that  all  does  in  the  herd  bred  after  this  date. 


NORTH  KINGS  RIVER  DEER  HERD  161 

October  1  or  1  September  should  be  used  in  herds  that  breed  earlier.  Regressions 
were  explored  for  growth  differences  according  to  litter  size  and  fetus  sex.  The 
influence  of  doe  age  is  reflected  in  litter  size,  as  most  single  fetuses  came  from 
yearling  and  2-year-old  does  (Salwasser  et  al.  1978).  Abnormally  early-  or 
late-conceived  fetuses  were  excluded  form  our  development  of  final  growth 
curves.  The  biological  significance  of  differences  in  growth  equations  was  judged 
according  to  the  difference  in  estimated  age  at  a  given  size. 

RESULTS  AND  DISCUSSION 

The  initial  fit  of  all  three  parameters  to  the  liner  model  Y  =  a  +  b,,  was 
sufficiently  good  that  it  was  unwarranted  to  explore  transformations  or  non- 
linear models  (HFL  against  days,  r^  =  .859).  This  is  consistent  with  the  findings 
of  Hudson  and  Browman  (1959),  Nellis  (1966),  and  Short  (1970)  that  these  are 
linear  growth  phenomena  in  mid-  to  late-term  deer  fetuses.  All  three  parameters 
are  suitable  for  use  as  aging  criteria. 

However,  hindfoot  length  is  the  easiest  to  measure  accurately.  Since  it  also 
had  the  best  correlation  with  number  of  days  since  1  November  (r  =  .94) 
(Figure  1 ),  we  selected  hindfoot  length  as  the  best  parameter  for  aging  fetuses. 

Six  fawns,  estimated  to  be  from  1  to  3  days  old,  were  captured  in  1975.  Their 
average  hindfoot  length  was  237  mm  (range  232-246  mm).  Their  average 
weight  was  3,075  g  (range  2,800-3,250  g)  (Holl  1976).  The  smallest  captured 
fawn  was  the  runt  of  a  set  of  twins.  We  inferred  from  the  captured  fawn 
data — and  from  Cowan  and  Wood  (1955);  Hudson  and  Browman  (1959); 
Robinette,  Baer,  Pillmore  and  Knittle  (1973) — that  a  single  fawn,  or  one  of  a  set 
of  twins,  must  exceed  3,000  g  to  qualify  as  a  full-term  fetus.  Nine  fetuses  met 
this  criterion,  five  singles  and  two  sets  of  twins.  When  pooled  with  the  captured 
fawn  data,  the  estimated  average  size  of  a  full-term  fetus  was:  HFL  =  231  mm 
(S.D.  =  16,  range  192-255  mm),  weight  =  3,254  g  (S.D.  =  219,  range  2,800- 
3,668  g). 

When  the  estimated  average  hindfoot  length  of  a  newborn  fawn  was  inserted 
into  the  regression  model  for  change  in  hindfoot  length  of  all  fetuses  since  1 
November,  an  age  of  235  days  was  predicted.  We  assumed  204  days  to  be  the 
average  gestation  period  of  California  mule  deer.  Dixon  (1934)  reported  207 
days,  Robinette  and  Cashwiler  (1950)  reported  202  days,  and  Short  (1970) 
reported  200  days  as  average  gestation  periods  for  the  species  of  Odocoileus. 
Therefore,  we  adjusted  the  y-intercept  of  the  model  downward  by  31  days  to 
yield  a  predicted  age  of  204  days  when  hindfoot  length  reached  231  mm.  It  was 
further  assumed  that  the  regression  models  for  other  parameters  overestimated 
fetus  age  by  31  days  and  adjusted  the  models  for  predicting  fetal  age  (Table  1 ). 

TABLE  1.     Regression  Equations  for  Predicting  Fetus  Age  from  Hindfoot  Length,  Contour 
Length,  or  Eye  Lens  Weight  Regardless  of  Fetus  Sex  or  Litter  Size 

n         Regression  equation  r  i^         S.  E.  b^ 

151        Age  =  68 -I-    .59  (HFL  in  mm) 960  .921  .014 

151        Age  =  45-1-    .26  (Contour  in  mm) 945  .893  .007 

106        Age  =76 -I- 1.01  (Lens  weight  in  mg)  945  .893  .035 

S.  E.  b.  is  the  standard  error  of  the  slope  coefficient. 

The  influence  of  fetal  sex  and  litter  size  on  hindfoot  length  was  examined  with 
the  linear  regression  model  (Table  2).  Fetal  sex  apparently  had  little  effect  on 
late-term  size  (Table  3).  Males  were  slightly  larger  at  100  days,  but  size  differ- 


162 


CALIFORNIA  FISH  AND  CAME 


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Hindfoot     Length    (mm) 

Scattergram  of  fetal  hindfoot  length  versus  number  of  days  since  November  1  to  date 
of  collection.  The  dashed  line  represents  a  45-day  span  and  illustrates  the  linear  relation- 
ship of  hindfoot  growth  with  time. 


ences  diminished  to  essentially  none  at  birth.  Litter  size  did  make  a  difference, 
however.  Single  fetuses  were  smaller  at  100  days,  perhaps  reflecting  the  fact  that 
most  singles  came  from  yearling  and  2-year-old  does  that  were  breeding  for  the 
first  time.  By  200  days,  singles  exceeded  twins  by  1 5  mm  in  hindfoot  length.  Until 
the  causes  of  these  differences  become  known,  we  advise  the  use  of  different 
aging  equations  for  singles  and  twins.  Since  these  models  were  based  on  fetuses 
with  hindfoot  lengths  ranging  from  50  mm  to  that  at  full  term,  the  models  are 
suitable  for  aging  any  fetuses  over  100  days  old  (or  fetuses  from  does  collected 
after  February  in  the  North  Kings  herd).  Because  of  environmental  variations 
between  years  and  natural  variations  between  does,  the  late-term  ages  derived 


NORTH  KINGS  RIVER  DEER  HERD  163 

from  the  aging  equations  should  be  interpreted  as  being  accurate  to  ±  5  days 
at  best. 

TABLE  2.     Fetus  Sex  and  Litter  Size  Influences  on  Hindfoot  Growth 

Fetuses                                                n  Regression  equation                   r  P  S.  E.  b^ 

All  151  Age  =  68 -I- .59  (HFL  in  mm)  .960  .921  .014 

Males 78  Age  =  65  +  .60  (HFL  in  mm)  .960  920  .020 

Females 73  Age  =  71  +  .57  (HFL  in  mm)  .961  925  .019 

Singles 28  Age  =  75  +  .53  (HFL  in  mm)  .963  .928  .029 

Twins 114  Age  =  65  +  .61  (HFL  in  mm)  .963  .928  .016 

'  S.  E.  b.  is  the  standard  error  of  the  slope  coefficient 

TABLE  3.     Relative  Growth  of  Fetuses  According  to  Equations  Presented  in  Table  2 

Hindfoot  length  (mm)  at 

Fetuses                                                                 Regression  equation  100  days  150  days  200  days 

All  Age  =  68  +  .59  (HFL  in  mm)  54  139  224 

Males Age  =  65  +  .60  (HFL  in  mm)  58  142  225 

Females Age  =  71  +.57  (HFL  m  mm)  51  139  226 

Singles Age  =  75  +  .53  (HFL  in  mm)  47  142  236 

Twins Age  =  65  +  ,61  (HFL  in  mm)  57  139  221 

We  believe  that  the  use  of  a  time  series  analysis  of  fetal  growth  with  known 
size  of  newborn  fawns  is  a  suitable  alternative  in  developing  fetal  age  curves 
when  known-age  fetuses  are  not  available.  Given  a  time  series  collection  of 
pregnant  does  and  information  on  newborn  fawn  size,  a  fetal  age  predictor  could 
be  developed  for  any  wild  deer  herd.  Special  care  should  be  used,  however,  in 
applying  the  assumptions  about  length  of  gestation  period  and  average  size  of 
newborn  fawns  to  populations  that  differ  from  those  reported  in  the  literature. 
Also  the  time  series  method  described  here  should  not  be  used  in  studies  in 
which  fewer  than  20  fetuses  are  available. 

To  determine  breeding  and  fawning  periods,  the  age  of  a  multiple  litter  was 
assumed  to  be  the  age  of  the  largest  fetus.  The  age  of  each  litter  was  extrapolated 
to  determine  conception  date.  Average  fawning  date  was  assumed  to  occur  204 
days  after  the  conception  date  (Figure  2). 

The  earliest  breeding  occurred  on  6  November  ( 1 974 ) ,  the  latest  on  3  Febru- 
ary (1973),  probably  during  the  second  or  third  estrus  period.  Two-year-old 
does  were  involved  in  both  cases.  In  all  other  years  breeding  commenced  during 
the  second  week  of  November  and  terminated  during  the  third  week  of  Decem- 
ber. The  mean  dates  of  breeding  ranged  from  25  November  (1972)  to  10 
December  (1971).  Over  the  5-year  period,  the  mean  breeding  date  was  1 
December,  and  75%  of  all  breeding  occurred  within  8  days  of  that  date. 

Fawning  on  the  North  Kings  range  may  begin  as  early  as  29  May,  but  the  first 
fawns  in  most  years  will  be  born  during  the  first  week  in  June.  The  peak  2  weeks 
of  fawn  drop  occur  between  14  June  and  30  June.  Sixty  percent  of  the  fawns  are 
born  during  this  period.  Approximately  one-fourth  of  the  fawns  are  born  in  early 
July.  Yearlings  and  2-year-old  does  bred  and  fawned  about  1  week  after  prime 
age  does. 

The  breeding  and  fawning  periods  of  the  North  Kings  herd  are  earlier  than 
those  reported  for  the  Sequoia  and  Jawbone  herds  on  the  Sierra  Nevada  west 
slope  ( Bischoff  1 957 ) .  The  periods  are  similar  to  those  of  some  black-tailed  deer, 
O.  h.  columblanus,  herds  in  California. 


164 


CALIFORNIA  FISH  AND  CAME 


"CD 


o 


c: 

O 


Breeding      Dotes 


100 


90 


80 


70 


60 


50 


40 


30 


20 


Now         Nov.  Nov.        Nov.         Nov.  Dec. 

1-7        8-14       15-2!      22-28     29-5  6-12 

1 


Dec.        Dec. 
13-19     20-26 


T 


T 


T 


T 


Cumulative 


Q  li l.limi.lTTTTT 


May         May         June 


June 


June 


June 


23-30      31-6 


7-13       14-20      21-27     28-4 


July         July 
5-11        12-19 


Fawning      Dates 


Figure  2.     Bar  histogram  of  conception  and  breeding  dates  of  California  mule  deer  in  the  North 
Kings  River  herd  during  1971-75. 


ACKNOWLEDGMENTS 
We  are  pleased  to  acknowledge  the  assistance  and  advice  of  Oscar  Brunetti, 
William  Longhurst,  Guy  Connolly,  and  Karen  Shimamoto.  John  Kie  offered  valu- 
able comments.  Nobu  Asami  of  U.C.  Berkeley  prepared  the  manuscript. 


NORTH  KINGS  RIVER  DEER  HERD  165 

REFERENCES 

Armstrong,  R    A.     1950.     Fetal  development  of  northern  white-tailed  deer.  Am.  Midi.  Natur.  43(3):  650-666. 
Bischoff,  A.  I.     1957.     The  breeding  season  of  some  California  deer  herds   Calif.  Fish  Came  43(1 ):  91-96. 
Chattin, )   E      1948.     Breeding  season  and  productivity  in  the  Interstate  deer  herd.  Calif  Fish  Came  34(1 ):  25-31. 
Cowan,  I.  McT.,  and  A. ).  Wood. .    1955.     The  growth  rate  of  the  black-tailed  deer  Odocoileus  hemionus  colum- 

bianus.  ).  Wild!.  Manage.  19(3):  331-336. 
Dixon,  J.  S.     1934.     A  study  of  the  life  history  and  food  habits  of  the  mule  deer  in  California:  Part  I.  Life  history. 

Calif.  Fish  Came  20(3):  181-282. 
Holl,  S.  A.     1976.     Fawn  production,  habitat  requirements,  and  growth  in  the  North  Kings  deer  herd,  Fresno 

County,  California.  MA.  Thesis,  California  State  University,  Fresno    128  pp. 
Holl,  S.  A.,  H.  Salwasser,  and  B.  Browning.     1979.     Diet  composition  and  energy  reserves  of  California  mule  deer 

during  pregnancy.  Calif.  Fish  Came  65(2):  6&-79. 
Hudson,  P.,  and  L.  C.  Browman.     1959      Embryonic  and  fetal  development  of  the  mule  deer.  ).  Wildl.  Manage. 

