Pacific Science (1987), vol. 41, nos. 1-4© 1988 by the University of Hawaii Press . All rights reserved

Embryo Ecology of the Pacific Surf Smelt, Hypomesus pretiosus(Pisces: Osmeridae) 1 , 2 , 3

DOUGLAS P . MIDDAUGH,4 MICHAEL J. H EMMER,4 AND DANIEL E. PENTTILA 5

ABSTRACT: A study of the ecology of developing embryos of the Pacific surfsmelt, Hypomesus pretiosus, was conducted. Embryos were maintained in thelaboratory at 7.6, 12.1, and 17.6°C and the time to specific embryonic stagesdetermined. Embryos held at 7.6°C developed to stage 24, 18 days after collec­tion; those held at 12.1°C hatched after 13 days; at 17.6°C hatching occurred 8.5days after collection. Embryos maintained at 15°C and salinities of 20, 25, and30%0 averaged 84% survival. There was no significant difference in survivalbetween the groups (ANOV A, P = 0.53).

Field observations indicated that embryos are spawned in patches in the upperintertidal zone near the time of high tide. They are attached to gravel substratesby the zona radiata membrane which ruptures and quickly turns inside out atthe time embryos are fertilized . After several days of development, stage 18 to22 embryos detach from the original spawning substrates and are washed sea­ward and down into the gravel substrate in the intertidal zone. However, therewas no significant difference (ANOVA, P ::2: 0.09) in the number of eggs foundat each of 4 depth strata in the upper, middle , and lower intertidal zones.

THE PACIFIC SURF SMELT, Hypomesus pretio­sus, is a small fish of the family Osmeridae thatoccurs from northern California to southernAlaska and utilizes upper intertidal gravelsubstrates for spawning (Hart 1973). Studiesof spawning locations and behavior suggestthat a number ofphysical and geological vari­ables may limit the sites available for repro­duction of this species. Within Puget Sound,the known spawning grounds of this speciesare quite disjunct, with long distances ofoutwardly suitable-appearing beaches which

1 Manuscript accepted February 1986.2 Contribution No . 557 of the Gulf Breeze Laboratory.3The information in this document has been funded

wholly or in part by the U.S . Environmental ProtectionAgency. It has been subject to the Agency's peer andand administrative review and approved for publication.Mention of tradenames or commercial products does notconstitute endorsement or recommendation for use.

4H.s. Environmental Protection Agency, Gulf BreezeEnvironmental Research Laboratory, Sabine Island ,Gulf Breeze, Florida 32561.

5Washington Department of Fisheries, 7600 SandPoint Way, N.E., Seattle, Washington 98115.

44

have apparently never supported surf smeltspawning activity (Penttila 1978).

The inside waters of Washington State areinhabited by ten or more spawning stocks ofsurf smelt presumed to be more-or-less geneti­cally isolated. The relative youth of the PugetSound Basin since the last Quaternary glacialretreat has resulted in, as yet, only verysmall meristic differences between Washing­ton's various disjunct surf smelt populations(Schaefer 1936; Kalambi 1965). Dependingon the stocks being considered, surf smeltspawning in Washington State occurs virtu­ally year-round, except for the month ofApril, with generally a 4 to 5 month spawningseason for given stocks.

On the outer coast of the Olympic Penin­sula, Washington, H. pretiosus spawns oncove beaches that consist of fine gravel andcoarse sand (Thompson et al. 1936). Gravelbeaches in Puget Sound are also utilized forspawning.

At Utsalady Bay, Washington, summer­spawning H. pretiosus always spawned inintertidal areas protected from direct sunlightby the shadows of large trees growing along

hiM

Embryo Ecology of Hypomesuspretiosus-MIDDAUGH, HEMMER, AND PENTfILA 45

the beach. Spawning runs occurred duringdaytime and females deposited eggs at anintertidal elevation of approximately 2.5 to3.5m above mean low water (MLW). Eggswere buried in the gravel to a depth of 1.0 to3.0cm by wave action (Loosanoff 1937).

Our study of winter-spawning H . pretiosus,conducted during January 1985, was designedto determine rates of development and sali­nity tolerance of embryos in laboratory tests .We also studied a spawning beach at FidalgoBay, Washington, and determined the distri­bution of embryos within gravel substratesat locations in the upper, middle , and lowerintertidal zones.

