Southwestern Association of Naturalists
Aspects of the Ecology of the Hitch, Lavinia exilicauda (Cyprinidae), a Persistent Native
Cyprinid in Clear Lake, California
Author(s): R. Eugene Geary and Peter B. Moyle
Reviewed work(s):
Source: The Southwestern Naturalist, Vol. 25, No. 3 (Nov. 14, 1980), pp. 385-390
Published by: Southwestern Association of Naturalists
Stable URL: http://www.jstor.org/stable/3670695 .
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THE SOUTHWESTERN NATURALIST 25(3):385-390
NOVEMBER
14, 1980
ASPECTS OF THE ECOLOGY OF THE HITCH,
LAVINIA EXILICAUDA (CYPRINIDAE),
A PERSISTENT NATIVE CYPRINID IN
CLEAR LAKE, CALIFORNIA
R. EUGENE
GEARY1 AND PETER B. MOYLE
ofWildlifeand FisheriesBiology,
Department
of California,
University
Davis, CA 95616
of Clear Lake hitch(Lavinia exilicauda
ABSTRACT. Growth,diet,and fecundity
to see if any changeshad takenplace followingthe establishchi) wereinvestigated
mentof a largepopulationof Mississippisilversides(Menidia audens) in the lake.
No changeswere found.Hitch seem to avoid competingwith silversidesfor zooplanktonby beinglimneticin all exceptthe earlylife historystages.Fecunditywas
foundto be higherthan that of BeardsleyReservoirhitch,but considerablylower
thana previousestimatehad indicated.
The Clear Lake hitch (L. e. chi Hopkirk 1973) is one of only four (out of
12) native species that has managed to persistin large numbersin Clear Lake,
Lake Co., California, followingvarious environmentalperturbationsand the
establishmentof 16 exotic species (Moyle 1976). The hitch is a large (to 35
cm standard length), plankton-feedingcyprinidthat spawns in the intermittent streamsthat enter the lake and is taken in small numbersby a commercial fishery.Although brief studies of its feeding habits were undertaken by
Lindquist, Deonier, and Hanley (1943), and of its growthand reproduction
by Murphy (1948), no studies have been undertakensince the establishment
in the lake of the Mississippisilversides (Menidia audens) in 1967 (Cook and
Moore 1967). The silversidesis a small planktivorethat now dominatesthe inshore areas. It has been introducedinto reservoirsin Oklahoma and California
and appears to be extendingits range rapidly (Moyle 1976). An additional
aspect of hitchbiology needing to be examined was the extremelyhigh fecundity (112,000 eggs/female) reportedby Murphy (1948), which was in contrast to the much lower fecundities (about 3,000 to 26,000 eggs/female)
reportedby Nicola (1974) forL. e. exilicauda fromBeardsley Reservoir,California.The purpose of this study,therefore,was to examine the feedinghabits
and growth rates of Clear Lake hitch, for comparison with pre-silversides
studies, and to reexamine their fecundity.
1 Presentaddress:
Dept. EngineeringResearch,PacificGas and ElectricCo., 3400
Crow Canyon Road, San Ramon,CA 94584.
385
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STUDY AREA. Clear Lake is a large (16,194 ha), warm,eutrophiclake located
in the Coast Range of centralCalifornia,
at an elevationof 404 m. It has threedistinctarms;thisstudywas conductedprimarily
in the upperarm (Upper Lake), into
whichmosthitchspawningstreamsflow.A detaileddescription
of the lake and its
limnologycan be foundin Goldmanand Wetzel (1963).
METHODS. Collectionsweremade monthlyfromAprilthroughSeptember1976.
These collectionsweremade usinga 10.9 x 1.2 m seinewith0.3 cm bar mesh (priin collectingyoungof the year), a 91.4 x 2.4 m seine with2.5 cm
marilyeffective
bar mesh,a 24.4 x 1.8 m seine with1.27 cm bar mesh,and a four-seam
ottertrawl
fittedwithan 0.3 cm meshbag. Additionalcollectionswere made withthe trawlin
1977. For adult fish,weightwas measuredto the nearestgram,using a 300 g Pesola springbalance; forklengthand standardlengthwere measuredto the nearest
and scale sampleswere takenfrommost fish.Samples of youngof the
millimeter
solution,as were any
year hitchwere preservedin a 4% bufferedformaldehyde
adults saved for gut analysisand fecunditycounts.