23(3):  295-304. 
Lassen,  R.  W.,  C.  M.  Ferrel,  and  H.  Leach.     1952.     Food  habits,  productivity  and  condition  of  the  Doyle  mule 

deer  herd.  Calif.  Fish  Came  38(2):  211-224. 
Nellis,  C.  H.     1966.     Lens  weights  of  mule  deer  fetuses.  ].  Wildl.  Manage.  30(2):  417-419. 
Robinette,  W.  L.,  and  |.  S.  Cashwiler.     1950.     Breeding  season,  productivity,  and  fawning  period  of  the  mule  deer 

in  Utah.  ).  Wildl.  Manage.  14(4):  457^69. 
Robinette,  W.  L.,  C.  H.  Baer,  R.  E.  Pillmore,  and  C.  E.  Knittle.     1973.     Effects  of  nutritional  change  on  captive  mule 

deer.  ).  Wildl.  Manage   37(3):  312-326. 
Salwasser,  H.,  S.  A.  Holl,  and  C.  A.  Ashcraft.     1978      Fawn  production  and  survival  in  the  North  Kings  deer  herd 

Calif.  Fish  Came  64  ( 1 ) :  38-52. 
Short,  C.     1970.     Morphological  development  and  aging  of  mule  and  white-tailed  deer  fetuses.  J.  Wildl.  Manage. 

34(2):  383-388. 
Taber,  R.  D.     1953.     Studies  of  black-tailed  deer  reproduction  on  three  chaparral  cover  types.  Calif.  Fish  Came 

38(2):  177-^43. 
Verme,  L.  j.     1963.     Effect  of  nutrition  on  growth  of  white-tailed  deer  fawns.  Trans.  N    Am   Wildl.  Conf    28: 

431^»43. 
1977.     Assessment  of  natal  mortality  in  upper  Michigan  deer.  J.  Wildl.  Manage.  41(4);  700-708. 


166  CALIFORNIA  FISH  AND  CAME 

NOTES 

HEMATOLOGICAL  STRESS  RESPONSE  OF  RAINBOW 
TROUT,  Salmo  gairdneri,  TO  A  SIMULATED  GEOTHERMAL 

STEAM  CONDENSATE  SPILL 

Steam  condensate  is  a  by-product  of  electrical  power  production  using  geo- 
thermal  steam  at  the  Geysers,  Sonoma  County,  California.  The  condensate  is 
ordinarily  returned  to  the  production  zone  by  reinjection  well,  but  during  1974 
and  1975  eleven  major  spills  occurred  in  which  the  condensate  reached  nearby 
streams.  Although  fish  kills  resulted  from  some  of  these  spills  (Department  of 
Fish  and  Game  unpublished  data),  the  sublethal  effects  of  the  condensate  re- 
main undocumented. 

Blood  hematology  has  been  used  by  some  researchers  to  monitor  sublethal 
stress  response  of  rainbow  trout  (Blaxhall  1972,  Courtois  1975,  McLeay  1975). 
This  study  was  undertaken  to  determine  if  hematological  characteristics  of  rain- 
bow trout  are  affected  after  exposure  to  stream  condensate  under  simulated 
stream  conditions. 

At  condensate  concentrations  of  5  to  29%,  LeGore  and  Bowen  (1976)  found 
50%  of  the  rainbow  trout  died  within  96  hours.  During  low  flow  (5  cfs)  periods 
in  streams  adjacent  to  the  Geysers,  large  spills  of  condensate  (e.g.,  182,000  liters 
in  4  min  on  September  5,  1975)  could  exceed  these  concentrations.  The  conden- 
sate would  be  gradually  diluted  and  carried  downstream.  Little  is  known  about 
the  degree  of  stress  placed  upon  fish  exposed  to  spills  of  condensate  at  low 
concentrations.  Monitoring  the  hematological  stress  response  of  rainbow  trout 
to  the  condensate  would  be  valuable  in  assessing  its  effect  on  fish  in  their  natural 
habitat. 

To  approximate  a  condensate  spill,  56.8  liters  of  condensate,  collected  from 
Geysers  Power  Plant  Unit  6  was  added  to  a  500-liter  tank  containing  378.5  liters 
of  filtered  river  water  and  20  shasta  strain  rainbow  trout  from  the  American  River 
Fish  Hatchery  averaging  1 14  g  wet  weight  and  22  cm  fl.  This  represented  a  1 5% 
volume/volume  addition  to  a  stream.  The  added  condensate  slowly  overflowed 
through  a  standpipe  drain  which  kept  the  water  level  constant.  An  identical  tank 
with  20  fish  served  as  an  untreated  control  group.  Water  in  both  tanks  was 
exchanged  at  the  rate  of  60  liters/ hr.  Air  was  bubbled  in  the  tanks  through  porous 
stones.  Carbon  dioxide,  ammonia,  and  oxygen  levels  were  monitored  in  each 
tank  using  Hach""  prepared  reagents.  These  parameters  were  altered  when 
steam  condensate  was  added  to  water  in  preliminary  tests. 

Blood  from  fish  in  both  the  control  and  test  tanks  was  collected  immediately 
after  beginning  the  test  and  at  2  hr,  23  hr,  and  93  hr.  Individual  fish  were  used 
only  once  during  the  test  and  were  not  returned  to  the  test  tank.  Five  fish  from 
each  tank  were  anesthetized  with  MS-222  (tricaine  menthanesulfonate),  and  a 
heparinized  syringe  was  used  to  remove  a  blood  sample  via  cardiac  puncture. 
Hematocrit  (PCV)  and  total  hemoglobin  (Hb)  (cyanmethemoglobin  form) 
levels  were  established  using  standard  techniques  (Blaxhall  1972)  and  serum 
protein  values  were  determined  with  a  hand  refractometer  (Courtois  1975,  1976; 
Schalm  1975). 

Extreme  physiological  differences  were  evident  between  control  fish  and  test 
fish  blood  parameters,  during  these  tests.  This  indicates  that  even  small  concen- 


NOTES  167 

trations  of  geothermal  steam  condensate  will  stress  rainbow  trout. 

Amounts  of  ammonia  (30  mg/l)  and  carbon  dioxide  (90  mg/l)  were  very 
high  up  to  23  hr  after  addition  of  the  condensate  but  had  returned  to  pre-test 
levels  by  93  hr.  Dissolved  oxygen  decreased  by  1.0  ppm  following  introduction 
of  condensate  but  returned  to  the  control  level  for  the  remainder  of  the  test 
period.  These  features  of  condensate  may  cause  the  most  stress  for  fish  popula- 
tions during  a  spill. 

The  mean  corpuscular  hemoglobin  concentration  (MCHC)  is  a  sensitive 
indicator  of  stress  in  fish  and  was  determined  using  hematocrit  and  hemoglobin 
values  MCHC  =  Hb/PCV  (100)  (Schalm  1975).  MCHC  increased  sharply 
(  -(_1.5  g/lOO  ml)  following  addition  of  the  condensate,  dropped  below  normal 
(_1.3g/100ml)  and  then  remained  significantly  (95%  confidence  level)  above 
control  values  (+3.4  g/100  ml)  for  the  duration  of  the  test,  indicating  an 
increase  in  mobilization  of  new  blood  cells  from  storage  locations.  This  is  a 
typical  response  to  a  stressful  situation. 

Hatchery-raised  fish  were  used  because  of  their  resistance  to  the  stress  of 
handling  but  this  increased  tolerance  may  have  dampened  response  results. 
Stress  response  of  rainbow  trout  over  a  longer  term  is  not  known  and  would  be 
of  interest. 

Doudoroff  and  Katz  ( 1 953 )  have  shown  that  sublethal  pollution  can  alter  the 
size  and  structure  of  wild  fish  populations.  This  preliminary  study  indicates  that 
spills  of  geothermal  steam  condensate  into  small  streams  will  influence  wild 
populations  of  rainbow  trout. 

ACKNOWLEDGMENT 

We  gratefully  acknowledge  the  assistance  and  space  provided  by  the  Water 
Pollution  Control  Laboratory,  California  Department  of  Fish  and  Game,  Rancho 
Cordova,  CA,  for  this  experiment. 

REFERENCES 

Blaxhall,  P.  C.      1972.     The  hematological  assessment  of  the  health  of  fresh  water  fish    A  review  of  selected 

literature.  )our.  Fish    Bio.,  4:  593-604. 
Courtois,  L.  A.     1975.     Hematological  assessment  and  toxicity  of  antimycin  A  to  golden  shiners,  Notemigonus 

crysoleucjs.  Prog.  Fish-Cult.,  37(4):  202-204. 
1976.     Hematology  of  juvenile  striped  bass,  Morone  saxatllls  (Walbaum),  acclimated  to  different  envi- 
ronmental conditions.  Comp.  Biochem.  Physiol.,  54A:  221-223. 
Doudoroff,  P,  and  M.  Katz.     1953.     Critical  review  of  literature  on  the  toxicity  of  industrial  wastes  and  their 

components  to  fish.  Sewage  Ind.  Wastes,  25:  802-839. 
LeCore,  R.  S.,  and  W    Bowen.     1976.     Aquatic  toxicity  experiments  at  the  Geysers,  California.  Document  No. 

75-074  FR.  Parametrix,  Inc.  Seattle,  Wash.  139  p. 
McLeay,  D.  ].     1975.     Sensitivity  of  blood  cell  counts  in  juvenile  coho  salmon    (Oncorhynchus  kisutch)  to 

stressors  including  sublethal  concentrations  of  pulpmill  effluent  and  zinc.  Can.  Fish.  Res.  Bd.,  ).,  32(12): 

2357-2364. 
Schalm,  O.  W.     1975.     In  Veterinary  hematology.  Lea  and  Febigeler,  Philadelphia,  p    1-12,  66. 

— James  A.  Steele,  Region  3,  Yountville,  and  Louis  A.  Courtois,  Environmental 
Services  Branch,  Sacramento,  California  Department  of  Fish  and  Game.  Mr. 
Steele  and  Mr  Courtois  are  now  with  Inland  Fisheries  Branch,  Sacramento. 
U.S.  Fish  and  Wildlife  Service  Contract  14-16-0001-6048  RBS,"Geothermal 
Resources  Assessment  Study".  Accepted  for  publication  October  1977. 


168  CALIFORNIA  FISH  AND  GAME 

OBSERVATIONS  OF  FINGERLING  CHINOOK  SALMON  IN 

THE  STOMACHS  OF  YELLOW  PERCH  FROM  THE 

KLAMATH  RIVER,  CALIFORNIA 

In  a  study  to  determine  the  relationship  between  yellow  perch  (Perca  flavesc- 
ens)  and  young  salmonids,  Coots  (1956)  examined  the  stomachs  of  731  perch 
collected  from  March  1951  through  March  1952  from  the  Klamath  River  in 
California  and  found  no  salmonids.  Additional  perch  stomachs  were  examined 
during  a  trapping  operation  for  downstream  migrant  chinook  salmon  (Oncor- 
hynchus  tshawytscha )  fingerlings  in  February,  March,  and  April  1952,  but  salmo- 
nids were  not  noted  in  their  stomachs. 

Under  artificial  conditions  in  live  traps  and  aquarium  tests  with  adult  perch 
and  fingerling  salmon.  Coots  (1956)  found  that  perch  would  eat  the  salmon  if 
given  the  opportunity. 

On  7  May  1976,  the  stomachs  of  44  yellow  perch  taken  from  the  Klamath 
River  were  examined  for  the  presence  of  fingerling  chinook  salmon.  These 
samples  were  collected  from  the  Klamath  River  in  Siskiyou  County  about 
100  m  downstream  from  the  mouth  of  Bogus  Creek  just  below  the  Iron  Gate  Fish 
FHatchery.  They  were  taken  in  slack  water  near  a  brushy  bank  with  a  boat- 
mounted  electrofisher. 

Fingerling  chinook  salmon  were  found  in  35  (80%)  of  the  perch  stomachs. 
Each  of  these  stomachs  contained  one  to  five  salmon,  3.2  to  4.4  cm  fork  length 
(fl).  The  average  length  of  yellow  perch  with  chinook  salmon  in  their  stomachs 
was  15.0  cm  fl  with  a  range  of  12.2  to  19.8  cm  fl. 

At  times,  yellow  perch  and  fingerling  salmon  apparently  utilize  the  slack  water 
area  where  the  perch  were  captured,  thus  providing  the  opportunity  for  perch 
to  prey  on  young  salmon.  If  there  were  extensive  areas  with  the  proper  condi- 
tions, perch  predation  on  salmon  fingerlings  could  be  an  important  factor  in 
salmon  survival. 

REFERENCE 

Coots,  Millard.     1956.     The  yellow  perch,  Perca  flavescens  (Mitchlll),  in  the  Klamath  River.  Calif.  Fish  Came, 
42(3):  219-228. 