MATERIALS AND METHODS

Study Sites

Field observations were made in January1985 along the eastern shoreline of FidalgoBay, Washington, 48°29' N latitude, 122°35' Wlongitude (Figure 1). This area is character­ized by pocket beaches with gravel substrates,and a tidal range of 2.8 to 3.0 meters . Thebeaches where H . pretiosus spawned usuallyhad large boulders, diameter 1-2 m, in theextreme upper intertidal zone.* Some areaswere shaded by willow trees, Salix sp., orbig leaf maples, Acer macrophyllum. Observa­tions of embryo developmental rates and timeto detachment from spawning substrates weremade at the University ofWashington, FridayHarbor Laboratories (FHL), using naturallyspawned embryos collected from Fidalgo Bay.Salinity tolerance tests were conducted atthe U.S. Environmental Protection Agency,Environmental Research Laboratory (ERL)in Gulf Breeze, Florida.

Embryo Development

Gravel substrates with attached H. pretio­sus embryos were collected from the upper

*The boulders were derived almost tot ally from high­way riprap placement. The March Pt. peninsula 's naturalgeology is ero ding Quaternary glacial hills, which feedsand /gravel to the beach system.

intertidal zone at Fidalgo Bay on 11 January1985, placed in vacuum bottles to preventabrupt temperature fluctuations and trans­ported to FHL. The substrate/embryo tem­perature was 9.3°e. Replicate groups of 20embryos were gently teased from the spawn­ing substrate and examined under a dissectingmicroscope to confirm stage synchrony. Allembryos were in the early high blastula stage .This developmental stage corresponds tostage 8 of Lagler et al. (1977). A synopsisofdevelopmental stages observed in this studyand corresponding numerical stages weresummarized by Lagler et al. (1977), and here­after, are identified by the numerical valuesdefined in Table 1.

Gravel substrate with attached stage 8embryos were distributed among six replicate250 ml glass containers. Fifty ml of filtered(l.O/lm) seawater, 28-30%0 and lOoe, wasadded to each pair of containers, which werethen covered with plastic closures. This pro­cedure allowed embryos to develop in a moi statmosphere without being inundated. Onepair of replicate containers was maintained at17.6°e in a water bath, after a 6-hour adjust­ment period from 10°e. A second pair washeld at a room temperature of approximately12.1°e and the third pair was maintainedin ambient temperature seawater at approx­imately 7.6°e, after 6 hours acclimationfrom 100 e. Samples were taken daily and thedevelopmental stage and viability determinedfor 15 to 30 embryos from each replicate.These embryos were then discarded. Filtered(Lfl um) and temperature-adjusted seawaterwas used to triple rinse developing embryos inrespective replicate containers at 2 to 3 dayintervals. The photoperiod was 12L: 12D;light intensity was 175 lux provided by fluo­rescent lamps .

Stage 8 embryos for salinity tolerance testswere collected on 10 January 1985. Embryos,attached to gravel spawning substrates wereplaced in 500 ml vacuum bottles. Approxi­mately 50rnl of seawater, 9.3°e, 30%0, was thenadded to each bottle to ensure that embryosremained moist during shipment to ERL/GulfBreeze. Upon arrival at the laboratory on 14January, stage 15 embryos were gently teasedfrom gravel substrates and randomly distrib-

46

N

PACIFIC SCIENCE, Volume 41, 1987

WASHINGTONSTATE

FIGURE I . Site map of Fidalgo Bay and the coastal region of Washington State . Contours are in meter s above meansea level.

Embryo Ecology of Hypomesus pretiosus-MIDDAUGH, H EMMER, AND P ENTfILA

TABL E I

EMBRYONIC S TAGES O BSERVED IN Hypomesus pretiosus AND CORRESPONDI NG N UMERICAL STA GES D ESCRIBED BY

L AGL ER ET AL. (1977)

47

EMBRYONIC STAGES OBSERVED IN H . pre tiosus

Early high blastulaLate high blastulaEarly gastrulaMiddle gastrulaLate gastrulaInitial formation of rud imentary optic vesicles and first somitesExpansion of forebra in to form optic vesiclesAppearance of 4 to 14 pairs of somitesPericardium established , nonchambered tube-like heart is visible and pulsingMotility of developing embryoOnset of circulationMelanophores appe ar in pericard ium limited circulation in yolk vesselsPectoral fin buds appa rentFormation ofliverPrehatch embryoNewly hatched larva

