Introduction

The family Embiotocidae is comprised of 23 spe-cies, all of which bear young at very advancedstages of development . This family of fishes repre-sents an unusual opportunity to study life historyvariation; in addition to their viviparity, mostspecies are unexploited, all except one species aremarine, and the marine fauna is not diluted byintroduced species, so the environmental factorsinfluencing the distribution and abundance of thespecies today are likely to have had a strong effecton the evolution of their life histories . Therefore,the patterns of life history variation should be clear

Environmental Biology of Fishes Vol . 10, No . 3, pp . 1 5 9-171, 1984© Dr W. Junk Publishers, The Hague .

Life history variation among female surfperches (Perciformes: Embiotocidae)

Donald M . BaltzDepartment of Wildlife and Fisheries Biology, University of California, Davis, CA 95616, U .S.A .

Keywords: Age, Environmental predictability, Fecundity, Growth, Longevity, Microhabitat, Reproductivestrategy, Viviparity

Synopsis

Life history variation within the family Embiotocidae is extensive and involves differences in age of firstreproduction, fecundity schedules, growth rates, longevity and size of young . Based on maximum reportedbody lengths, there are three distinct size groups among the family's 23 species . Small species do not exceed215 mm TL, medium-size species attain 275 to 335 mm TL, and the large species attain 380 to 470 mm TL . Thelongevity of surfperches varies from two to ten years, growth is indeterminate, and females of the medium-and large-size groups may delay first reproduction beyond age one . With one exception, all species showincreasing length-specific fecundities . The life history characteristics of females differ among the three sizegroups. Relative to smaller species, the largest species have moderately high fecundity, delayed maturity andlong life . Medium-size species have low fecundity, may delay maturity for 1 to 3 years and have intermediatelife spans . Small species have generally higher, but variable, fecundity, do not delay maturity, and are shortlived. Among the small North American species, the trend in fecundity varies inversely with environmentalpredictability . Fecundity is highest in the species which occupies highly seasonal freshwater environments .Coastal species produce moderately large broods and species which occupy stable deep water environmentsproduce the smallest broods .

at the intrafamilial level as suggested by Stearns(1980) and unclouded by problems encounteredwith many freshwater taxa, especially highly modi-fied environments, modified gene pools, and thepresence of exotic competitors and predators . Mostembiotocids are important constituents of tempe-rate subtidal marine communities of the NorthPacific Ocean (Ebeling et al . 1980a, b) . Three speciesare found only in the waters around Japan (Hayase& Tanaka 1980a, b, c), while nineteen species occuroff the coast of western North America (Miller &Lea 1972) . Only one species, the tule perch, occu-pies freshwater habitats and is confined to threecontiguous drainages in central California (Baltz &

1 6 0

Moyle 1981, 1982) . Life history variation in thefamily is extensive and involves differences in age offirst reproduction, longevity, age-specific and length-specific fecundity, size of young, maximum sizeattained, and growth rates . Warner & Harlan (1982)have examined reproductive strategies among malesurfperches, with particular reference to sexualselection between age classes of the dwarf surf-perch, Micrometrus minimus . This paper examineslife history variation among female surfperches anduses environmental correlations to show how selec-tive pressures influence life histories .

Methods

General life history information for most of the 23species was obtained from the literature (Table 1) .Life history data describing variation among fe-males in age of first reproduction, longevity, age-specific fecundity, maximum size and growth rates

Table 1 . The common and scientific names of the surfperches and sources of general life history information . Current knowledge ofsurfperch ecology does not generally justify division of the species into perch, seaperch and surfperch ; therefore, I have not used thecommon names recommended by Robbins et al . (1980) .

are summarized by 21 variables (Table 2) for 15marine species and three populations of tule perch .Empty cells in the data set were estimated orassigned a value of zero, as appropriate . Threeadditional variables are implicit in Table 2 : long-evity was taken to be the oldest reported age, age offirst reproduction was the age at which 50 percentor more of the females produced a brood, and re-productive life span was defined as the inclusive inter-val between the age of first reproduction and theoldest reported age (Roff 1981) . Mean length at agehas been estimated in several ways by differentworkers. Length at age has been back-calculated bysome, but others have used observed length at thetime of parturition . The latter approach is valid formost embiotocids because parturition is confined toa few weeks in the spring or summer and only onebrood is produced per year. Back calculation oflength at age may underestimate female length atparturition if the growth check is formed during thewinter. Growth rates differ between males and