—  Trygve  F.  Dahle,  III,  Inland  Fisheries,  California  Department  of  Fish  and  Game, 
627  Cypress  Ave.,  Redding,  CA  96001.  Present  address:  4556  Myrtle  Ave, 
Eureka,  CA  95521.  Accepted  for  publication  April  1978. 

AN  ABNORMALLY  PIGMENTED  SHORTSPINE  THORNY- 
HEAD,  SEBASTOLOBUS  ALASCANUS^^fKH 

On  April  17,  1975  a  black  shortspine  thornyhead  was  caught  by  the  trawler 
Helen  Louise  •^\\\\q  fishing  off  Coos  Bay,  Oregon,  in  about  300  fm.  The  striking 
color  abnormality  was  brought  to  my  attention  by  skipper  Tom  McDonald  and 
his  crewman. 

The  entire  fish  was  darkly  pigmented,  closely  resembling  the  coloration  of  a 
sablefish,  Anoplopoma  fimbria.  It  was  landed  with  about  2200  kg  of  normally 
pigmented  (red)  shortspine  thornyheads.  It  was  a  female  452  mm  total  length, 
in  excellent  condition.  This  is  the  only  such  color  abnormality  I  have  observed 
for  this  species  in  over  6  years  of  sampling  trawl  catches  in  the  Newport- 
Brookings,  Oregon  area. 

—  William  H.  Barss,  Marine  Region,  Oregon  Department  of  Fish  &  Wildlife, 
Marine  Science  Drive,  Newport,  Oregon  97365. 


NOTES  169 

A  JUVENILE  OCEAN  TRIGGERFISH,  CANTHIDERMIS 

MACULATUS  (BLOCH),  (PISCES,  BALISTIDAE) 

FROM  THE  GULF  OF  CALIFORNIA 

On  20  August  1972,  while  dipnetting  juvenile  fishes  at  the  docks  inside  San 
Carlos  Bay,  Sonora,  Mexico,  I  collected  an  ocean  or  rough  triggerfish,  12.8  mm 
standard  length  (sl).  The  fish  was  swimming  under  a  small  raft  of  seaweed, 
Sargassum  sp,  in  the  company  of  a  clinid,  Exerpes  asper,  which  is  locally  abun- 
dant in  the  Sargassum  habitat.  The  distinctively  low  meristic  counts  (D.  Ill,  23; 
A.  20;  P,.  14)  were  within  the  ranges  presented  by  Berry  and  Baldwin  (1966), 
and  the  general  body  form  agreed  with  their  illustration.  However,  the  pectoral 
fins  were  more  lobed  than  they  showed,  the  upper  rays  being  four  times  the 
length  of  the  lower  rays. 

Canthidermis  maculatus  has  a  circumtropical  distribution,  being  found  both 
inshore  (rarely)  and  in  surface  waters  of  the  open  ocean.  It  is  the  most  wide- 
ranging  and  probably  the  most  abundant  triggerfish  in  the  eastern  Pacific,  where 
it  has  been  reported  from  Haucho,  Peru,  to  waters  off  central  Mexico  ( Berry  and 
Baldwin  1 966) .  Of  the  six  triggerfishes  reported  from  the  eastern  Pacific  by  Berry 
and  Baldwin  (1966),  three  are  residents  in  the  Gulf  of  California:  Balistes polyle- 
/9/5Steindachner,  Pseudobalistes  naufragium  (Jordan  and  Starks),  and  Sufflamen 
verres  (Gilbert  and  Starks).  The  addition  of  Alutera  scripta  (Osbeck),  some- 
times placed  in  the  family  Monacanthidae,  raised  the  total  to  four  (Boyd  W. 
Walker,  pers.  commun.).  My  triggerfish  is  the  fifth  balistid  recorded  from  the 
Gulf  of  California. 

From  28  June  to  21  July  1972,  I  collected  about  2,750  juvenile  fishes  of 
approximately  40  species,  in  association  with  floating  mats  of  Sargassum  (Behr- 
stock  1975).  The  collecting  was  done  just  outside  the  mouth  of  San  Carlos  Bay, 
about  1  km  from  the  Canthidermis  maculatus  coWecUon  site.  My  samples  includ- 
ed 20  juveniles  of  the  finescale  triggerfish,  Balistes  polylepis,  a  common  species 
in  the  Gulf  of  California.  Although  most  of  the  species  I  collected  probably  have 
spawning  populations  in  the  vicinity  of  San  Carlos  Bay,  some,  such  as  Canthider- 
mis maculatus,  may  have  been  swept  up  the  east  side  of  the  Gulf  by  the  southerly 
winds  which  predominate  during  the  summer  (Roden  1958;  Roden  and  Groves 
1959)  and  represent  expatriates  from  Pacific  Ocean  populations. 

ACKNOWLEDGMENTS 

For  their  comments  on  the  distribution  of  triggerfishes  and/or  locality  data  for 
specimens  under  their  care  I  would  like  to  thank:  Boyd  W.  Walker  and  Robert 
R.  Harwood,  University  of  California,  Los  Angeles;  Richard  FH.  Rosenblatt, 
Scripps  Institution  of  Oceanography;  Matthew  R.  Gilligan,  University  of  Arizona; 
and  John  E.  Fitch,  California  Department  of  Fish  and  Game.  Permission  to  collect 
fishes  in  Mexican  waters  (Permit  No.  4995)  was  secured  through  the  office  of 
the  Secretaria  de  Industria  y  Comercio,  Subsecretaria  de  Pesca,  Direccion  Gen- 
eral de  Regiones  Pesqueras,  Mexico  City,  Mexico.  Also,  I'd  like  to  thank  Gary 
Friedrichsen  of  Areata,  California,  for  providing  transportation  and  stimulating 
conversation  on  a  most  worthwhile  field  trip. 


170 


CALIFORNIA  FISH  AND  CAME 


REFERENCES 

Behrstock,  R.  A.     1975.     Juvenile  development  oi  Trachinotus  kennedyi S\e\ndAchnex  (Pisces:  Carangidae)  from 
the  eastern  Pacific,  with  notes  on  its  ecology.  Master's  Thesis.  Humboldt  State  University.  55  pp. 

Berry,  F.  H.,  and  W.  ).  Baldwin.     1966.     Triggerfishes  (Balistidae)  of  the  eastern  Pacific.  Calif.  Acad.  Sci.,  Proc. 

34(9):  429-474. 
Roden,  C.  I.  1958.     Oceanographic  and  meteorological  aspects  of  the  Gulf  of  California.  Pac.  Sci.  12(1 ):  21-45. 

Roden,  G.  I.,  and  C.  W.  Groves.     1959.     Recent  oceanographic  investigations  in  the  Gulf  of  California.  ).  Mar. 
Resour    18(1):  10-35. 

— Robert  A.  Behrstock,  Department  of  Fisheries,  School  of  Natural  Resources, 
Humboldt  State  University,  Areata,  California  95521.  Accepted  for  publication 
May  1978. 


A  PACU  {COLOSSOMA,  FAMILY  CHARACIDAE)  CAUGHT 

IN  THE  SACRAMENTO  RIVER 

On  10  October  1977,  a  piranha-like  fish  was  caught  by  16-year  old  Jinnmy 
Seidel  of  Sacramento,  while  fishing  for  catfish  using  a  hook  baited  with  an 
earthworm.  The  fish  was  caught  on  the  Yolo  County  side  of  the  Sacramento 
River  near  Elkhorn  Ferry  just  above  Sacramento.  Reports  that  the  fish  was  an 
illegal  piranha  led  to  its  seizure  by  the  Department  of  Fish  and  Game  for  identifi- 
cation. The  frozen  specimen  was  identified  by  the  senior  author  as  a  pacu,  a 
largely  vegetarian  characin  of  the  genus  Colossoma.  (Figure  1  )  The  fish  was 
thawed,  measurements  and  counts  made,  scale  samples  taken,  and  the  gut 
removed;  the  stomach  and  intestine  were  empty,  the  lumen  of  minimum  diame- 
ter. 

■p" 


Figure  1.     A  pacu,  Colossoma  nigripinnus,  332  mm.  total  length,  caught  in  the  Sacramento  River, 
October  10,  1977.  Photograph  by  Martin  R.  Brittan. 


NOTES 


171 


The  fish  was  a  subadult  male  of  332  mm  tl,  294  mm  fl,  255  mm  SL,  having 
lost  the  spotted  and  barred  juvenile  pattern  characteristic  of  Colossoma  up  to 
about  150  mm  SL  and  attained  the  adult  coloration,  in  which  the  back  is  silver- 
black,  the  underside  of  the  head  and  anterior  belly  pinkish-orange  (turning 
silvery  after  death),  and  the  rest  of  the  body  blackish,  except  for  the  brownish 
opercle.  The  silvery-black  back  and  the  blackish  lower  flanks  are  delineated  by 
an  irregular  "zig-zag"  wash  (see  photo).  The  greatest  body  depth  is  120  mm 
(47%  of  SL),  head  length  88  mm  (34%  of  SL),  orbit  15  mm  (17%  of  head 
length),  predorsal  distance  148  mm  (58%  of  SL),  preanal  distance  185  mm 
(73%  of  SL),  prepelvic  distance  132  mm  (52%  of  SL).  There  are  90  to  95  scales 
in  the  lateral  line  (about  10  on  the  caudal  base);  transverse  line  about  25  scales 
from  dorsal  to  lateral  line  and  24  from  lateral  line  to  midbelly;  predorsal  scales 
about  47;  about  25  midventral  serrae  to  origin  of  ventrals  plus  26  to  anus;  8-9 
rows  of  ventral  sheath  scales.  Dorsal  iv,14;  anal  iv,22;  pectoral  i,17.  Teeth  in 
upper  jaw  in  two  rows,  the  10  in  the  outer  row  with  an  outer  incisiform  edge, 
the  central  teeth  with  dark  tips.  The  six  teeth  in  the  inner  row  have  an  inner  and 
outer  incisive  edge  (not  so  sharp  as  that  of  the  outer  teeth)  with  a  shallow 
concavity  between.  ( Figure  2 )  The  teeth  in  the  lower  jaw  total  1 2  in  a  single  row, 
becoming  progressively  smaller  and  simpler,  the  center  ones  incisorlike,  the 
lateral  ones  becoming  conical.  (Figure  3)  The  opercle  and  subopercle  exhibit 
posteriorly-diverging  radiating  striae. 


Figure  2.     Head  of  pacu,  showing  upper  dentition  and  fleshy,  flap-like  lower  lip.  Photograph  by 
Martin  R.  Brittan. 


172 


CALIFORNIA  FISH  AND  CAME 


Figure  3.     Lov/er  dentition  of  pacu.  Photograph  by  Martin  R.  Brittan. 


The  original  descriptions  of  the  six  nominal  species,  mostly  dating  from  the 
early  and  middle  19th  century,  are  sketchy  and  based  on  one  or  only  a  few 
specimens.  There  have  been  no  recent  revisions  of  the  genus  and  scientific 
specimens  are  few,  although  Colossoma  are  common  food  fishes  in  tropical 
fresh  waters  of  South  America.  The  specimen  closely  compares  to  some  in  the 
California  Academy  of  Sciences  identified  by  Stanley  W.  Weitzman  and  William 
I.  Follett  as  Colossoma  nigripinnus  Cope.  Specimens  identified  as  Colossoma 
bidens  had  much  smaller  scales.  The  senior  author  tentatively  identified  the 
Sacramento  specimen  as  C.  nigripinnus. 

The  specimen  showed  no  evidence  of  disease  or  parasites.  How  long  it  had 
been  in  the  river  is  not  known,  but  since  pacus  and  piranhas  are  generally 
sympatric  and  have  comparable  ecological  requirements,  some  deductions  can 
be  made.  Temperatures  in  the  Sacramento  River  were  unusually  high  during 
summer  1977,  a  drought  year,  and  between  mid-May  and  mid-October  were 
above  18  C  which  is  approximately  the  minimum  temperature  at  which  most 
tropical  lowland  fishes  can  maintain  themselves.  Temperatures  at  which  such 
fishes  could  comfortably  exist  occurred  between  mid-)une  and  mid-September: 
June  28,  25.1  C;  July  28,  24.8  C;  August  8,  25.0  C;  September  13,  23.3  C.  The 
higher  temperatures  are  within  breeding  range.  During  most  years  midsummer 
temperatures  average  about  20-21  C,  and  in  some  years  run  as  low  as  17-18  C. 
Mid-winter  temperatures  range  from  6.5  to  9.0  C  and  would  be  lethal.  Evidence 
that  the  fish  did  not  over-winter  comes  from  the  scales,  which  exhibited  no 
growth  rings  or  stress  checks. 