CORRESPONDING NUMERI CAL

STAGES DESCRIBED BY

L AGL ER ET AL. (1977)

Stage 8Stage 9Stage 12Stage 13Stage 14Stage 15Stage 16Stage 18Stage 20Stage 21Stage 22Stage 23Stage 24Stage 25Stage 31Stage 32

uted among treatments. Each treatment con­sisted of triplicate samples of 20 eggs in­cubated in individual 20 cm diameter glassculture dishes containing II of sterilized sea­water. Salinities of 20, 25, and 30%0 were usedat temperatures of 15and 20 ± 1°C. Embryoswere observed at 48-hour intervals untilhatching occurred. During each observation,dead embryos (opaque-white) were removedfrom respective treatments and enumerated.The photoperiod was I2L : I2D; light inten­sity was 1751ux provided by fluorescentlamps. A temperature-compensated refrac­tometer was used to measure salinity. Animmersion thermometer with O.I oC gradua­tion s was used to measure water temperature.

Field Observations

Replicate core samples, 5 cm diameterx 4 em deep , were taken from the upper inter­tidal (2.8-3.0m above MLW), the middleintertidal (1.3-1.6m above MLW), and thelower intertidal zones (0.2-0.6 m above ML W)on 25 January 1985. Core s were split at 1.0cmdepth intervals to yield strata from 0-1 , 1-2,2-3, and 3-4 em deep . Respective strata were

placed in individual glass containers and theembryos subsequently enumerated and stagesidentified with a dissecting microscope .

At the time of collection of embryos, con­current measurements of relative humidityand air temperature were taken with anAtkins Model 90023-30 Digital Psychrom­eter. Substrate temperatures corresponding tostrata depths in core samples were measuredwith a Bailey Instruments BAT- 4 LaboratoryThermometer with a MT 29/1 microprobe.

Statistical Analysis

Statistical analyses were conducted whenappropriate (SAS Institute Inc. 1982). Salinityeffects on embryo survival were analyzed byone-way analysis of variance (ANOVA) onpercentage survival data, using a modificationof the arcsin transformation to account forunequal cell sizes (Chanter 1975). A two-wayANOVA, with loglo transformation of thefield core data, was used to evaluate the maineffect of intertidal zone , depth of strata, andpossible interaction on egg numbers. All post­hoc analyses were conducted by the Bonfer­roni multiple comparison method at ()( = 0.05.

48 PACIFIC SCIENCE, Volume 41 , 1987

o AM81ENT ROOM 12.l oC

320

280

240

!Q 2 0 0:::>0I

160

~i=

120

BO

40

08

• AMBIENT SEA 7.6° C

• 17.6° C

12 13 14 15 16 18 20 21 22 23 24

STta:

o HATCHED

31 32

F IGU RE 2. Developmental times for H . pretiosus embryos held at 7.6,1 2.1, or 17.6°C. Stages observed correspondto those outlined in Table I .

RESULTS

Laboratory Observations

Developmental rates of H. pretiosus em­bryos maintained at ambient seawater tem­perature (x = 7.6°e, SO = 0.47, N = 24),ambient room temperature (x = 12.1°e, SO =2.6°e, N = 24) and in a heated water bath(x = 17.6°e, SO = 0.84, N = 24) are shown inFigure 2. Development ofembryos proceededvery slowly in ambient temperature seawaterand no eggs hatched during 18 days of obser­vation. In contrast, those maintained atambient room temperature hatched after 13days . At 17.6°e hatching occurred 8.5 day safter collection. The respective percentagesurvival until stage 32 at 17.6°e and 12.1°ewas 77 and 88% . In ambient seawater 7.6°e,survival was 78% through stage 24. Becauseobservations ended on day 18, we were unableto determine the time to hatch of embryosmaintained at 7.6°e. No significant differencesin survival were found among embryos devel­oped to stage 32 (just after hatching) at 17.6

and 12.1°e,or stage 24 at 7.6°e (ANOYA,P = 0.67).

