THE INFLUENCE OF TEMPERATURE ON LARVAL AND JUVENILE GROWTH IN THREE SPECIES OF SOUTHERN CALIFORNIA ABALONESl

DAVID L. LEIGHTON2

ABSTRACT Larvae of the abalones Haliotis rufescens, H. corrugata, and H. (ulgens displayed most rapid growth and best survival at 15°_18°, 18°_21°, and 20°·23°C, respectively. Survival oflarvae and postlarvae was poor above these optimal ranges. However, juveniles 3 mo to 1 yr old were tolerant of a broader temperature range. The warm-waterspecies, H. fulgens, increasedin shell length atan average rateof 88/l per day at 26°C. Mean shell elongation rates were 77 and 64 p per day in H. rufescens and in H. corrugata at their respective optima.

An expanding body ofliterature exists concerning MATERIAL AND METHODS aspects of the biology and culture of the abalone Haliotis (e.g., Sakai, 1962; Oba, 1964; Tamura, Ripe abalone were collected off southern 1966; Imai, 1967; Tanaka, 1969; Shibui, 1971a; California by diving. In transportation to the and McBeth, 1972, which succeeded the pioneer­ laboratory, care was taken to avoid subjecting the ing studies ofMurayama, 1935, and Ino, 1952). In animals to desiccation or other physical shock these studies little attention was directed to prob­ which might have induced premature release of lems of larval development, and essentially no gametes. Adult abalone were allowed a laboratory information has been obtained on the limitations "conditioning period" of about 2 wk before at­ imposed by temperature ongrowth andsurvival of tempts were made to induce spawning. Water larvae and postlarvae with the single exception of temperature in tanks containing abalone of both the observations on H. sorenseni, reported by sexes was raised approximately 5°·8°C above am­ Leighton (1972). In 1962, Kan-no and Kikuchi bient, following the thermal shock method ofIno related results of a 3-wk experiment in which (1952) and Oba (1964); a procedure which was only juvenile H. discus hannai were reared at five dif­ occasionally successful. Most productive spawn­ ferent temperatures, but most investigators have ings in terms ofquantity and viability were those merely reported the range oftemperature prevail­ which occurred spontaneously in the laboratory. ing during observations (e.g., Oba, 1964; Shibui, Natural cues and events associated with "mass 1971b). spawnings" are not well understood (Owen and This paper describes results of experiments in Meyer, in press) and were not investigated in this which groups oflarvae, postlarvae, and juveniles study. were reared at a series oftemperatures encompas­ Fertilizedeggs were collected as soon as possible sing the natural range to examine the influence of after their release. The eggs, which settle rather these factors on developmentandsurvival. Larvae rapidly, were siphoned or pipetted into freshly were obtained from three American west coast filtered seawater (Cuno filter unit,3 ca. 5 J.1) at species spawned in the laboratory: The red the same temperature as that of the spawning abalone, H. rufescens, the pink abalone, H. cor­ environment. Repetition of the process several rugata, and the green abalone, H. fulgens. times, each time using freshly filtered seawater, was usually sufficient to wash eggs free ofexcess sperm and debris. Incubation was carried out at 'This work is a result ofresearch sponsored by NOAA Office of Sea Grant U.S. Department ofCommerce, under Grant # UCSD ambient temperatures and larvae treated as de­ 2·35208 with the Institute of Marine Resources in cooperation scribed elsewhere (Leighton, 1972). with California Marine AsSQciates, Cayucos, Calif. The study was carried out in the aquarium laboratory of the Southwest While some experiments were performed with Fisheries Center, National Marine Fisheries Service, NOAA, La eggs at early cleavage stages, most observations Jolla. Calif. 2ScrippsInstitution ofOceanography, UniversityofCalifornia at San Diego, La Jolla, CA 92037; present address: California 'Reference to trade names doos not imply endorsement by the Marine Associates, P.O. Box 136, Cayucos, CA 93430. National Marine Fisheries Service, NOAA.

Manuscript accepted December 1973. FISHERY BULLETIN: VOL. 72, NO.4, 1974. 1137 FISHERY BULLETIN: VOL. 72. NO. 4