NOTES  173 

Gery  (1973)  and  Sterba  (1962)  give  maximum  lengths  of  60-80  cm  and  a 
weight  of  10  kg  for  Colossoma.  Lovshin,  et  al.  (1974)  report  seeing  the  larger 
pacus,  called  tambaqui,  reaching  a  maximum  length  of  89  cm  and  a  weight  of 
over  13  kg  in  the  Manaus,  Brazil,  market;  they  also  report  that  fishermen  say 
tambaqui  exceed  20  kg.  Colossoma  grow  rapidly  in  sufficiently  roomy  aquaria, 
as  much  as  an  inch  a  month.  They  are  frequently  a  problem  when  they  outgrow 
an  aquarium.  Our  specimen  was  probably  released  into  the  river  sometime  after 
early  June,  probably  a  few  days  before  being  caught,  in  view  of  the  empty 
digestive  tract,  since  there  is  considerable  algae  and  vegetable  debris  in  the  river. 
It  is  unlikely  that  this  species  or  others  with  the  same  temperature  requirements 
( ould  overwinter  in  Northern  California  waters.  However,  any  new  hot  water 
discharge  into  natural  waters  should  be  considered  to  be  capable  of  creating 
survival  and/or  reproductive  conditions. 

REFERENCES 

Gery,  ).  1973.  Characins  and  electric  eels.  In  Crzimek,  B.,  Crzinnek's  aninnal  encyclopedia.  Van  Nostrand 
Rheinhold  Company,  New  York.  531  p. 

Lovshin,  A.  B  ,  A  B  da  Silva,  |.  A  Fernandez,  and  A.  Carneiro-Sobrinho.  1974.  Preliminary  pond  culture  test 
of  pirapatinga  (Mylossoma  bidens)  and  tambaqui  {Colossoma  bidens)  from  the  Amazon  River  basin.  In 
Symposium  on  aquaculture  in  Latin  America    FAO/CARPAS  publication  6/74/SE24:  1-9. 

Sterba,  G.     1962.     Freshwater  fishes  of  the  world.  Studio  Vista,  London.  878  p 

— Martin  R.  Brittan,  California  State  University,  Sacramento,  CA  95819,  and  Gary 
D.  Grossman,  University  of  California,  Davis,  CA  95616.  Accepted  for  publica- 
tion January  1978. 

EFFECT  OF  FIRST  PECTORAL  FIN  RAY  REMOVAL  ON  SUR- 
VIVAL AND  ESTIMATED  HARVEST  RATE  OF  W^HITE  STUR- 
GEON IN  THE  SACRAMENTO-SAN  JOAQUIN  ESTUARY 

INTRODUCTION 

Sturgeon  ages  commonly  are  estimated  from  annual  growth  patterns  in  cross 
sections  of  the  first,  or  anterior,  ray  of  the  pectoral  fin.  However,  removal  of  fin 
rays  during  a  tagging  study  may  affect  survival  of  the  fish  and  bias  estimates  of 
population  parameters  estimated  from  tag  recoveries.  Several  authors  have 
released  sturgeon  after  removal  of  the  anterior  pectoral  fin  ray  without  discussing 
the  effect  on  subsequent  survival  (Cuerrier  and  Roussow  1951;  Pycha  1956; 
Priegel  1973).  Bajkov  (1949)  stated  that  white  sturgeon  (Acipenser  transmon- 
tanus)  appear  to  withstand  removal  of  a  fin  ray  without  any  damage,  but  offered 
no  evidence  for  his  conclusions. 

To  determine  the  effect  of  pectoral  fin  ray  removal  on  survival  and  estimated 
harvest  rate  of  white  sturgeon,  I  evaluated  tag  returns  from  the  Sacramento-San 
Joaquin  Estuary,  California. 

METHODS 
In  fall  1974  sturgeon  were  captured  with  trammel  nets  in  San  Pablo  Bay  and 
tagged  with  disc  dangler  tags  placed  beneath  the  anterior  part  of  the  dorsal  fin. 
Capture  and  tagging  methods  have  previously  been  described  (Chadwick  1963; 
Miller  1 972 ) .  Five  dollar  reward  tags  were  used  exclusively  to  assure  a  high  rate 
of  angler  response. 


174  CALIFORNIA  FISH  AND  CAME 

To  determine  the  age  composition  of  tagged  fish,  the  first  ray  of  the  left 
pectoral  fin  was  removed  from  every  second  sturgeon  tagged.  Prior  to  tagging, 
the  fish  was  placed  on  its  right  side  on  the  boat  deck  and  the  fin  ray  was  severed 
as  close  to  its  articulation  as  possible.  Large  cutting  pliers  or  a  small  hand  saw 
were  used  to  cut  the  ray.  This  procedure  required  less  than  1  minute  per  fish. 
To  facilitate  analysis,  fin  rays  were  removed  only  from  fish  with  odd  numbered 
tags.  For  convenience,  I  will  refer  to  fish  with  the  fin  ray  removed  as  odd 
numbered  and  those  with  intact  pectoral  fins  as  even  numbered. 

Harvest  rates  were  calculated  from  first  year  returns  of  each  tag  type.  Confi- 
dence limits  for  harvest  rates  were  estimated  assuming  tag  returns  followed  a 
Poisson  distribution. 

I  analyzed  3  years  of  tag  returns  to  determine  the  effect  of  pectoral  fin  ray 
removal.  Returns  of  odd  and  even  numbered  tags  were  compared  using  a 
standard  chi-square  test  of  independence  (Sokal  and  Rohlf  1969).  Mortality  due 
only  to  fin  ray  removal  was  estimated  as:  1 — ratio  of  odd:even  tag  return  per- 
centages. I  estimated  survival  separately  for  odd  and  even  numbered  tags  using 
a  linear  regression  of  logarithm  of  returns  against  time  (Ricker  1975).  The  an- 
tilogarithm  of  the  slope  of  the  regression  line  is  an  estimate  of  annual  survival. 

RESULTS  AND  DISCUSSION 

A  total  of  71 2  legal  sized  (>  1 01 .6  cm  total  length )  white  sturgeon  was  tagged 
in  1974.  Of  those,  358  had  the  first  ray  of  the  left  pectoral  fin  removed  and  354 
did  not. 

The  tag  returns  indicate  fin  ray  removal  caused  mortality  (Table  1 ).  During 
the  first  year,  13  odd  numbered  and  20  even  numbered  tags  were  returned, 
yielding  harvest  rate  estimates  of  0.036  and  0.056,  respectively.  The  respective 
95%  confidence  intervals  were  0.019-0.060  and  0.036-0.085.  While  the  differ- 
ence in  these  return  rates  was  not  statistically  significant,  the  difference  was 
significant  at  the  end  of  2  {X^=  5.24,  P  <  0.025 )  and  3  ( ^^  =  8.20,  P  <  0.005 ) 
years  due  to  continued  higher  returns  of  even  numbered  tags. 

The  decrease  in  the  ratio  of  odd:even  tag  return  percentages  was  relatively 
small  after  the  first  year,  indicating  that  most  mortality  due  to  fin  ray  removal 
occurred  in  the  first  year.  However,  the  fact  that  this  ratio  did  decrease  suggests 
some  mortality  occurred  during  the  second  year  also  (Table  1 ). 

After  the  first  year,  estimated  annual  survival  of  odd  numbered  sturgeon  was 
0.88  and  estimated  survival  of  even  numbered  fish  was  0.95  (Figure  1 ).  These 
estimates  are  imprecise  since  return  sample  sizes  are  small  and  the  points  do  not 
fall  in  a  straight  line. 

I  conclude  that  removing  the  first  ray  of  the  pectoral  fin  of  white  sturgeon 
causes  substantial  mortality  during  the  first  year  and  less  mortality  thereafter. 
Also,  consistently  greater  returns  of  even  number  tags  in  all  3  years  indicates  that 
mortality  from  pectoral  fin  ray  removal  results  in  an  underestimate  of  exploita- 
tion and  that  the  best  estimate  of  exploitation  rate  is  based  on  even  numbered 
tags  alone.  If  fin  ray  removal  is  used  in  conjunction  with  a  sturgeon  tagging 
program,  estimates  of  population  parameters  derived  from  tag  recoveries  may 
exhibit  serious  bias. 


NOTES 


175 


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176 


CALIFORNIA  FISH  AND  CAME 


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RETURN    YEAR 


FIGURE  1 .  Tag  returns  from  white  sturgeon  tagged  in  San  Pablo  Bay  in  fall  1 974.  The  antilogarithm 
of  slope  is  an  estimate  of  annual  survival  rate  (S).  Slope  and  survival  are  calculated 
separately  for  odd  numbered  fish  with  the  first  ray  of  the  left  pectoral  fin  removed  (a) 
and  even  numbered  fish  with  no  fin  ray  removed  (b). 


NOTES  177 

ACKNOWLEDGMENTS 
Richard  Fenner  and  Salvatore  Mercuric  assisted  in  the  tagging  operation  and 
Donald  Stevens  reviewed  the  manuscript.  I  thank  these  individuals  for  their  help. 
This  work  was  perfornned  as  part  of  Dingell-Johnson  Project  California  F-9-R,  "A 
Study  of  Sturgeon  and  Striped  Bass",  supported  by  Federal  Aid  to  Fish  Restora- 
tion funds. 

REFERENCES 

Bajkov,  A.  D  1949.  A  preliminary  report  on  the  Columbia  River  sturgeon.  Oregon  Fish  Comm.  Res.  Briefs  2(2): 
3-10. 

Chadwick,  H.  K.  1963.  An  evaluation  of  five  tag  types  used  in  a  striped  bass  mortality  rate  and  migration  study. 
Calif.  Fish  Came  49(2):  64-83. 

Cuerrier,  J. -P.,  and  G.  Roussow.  1951.  Age  and  growth  of  lake  sturgeon  from  Lake  St.  Francis,  St.  Lavi/rence 
River.  Report  on  material  collected  in  1947.  Can.  Fish  Cult.  10:  17-29. 

Miller,  L.  W.  1972.  White  sturgeon  population  characteristics  in  the  Sacramento-San  loaquin  Estuary  as  meas- 
ured by  tagging.  Calif.  Fish  Came  58(2);  94-101. 

Priegel,  G.  R.  1973.  Lake  sturgeon  management  on  the  Menominee  River.  Wise.  Dept.  Nat.  Res.,  Tech.  Bull. 
No.  67,  20  pp. 

Pycha,  R.  L.     1956.     Progress  report  on  white  sturgeon  studies.  Calif.  Fish  Game  42(1):  23-35. 

Ricker,  W.  E.  1975.  Computation  and  interpretationof  biological  statistics  of  fish  populations.  Fish.  Res.  Bd.  Can. 
Bull.  191,  382  pp. 

Sokdl,  R.  R.,  and  F    |    Rohlf.      1969.     Biometry.  W.  H    Freeman  and  Company,  San  Francisco,  776  pp. 

— David  W.  Kohlhorst,  California  Department  of  Fish  and  Game,  4001  North 
Wilson  Way,  Stockton,  California  95205.  Accepted  for  publication  August 
1978. 

EVIDENCE  OF  SUCCESSFUL  REPRODUCTION  OF  STEEL- 
HEAD  RAINBOW  TROUT,  SALMO  GAIRDNERI  CAIRO- 
NERh  IN  THE  VENTURA  RIVER,  CALIFORNIA 

In  recent  years  there  have  been  scattered  reports  of  adult  steelhead  trout  being 
caught  in  the  Ventura  River,  Ventura  County,  fish  which  could  be  remrrants  of 
a  run  that  once  numbered  4-5,000  adults  (Clanton  and  Jarvis  1946).  The  ques- 
tion has  remained,  however,  whether  these  fish  were  strays  from  other  river 
systems  or  whether  they  could  be  progeny  of  successful  steelhead  reproduction 
in  the  Ventura  River  (Mark  Capelli,  Friends  of  the  Ventura  River,  pers.  com- 
mun.).  This  note  briefly  describes  a  useful  technique  for  identifying  juvenile 
steelhead  and  provides  data  supporting  their  presence  in  the  Ventura  River. 

Rybock,  Norton,  and  Fessler  ( 1 975 )  showed  that  steelhead  trout  juveniles  can 
be  distinguished  from  resident  rainbow  trout  on  the  basis  of  otolith  nuclei  (ON) 
dimensions.  Since  spawning  steelhead  trout  females  are  substantially  larger  than 
spawning  resident  rainbow  trout  females  and  have  larger  eggs  and  emergent 
larvae,  the  earliest  formed  otolith  morphological  mark  (the  ON,  or  metamorphic 
check)  has  a  larger  width  and  length  in  steelhead  trout  than  in  resident  rainbow 
trout.  Statistically  significant  differences  between  the  ON  size  distributions  of 
different  samples  indicate  the  existence  of  distinct  fish  populations. 