During intermittent changes of seawater inincubation cups , we noted that H. pretiosusembryos detached from the gravel substrates.This detachment occurred after approxi­mately 148 hours at 17.6°e (stages 21 to 23),200 hours at u .i -c (stages 18-20), and 310hours at 7.6°e (stages 22 to 24).

No significant difference (ANOYA, P =0.53) was found in embryo survival throughhatching at 15°e for individuals incubated atsalinities of 20, 25, and 30%0 (respective sur­vival, 82, 83, and 87%). Results were gen­erally similar at 200e for individuals incubatedat 20 and 25%0 (respective survival 87 and78%) , but not at 30%0 salinity (survival 47%).However, no significant difference (ANOYA,P = 0.11) was found in survival of embryoshatching at the three test salin ities.

Field Observations

Relati ve humidity and temperature datacollected at Fidalgo Bay are summarized in

Embryo Ecology of Hypomesus pretiosus-MIDDAUGH, H EMMER, AND PENTTILA

TABLE 2

ENVIRONMENTAL VARIABLE MEASURED ALONG SHORELINEOF EASTERN FIDALGO BAY ON 25 JANUARY 1985

49

INTERTIDAL ELEVATION ABOVE MLW

ELEVATIONS IN CENTIMETERS UPPER MIDDLE LOWER(em) ABOVE ( + ), BELOW (-), OR + 2.5- 3.0 m + 1.3-1.5 m + 0.2- 0.6 m

AT THE SUBSTRATE SURFACE(0) SHADED SUNLIGHT SUNLIGHT SUNLIGHT

(Elevation)+1 em reI. humidity % 98 93 99 96+ 1 em air temp "C 9.6 9.4 9.3 9.7

Oem substra te temp "C 9.2 10.1 9.3 9.5- 1 em substra te temp "C 5.0 9.1 9.0 7.5- 2 em substrate temp "C 4.9 8.5 8.1 6.0- 3 em substrate temp "C 4.9 8.3 7.9 6.0- 4 em substrate temp "C 4.8 7.8 7.9 6.0

Table 2. Measurements were taken at twolocations in the upper intertidal zone, oneshaded and the other in full sunlight. Relativehumidity measured 1ern above the substratesurface in the shaded area was substantiallyhigher than measured at a similar intertidalelevation in full sunlight. While air tempera­tures were similar at I ern, substrate tempera­tures on and below the surface were higher inareas of the intertidal zone where full sunlightwas present. Middle and lower intertidalloca­tions , in full sunlight, had high relative humi­dities. The middle and lower intertidal sub­stra te temperatures trended downward, bothat the surface and below, when compared withthe upper intertidal location that was also infull sunlight.

Grain size distributions for surf smeltspawning substrates from March Point, theeastern shoreline of Fidalgo Bay, and Wea­verling Spit are shown in Figure 3. These datawere collected during the 1981 -1983 spawn­ing seasons from areas where observationswere made in the current study (Penttila,unpub. data) . Samples were taken in the mid­dle to upper intertidal zone (1.3 to 2.5 m aboveMLW) from the surface to approximately2.0 em deep , from representative smelt spawn­bearing beach material.

The relative frequencies of occurrence ofseveral embryonic stages at locations in theintertidal zone in this study are summarizedin Figure 4. The frequency distributions were

based on the number of embryos in eachdevelopmental stage at each intertidal eleva­tion and substrate depth divided by the totalnumber of embryos collected at all elevationsand depths. Thus, the relative frequencies ofoccurrence for respective embryos stages andlocations are directly comparable (Simpson etal. 1960).

Most of the embryos collected in the upperintertidal zone at 0-1 ern deep were in stage9 (late high blastula). This group comprisedmore than one-fifth of the total number ofembryos found. The 1 to 2, 2 to 3, and 3 to4 em deep strata in the upper intertial zoneyielded a high proportion of embryos withchambered hearts (stage 22) and a few instages 21 and 23. The stage 22 group wasevident in all four strata from the middle inter­tidal zone , although at a lower relative fre­quency. Some individuals in stages 16through32 were also present in these samples .

While stage 22 embryos were found in allstrata from the lower intertidal zone , stage18 embryos were dominant. A few stage 23individuals were also present.