Common name Scientific name Sources

Barred surfperch Amphistichus argenteus Carlisle et al . 1960Calico surfperch A . koelzi no dataRedtail surfperch A . rhodoterus Bennet & Wydoski 1977Kelp surfperch Brachyistius frenatus Baltz unpublishedShiner surfperch Cymatogaster aggregata Gordon 1965, Wilson & Millemann 1969, Anderson & Bryan 1970Island surfperch C. gracilis no dataBlack surfperch Embiotoca jacksoni Isaacson & Isaacson 1966, Behrens 1977Striped surfperch E. lateralis Swedberg 1965, Gnose 1967Spotfin surfperch Hyperprosopon anale Baltz & Knight 1983Walleye surfperch H. argenteum Anderson & Bryan 1970, DeMartini et al. 1983Silver surfperch H. ellipticum Wydoski & Bennet 1973Rainbow surfperch Hypsurus caryi Behrens 1977Tule perch Hysterocarpus traski Baltz & Moyle 1982Reef surfperch Micrometrus aurora Hubbs 1921Dwarf surfperch M. minimus Hubbs 1921, Warner & Harlan 1982Sharpnose surfperch Phanerodon atripes Smith 1964, Baltz unpublishedWhite surfperch P. furcatus Anderson & Bryan 1970, Banerjee 1971, 1973, Goldberg 1978Rubberlip surfperch Rhacochilus toxotes Baltz unpublishedPile surfperch R. vacca Wares 1971Pink seaperch Zalembius rosaceus Goldberg & Ticknor 1977, Goldberg unpublished

Ditrema temmincki Abe 1969, Hayase & Tanaka 1980bD. viridis Abe 1969, Hayase & Tanaka 1980bNeoditrema ransonneti Hayase & Tanaka 1980b

Table 2 . Maximum size and mean lengths and fecundities at age of female surfperches .

° Gotshall (1981)Yamane (1964)Wydoski (1969)Baltz (unpublished data)

females in some species (Warner & Harlan 1982) ;therefore, where appropriate and available the meanlength of females at various ages has been used .Where the mean fecundity at a specific age was notavailable, it was estimated from the length-fecundityrelationship using mean length at that age. Principalcomponent analysis (BMDP 4M) using the correla-tion matrix was used to examine variation in age-specific lengths and fecundities (Table 2, variables 2through 21, inclusive) (Brown & Dixon 1977) . Length-fecundity relations were compared graphically .

Table 3 . Correlations between selected life history variables .

* P<0.05** P<0.01

Results

The longevity of surfperches varies from two to tenyears, growth is indeterminate (i .e. continues through-out life), all females show an age-specific increase infecundity, and the larger species delay first repro-duction beyond age one (Table 2) . Many of the sixlife history variables (i .e . age, length, and brood sizeat first reproduction, longevity, reproductive lifespan, and maximum length) implicit in Table 2 aresignificantly correlated (Table 3) . Maximum length

1 6 1

Species MaximumTL (mm)

Mean SL at age Mean fecundity at age

I II III IV V VI VII VIII IX X I II III IV V VI VII VIII XI X

Pile surfperch 442 87 .0 145 .0 192 .0 224.0 255 .0 274.0 292 .0 312 .0 328 .0 332.0 0.0 0.0 0.0 18 .0 22.4 28 .7 31 .7 39 .8 52.5 52 .0Barred surfperch 432 126 .5 171 .8 221 .3 243 .3 268 .2 284.1 297 .2 296 .0 337 .0 0.0 8 .4 24.5 31 .7 39 .9 45 .1 49 .4 49 .0 62.4Redtail surfperch 406 78 .1 124.3 203 .5 218 .2 227 .0 251 .0 275 .7 292 .2 0.0 0.0 0.0 8 .7 11 .9 18 .4 25 .4 33 .7Black surfperch 390 125 .0 149 .0 173 .0 208 .0 239 .0 261 .0 296 .0 0.0 4.3 8 .6 14.9 20.5 24.5 30.7Striped surfperch 381 130.0 173 .0 216.0 233 .0 262.0 277 .0 297 .0 0.0 0.0 18 .0 21 .0 30.0 31 .0 32 .0

White surfperch 340° 110 .2 160.1 186 .7 203 .8 215 .5 231 .5 233 .7 0 .0 10 .1 16 .8 21 .0 24 .0 28 .0 28 .5Walleye surfperch 305 110 .0 130.0 140.0 151 .0 6 .0 8 .0 10 .0 11 .0Silver surfperch 267 81 .8 127 .5 147 .9 165 .9 184.3 0 .0 3 .4 8 .0 12 .1 16 .3Ditrema temmincki 288' 123 .0 135 .6 162 .7 179 .8 9 .2 12 .0 18 .9 22 .8