Nine  dorsal  fin  clipped  juvenile  steelhead  trout  and  11  wild  rainbow  trout 
were  captured  on  February  16,  1977  by  electroshocking  a  stretch  of  the  middle 
Ventura  River  10.5-12.9  km  above  the  mouth.  The  marked  steelhead  trout  were 
survivors  of  a  July  1 976  plant  of  1 1 ,000  fingerlings.  An  additional  seven  unmarked 
rainbow  trout  were  captured  in  the  upper  Ventura  River  (22.6  km  above  the 


178 


CALIFORNIA  FISH  AND  CAME 


mouth)  on  February  17,  1977.  This  location  is  above  Robles  Diversion  Dam, 
completed  in  1959,  which  prevents  upstream  migration  of  fish  under  most  flow 
conditions. 

Otoliths  were  removed,  stored  in  100%  glycerin,  and  measured  using  an 
ocular  microscope  (see  McKern,  Norton,  and  Koski  1974  and  Rybock  et  al.  1975 
for  details  of  the  procedure). 

Despite  clearing  in  glycerin,  20%  ( 1 1  /54)  of  the  otoliths  were  unreadable.  All 
but  two  fish,  however,  had  at  least  one  readable  otolith.  ON  measurements 
recorded  for  the  Ventura  River  trout  were  within  resident  and  steelhead  trout 
ON  width  and  length  ranges  reported  from  other  Pacific  coastal  streams 
(McKern  et  al.  1974,  Rybock  et  al.  1975).  Only  ON  widths  were  consistently 
distinct  enough  to  accurately  measure  in  all  readable  otoliths. 

The  comparison  of  ON  widths  showed  distinct  distributions  for  unmarked 
trout  taken  from  above  Robles  Diversion  Dam  and  marked  steelhead  trout  taken 
from  the  middle  Ventura  River  (Figures  la  and  1c).  The  ON  width  distribution 
for  unmarked  trout  taken  from  the  middle  Ventura  River,  however,  spanned 
nearly  the  entire  range  of  both  marked  and  unmarked  trout  (Figure  16).  Differ- 
ences in  the  mean  ON  widths  of  the  three  groups  were  analyzed  by  the  "t"  test 
for  small  samples   (Alder  and  Roessler  1968).  The  differences  between  the 


0) 

E 

3 


5 
4  h 

3 
2 


0 


0 


5  r 
4 

3 
2 
I  h 


5  r 

4 

3 
2 
I  h 


.225 


n  =  7 

w=  0.268  ±0.0224 


(A) 


n  =  10 

w=  0.341  ±0.0512 


(B) 


n  =  8 

w=  0.390  +  0.0166 


(C) 


J 


258       .290        .322       .354       .386        .419       .451 


Otolith  Nuclei  (  mm  ) 


Figure  1.  Frequency  distributions  and  means  (±1  S.D. )  of  ON  widths  (millimeters)  representing: 
(A)  unmarked  rainbow  trout  above  Robles  Diversion  Dam,  Ventura  River,  (B)  un- 
marked rainbow  trout  from  below  Robles  Diversion  Dam,  and  (C)  marked  steelhead 
rainbow  trout  from  below  Robles  Diversion  Dam. 


NOTES  179 

means  were  all  significant  (p<0.05),  particularly  between  the  trout  collected 
above  Robles  Diversion  Dann  and  the  marked  steelhead  (p<0.001). 

Unmarked  trout  captured  in  the  middle  Ventura  River  included  fish  having 
ON  widths  within  the  resident  rainbow  trout  and  steelhead  trout  ranges.  The 
former  group  is  either  wild  resident  rainbow  trout  or  planted  rainbow  trout  that 
have  moved  downstream  from  the  Department  of  Fish  and  Game  catchable 
trout  release  sites  25  to  32  km  above  the  mouth.  The  latter  group  is  either  wild 
steelhead  trout  or  hatchery  steelhead  trout  with  regenerated  dorsal  fins.  Since 
the  marked  steelhead  were  dorsal  fin  clipped  only  8  months  prior  to  the  study, 
it  is  unlikely  that  they  would  be  misidentified. 

The  existence  of  wild  steelhead  trout  juveniles,  as  judged  by  the  otolith  results, 
implies  that  some  natural  spawning  and  subsequent  adult  return  occurs  in  the 
river.  However,  many  questions  concerning  these  fish  remain:  ( i )  what  percent- 
age of  the  adult  steelhead  entering  the  Ventura  River  originate  elsewhere,  (ii) 
what  is  the  proportion  of  steelhead  trout  in  the  rainbow  trout  population  below 
the  diversion  dam,  (iii)  do  any  steelhead  trout  pass  the  diversion  dam  and 
spawn  in  the  upper  river,  and  ( iv )  what  can  be  done  to  more  effectively  protect 
and  enhance  the  natural  steelhead  trout  run? 

ACKNOWLEDGMENTS 
Don  Kelley,  L.  B.  Boydstun  (California  Department  of  Fish  and  Game),  Mark 
Moore,  and  Linda  Hagen  assisted  in  collecting  the  fish.  Special  thanks  go  to  Don 
Kelley  who  provided  the  collecting  equipment  and  reviewed  the  manuscript. 
Mark  Moore  and  Mark  Capelli  also  reviewed  the  manuscript. 

REFERENCES 

Alder,  H    L  ,  and  E.  B.  Roessler.     1968.     Introduction  to  probability  and  statistics.  W.  M.  Freeman  and  Co.,  San 

Francisco.  333  p. 
Clanton,  D.  A.,  and  ).  W.  jarvis.     1946.     Field  inspection  trip  to  the  Matilija-Ventura  watershed  in  relation  to  the 

construction  of  the  proposed  Malilija  Dam    (Unpublished  report  dated  May  8,  1946  on  file  at  Fillmore 

Hatchery,  Calif.  Dep.  Fish  and  Came,  Fillmore.) 
McKern,  ).  L.,  H.  F.  Horton,  and  K.  V.  Koski.     1974.     Development  of  steelhead  trout  (Salmo  gairdneri)  otoliths 

and  their  use  for  age  analysis  and  for  separating  summer  from  winter  races  and  wild  from  hatchery  stocks. 

Canada,  Fish.  Res.  Bd.,  lour.,  31(81;  1420-1426. 
Rybock,  J.  T.,  H.  F.  Horton,  and  j.  L.  Fessler.     1975.     Use  of  otoliths  to  separate  juvenile  steelhead  trout  from 

juvenile  rainbow  trout.  Fishery  Bull.,  73(3):  654-659 

—  William  E.  Tippets,  2508  Warrego  Way,  Sacramento,  CA  95826.  Accepted  for 
publication  September  1978. 

NOTES  ON  A  HYBRIDIZATION  EXPERIMENT 
BETWEEN  RAINBOW  AND  GOLDEN  TROUT 

In  an  earlier  note  (Gold,  Pipkin,  and  Gall  1976),  we  presented  the  results  of 
a  fortuitous  hybridization  experiment  between  a  rainbow  trout,  Salmo gairdneri, 
female  and  a  golden  trout  Salmo  aguabonita  male.  The  hatch  and  developmental 
data  from  that  cross  were  limited,  but  supported  field  observations  that  hybridi- 
zation between  the  two  species  could  occur  with  ease  (Dill  1950;  Schreck  and 
Behnke  1971;  Gold  and  Gall  1975).  This  note  is  a  follow-up  on  that  cross. 

By  7  May  1975,  only  one  of  the  six  RT  x  GT  hybrid  fingerlings  remained  alive, 
the  rest  having  succumbed  to  Chondrococcus  columnaris  infection  or  gill  dis- 
ease. On  31  December  1976,  the  survivor,  a  2-year-old  female,  was  stripped  of 


180  CALIFORNIA  FISH  AND  GAME 

641  normal-sized  eggs.  These  were  divided  into  four  lots  of  roughly  160  eggs 
each  and  fertilized  with  the  sperm  of  four  2-year-old  males  from  the  domesticat- 
ed rainbow  trout  strain  RTD  (Gall  1975).  The  males  were  3  months  past  their 
spawning  peak,  but  when  examined  had  numerous  motile  sperm.  No  golden 
trout  males  were  available  for  the  complementary  backcross.  The  four  lots  of 
fertilized  eggs  were  water  hardened  and  incubated  in  separate  chambers  of  a 
Heath-Tecna  incubator.  Water  temperatures  during  incubation  ranged  from 
9-1 3  C  ( median  =  1 1  C ) .  At  this  temperature,  RTD  eggs  normally  eye-up  within 
13  days  and  hatch  within  29  days  (Gall  and  Pipkin,  unpublished  data). 

None  of  the  backcross  embryos  developed  normally.  After  17  days,  roughly 
80%  of  the  eggs  showed  no  indication  of  embryonic  development.  The  remain- 
der displayed  a  single,  large,  dark  spot  (not  a  true  "eye")  accompanied  by 
several  hemorrhagic  streaks.  Some  of  these  "spots"  grew  larger,  but  by  6  Febru- 
ary none  of  the  embryos  had  hatched.  On  15  February  all  embryos  had  ceased 
development  and  were  discarded.  A  systems  failure  at  the  Davis  hatchery  on  16 
June  1976  resulted  in  the  death  of  the  hybrid  female. 

Meristic  and  morphometric  data  from  the  hybrid  are  compared  with  mean 
values  for  rainbow  and  golden  trout  from  our  unpublished  data  (Table  1). 
Hybrid  indices  computed  after  Hubbs  and  Juronuma  (1942)  were  intermediate 
(.16-.83)  for  8  of  27  characteristics. 

Life  colors  of  the  hybrid  were  more  or  less  typical  of  5.  aguabonita  (  Evermann 
1905),  although  much  less  pronounced.  Parr-type  marks,  typical  of  adult  5. 
aguabonita  but  not  adult  5.  gairdneri,  were  not  present.  The  dorsal,  caudal,  and 
adipose  fins  were  moderately  spotted,  but  the  body  was  almost  immaculate 
(Figure  1  ).  Approximately  20-25  small  spots,  crescent-shaped  and  diffuse  as  in 
5.  gairdneri,  were  present  on  the  dorsal  region  of  the  caudal  peduncle,  posterior 
to  the  adipose  fin.  The  parents  of  the  hybrid,  S.  gairdneri  (  9  )  and  5.  aguabonita 
{(S),  were  heavily  and  moderately  spotted,  respectively.  The  paucity  of  spots 
on  the  body  of  the  hybrid  was  suggestive  of  the  pattern  typical  of  the  Paiute 
cutthroat  trout  (Ryan  and  Nicola  1976). 

Data  indicative  of  interspecific  hybridization  among  western  trouts  are  abun- 
dant, and  have  stemmed  by-in-large  from  field  studies  where  one  species  was 
introduced  (by  man)  into  waters  occupied  by  a  second  species  (e.g.  Schreck 
and  Behnke  1971;  Behnke  1972;  Gold  and  Gall  1975).  As  a  result,  it  has  been 
generally  assumed  that  reproductive  isolating  mechanisms  among  most  western 
trouts  are  less  than  complete,  and  that  forced  sympatry  will  usually  result  in 
introgressive  hybridization.  The  sympatric  coastal  cutthroat,  5.  clarki  clarki,  and 
anadromous  rainbow  trout,  5  gairdneri,  are  among  the  few  cited  exceptions 
(Behnke  1972).  Miller  (1972),  however,  has  pointed  out  that  there  is  little  if  any 
experimental  data  on  western  trouts  regarding  mating  discrimination  or  fertility 
of  hybrids. 