Statistical analyses (ANOVA) for the num­ber of eggs at each intertidal location andsubstrate depth revealed no significant in­teraction (P = 0.86) between locations anddepths. Moreover, no significant differencesexisted between locations in the number ofeggs found at each of four depths (P ~ 0.09).However, there was a significant difference

50 PACIFIC SCIENCE, Volume 41,1987

01\1 \ .-. WEAVERLING SPIT

IA--~""I. \..~ 0 ---0 EAST FIDALGO BAY

I ,,\ '-A------A

I -\ \MARCH POINT

1\ \

~~0..... \ \\ \\ \,

~ \.~/.,',\ \I,'" 0/,' "\e{ \ \

iJ A,,:

53.9 26 .7 13.3 6 .7 3.3 1.7 0.8 0.4 0 .2 0 .1 01

MESH SIZE (rnrn)

25

20

~IQw3: 15ra::0

t-""10

~~

5

FIGURE 3. Grain size analyses for spawning substrates taken from the upper intertidal zone at March Point ,Weaverling Spit , and the eastern shore of Fidalgo Bay.

(P = 0.003) in the total number of eggs foundat each intertidal location. Post-hoc analyses(Bonferroni) indicated a significant difference(ex = 0.05) between the number of eggs col­lected from the upper and lower intertidalzone , but the middle intertidal was not differ­ent from either the upper or lower intertidalzones .

DISCUSSIO N

Spawning by surf smelt takes place nearthe time of high tide. At Utsalady Beach,Washington, Loosanoff (1937) observed re­pro duction on flood tides that reached 2.5 to3.5 m above MLW. Daily activity intensifiedon an increasing high tide series and peakedon late afternoon flood tides, especially whenthe time of high water coincided with sunset.Penttila (1978) collected ripe surf smelt atPenn Cove, Whidbey Island, and UtsaladyBeach, Camano Island, Washington, at bi-

weekly intervals during high tides, shortlybefore sunset.

We noted spawning patches in the upperintertidal zone at Fidalgo Bay on January IIand 25. Embryos on both occasions were instage 8 (ear ly high blastula). It is possible thatthese patches resulted from spawning duringhigh tides on January 9 and 23. On both dates,high tides of 2.2 to 2.4 m above MLWoccurredapproximately 30 minutes before sunset.

During the several month-long spawningseason of a surf smelt stock, spawning occursat irregular intervals on any given stretchof beach. Super-imposition of new spawnpatches upon older spawn already incubatingembryos within the substrate is quite common.In fact, field-sampling of smelt-spawn-bearingbeach material on winter spawning groundsin Puget Sound shows most substrates to beincubating from two to four distinct spawningevents , with as many as seven to eight differ­ent ages noted occasionally (Penttila 1978).

Hypomesus pretiosus eggs are adhesive and

Embryo Ecology of Hypomesus pretiosus-MIDDAUGH, HEMMER, AND PENTfILA 51

LPPER INTERTIDAL MIDDl£ INTERTIDAL l...ONER INTERTIML

.208

N =35

N =14

N =16N =36

N =36

N =36

2832

2832

N =76

N =57

N = 122.101.'j

~ .00zwCt:Ct:~UUo

.10j.0 5

W~

ttiii .0 0 ~~-:::-T7~

Ct:

.IOJ.0 5

LLo>- .00 .....,........,.......,-f"'"

~W

§Ct:LL

Eo(\J

I

Eu

I

o

Eu

rr>I

(\J

I

two

wozwcrcr=>uuo

N=II

IHVlg "61 Iei21I:i23126i2eii!iEMBRYONIC STAGE

N =42

~EMBRYONIC STAGE

N =52

6

EMBRYONIC STAGE

.IOJ.0 5

.00 fIIIIl-:-T.".....~

EuV

I

rr>

FIGURE 4. Relative frequency of embryonic stages of H. pretiosus collected from a pocket beach on the easternshore of Fidal go Bay.

readi ly attach to gravel substrates. Attach­ment occurs immediately upon fertilization asthe zona radiata membran e is ruptured andquickly turns inside out. The inver ted zonaradiata adheres to any surface that it contacts(Loosanoff 1937). Upon attachment, the zonaradiata forms a small pedestal-like structurewith the fertilized egg resting at the top.