Ditrema viridis 215' 124.8 142.0 164.1 182.0 17 .0 22.8 40.2 60.5Spotfin surfperch 199 ` 103 .0 116.0 121 .0 7 .1 11 .4 14.0Shiner surfperch 178 82.3 98.8 105.0 115 .8 119.4 122.2 5 .8 9.3 11 .1 15 .4 15 .0 20.0Reef surfperch 180 89 .2 106 .8 124.3 124 .7 9 .6 14 .8 20 .0 19 .0Dwarf surfperch 159 68 .7 89 .4 106 .9 110 .5 114 .0 129 .0 7 .3 16 .2 20 .9 22 .0 23 .0 22 .0Neoditrema sp . 145 108 .0 117 .3 10 .5 12 .6Tule perch populations

Russian River 139° 76 .9 77 .7 90.7 102 .0 21 .2 21 .4 38 .3 40.5Suisun Marsh 171° 81 .7 84.3 108 .2 116 .3 118 .1 129 .5 18 .5 20.5 36 .3 42 .5 42 .6 59 .0Clear Lake 165 ° 96 .8 94.1 115 .5 118 .5 116.3 123 .2 129 .2 17 .3 16.0 31 .7 37 .8 40.0 45 .8 51 .8

At first reproduction Maximumlongevity

Reproductivelife span

MaximumTL (mm)

Length Fecundity

Age first reproduction 0 .9277* * -0.1876 0.7384* * 0 .3595 0 .8175**Length first reproduction -0.2463 0.4941* 0 .3185 0 .9023**First brood size -0.0696 0 .0279 -0.4024Longevity 0.8947* * 0.7180**Reproductive life span 0.4521

162

Table 4 . Variable loadings for principal components one throughthree . Magnitude of loading indicates importance of variable inprincipal component and sign indicates relationship to othervariables . Input variables are mean standard lengths and meanfecundities at specific ages for 18 surfperch populations in Table 1 .

is positively correlated with age and length at firstreproduction and with longevity . Longevity is alsopositively correlated with age and length at firstreproduction and reproductive life span . First broodsize is not significantly correlated with any variable,and reproductive life span is correlated only withlongevity .

Principal component analysis of age-specific data(i .e . variables 2 through 21 in Table 2) on fecundityand female size (SL) suggests several life historycategories, within the family (Fig . 1). Three tuleperch populations, and Ditrema viridis group to-gether as small, high fecundity species . Five largeand one medium-size species with delayed maturityform a second distinct group . The remaining speciesform a diffuse group of small- and medium-sizefishes with low to moderate fecundity . The first twocomponents explain 64% of the variation, and thefirst three components explain 77% (Table 4) .

3

2

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/•TULE, SM `•

TULE, CLJ.•' D/TREMA V/R/D/S/

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. BARRED': -

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'• •STRIPED

SHINER'+ • %.•B LACKREEF• • •

iDTEMM/NCK/

PILESILVER,,

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S POTFIN .̀'•...•NEDD/77JEMA.. . . . .. ... . .. . .. ... .. .. .. . .

LIII

-2 -I 0PCI

"FEMALE SIZE'

I 2 3

Fig . 1 . Plot of species' scores for principal components one andtwo. Principal component one is weighted heavily by sizevariables and to a lesser extrent by fecundity variables . Principalcomponent two is weighted primarily by fecundity variables .

Fig . 2. The maximum sizes (mm TL) reported indicate that thespecies group easily into small, medium and large size categories .Illustrations of California marine species by D .J . Miller fromMiller & Lea (1972) and of tule perch by C . van Dyck .

Input variable PC1 PC2 PC3

SLI 0.240 0 .071 -0.562SL2 0.686 -0.160 -0.466SL3 0.764 0.117 -0.323SL4 0 .758 0.195 -0.275SL5 0.880 0.102 -0.210SL6 0.879 0.194 -0.169SL7 0.910 0 .063 -0.243SL8 0.800 -0.089 0.397SL9 0 .763 0.060 0 .501SLIO 0.546 -0.217 0.656

F1 -0.715 0 .533 0 .343F2 -0.714 0.577 0.250F3 -0.365 0.869 0 .036F4 -0.091 0 .873 0 .131F5 0.554 0.612 -0.063F6 0 .531 0.649 0 .011F7 0.784 0.330 -0.170F8 0.811 -0.022 0.377F9 0.758 0.086 0.466F10 0.546 -0.217 0.656