The  failure  to  obtain  backcross  progeny  from  the  RT  x  GT  hybrid  female  may 
reflect  a  barrier  to  hybridization  between  the  two  species.  The  experimental 
conditions  under  which  the  backcross  was  made  were  far  superior  to  those  of 
the  original  parental  cross,  and  there  was  partial  embryogenesis  in  about  20% 
of  the  fertilized  eggs.  It  is  conceivable  that  "hybrid  breakdown"  (Dobzhansky 
1970)  was  the  cause  of  embryonic  mortality,  and  that  reproductive  isolating 


Salmo 

S 

almo 

gairdneri 

aguabonita 

(n  =  20) 

in 

=  32) 

21.4 

10.4 

59.6 

33.3 

12.3 

12.1 

11.3 

10.7 

14.6 

15.7 

10.1 

9.0 

22.0 

23.9 

18.8 

19.9 

62.5 

60.0 

121.5 

117.3 

135.8 

183.0 

NOTES  181 

TABLE  1.     Morphological  Data  t  of  RT  x  CT  Hybrid,  Salmo  gairdneri,  and  Salmo  aguabonita 

Hybrid 
Character  (n  =  1) 

Standard  length,  cm 26.9 

Pyloric  caecae  43* 

Dorsal  fin  rays  11 

Anal  fin  rays 1 1 ' 

Pectoral  fin  rays 16 

Pelvic  fin  rays 9 

Branchiostegal  rays  (total) 22 

Gill  rakers  (left) 18 

Vertebrae 62* 

Scales,  lateral  line 1 23 

Scales,  lateral  series 1 54* 

Scales  above  lateral  line 30 

Scales  below  lateral  line 31 

Interneural  bones 1 3 

Interhaemal  bones 1 3 

Thousands  of  standard  length 

Body  depth 264* 

Head  length  233 

Head  width 145 

Least  interorbit 70 

Occiput  to  snout  length  167 

Maxilla  length 93* 

Caudal  peduncle  length 146 

Caudal  peduncle  depth 1 1 3 

Predorsal  length 470 

Preanal  length 751 

Prepectoral  length 265 

Prepelvic  length 544 

Dorsal,  base  length  141 

Anal,  base  length 116 

Pectoral  length 163* 

Pelvic  length 1 38* 

Eye  diameter 43 

•  Values  intermediate  tjetween  means  of  parental  species  (cf  texti 

\  Data  for  S.  gairdneri  m\A  S.  aguabonitu  represent  sample  means  fX). 

mechanisms  among  western  trouts  are  more  complete  than  presently  believed. 
Busack  (1977),  for  example,  has  recently  presented  evidence  of  two  closely 
related  inland  cutthroat  trout  forms  which  coexist  sympatrically  without  appar- 
ent gene  exchange.  The  introgression  frequently  observed  among  western  trouts 
in  nature  may  indicate  the  well-known  relationship  between  hybridization  and 
habitat  disruption  (Anderson  1949). 


268 

248 

235 

289 

126 

134 

75 

74 

177 

209 

87 

125 

164 

148 

104 

101 

509 

536 

782 

773 

219 

252 

558 

560 

139 

140 

91 

101 

127 

181 

103 

145 

45 

71 

182 


CALIFORNIA  FISH  AND  CAME 


Figure  1.     Lateral  view  of  female  Salmo  gairdneri  -x.  Salmo  aguabonita  hybrid. 


ACKNOWLEDGMENTS 

We  thank  S.  J.  Nicola  for  reading  an  early  draft  of  this  note.  The  study  was 
supported  by  Federal  Aid  in  Fish  Restoration  funds  as  California  project  D-J 
F-28-R,  Trout  Genetics. 

REFERENCES 

Anderson,  E.  A.     Introgressive  hybridization.  )ohn  Wiley  and  Sons,  Inc.,  New  York,  109p. 

Behnke,  R.  ).     1972.     The  systematics  of  salmonid  fishes  of  recently  glaciated  lakes.  Canada,  Fish.  Res.  Bd., ).,  29: 

639-671. 
Busack,  C.  A.     1977.     Genetic  variation  among  populations  of  Paiule  trout  iSalmo  clarkl seleniris) .  Qf^-  Univ.  of 

Calif.;  1977.  155p.  M.S.  Thesis. 
Dill,  W.  A.     1950.     A  report  on  the  golden  trout  fishery  of  California.  Calif.  Dept.  Fish  and  Game,  Inland  Fish. 

Admin.  Rep.,  50-44.  28p.  (mimeo). 
Dobzhansky,  T.     1970.     Genetics  of  the  evolutionary  process.  Columbia  Univ.  Press,  New  York  and  London. 

505p 
Evermann,  B.  W.     1905.     The  golden  trout  of  the  southern  High  Sierras.  U.  S.  Bur   Fish.  Bull.,  25:  1-51. 
Call,  G.  A.  E.     1975.     Genetics  of  reproduction  in  domesticated  rainbow  trout.  ).  Anim.  Sci.,  40:  19-28. 
Gold, ).  R,  and  C.  A.  E.  Gall.     1975.     The  taxonomic  structure  of  six  golden  trout  (Salmo  aguabonita)  populations 

from  the  Sierra  Nevada,  California.  Calif.  Acad.  Sci.,  Proc,  XL(IO):  243-263. 
Cold,  ).  R.,  R.  E.  Pipkin,  and  G.  A.  E.  Call.     1976.  Artificial  hybridization  between  rainbow  (Salmo galrdneri)  and 

golden  trout  (Salmo  aguabonita) .  Copeia,  1976(3):  597-598. 
Hubbs,  C.  L.,  and  K.  Kuronuma.     1942.     Analysis  of  hybridization  in  nature  between  two  species  of  Japanese 

flounders.  Papers  Michigan  Acad.  Sci.,  Arts,  Letters,  27:  267-306. 
Miller,  R.  R.     1972.     Classification  of  the  native  trouts  of  Arizona,  with  the  description  of  a  new  species,  Salmo 

apache.  Copeia,  1972(3);  401^22. 


NOTES  183 

Ryan,).  H.,  andS. ).  Nicola.     1976.     Statusof  the  Paiute  cutthroat  trout,  S^/mo  c/arki  se/eniris  Snyder,  in  California. 
Calif.  Dept.  Fish  and  Game,  Inland  Fisheries  Admin.  Rep.,  76-3  (mimeo). 

Schreck,  C.  B.,  and  R.  ).  Behnke.     1971.     Trouts  of  the  upper  Kern  River  basin,  California,  with  references  to 
systematics  and  evolution  of  western  North  American  Salmo.  Canada,  Fish.  Res.  Bd.  ].,  28:  987-998. 

— /  R-  Gold,  R.  E.  Pipkin,  and  G.  A.  E.  Gall,  Fisheries  Biology  Research  Facility, 
Department  of  Animal  Science,  University  of  California,  Davis,  California 
95616.  Dr.  Gold's  present  address:  Genetics  Section,  Texas  A&ivl  University, 
College  Station,  Texas  77843.  Accepted  for  publication  November  1978. 


CALIFORNIA  CONDOR  SURVEY,  1978 

A  cooperative  survey  of  California  Condors,  Gymnogyps  californianus,  was 
conducted  17  and  18  October  1978.  Fifty  observation  stations  were  staffed  by 
110  observers  from  noon  until  condor  flight  activity  ceased  each  day,  usually 
about  5:00  p.m.  All  condor  observations  were  recorded  by  time  of  day,  direction 
of  travel,  age  of  birds  (adult,  immature,  or  undetermined),  and  distinguishing 
characteristics  of  individual  birds  (e.g.,  missing  flight  feathers).  Total  sightings 
were  later  evaluated  to  arrive  at  a  probable  minimum  number  of  condors  seen. 
Evaluation  procedures  remained  the  same  as  in  previous  surveys  (see  Mallette 
and  Borneman,  California  Fish  and  Game  52(3) :1 85-203,  1966).  Records  were 
also  kept  of  other  raptorial  birds  seen  during  the  survey. 

Most  stations  reported  high  broken  cirrus  clouds  on  1 7  October  but  thick  haze 
reduced  visibility  at  most  lowland  stations.  Temperatures  at  higher  elevations 
were  1 5.5  C  to  21 .0  C;  lower  stations  reported  21  C  to  30  C.  Winds  were  mostly 
from  the  southwest  at  less  than  16  kmph.  FHowever,  some  higher  elevations 
reported  winds  of  32  to  48  kmph. 

On  1 8  October,  winds  shifted  to  the  southeast  and  decreased  somewhat.  FHigh 
clouds  increased,  and  temperatures  rose  slightly  at  all  stations. 

Thirty-six  total  condor  sightings  were  reported  by  11  stations  on  17  October; 
these  represented  a  minimum  of  12  individual  condors  (7  adults,  3  immatures, 
2  unclassified).  On  18  October,  15  stations  reported  50  sightings;  analysis  in- 
dicated these  represented  at  least  13  condors  (7  adults,  4  immatures,  2  unclassi- 
fied). 

We  do  not  know  what  proportion  of  the  total  population  was  accounted  for 
on  this  survey,  but  other  data  collected  in  1978  indicate  that  less  than  one-half 
of  the  condors  were  seen.  Apparently  some  birds  remained  outside  the  survey 
area  during  the  2-day  period.  One  encouraging  note  is  that  at  least  four  immature 
( under  5  years  of  age )  condors  were  seen,  about  as  many  as  our  nesting  surveys 
have  accounted  for  since  1974.  This  indicates  excellent  survival  during  the  first 
few  years  of  life  and  also  suggests  that  our  recent  estimates  of  condor  production 
may  have  been  somewhat  low. 

Eleven  other  raptor  species  were  observed  (Table  1 ). 

This  report  was  prepared  with  the  approval  of  the  California  Condor  Recovery 
Team  and  is  a  contribution  from  Endangered  Wildlife  Program,  E-W-3,  California 
Department  of  Fish  and  Came,  Nongame  Wildlife  Investigations. 


184  CALIFORNIA  FISH  AND  GAME 

Table  1.     Raptors  Observed  During  the  Condor  Survey,  17  and  18  October  1978 

Numbers 
Species  17  Oct.  18  Oct. 

Turkey  Vulture  (Cathartes  aura)  203  368 

Golden  Eagle  {Aquila  chrysaetos) 82  73 

Sharp-shinned  Hawk  (Accipiter  slriatus)  20  18 

Cooper's  Hawk  (A.  cooperii] 26  16 

Red-tailed  Hawk  [Buteo  jamaicensis) 200  173 

Swainson's  Hawk  [B.  swainsoni) 2  38 

Ferruginous  Hawk  (B.  regalis)  6  3 

American  Kestrel  i  Faico  sparverius)  53  51 

Prairie  Falcon  (F.  mexicanus) 5  2 

Peregrine  Falcon  (F.  peregrinus)  1  — 

Marsh  Hawk  (Circus  cyaneus) 4  6 

Unidentified  raptors 42  _37 

644  785 

— San  ford  R.  Wilbur,  U.  S.  Fish  and  Wildlife  Service,  1190  E.  O/ai  Ave.,  Ojai, 
California  93023;  Robert  D.  Mallette,  California  Department  of  Fish  and  Game, 
1416  Ninth  St.,  Sacramento,  California  95814;  and  John  C  Borneman,  National 
Audubon  Society,  2208  Sunridge  Drive,  Ventura,  California  93003.  Accepted 
for  publication  February  1979. 

THE  RELATIONSHIP  BETWEEN  MEGALOPAE  OF  THE 

DUNGENESS  CRAB,  CANCER  MAGISTER,  AND  THE 

HYDROID,  VELELLA  VELELLA,  AND  ITS  INFLUENCE 

ON  ABUNDANCE  ESTIMATES  OF 

C  MAGISTER  MEGALOPAE 

INTRODUCTION 

Crab  fishermen  have  long  noted  crab  megalopae  hanging  onto  floating  objects 
and  crab  trap  lines.  Weymouth  (1918)  noted  the  presence  of  Dungeness  crab, 
Cancer  magister,  megalopae  on  bells  of  several  pelagic  jellyfishes.  The  tendency 
of  crab  megalopae  to  attach  to  floating  objects  could  make  them  unavailable  to 
abundance  surveys  conducted  with  plankton  nets  sampling  the  open  water 
column.  In  May  1975,  I  noted  C  /r7a^/5^er megalopae  among  the  tentacles  of  the 
neustonic  hydroid  Velella  velella.  This  hydroid  occurred  in  high  densities  in  the 
spring  of  1975  while  this  year  class  of  C  mj^/s^e/' megalopae  were  making  their 
inshore  movement  to  crab  nursery  areas  (Lough  1976).  I  investigated  the  degree 
of  association  between  these  two  organisms  to  see  whether  a  significant  propor- 
tion of  megalopae  was  removed  from  the  water  column. 

MATERIALS  AND  METHODS 
V.  velella  were  sampled  individually  with  dip  net  on  9  May  1975  from  the 
Bodega  Marine  Laboratory's  research  boat.  Stations  were  made  along  a  transect 
from  Bodega  Bay,  California,  to  24  km  offshore  in  a  southwest  direction.  These 
stations  were  opportunistically  determined  due  to  the  patchy  distribution  of  V. 
velella.  The  individual  hydroids  were  examined  and  associated  crab  megalopae 
were  removed  and  counted.  The  gut  contents  of  five  megalopae  obtained  from 


NOTES  185 

I/,  velella  were  examined  for  hydroid  tissue.   V.  velella  washed  ashore  were 
sampled  and  checked  for  the  presence  of  crab  megalopae. 

A  similar  cruise  was  taken  along  the  same  transect  in  May  1976. 