During laboratory incubation of H . pretio­sus at 17.6°C, we noted embryo detachmentfrom the gravel substrate at stages 21 to23. The pedestal (zona radiata) remained

attached to the developing embryo for 12 to24 hours, then disappeared . A simila r phe­nomenon was noted in embryos incubated ata mean room temperature of 12.1°C. How­ever, these embryos were in stages 18 to 20when detachment occurred. Only a few stage22 to 24 embryos incubated at an ambientseawater temperature of 7.6°C detached fromsubstrates during this study.

Loosanoff (1937) found that summer­spawned H . pretiosus embryos at UtsaladyBeach, Washington, deposited on gravel at an

52

elevation of approximately 2.5 to 3.5 m abo veML W detached from spawning substrates tendays after fertilization. From his description ,it is apparent that these embryos were in anad vanced stage of development. Hatching ofembryos from Utsalady Beach occurred oneday after detachment from gravel substrates.

.Repeated tests revealed that embryos alwayshatched on the eleventh da y after fertilization.It was also learned that embryos had to beinundated and agitated to stimulate hatching(Loosanoff 1937). A similar need for sub­mergence and agitation to stimulate hatchingin the California grunion, Leuresthes tenuis,was noted for embryos that had been incu­bated in sand (Walker 1952). In contrast,David (1939) and Goodman et al. (1985)maintained L. tenuis embryos in quiet waterfor 12 to 15 days , then subjected them toagitation, whereupon hatching occurred.

In this study, H. pretiosus embryos wereincubated in glass containers that were par­tially filled with seawater. Detachment ofembryos from the gravel substrate resulted inincubation under water during the ad vancedstages of embryogenesis at 17.6°C and atambient room temperature of 12.1°C. Nohatching was noted among these embryosprior to daily agitation by inversion of theincubation cups. Hatching was noted 10 to 30minutes after agitation.

The detachment phenomenon and move­ment of embryos both in a seaward directionand to a lower stratum in intertidal substratesat Fidalgo Bay, Washington, appears to reducethe likelihood of thermal stress and desicca­tion. The lowest relative humidity and highestsubstrate temperature were recorded in theupper intertidal zone in sunlight. Relativehumidity and temperature were not as extremeat the same elevation in a location shaded byover-hanging willow trees (Table 2).

We noticed that newly spawned eggs oc­curred most often in patches (1 to 2 m diam­eter) in the upper intertidal zone where treesor large boulders provided shade. H . pretiosusat Utsalady Beach during the summer alwaysdeposited eggs in locations shaded from directsunlight. Loosanoff (1937) noted that eggs un­buried and uncovered by water for up to 36hours were dry and shrunken. However, when

PACIFIC SCIENCE, Volume 41, 1987

placed in seawater these eggs acquired nor­mal shape rapidly, developed successfully, andproduced normal larvae.

A study by Penttila (1978) revealed that apreponderance of substrates where spawningoccurred at Utsalady Beach ranged between 1and 7 mm in diameter. Similar substrates werepresent along the eastern shore of Fidalgo Baywhere Hypomesus spawned during this study(Figure 3). Sorting and resorting of this mate­rial by wave action generally resulted in largermaterial at the surface. Developing embryossifted to lower strata where capillary moistureprevented desiccation while allowing ade­quate aeration. Embryos that were attachedto very large gravel or to sand, thus forminglight-weight particles with large surface areas,were not sorted to deeper strata and werelikely to be exposed to desiccation and ther­mal stress (Penttila 1978).

Survival ranged from 78 to 87% at five ofthe six temperature and salinity combinationswe tested. However, a decrease in hatchabilityto 47% was noted for embryos maintained at20°C and 30%0 salinity. While not statisticallydifferent from other salinities tested at 20°C,this combination ob viously was stressful toincubating embryos. High and low tempera­ture stress, desiccation, and exposure torapidly fluctuating salinity during rainfallevents and daily tidal inundations are vari­ables that continually challenge H. pretiosusembryos. Indeed, embryos from winter (Sep­tember-March) spawn samples in SouthernHood Canal, Washington, have been observedfrosted with ice crystals. Although embryosmay be subjected occasionally to weeks offreezing weather during a particularly harshPuget Sound winter, the net result seems to bea great lengthening of the incubation period(to 90 days or more) , but not necessarily highermortalities (Penttila 1985, pers. comm.). Incontrast, summer spawners (June-Septem­ber) deposit embryos in the upper inter­tidal zone at Utsalady Beach where they areexposed to daily temperatures ranging from15.5 to almost 26°C (Loosanoff 1937). Incu­bating California grunion, L. tenuis, embryoswere subjected to similar temperatures, 16 ton oc, at a depth of 7 to 15em below the sur­face; concurrent surface temperatures ranged