Variance explained 9 .48 3 .29 2 .71Cumulative percent 47 .4 63 .8 77 .4

Examination of variable loadings (Table 4) in-dicates that principal component one is primarily asize variable ; however, loadings for several fecun-dity variables are also high and for ages onethrough four they are negative, indicating thatfecundity at ages one through four is inverselyrelated to female size (i .e . delayed reproduction isdirectly related to female size) . All species whichhad positive scores for principal component onedelayed first reproduction for one or more years(Fig. 1) . Only one species with delayed repro-duction, the silver surfperch, had a negative scoreand grouped with the species which did not delayreproduction ; however, silver surfperch from lowerlatitudes may not delay reproduction . Principalcomponent two loaded heavily for fecundity vari-ables, and size variables were of lesser importanceSize variables were most important in principalcomponent three and several fecundity variableswere of secondary importance .

Principal component analysis and simple correla-tions among life history variables (Table 3) indicatethe importance of size in surfperch life histories .Based on maximum reported lengths (TL), the 23species of embiotocids now recognized (Abe 1969,Wydoski 1969, Hubbs et al . 1979, Robins et al .1980) fall into three distinct size groups (Fig . 2) .Species in the smallest size group do not exceed 215mm TL. The medium-size species attain 275 to 335

0m

80

70

60

50

40

30

20

10

SMALL

MEDIUM

TULE, CL

mm TL, and the largest species attain 380 to 470mm TL. Variation in fecundity is also size-related :the large-size group has moderately high length-specific fecundity, the medium-size group has lowfecundity, and the small-size group has generallyhigh, but variable, fecundity (Fig . 3) . A comparisonof length-specific fecundities indicates that mostspecies show increasing trends (Fig . 3, Table 5) .Only one species, the pink seaperch, has a fecundityschedule which does not increase significantly withfemale SL; however, this may be an artifact ofcapture in deep water since nearterm females tendto abort young when brought to the surface (LindaBritschgi personal communication) .

Among the small species, longevity varies fromtwo to seven years and fecundity schedules arehighly variable . Reproduction is not generally de-layed beyond age one ; however, under circumstancesresulting in poor growth, tule perch (Baltz 1980)and shiner surfperch (Gordon 1965) may not pro-duce a brood at age one . The tule perch has thehighest fecundity of any species in its size group andthe highest length-specific fecundity of any surf-perch. In absolute terms the maximum fecundity ofthe tule perch is only ihiatched or exceeded by theoldest individuals of some of the largest species .Among the small North American species, the trendin brood size decreases from freshwater throughcoastal to offshore marine species . The coastal

FEMALE STANDARD LENGTH (mm)

Fig. 3. The length-specific fecundities of preparturient embiotocids . Regression lines are extended from smallest to largest (mm SL)reproductive females recorded in the sample analyzed .

LARGE

1 6 3

164

species, kelp surfperch, dwarf surfperch and reefsurfperch have moderately large broods (2-50 young)and occupy kelp forest and intertidal habitats(Table 6). The two deep water species, pink sea-perch and spotfin surfperch, produce small broods(mean = 7 young for pink seaperch [Goldberg &Ticknor 1977] and range = 4-20 young for spotfinsurfperch [Baltz & Knight in press]) .

The three Japanese embiotocids include two smallspecies and one medium-size species . Available in-formation indicates that all of the Japanese embio-tocids are short lived (2-4 yrs) and none delay firstreproduction (Abe 1969, Hayase & Tanaka 1980b) .

One small species, Ditrema viridis, is second only tothe tule perch in length-specific fecundity (Table 5,Fig . 3) . The other small species, Neoditrema ranson-neti, is not well known ; adults are found inshoreprior to parturition (March-August) but then dis-appear for the remainder of the year (Hayase &Tanaka 1980a), probably into deeper water. Thethird Japanese species, Ditrerna temmincki, is in-cluded in the medium size group .

Among the medium-size species longevity is fourto seven years, first reproduction is not delayedbeyond age three, and mean fecundity does notexceed 30 in the oldest individuals . A variety of

Table 5. Age, length and fecundity at first reproduction and fecundity parameters of female surfperch . Linear regression of embryonumber on female standard length (mm) .