RESULTS 
Samples  obtained  from  stations  between  0.8  km  and  10.0  km  from  shore 
showed  the  presence  of  C.  magister  megalopae  on  16-88%  of  the  hydroids 
(Table  1 ).  No  megalopae  were  found  on  V.  velella  which  were  either  beached 
or  beyond  10.0  km. 

Table  1.     Sampling  Data  and  Degree  of  Association  of  Velella  velella  and  Cancer  magister 
Megalopae 

Distance  from        No.  V.  velella       No.  with     Percent  V.  velella 
Station  shore  (km)  sampled         crab  larvae    with  crab  larvae 

1 onshore  200                     0                      0.0 

2 0.8  35  13  37.1 

3 1.6  32  22  68.8 

4 4,8  25  22  88  0 

5 8.0  10                     5  50.0 

6 9.6  25                       4  16.0 

7 11.2-24.0  100                      0'                     0.0 

In  59  of  the  observed  crustacean-hydrozoan  associations,  only  1  C.  magister 
megalopa  was  present  per  individual  hydroid.  In  six  instances  two  were  ob- 
served and,  in  one  case,  three  were  present  on  a  single  V.  velella.  In  all  cases, 
the  megalopae  were  among  the  gonozooids  underneath  the  hydroid  float.  Ap- 
parently no  megalopae  were  harmed  by  the  hydrozoan  nematocysts;  all  were 
active  and  in  good  condition. 

Other  animals  present  on  the  hydrozoan  were  megalopae  of  another  Cancer 
species,  adult  barnacles  of  a  Zep^5  species,  and  barnacle  cyprid  larvae.  Animals 
found  inside  the  gonozooids  were  apparent  food  items  and  consisted  of  zoeae 
of  the  crab  Pugettia  producta,  barnacle  cyprids,  and  a  cumacean. 

The  guts  of  the  five  megalopae  were  filled  with  tissue  containing  large  numbers 
of  unreleased  V.  velella  nematocysts.  One  megalopa  was  preserved  in  the  act 
of  eating  an  entire  gonozooid  with  its  attached  medusae  buds. 

During  the  dip  net  sampling  in  May  1975,  few  free  swimming  megalopae  were 
observed.  Personnel  from  the  California  Department  of  Fish  and  Came  also 
observed  C.  magister  megalopae  on  V.  velella  outside  San  Francisco  Bay  but 
found  that  megalopae  were  not  present  in  plankton  net  samples  taken  when  V. 
velella  was  present  (Tasto  et  al.  1977). 

No  V.  velella  were  found  during  the  May  1976  cruise,  nor  were  any  observed 
in  coastal  waters  or  on  the  beach  in  the  Bodega  Bay  area  that  year;  however 
C.  m.s^/^/e/' megalopae  were  abundant  and  could  be  seen  swimming  near  the 
surface.  I  was  able  to  observe  these  larvae  as  two  distinct  bands,  one  about  2-km 
wide  from  1  km  offshore  and  another  approximately  5-km  wide  from  8  km 
offshore.  A  visual  estimate  of  the  average  abundance  indicated  a  density  of 
roughly  1  /m^. 

DISCUSSION 

V.  velella  appears  to  provide  several  benefits  to  megalopae  of  C.  magister.  It 
provides  (i)  an  abundant  source  of  food,  (ii)  shelter  from  predatory  pelagic 


186  CALIFORNIA  FISH  AND  GAME 

fishes  such  as  salmon  which  feed  on  them  (Anon.  1949),  and  (iii)  possible 
transportation  into  nearshore  juvenile  crab  habitats.  It  is  not  known  whether  the 
presence  of  V.  velella  makes  a  significant  contribution  to  year  class  abundance 
of  Dungeness  crabs.  These  hydroids  only  occur  sporadically  along  the  central 
California  coast  and  their  presence  is  unpredictable  from  year  to  year. 

Ccincer  nicigister  vr[C^A\o\iA^  were  not  present  in  the  surface  waters  or  in  net 
samples  when  V.  velella  was  abundant,  even  though  the  crabs  were  abundant 
on  the  hydroids.  Most  surveys  conducted  to  assess  crab  larval  abundance  rely 
on  sampling  with  plankton  nets  (Sandifer  1973;  Lough  1976;  Tasto  et  al.  1977). 
Several  million  V.  velella  were  present  in  the  coastal  waters  near  Bodega  Bay 
in  1975  so  the  total  number  of  crab  megalopae  associated  with  this  hydroid 
could  have  been  very  high.  The  presence  of  V.  velella,  therefore,  must  be 
accounted  for  in  any  attempt  to  estimate  Cancer ma^/s/ermegalopal  abundance. 

ACKNOWLEDGMENTS 
I  would  like  to  thank  Cadet  Hand  and  Jerry  Tinkess  of  the  Bodega  Marine 
Laboratory  for  graciously  allowing  me  the  use  of  the  facilities.  This  work  is  a 
result  of  research  sponsored  by  NOAA,  Office  of  Sea  Grant,  Department  of 
Commerce,  under  grant  #04-6-158-44110.  The  U.S.  Government  is  authorized 
to  produce  and  distribute  reprints  for  governmental  purposes  notwithstanding 
any  copyright  notation  that  may  appear  hereon. 

REFERENCES 

Anonymous      1949.     Crab  larvae  as  food  for  the  silver  salmon  at  sea.  Fish   Comm   Oregon  Res.  Briefs  2:  17. 
Lough,  C.     1976.     Larval  dynamics  of  the  Dungeness  crab,   Cancer  magisler,  off  the  central  Oregon  coast, 

1970-71.  U.S.  Fish  Wildl.  Serv  ,  Fish    Bull.  74:  353-376. 
Sandifer,  P.     1973      Distribution  and  abundance  of  decapod  crustacean  larvae  in  the  York  River  estuary  and 

adjacent  lower  Chesapeake  Bay,  Virginia,  1968-1969.  Ches.  Sci,  14:  235-257. 
Tasto,  R.  N.,  P   N    Reilly,  D   D   Mogelberg,  and  S.  E   Hatfield.     1977.     Crab  critical  stage  project  studies.  Pages 

10-29  in  H.  C.  Orcutt,  compiler.  Dungeness  crab  research  program,  report  for  the  year  1977.  Calif.  Dept.  Fish 

Came,  Mar.  Resour.  Admin    Rep.  77-22. 
Weymouth,  F.     1918.     Contributions  to  the  life  history  of  the  Pacific  edible  crab.  Canada,  B.C.  Comm.  Fish,  Rep. 

for  1917  (3):  81-90. 

— Daniel  E.    Wickham,    University  of  California,   Bodega  Marine  Laboratory, 
Bodega  Bay,  California  94923.  Accepted  for  publication  February  1979. 

WINTE-R  FOOD  HABITS  OF  FISHERS,  MARTES  PENNANTI, 
IN  NORTHWESTERN  CALIFORNIA 

Very  little  is  known  about  food  habits  of  California  fishers.  Most  information 
on  this  uncommon  mustelid  is  summarized  by  Grinnell,  Dixon,  and  Linsdale 
(1937).  Recently  a  study  of  fisher  abundance  and  distribution  in  California  was 
completed  by  Schempf  and  White  (1977).  Currently,  Humboldt  State  Univer- 
sity, the  U.S.  Forest  Service,  and  the  California  Department  of  Fish  and  Game 
are  cooperating  in  a  study  of  fishers  in  a  study  area  in  Trinity  National  Forest, 
Trinity  County. 

Chief  foods  of  fishers  in  the  Pacific  coastal  states  are  porcupines,  squirrels, 
woodrats,  mice,  marmots,  mountain  beavers,  quail,  and  grouse  (Ingles  1965). 
A  study  conducted  in  Ontario,  Canada,  revealed  that  porcupines,  muskrats,  and 
snowshoe  hares  dominated  the  winter  diet;  a  variety  of  other  prey,  such  as 
squirrels,  voles,  mice,  shrews,  grouse,  and  jays  was  also  consumed  ( Clem  1 975 ) . 


NOTES  1 87 

Mice,  squirrels,  shrews,  birds,  fruit,  and  carrion  were  items  most  commonly 
found  in  fisher  stomachs  in  a  New  Hampshire  study  (Kelly  1977). 

From  December  1977  through  February  1978,  eight  fisher  carcasses  obtained 
from  the  Trinity  County  study  area  were  made  available  for  food  habits  study. 
Admittedly,  the  sample  size  is  small,  but  fishers  have  been  protected  in  California 
since  1946  and  opportunities  to  investigate  their  food  habits  are  extremely 
limited. 

The  vegetation  of  the  study  area  consists  of  a  mosaic  of  plant  communities 
including  Klamath  montane  forest  with  Douglas-fir,  Klamath  montane  forest  with 
yellow  pine,  Coast  Range  montane  forest,  Oregon  oak  forest;  mixed  evergreen 
forest  with  chinquapin,  and  mixed  evergreen  forest  with  rhododendron  (Kuch- 
ler  1977).  Elevations  range  between  610  and  1,070  m. 

METHODS  AND  MATERIALS 

Stomach  contents  were  removed  from  fisher  carcasses  and  preserved  in  10% 
formalin.  Identification  was  made  by  the  Food  Habits  Section  of  the  California 
Department  of  Fish  and  Game's  Wildlife  Investigations  Laboratory  at  Sacra- 
mento. 

All  food  material  was  washed  and  screened  in  a  sieve  measuring  14  squares 
per  cm.  Examination  was  done  with  a  dissecting  microscope  and  all  identifiable 
items  were  grouped  by  categories.  Hair  was  examined  with  a  compound  micro- 
scope. Plant  and  insect  fragments  and  mammalian  teeth  and  hair  were  identified 
by  comparing  them  with  known  reference  materials  and  by  referring  to  appropri- 
ate texts. 

Items  were  tallied  by  frequency  of  occurrence.  Volumes  were  visually  estimat- 
ed in  increments  of  5%;  volumes  estimated  to  be  less  than  5%  were  recorded 
as  a  trace. 

RESULTS  AND  DISCUSSION 

The  most  significant  food  item,  both  by  frequency  of  occurrence  and  by 
volume,  was  false  truffle  (subterranean  fungi)  (Table  1 ).  False  truffles  have  not 
been  recorded  in  previous  fisher  studies;  in  our  study,  spores  and  tissue  occurred 
in  four  samples.  Three  of  these  samples  also  contained  hair  from  western  harvest 
mice,  deer  mice,  and  black-tailed  deer.  False  truffle  is  eaten  by  squirrels  and 
other  rodents  in  the  southern  United  States  (Miller  and  Halls  1969)  and  western 
gray  squirrels  in  California  have  similar  food  habits  (Stienecker  and  Browning 
1970;  Steinecker  1977).  Whether  fishers  selectively  feed  on  fungi  or  acquire 
them  indirectly  from  their  prey  has  not  been  resolved.  However,  one  sample 
contained  90%  false  truffle  by  volume,  compared  with  10%  western  harvest 
mouse  hair.  None  of  the  samples  contained  squirrel  hair  and  fungi  together. 
Selection  of  fungi  by  fishers  is,  therefore,  a  possibility. 

The  second  most  important  food  item  by  volume  was  bovine;  however,  this 
food  item  occurred  in  only  one  of  eight  samples  (12.5%)  and  was  probably 
carrion.  Fishers  were  found  to  feed  on  carrion  in  the  White  Mountains  of  New 
Hampshire  (Kelly  1977). 

Deer  hair  was  identified  in  two  stomachs.  The  occurrence  of  deer  in  fisher 
digestive  tracts  has  also  been  reported  by  other  researchers.  Frequency  of  occur- 
rence of  deer  was  2.8%  in  fishers  studied  in  Ontario,  Canada  (Clem  1975).  In 
the  New  Hampshire  study,  deer  hair  found  in  fisher  stomachs  was  attributed  to 
carrion  or  trap-bait  (Kelly  1977). 