For age and growthanalysis,about six to 10 non-regenerated
scales weremounted
betweentwo glass microscopeslides and seriallylabeled. The scales were read in
a modified
microfilm
of 28.5 x. Scale radii forthe sample
reader,witha magnification
were measured,the median radius calculated,and, for two to fourscales of near
medianradius,the distancefromthe scale focusto each annulusand the scale edge
at the leftlateralmarginwas measured.These measurements
wereaveragedforeach
fish.Criteriaused to determinethe presence of an annuluswere crossingover,
crowdingof circuli,and startsand stopsof lateralrays.When therewas a question
of age, the scales were read by a secondparty.If no agreementcould be reached,
the scales were discarded.Since the calculationsfor this studywere done using
standardlength(SL) and the previousworkon hitchlifehistoryused forklength
factorwas calculatedto allow comparison:FL = 2.60 + 1.1 x SL
(FL), a conversion
(r = 0.99). Comparisonof the 1976 data withthose of Murphy(1948) was made
because the older data were availableonlyin thatform.
graphically
For fecunditydeterminations,
ovarieswere removedfrom 18 preservedfemales
in the laboratory,
air dried overnight,
and weighedto the nearest0.01 gram.Four
fromboth ovaries,pooled, and weighedto the nearsampleswere takenarbitrarily
est 0.01 g, and the numberof eggs in the samplewas counted.The numberof eggs
per gramwas thencalculated,and used to estimatethenumberof eggs in the ovary.
Pooled sampleweightsrangedfrom5 to 17% of the totalovaryweight.
For diet determination,
the contentsof the "stomachs"of 168 fishwere examined.
The "stomach"was taken as the initialportionof the intestinedown to the first
bend. The point-volume
method(Hynes 1951) was used to estimatethe percent
contribution
of each food item to the diet.
RESULTS. Age and Growth.-The body length-scale radius relationship
was plotted for all the fishexamined and found to be linear (r = 0.80), but
formuladescribed
directlyproportional,so the modifieddirect proportionality
by Tesch (1971) was used for back-calculation.The size at scale formation
used was 22 mm, which was also the average size of the smallestscaled hitch
collected. Comparison of back calculated lengthsusing a t-testshows that female hitch are significantly
larger than male hitch (a < 0.001) at all ages except age V, where the differenceis non-sigificant,
presumablydue to the small
size.
sample
Comparison of resultsof the age and growthanalysis fromthis study with
the resultsof Murphy (1948) shows that the growthrate of Clear Lake hitch
has remainedabout the same since 1947. The female hitchfromthe 1976 sam386
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TABLE 1. Back-calculatedlengthsin mm at each annulusfor male and female
hitchfromClear Lake.
FEMALES
Annulus
I
II
Year
Class
N
1974
1973
1972
1971
27
48
30
1
119
107
106
122
106
110
Combined
III
IV
V
193
176
162
166
219
203
216
234
246
264
176
213
234
264
III
IV
V
MALES
Year
Class
N
1975
1974
1973
1972
1971
7
43
37
8
2
105
100
106
89
92
163
165
139
120
203
177
151
209
179
200
Combined
97
102
161
196
203
200
I
Annulus
II
pie have a slightlysmalleraveragesize than thosefromthe 1947 sample,
whilethemale hitchin 1976 wereslightly
largerthanthoseof 1947. In both
are minor,and probablydue to naturalvariation.Alcases, the differences
relationrates,the length-weight
thoughmales and femalesgrewat different
lines forthe
shipsforboth sexeswere similar.Comparisonof the regression
difdata, usinganalysisof covariance,showedno significant
log-transformed
ferencein theirslopes (P > 0.01). The data forbothsexeswerethenpooled,
to give the equation:W = 2.17 SL3 (r = 0.98, whereW = weight).
Because 18 samples(mostwith n = 20) of youngofyearhitchweretaken
duringthe 80 days followinghatchingin earlyApril,growthwas examined
duringthisperiod. Growthwas linear (r= 0.94) forlengthvs days since
witha growthrateof approximately
0.45 mm/day,
and an average
hatching,
size of 40 mmat the end of 80 days.
was plottedagainstweight,standardlength,and
Fecundity.-Fecundity
forklength,withall threeshowinga largespreadabouttheline.The average
ofthe 18 fishexaminedwas about36,000,rangingfromabout9,000
fecundity
(in a 212 mmSL fish)to 63,000 (in 312 mmSL fish).Curveswere fittedto
the data by computerand the best fitting
curvewas the linearequationfor
the weight-fecundity
F = 7154 + 106W (r =0.65). The best
relationship,
fittingcurve for forklengthwas the linear equation F = 52299 + 353 L
curveforstandardlengthwas F = -30384
(r = 0.57), whilethe best fitting
+ 504 L (r = 0.57). The forklength-fecundity
will be the only
relationship
one referred
to in comparisonwiththe data of Nicola (1974) and Murphy
(1948), since it is the onlyrelationship
theyused.
387
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5-
-_
4
4-
1976 --*
\
1948 ---
z
Z 3o
1948 --^ .
1976 e------
2-
LLI
11
C)
D O0
1
W
iR
0 I00100
200
200
300
300
FORK LENGTH(mm)
Fig. 1. Fork length and age at capture of male and female hitch from spawning runs in
streams tributaryto Clear Lake, in 1976 and 1947.
Food Habits.-Of 168 hitchstomachsexamined,only94 containedidentifiablefooditems.The remainder
wereemptyfora varietyofreasons,includor
ing the timeof collection,methodof collection,methodof preservation,
chance.All stomachstakenfromspawningfishwereempty,as werestomachs
of adult fishtakenearlyin the morning.