1 Fecundities for pink seaperch and white surfperch are suspiciously low and may reflect problems with capture techniques used .* P<0 .05** P<0.01

At first reproductionLength-specificfecundity parameters

Age Length Fecundity N a b I

Rubberlip surfperch - 15 -18.37 0.112 0 .827**Pile surfperch 4 224 11 .7 75 -66.05 0.347 0 .795**Barred surfperch 2 172 8 .0 72 -49.65 0.335 0.714**Redtail surfperch 4 218 9 .7 168 -40.86 0.232 0.788**Black surfperch 2 149 5 .7 116 -12.18 0.120 0 .671**Striped surfperch 3 216 9 .6 30 -27.79 0.173 0.740**

White surfperch' 2 160 6 .2 77 - 3 .75 0 .062 0.391**Rainbow surfperch - 148 -15.18 0.154 0.753**Calico surfperchWalleye surfperch

no data1 110 5 .9 104 - 9 .00 0 .135 0.590**

Sharpnose surfperch - 16 -49.24 0.346 0.734**Silver surfperch 2 128 3 .5 12 -25.80 0.229 0.681*Ditrema temmincki 1 123 8 .5 74 -21 .90 0 .247 0.881**

Ditrema viridis 1 125 14.5 22 -71 .67 0 .689 0.918**Kelp surfperch 1 81 14.1 13 -24.71 0 .480 0.848**

Pink seaperch 22 3 .20 -0.0001 -0.002NS

Island surfperchShiner surfperch

no data1 82 4.8 150 - 9 .20 0 .171 0.926**

Reef surfperch 1 89 9 .8 48 -15.81 0 .288 0.846**

Dwarf surfperch 1 69 7 .5 42 -15.31 0 .333 0 .944**

Spotfin surfperch 1 103 7 .8 46 -13.80 0.210 0.873**

Neoditrema sp . 1 108 10.3 15 -10.34 0 .191 0.562*

Tule perch populationsRussian River 1 77 21 .5 78 -49.22 0 .918 0 .871**

Suisun Marsh 1 82 17 .7 51 -42.97 0 .740 0 .914**Clear Lake 1 97 14 .5 127 -62.94 0.850 0 .884**

Table 6 . The maximum depths (m) and microhabitats of surfperches . Unless otherwise indicated maximum depth is that reported byMiller & Lea (1972) .

microhabitats is utilized by the medium-size species(Table 6) . The rainbow and walleye surfperches arefound in the inner-marginal region of kelp forests,generally between the kelp forest and shore. How-ever, both species make complicated movements .Rainbow surfperch follow a narrow thermal pre-ference (Terry & Stephens 1976) and appear anddisappear seasonally from shallow reef habitats(Ebeling et al . 1980a) . Walleye surfperch make dielmigrations - offshore at night into kelpbeds wherethey disperse to forage for plankton and inshoreduring the day where they school (Ebeling & Bray1976, Ebeling et al . 1980a) . The white surfperch isthe largest member of this size group and is the onlymedium-sized commuter, i.e . it occasionally schoolsin midwater, between the bottom and the kelpcanopy, while not foraging . The white surfperchand other surfperches characterized as commutersare generally benthic feeders which enter the mid-water zone between foraging periods where they

16 5

may school in multispecific assemblages (Ebelingpersonal communication) . The sharpnose surfperchoccurs in deep water, but apparently moves inshoreduring spring and summer months prior to parturi-tion . The calico surfperch occupies the sandy beachsurf zone to a maximum depth of 9 m . The silversurfperch also occupies the sandy beach surf zonebut has been reported in deep water .

Among the largest species, longevity is seven toten years, first reproduction is delayed for one tofour years and mean fecundity exceeds 60 in theoldest individuals. Members of this size groupoccupy less protected habitats than the other spe-cies. The two largest species, the rubberlip and pilesurfperches, are strictly benthic feeders and arecharacterized as commuters (Table 6) because oftheir habit of schooling in midwater when notforaging (Ebeling personal communication) . Thebarred and redtail surfperches, occupy sandy beachsurf zone habitats . The black and striped surf-

Maximum Microhabitat Source

Rubberlip surfperch 46 Commuter Ebeling et al . 1980aPile surfperch 74 Commuter Ebeling et al . 1980aBarred surfperch 74 Sandy surf zone Carlisle et al . 1960Redtail surfperch 18 Sandy surf zone Frey 1971Black surfperch 40 Inner-marginal/Bottom Ebeling et al . 1980aStriped surfperch 17 Kelp-rock Ebeling et al . 1980a

White surfperchRainbow surfperchCalico surfperch

43409

CommuterInner-marginalSandy surf zone

Ebeling et al . 1980aEbeling et al . 1980aFrey 1971

Walleye surfperchSharpnose surfperch

18229

Inner-marginalInshore

Ebeling et al . 1980aSmith 1964, Lea 1972

Silver surfperchDitrema temmincki

Ditrema viridisKelp surfperchPink seaperchisland surfperchReef surfperchDwarf surfperchSpotfin surfperchShiner surfperchNeoditrema ransonnetiTule perch