188  CALIFORNIA  FISH  AND  GAME 

TABLE   1.     Stomach  Contents  of  Eight  Fishers  Collected  During  the  1977-78  Winter  Season 
in  Trinity  County,  California 

Frequency        Volume 
Food  item  (%l  (%) 

Plant 

False  truffle  (Ifh/zopogonsp),  (spores  and  tissues) 50.0  28.0 

-Bark 50.0  7.5 

Douglas-fir  { Pseudotsuga  msnziesii) ,  (leaves)  50.0  0.6 

White  fir  (Abies  concolor),  (leaves)  12.5  0.6 

Ceanothus  iCeanothus  sp),  (leaves)  12.5  T 

Oak  [Quercus  sp),  (leaves)  .■ 12.5  T 

Forb  (Dicotyledneae),  (leaves)  12.5  T 

Grass  (Cramineae),  (leaves  and  stems)  12.5  T 

Moss  { Selaginella  sp) ,  (leaves  and  stems)  12.5  T 

Animal 

Fisher  (Martes  pennanti) ,  (hair) 62.5*  0.6 

Black-tailed  deer  (Odocoileus  hemionus) ,  (hair) 25.0  8.8 

Deer  mouse  (/'eramyscw  sp),  (hair)  25.0  3.1 

Beetle  (Coleoptera),  (larvae,  exoskeleton) 25.0  T 

Bovine  (Bostaurus),  (hair,  flesh) 12.5  11.3 

Brush  rabbit  (Sylvilagus  bachmanh  12.5  10.0 

Broad-handed  mole  (Scapanus  latimanus) ,  (hair) 12.5  8.1 

Western  gray  squirrel  (Sciurus  gnseus) ,  (hair  and  teeth) 12.5  7.5 

Wesierr^  har\/es\  mouse  { Peithrodontomys  megalotus) ,  (hair)  12.5  1.3 

Mammal  claws 12.5  0.7 

Arthropoda  (fragments)  12.5  T 

Miscellaneous 

Grit 62.5  8.1 

Bone  fragments 12.5  2.5 

Flesh,  unidentified 12.5  1-3 

100.0 

T  =  Trace 

•  Usually  ingested  while  grooming. 

No  porcupine  remains  were  found  in  our  specimens,  but  evidence  of  porcu- 
pine-fisher interaction  in  the  study  area  has  been  reported;  1  of  10  live-captured 
fishers  and  2  necropsied  fishers  had  quills  embedded  in  their  hides  (C.  Mullis, 
student,  Humboldt  State  University,  pers.  commun.).  Similarly,  porcupine  was 
not  found  in  40  fisher  stomachs  examined  in  New  Hampshire,  but  15%  of  89 
fishers  contained  quills  in  their  pelts  (Kelly  1977). 

ACKNOWLEDGMENTS 
Tim  Burton,  California  Department  of  Fish  and  Game  Wildlife  Biologist,  and 
Curt  Mullis,  a  student  at  Humboldt  State  University,  provided  the  specimens  for 
examination.  Oscar  Brunetti,  California  Department  of  Fish  and  Game,  Wildlife 
Pathologist,  confirmed  the  identification  of  false  truffle. 

REFERENCES 

Clem,  M.  K.  1975.  Interspecific  relationship  of  fishers  and  martens  in  Ontario  during  winter  Pages  165-182  ir 
R.  Phillips  and  C.  Jonkel,  eds.  Proceedings  of  the  1975  predator  symposium.  Montana  For.  and  Conserv.  Exp 
Sta.,  Missoula,  MT. 

Crinnell, ).,  j.  S.  Dixon,  and).  M  Linsdale.  1937.  Furbearing  mammals  of  California.  Univ  Calif  Press,  Berkeley 
CA,  2  vols. 

Ingles,  L.  C.     1965.     Mammals  of  the  Pacific  states   Stanford  Univ.  Press,  Stanford,  CA.  506  pp. 


NOTES  1 89 

Kelly,  C.  M.     1977.     Fisher  biology  in  the  White  Mountain  National  Forest  and  adjacent  area.  Ph.D.  Dissertation. 

Univ.  of  Mass.  Amherst,  MA. 
Kuchler,  A.  W.     1977.     The  map  of  the  natural  vegetation  of  California.  Dep.  of  Ceogr.  Univ.  of  Kansas,  Lawrence, 

KS. 
Miller,  H.  A.,  and  L.  K.  Halls.     1969.     Fleshy  fungi  commonly  eaten  by  southern  wildlife.  Southern  For.  Exp.  Sta., 

New  Orleans,  LA.  28  pp. 
Schempf,  P.  F.,  and  M.  White.     1977.     Status  of  six  furbearer  populations  in  the  mountains  of  northern  California. 

U.S.  Dep.  of  Agri.,  For.  Serv.,  Calif.  Region.  51  pp. 
Stienecker,  W.,  and  B.  Browning.     1970.     Food  habits  of  the  western  gray  squirrel.  Calif.  Fish  Came  56(1 ):  36-48. 
Stienecker,  W.     1 977.     Supplemental  data  on  the  food  habits  of  the  western  gray  squirrel.  Calif.  Fish  Game  63  ( 1 ) : 

11-21. 

— William  E.  Crenfell,  California  Department  of  Fish  and  Came,  987  Jedsmith 
Drive,  Sacramento,  CA  95819,  and  Maurice  Fasenfest,  1542  Maple  Street,  San 
Mateo,  CA  94402.  Accepted  for  publication  September  1978. 

AN  ANTI-ROLL  BEACH  SEINE 

The  netting  of  a  beach  seine  will  often  roll  up  into  a  tight  "rope"  when  used 
where  submerged,  attached  plants,  such  as  eelgrass,  Zostera  marina,  are  present. 
When  this  occurs,  fishes  can  no  longer  be  caught  in  the  seine. 

My  observations  indicate  that  net  rolling  is  caused  by  attached  plant  leaves 
being  "caught"  by  the  netting  of  the  seine.  The  attached  leaves  "escape"  the 
seine  by  dragging  the  netting  down,  in  front  of,  below,  and  behind  the  foot  rope 
as  the  seine  passes  through  and  over  attached  vegetation.  This  causes  the  netting 
to  become  rolled  up  into  a  tight  "rope". 

An  anti-roll  beach  seine  was  constructed  for  use  in  eelgrass  areas.  It  was  made 
of  a  rectangular  piece  of  10-mm  stretched  mesh  cotton  netting  suspended 
between  two  wooden  poles  (Figure  1).  The  head  rope  was  buoyed  by  two 
120-mm  long  and  80-mm  wide  foam  floats.  The  main  foot  rope  was  weighted 
to  1 .1  kg  with  7-mm  wide  pencil  lead  that  was  bent  and  coiled  around  the  main 
foot  rope.  A  secondary  foot  rope  was  attached  to  the  netting  in  several  places 
as  well  as  to  the  ends  (Figure  1).  It  was  weighted  to  1.25  kg  in  the  manner 
described  for  the  main  foot  rope.  Four  chains  were  tied  with  nylon  twine  to  both 
foot  ropes  (Figure  1).  Each  chain  weighed  0.3  kg  and  was  constructed  of 
nineteen  42-mm  long  and  4.8-mm  thick  links. 

This  seine  did  not  roll  because  the  forward  and  downward  drag  of  the  eelgrass 
leaves  against  the  netting  was  counteracted  by  a  backward  drag  of  the  second- 
ary foot  rope  and  chains  against  the  middle  of  the  seine.  This  anti-roll  beach 
seine  can  be  used  to  capture  fishes  wherever  submerged  vegetation  causes  other 
beach  seines  to  roll. 

ACKNOWLEDGMENTS 
R.  Wisner,  Jr.  and  F.  Button  were  helpful  in  the  development  of  this  seine. 

Constructive  criticism  for  the  manuscript  was  provided  by  J.  A.  Wiens  and  R. 

Olson.  This  is  contribution  number  67  of  the  Behavioral  Ecology  Laboratory, 

Oregon  State  University. 

— Range  D.  Bayer,  Department  of  Zoology,  Oregon  State  University  Marine 
Science  Center,  Newport,  Oregon  97365.  Present  address:  423  S.  W.  9th,  New- 
port, Oregon  97365.  Accepted  for  publication  December  1978. 


190 


CALIFORNIA  FISH  AND  CAME 


Figure  1.     Back  view  of  the  anti-roll  beach  seine. 


NOTES 


191 


TERM  FETUSES  FROM  A  LARGE  COMMON  THRESHER 
SHARK,  ALOPIAS  VULPINUS 

Little  is  known  of  the  life  history  of  the  common  thresher  shark.  It  has  been 
determined  that  this  ovoviviparous  species  attains  maturity  at  a  length  of  approx- 
imately 4.2  m,  and,  on  a  worldwide  basis,  probably  reaches  a  maximum  length 
of  some  6  m  (Bigelow  and  Schroeder  1948).  Most  threshers  taken  in  California 
waters  are  less  than  2.4  m  in  length  (Roedel  and  Ripley  1950;  Fitch  1974), 
although  larger  specimens  are  often  captured  off  southern  California,  particularly 
by  anchovy  purse  seiners  and  barracuda  gill-netters  during  summer  months  (J. 
Fitch  and  D.  Schultze,  Calif.  Dept.  Fish  and  Game,  pers.  commun.).  Unfortu- 
nately, few  of  these  large  threshers  have  been  closely  examined  before  being 
cleaned.  This  note  describes  term  fetuses  taken  from  one  such  specimen. 

On  3  June  1977,  Michael  McCorkle  of  the  commercial  fishing  vessel  PIE  FACE 
landed  a  large  female  thresher  that  had  become  entangled  in  his  gill  nets  the 
previous  night.  The  nets  had  been  set  in  13  fm  of  water  approximately  2  nautical 
miles  off  Solimar  Beach  near  Ventura,  California.  The  length  of  the  fish  was 
estimated  at  greater  than  4.6  m  and  its  weight  was  measured  at  295  kg.  When 
the  thresher  was  cleaned,  four  large  fetuses  were  removed,  two  of  which  were 
badly  mutilated  in  the  process.  The  intact  specimens  were  donated  to  the 
University  of  California  at  Santa  Barbara,  and  subsequently  deposited  at  the 
Museum  of  Ichthyology  in  the  Department  of  Biological  Sciences. 


Figure  1.     Male  and  female  term  fetuses  of  the  common  thresher  shark.  Photograph  by  G.  M. 
Wellington,  June  1977. 


The  two  fetuses  had  been  very  near  birth,  as  evidenced  by  their  lack  of 
umbilical  scars  and  their  large  size  (Figure  1 ).  The  male  was  1417  mm  in  total 


192  CALIFORNIA  FISH  AND  CAME 

length  and  weighed  8.8  kg  fresh,  while  the  fennale  was  1386  mm  long  and 
weighed  7 .1  kg.  These  specimens  approach  the  maximum  fetal  size  of  1550  mm 
reported  by  Bigelow  and  Schroeder  (1948).  Moreover,  free-living  threshers 
considerably  smaller  than  the  fetuses  have  been  taken  off  California  ( Herald  and 
Ripley  1951 ),  as  well  as  off  the  eastern  United  States  (Bigelow  and  Schroeder 
1948). 

In  1954,  another  large  thresher  carrying  four  term  fetuses  was  captured  off 
Newport  Beach  (Joseph  1954).  Although  it  was  larger  than  the  one  reported 
here  (approximately  5.4  m)  the  fetuses  were  somewhat  smaller  and  still  exhibit- 
ed umbilical  scars. 

As  a  final  note,  the  litter  size  of  the  common  thresher  shark  is  invariably 
reported  as  ranging  from  two  to  four  pups  ( Bigelow  and  Schroeder  1 948;  Roedel 
and  Ripley  1950).  However,  McCorkle  (pers.  commun.)  once  captured  a 
thresher  that  carried  six  fetuses. 

ACKNOWLEDGMENTS 
In  addition  to  Michael  McCorkle,  I  wish  to  thank  my  colleagues  at  the  U.  C. 
Santa  Barbara  Marine  Science  Institute,  especially  Floyd  DeWitt,  who  obtained 
the  specimens,  and  Jerry  Wellington,  who  photographed  them.  John  Fitch  and 
Don  Schultze,  California  Department  of  Fish  and  Game,  kindly  provided  useful 
commercial  catch  data. 

REFERENCES 

Bigelow,  H.  B.,  and  W.  C.  Schroeder.     1948.     Sharks.  Pages  59-546  in  Fishes  of  the  western  North  Atlantic.  Part 
1.  Sears  Found.  Mar.  Res.,  Mem.  (1). 

Fitch,  J.  E.      1974.     Offshore  fishes  of  California.  5th  ed.  Calif.  Dept.  Fish  Came,  Sacramento.  80  pp. 

Herald,  E.  S.,  and  W.  E.  Ripley.     1951.     The  relative  abundance  of  sharks  and  bat  stingrays  in  San  Francisco  Bay. 

Calif.  Fish  Came  37:  315-329. 
Joseph,  D.  C.     1954.     A  record-size  thresher  from  southern  California.  Calif.  Fish  Came  40:  433^35. 
Roedel,  P.  M.,  and  W.  E.  Ripley.     1950.     California  sharks  and  rays.  Calif.  Dept.  Fish  Game,  Fish  Bull.  (75).  88 

PP 

— Mark  A.  Hlxon,  Department  of  Biological  Sciences  and  Marine  Science  Insti- 
tute, University  of  California,  Santa  Barbara  93 1 06.  Accepted  for  publication 
February  1979. 


Photoelectronic  composition  by 

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