Embryo Ecology of Hyp omesus pretiosus-MIDDAUGH, H EMMER, AND P ENTIILA 53

from 15 to 36°C. Similarly, Middaugh et al.(1983) measured substra te temp eratures of 19to 32°C at a depth of4 to 8 em where L. tenuisembryos were developing.

The eastern shoreline of Fidalgo Bay is char­acteri zed by a relatively short fetch to thewest. Thi s limited fetch reduces the height ofwaves breaking in areas where H. pretiosuseggs are depo sited. However, some sortingand re-sorting of substrates were observed. Itseems likely that init ial placement of eggs inshaded microhabitats at the substrate surface,followed by detachment and redistribution todifferent intertidal locations and substra tedepths, plays a majo r role in reducing theimpact of environmental variables on devel­op ing embryos along this spawning beach .

LITERATURE CITED

CHANTER, D. O. 1975. Modifications of theangular transformation. Applied Statis­tics 24(3) :354-359.

DAVID, L. R . 1939. Embryonic and early larvalstages of the gru nion, Leuresthes tenuis,and of the sculpin, Scorpaena guttata.Copei a (2) :75-81.

GOODMAN, L. R. , D. J. HANSEN, G. M. CRIPE,D. P. MIDDAUGH, and J . C. MOORE. 1985.A new earl y life-stage toxicity test using theCalifornia grunion (Leuresthes tenuis) andresults with chlorpyrifos. Ecotoxicologyand En vironmental Safety 10: 12-21.

HART, J . L. 1973. Pacific fishes of Canada.Fish. Res . Bd. of Canada. Bulletin 180,740p.

KALAMBI, V. R. 1965. Heterogeneity amongthree spawning populations of the surf

smelt , Hypomesus pretiosus (Girard) in thestate of Washington. Univ . of Washington,Ph .D . thesis, 154p.

LAGLER, K . F. , J . E. BARDACH, R. R. MILLER,and D . R. PASSINO. 1977. Ichthyology, 2nded. John Wiley and Sons, New York. 506 p.

LOOSANOFF, V. L. 1937. Th e spawning runof Pacific surf smelt, Hypomesus pretiosus(Girard). Intern at'l Revue der gesamterHydrobiologie und Hydrographie 36: 1-2,p.170-1 83.

MIDDAUGH, D. P., H. W. KOHL, and L. E.BURNETT. 1983. Concurrent measurementof intertidal environmental variables andembryo survival for the California grunion,Leuresthes tenuis, and Atlantic silverside,Menidiamenidia (Pisces: Atherinidae). Calif.Fish and Game 69(2) :89- 96.

PENTTILA, D . 1978. Studies of the surf smelt(Hypomesus pretiosus) in Puget Sound.Technical Report No. 42. Department ofFisheries , Washington State. 47 p.

SAS INSTITUTE INC. 1982. SAS user's guide:Stat istics. Cary , NC. 584 p.

SCHAEFER, M . B. 1936. Contribution to the lifehistory of the surf smelt, Hypomesus pre tio-:sus, in Puget Sound. Wash. St. Dept. Fish. ,Biol. Rep . 35-B. 45 p.

SIMPSON, G. G. , A. ROE, and R. C. LEWONTIN.1960. Quantitative Zoology. Harcourt,Brace and World, Inc. , New York. 440p.

THOMPSON, W. F ., and J . B. THOMPSON. 1919.The spawning of the grunion. Calif. FishGame Comm. Bull. 3 : 1-29.

THOMPSON, W. F. , and ASSOCIATES. 1936. Thespawning of the silver smelt , Hypomesuspretiosus. Ecology 17(1) : 158-168.

WALKER, B. W. 1952. A guide to the grunion.Calif. Fish and Game 38: 409-420.