110

31229

969

64146

9

Sandy surf zoneZostera belt/Open water

Zostera belt/Open waterKelp canopyDeep water/Sand-mud bottomInshoreRocky intertidalInner-marginalDeep waterUbiquitousCoastalFreshwater

Wydoski & Bennett 1973Hayase & Tanaka 1980a

Hayase & Tanaka 1980aEbeling et al . 1980aJ.M. Allen pers . comm .Feder et al . 1974Hubbs 1921Ebeling et al. 1980aBaltz & Knight 1983

Hayase & Tanaka 1980aBaltz 1980

1 6 6

perches are bottom oriented and have very similarlife histories . Hixon (1980) has described similarresource utilization by allopatric populations of thetwo species and demonstrated microhabitat dis-placement of black surfperch by striped surfperchin areas of sympatry . The similarity of the lifehistories of these species is evidenced by theirjuxtaposition in Figure 1 .

Presumably the size of young at birth increaseswith female size in all embiotocids ; however, thelength of young at parturition has been documentedfor only two species, the shiner surfperch (Wilson &Millemann 1969) and the redtail surfperch (Bennett& Wydoski 1977) . Positive correlations exist be-tween female size and the size of embryos in near-term females of barred surfperch, spotfin surfperch,tule perch and walleye surfperch . Analysis is com-plicated by the tendency for larger and older femalesof several species to initiate gestation and give birthearlier than smaller and younger females (Carlisle etal. 1960, Baltz 1980, Baltz & Knight 1983, DeMartiniet al . 1983) . Additional data on the size of embryosin Ditrema ternmincki and white surfperch suggestthat the tendency of larger females to produce largeryoung is significant throughout much of gestationand general throughout the family (Fig . 4) .

60EE 50xfz 400'30FMj 20R0Wz 10<W

Discussion

Life history variation among species in the familyEmbiotocidae should be interpreted in light ofvariation within species (DeMartini et al . 1983) ; un-fortunately, adequate data to compare populationswithin species is largely lacking . DeMartini et al .(1983) reviewed geographic life history variationwithin the shiner, walleye and white surfperches .Northern populations generally exhibit greater long-evity, larger body size, delayed maturity, higherfecundity and probably larger young at any agethan do southern populations . These adjustmentsprobably reflect compensation for slower growth inmore northern latitudes and permit populations tosustain their net reproductive rate . Slow growthresults in delayed maturity which is most easilyoffset by higher fecundity (Roff 1981) . Since the ageof first reproduction and interbrood interval cannotbe reduced below one year in the Embiotocidae,variation in fecundity is of primary importance inthe family (Cole 1954), and species or populationsmay respond to selection pressures by delaying theonset of reproduction beyond age one or changingthe length-specific fecundity schedule . Geographicvariation of life histories within species of marine

FEMALE STANDARD LENGTH (mm)

Fig. 4 . The mean standard length (mm) of near-term embryos increased with female standard length and nearness to parturition : A .Ditrema ternmincki, Tokyo Bay, Japan (Abe 1969) . Squares : collected 5 June 1963, y = 16.6 + 0 .26 x , N = 6, r = 0 .93, P > 0 .05 .Triangles : collected 28 May 1963, y = 7 .3 + 0 .278 x, N = 4, r = 0 .86, P>0 .05 . Circles : collected 20 May 1963, y = 20 .2 + 0.321 x,N = 44, r = 0.88, P < 0 .05 . B . White surfperch, Santa Monica Bay, California (S . Goldberg unpublished data) . Circles : collected 2 June1976, y = 31 .2 + 0 .123 x, N = 37, r = 0 .57, P <0 .05 . Triangles : collected 11 May 1977, y = -20 .0 + 0 .358 x, N = 26, r = 0 .76,P < 0 .05 . Squares : collected 19 March 1975, y = -4 .2 + 0 .160 x , N = 14, r = 0 .75, P < 0 .05 .

embiotocids is probably largely ecophenotypic, sinceelectrophoretic variability is low within mainlandpopulations of the three species studied thus far(Haldorson 1980, Darling et al . 1980, Baltz &Loudenslager 1983) . However, there is evidence forgenetic divergence of isolated Channel Island popu-lations of pile and striped surfperches from main-land populations (Haldorson 1980) and among tuleperch populations in three freshwater drainages . Atpresent it is unknown whether or not life historyvariation within any species of marine embiotocidhas a significant genetic basis, however, morpho-logical, electrophoretic, geological and comparativelife history data suggest a significant genetic com-ponent among tule perch populations (Baltz &Moyle 1981, 1982, Baltz & Loudenslager 1983) .