Typically,hitchcaughtduringthe
or eveningcontainedfoodin at leastsomeportionof the gut.
afternoon
The smallesthitchexamined(19-30 mmSL), all takeninshorein shallow
As the fishincreasedin
on adultand larvalchironomids.
water,fed primarily
size, Daphnia becamemoreimportant,
makingup about halfthe diet of the
31-50 mmsize class. Fish largerthan50 mm were generallyunavailableinshore,and theywere presumedto becomelimneticat about thissize. After
the fishbecomelimnetic,
on Daphnia,withother
theyfeedalmostexclusively
and adultmidgestakenin smallnumbers.
zooplankton
DISCUSSION. It is evidentthatneitherthe diet nor the growthratesof
Clear Lake hitchhave changedsincethe 1940's,despitethe introduction
of
the Mississippisilversides,
a potentialcompetitor
forzooplankton.
Hitchseem
to be able to avoid competingwithsilversidesby being presentin inshore
areas mainlyin springand earlysummer,when silversidespopulationsare
388
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TABLE 2. Percentcompositionby volumeof stomachcontentsof different
size
classes of Clear Lake hitchtakenApril- July,1976.
0
(S.L., mm)
19-30
31-50
51-200
201-270
N
27
24
26
12
3
?- "
14
48
84
98
3
6
5
<1
C
3
2
<1
3
-
<1
2
1
<1
i
<1
18
5.8
-
1
61
35
7
-
likelytobe lowest(H. W. Li, unpubl.data), and by becominglimneticin habit
once theyexceed 50 mmSL. These habitsof the hitchdo not seemto have
but wereprobablyevolvedas a way
developedin responseto the silversides,
of avoidingcompetition
with the inshore-oriented
(and now extinct)Clear
Lake splittail(Pogonichthys
ciscoides) (Moyle 1976). The ClearLake sculpin
(Cottusasper subsp.) also maintainslarge populationsin the lake, due in
partto the absenceof any ecologicallysimilarexoticspecies (Broadwayand
Moyle 1968).
Growthin Clear Lake hitchwas abouttwiceas fastas thatforhitchfrom
the onlyotherpopulationthathas been studied,forthe
BeardsleyReservoir,
first2 yearsof life (Nicola 1974). This is presumably
relatedto the higher
of Clear Lake, whichis severaltimesthatof Beardsley
primary
productivity
(Nicola 1974). Afterthe secondyear,when hitchof both populationsmatured,growthrates (as indicatedby annuallengthincrements)of the two
Clear Lake
populationswereabout equal. This may reflectthe greatereffort
hitchput intoreproduction.
Not onlywas theirabsolutefecundity
higherthan
as well. This,a 250 mmFL
Beardsleyhitch,but theirsize-specific
fecundity
hitchfromClearLake wouldhave a fecundity
ofabout36,000,whilea similar
fishfromBeardsleyReservoirwould have a fecundity
of about 14,600. Defecundities
estimated
for
Clear
Lake Hitch,the
spitethe comparatively
high
estimateof 112,000fora single250 mmFL femaleby Murphy(1948) is obviouslytoo highand in error.
LITERATURE CITED
BAGENAL, T. B., and E. BRAUM. 1968. Eggs and earlylife history.Pp. 166-
fortheassessment
offishproduction
in fresh
water(W. E. Ricker,
198,in Methods
ed.), IBP Handbook.
BROADWAY,J.E., and P. B. MOYLE. 1978. Aspectsof the ecologyof the prickly sculpin,Cottusasper, a persistentnativespecies in Clear Lake, California.Environ.Biol. Fish. 3:332-343.
COOK, S. F., and R. L. MOORE. 1970. Mississippisilversides,Menidia audens
(Atherinidae)establishedin California.Trans. Am. Fish. Soc. 99:70-73.
389
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HOPKIRK, J. D. 1973. Endemismin fishesof the Clear Lake Region. Univ.
CaliforniaPubl. Zool. 96:1-160.
aculeasticklebacks(Gasterosteus
HYNES, H. B. N. 1950. The foodof freshwater
tus and Pygoteuspungitius),witha reviewof methodsused in studiesof the food
of fishes.J. Anim.Ecol. 19:36-58.
LINDQUIST, A. W., C. D. DEONIER, and J. E. HANLEY. 1943. The relationship of fishto the Clear Lake gnat,in Clear Lake, California.CaliforniaFish, Game
29:196-202.
MOYLE, P. B. 1976. Inland Fishes of California.Univ. CaliforniaPress,Berkeley.
405 pp.
MURPHY, G. I. 1948. Notes on the biologyof the Sacramentohitch(Lavinia e.
exilicauda) of Clear Lake, Lake County,California.CaliforniaFish, Game 34:101110.
NICOLA, S. J. 1974. The life historyof the hitch,Lavinia exilicauda Baird
and Girard,in BeardsleyReservoir,California.CaliforniaDept. Fish, Game, Inland
Fish. Admin. Rept. 74-6.
390
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