The general life history characteristics of femaleembiotocids differ among the size groups . The ageat first reproduction is positively correlated withlength at first reproduction, longevity and maxi-mum size attained . The small species generally havemoderate to high fecundity, do not delay firstreproduction and are short lived . Medium-sizespecies have low fecundity, may delay reproductionup to three years and have intermediate longevities .The largest species delay reproduction for one tofour years, have moderately high fecundity and arerelatively long lived . The length-specific fecunditiesfor the size groups are 0 .171 to 0.918, 0.135 to0.247, and 0 .112 to 0 .347 young per mm SL for thesmall, medium and large species, respectively (Table5). The importance of size in embiotocid life histo-ries is probably related to predation and has corre-lations with other life history variables and micro-habitat utilization . Adults of the largest speciesappear to escape in size, since they occupy openhabitats and do not in general utilize complexcover. The smallest species are typically limited tohabitats which include complex cover, and themedium-size species are intermediate in their use ofcover. Young of most species occupy microhabitatswhich provide cover from predation . Only thesurprisingly large young of the largest species,rubberlip surfperch, have mouths of sufficient sizeto immediately adopt the `winnowing' foragingtechnique typical of adult rubberlip, black, andrainbow surfperches (Laur & Ebeling 1983) .

1 67

The most interesting trend in embiotocid lifehistories is found among the small species . Conside-ration of several physical variables indicates thatenvironmental predictability increases from highlyseasonal freshwater to stable offshore marine en-vironments and brood size among the small NorthAmerican embiotocids varies inversely with en-vironmental predictability . Temperature extremesdecrease substantially along a transect from fresh-water to offshore marine habitats occupied byembiotocids in central California . These extremesrange form 4 to 31°C in small streams (Baltz &Moyle unpublished data), 4 .5 to 27° C in the mainchannel near Freeport in the Sacramento River(U .S . Geological Survey Water Data Reports CA-78-4), 7 .6 to 16 .0° C in central California coastalwater north of San Francisco near Bodega Bay(SIO 1978-1981), and 8 .0 to 12.4°C in offshorewaters at a depth of 100 m in the vicinity of SanFrancisco (Churgin & Halminski 1974) .

Temperature is an important niche dimension formost fishes (Magnuson et al . 1979) and has beenshown to strongly influence spatial organizationwithin an embiotocid assemblage that includesrainbow, walleye and white surfperch, all of whichtrack narrow thermal preferences in their bathy-thermal distributions (Terry & Stephens 1976) .However, other species, including dwarf and blacksurfperches, appear to be more eurythermal andsubordinate temperature preference to other en-vironmental factors (Terry & Stephens 1976, Shrodeet al . 1982) . Small nearshore species which toleratelarge diel temperature variations, especially dwarfand reef surfperch, apparently subordinate tempe-rature preference to microhabitat preference. Thepink seaperch, which has the deepest bathymetricdistribution (Table 6), probably also has the nar-rowest temperature tolerance of any embiotocid .

Freshwater environments in California appear tobe less predictable than nearshore and offshorecoastal environments primarily because the vari-ability in precipitation makes freshwater systemssusceptible to floods and droughts . The Medi-terranean climate of central California is highlyseasonal, droughts are not unusual and winterfloods are common . Variable precipitation resultsin highly variable streamflow and differences in

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drainage characteristics, including size, also affectvariability (Leopold et al . 1964). Environmentalvariability affects aquatic macrophytes (Harris &Marshall 1963, Howard-Williams 1975, Westlake1975, Gaudet 1977) and consequently fishes (Hassler1970, Hynes 1970, Horwitz 1978). Among fresh-water environments occupied by tule perch, threesubspecies have been reognized and each of thesehas different life history characteristics that reflectthe relative predictability of the availability of com-plex cover for parturating females and for young(Baltz & Moyle 1982) . Essentially, tule perch long-evity and length at first reproduction vary directlywith environmental predictability, while the num-ber of young produced per female varies inversely .

The importance of cover to embiotocids is indi-cated by recent studies of the swimming perform-ance of rainbow surfperch (Dorn et al . 1979). Near-term females were unable to achieve the sustainedor burst swimming speeds typical of the species .Near-term females are probably more susceptible topredation and the preparturient females of many(especially smaller) species appear to seek out densecover. The timing and location of parturition inmost species places gravid females in microhabitatswhere cover, usually aquatic macrophytes, is avail-able for vulnerable females and their newly-bornyoung. Moreover, the young are born in a warm,productive habitat where growth is rapid . The pinkseaperch is the only species which does not givebirth nearshore. In contrast to other species whichmate in summer or autumn and bear young thefollowing spring or summer, the pink seaperchmates in spring and parturition occurs the followingwinter (Goldberg & Ticknor 1977) .

There is ample evidence that variation in physicalvariables in nearshore environments is less predict-able than in offshore coastal environments . Varia-tion in salinity, temperature, surge and scour, andvisibility is much greater at shallower depths (Quast1968, Valentine 1973) and influences subtidal com-munities (Rosenthal et al . 1974). Internal waves arealso stronger in nearshore waters and may causeshort term temperature variations of 3 or 4 0 C witha period of 5 to 10 minutes (T . Powell personalcommunication) .

In a study of the annual variability of kelp forest

fishes, Ebeling et al . (1980b) found that the abun-dances of canopy species, including kelp surfperch,were more variable than other microhabitat groups,and bottom species, including black surfperch, wereleast variable . Yearly differences in fish abundancewere related to differences in water clarity, tempera-ture and kelp density which varied considerablyamong years. Stands of giant kelp, Macrocystispyrifera, fluctuate widely in density and may dis-appear completely ; the mortality of adult plants isusually related to physical disturbances, particular-ly to storms (Rosenthal et al . 1974). The unpredict-able nature of the kelp canopy microhabitat mayexplain the reproductive strategy of the kelp surf-perch. Among North American embiotocids, thehigh fecundity of this species is second only to thatof tule perch and greater than the moderate fecun-dity of other small coastal species which occupymore predictable inner-marginal microhabitats . Thehigh fecundity of the kelp surfperch contrasts evenmore strikingly with the extremely low fecundity ofthe spotfin surfperch and pink seaperch which occupythe still more predictable offshore marine habitats .

One small embiotocid does not fit easily into thisscheme. The shiner surfperch occupies a variety ofestuarine and marine habitats and has fairly lowfecundity compared to other small species . There issome evidence that this species migrates seasonallyto deeper waters where it overwinters (Shaw et al .1974). Large numbers were collected off PalosVerdes, California, primarily in the winter at depthsof 60 to 140 m (J.M . Allen personal communica-tion). However, many young-of-year remain innearshore waters throughout the winter (Oden-weller 1975) and adults may only disperse in thecoastal waters where the densities are too low toshow good trends (G.M . Cailliet personal com-munication). There may be a connection betweenlow fecundity and migration since several medium-sized species also undergo onshore-offshore migra-tions, e .g. rainbow and white surfperches, and havelow length-specific fecundities compared to medium-sized species which do not migrate .

There is nearly a complete absence of life historydata on several species, including the calico surf-perch, an important commercial and sport species(Prey 1971), and data for other species, including

the rubberlip surfperch, is very incomplete . Thesharpnose surfperch is not well known, but basedon limited information on fecundity (Smith 1964,

Baltz unpublished data) I expect that its life historyis typical of the medium-size group . However, thisspecies has been recorded in very deep water (Miller& Lea 1972) and appears to fluctuate widely inabundance between years (Lea 1972) . Either ageand growth or fecundity data are lacking for severalother species . Studies of life history variation withinthese and other species of embiotocids are needed todescribe between year variation, variation amongpopulations, and to place variation among speciesin perspective .

Environmental variation appears to affect embio-tocid life history strategies by mediating the avail-ability of cover and the risk of predation . Embio-tocids use several life history tactics to offset preda-tion pressures . Large species appear to escape issize, but their young generally use complex cover .Species in the small and medium-size groups gainsome protection by using complex cover and/ormaking seasonal migrations . Several medium-sizespecies undergo offshore-onshore migrations : off-shore during productive times of increasing coveron offshore reefs, onshore during times of defolia-tion (Ebeling personal communication) . Such migra-tions may provide added protection for vulnerablelife history stages . Fecundity in the small size groupvaries inversely with environmental predictability .In the medium size group, fecundity is higher inspecies which do not migrate .

Acknowledgements

I am grateful to P .B. Moyle, J.M . Allen, G .M .Cailliet, E .E. DeMartini, A.W. Ebeling and T .Powell for criticisms and discussions of earlierdrafts of this manuscript, and to the many re-searchers who kindly made their original dataavailable for my use, including D . Behrens, D .Bennett, M . Bradbury, E. DeMartini, S . Goldberg,S. Hayase and P . Isaacson. This research wasfunded in part by a Sigma-Xi Grant-in-Aid ofResearch .

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Received 2.4 .1982

Accepted 3.1 .1983