were initiated with newly hatched trochophore Progeny of each spawning were maintained in larvae. Trochophores normally hatched from eggs the laboratoryfor over 1 yr providing comparative at 15°_18°C within 12 to 18 h. Shortly after hatch­ information on juvenile growth rate in aquaria. ing, larvae swim to the surface (negative geotaxis) Diatoms and minute filamentous algae served as and are easily drawn into a pipette for transfer to food during their first few months. Olderjuveniles experimental containers. were provided larger algae, Egregia laevigata, Thermal influence on development and survival Eisenia arborea, Macrocystis pyrifera, and of larvae and postlarvae was observed using a Laminaria farlowii. temperature gradient apparatus; an aluminum block (30 x 15 x 150 cm) bored to accommodate DEVELOPMENTAL FEATURES OF replicate series oftest tubes (25 mI). Cooling coils LARVAE,POSTLARVAE, AND and heatingelements at opposite ends maintained JUVENILES a temperature differential (range: 7°_31°C) with but slight fluctuation (±O.5°C per gradient posi­ While morphogenesis is gradual and does not tion) over the course of the average experiment progress in a stepwise manner, various stages of (2-4 wk). The apparatus is similar to that used larval and postlarval development are recogniz­ with H. sorenseni larvae (Leighton, 1972) and has able. Development rate was measured in terms of been thoroughly described elsewhere (Thomas, the time required for larvae to first gain features Scotten, and Bradshaw, 1963). distinctive to each stage. Eleven such stages are In the typical experiment duplicate series of10 passed from trochophore larva to circular-shelled tubes, each tube containing 20 ml of seawater, postlarva (Figure 1). Settlement (the crawling were placed in the thermal gradient with 50 eggs stage) marks the end oflarvallife. Postlarval de­ or larvae. Incubation was carried out in darkness. velopment then begins with the deposition of A foam urethane cover insulated the apparatus. peristomial shell and persists to formation of the Inspection ofthe tubes was made daily during the first respiratory pore ("notch stage," Leighton, first week and on alternate days thereafter to de­ 1972) at an age of 1-3 mo. Thenceforth to first termine the stage of development attained. As sexual maturity the abalone may be regarded as abalone larvae are lecithotrophic, feeding was not juvenile. necessary until settlement. Atthattime a mixture of three species of pennate diatoms (Nitzschia spp.). was supplied. Studies on postlarvae were also conducted using !:"IGURE 1.-1) Trochophore larva after hatching. 2) Cap-shell the temperature gradient block. Between two and early veliger larva. 3) Inflate-shell veliger (torsion stage). 4) five individuals were placed in each tube. Postlar­ Early operculate veliger (preeye spot). 5) Incipient cephalic ten­ vae 1-2 mo of age were picked individually from tacle stage operculate veliger. 6) Midformed cephalic tentacle walls of culture containers (Pyrex beakers or stage. 7) Digitate or branched cephalic tentacle stage. 8) Crawl· polyethylene pails) using a finely bevelled ap­ ing and settling stage. 9) Peristomial sheIl stage postlarva. 10) Midasymmetric shell postlarva. 11) Circular-sheIl postlarva. plicator stick. Several drops ofthe diatom culture were added to each tube twice weekly over the LabeIled structures: usual 2-wk observation period. e.g., ciliated girdle To examine the effect of temperature on the c.t., cephalic tentacle cten., ctenidium success of juveniles, groups of 8-12 individuals d.g., digestive gland were reared in six lO-liter polyethylene contain­ e., eye spot ers maintained at 12°,15°,18°,21°,24°, and 27°C e.t., epipodial tentacle (±1.00). Water was continuously aerated and the r., foot entire volume exchanged once a week. Food was int., intestine I. sh., larval shell either a mixture of unicellular and filamentous m., mantle algae cultured within each container under il­ m.o., mouth with odontophore lumination of a fluorescent lamp or fronds ofthe op., operculum brown alga, Egregia laevigata, collected in fresh p.s., peristomial shell condition every 3-4 days. Growth of juvenile r.m., retractor muscle r.s.m., right shell muscle abalones was measured for month-long intervals v., velum in these experiments. vis., viscera 1138 LEIGHTON: INFLUENCE OF TEMPERATURE ON ABALONES

---~-I.sh.

r.m. c.g. --+-t--vis.

e r.m.

r.m. f.

-lrl--===-..:\--r.s. m.

int.

1139 FISHERY BULLETIN: VOL. 72, NO.4

Incipient RESULTS Cephalic Tentacle Operculate /--48haurs In the course of the study six batches oflarvae Veliger Inflate-shell were obtainedfrom Haliotis rufescens, while three Veliger productive spawnings occurred withH. corrugata Cap-shell / ~----24 haurs Veliger andH·fulgens. Year-round spawning inH. rufes­ Trachaphare cens was predicted by Boolootian, Farmanfar­ Larva maian, and Giese (1962) and Young and DeMar­ Ratating Gastrula tini (1970) from field sampling for gonad indices. I Early Gastrula found spawning adults every month of the year (1969-71) in samples taken from Estero Bay (cen­ Blastula

tral California) and in the present study with H. Marula rufescens from southern California, laboratory spawnings were obtained in January, February, 4-16 Cell April, September, November, and December. Haliotis corrugata and H. fulgens spawned only S during the months of April, June, and October. Members of the shallowwater species, H. FIGURE 2.-Development of eggs of Haliotis rufescens held at different temperatures over a period of48 h. Mortality occurred cracherodii, held in the laboratory for another above 20°C after 14 h. study, spawned in early spring and early fall. Haliotis sorenseni produced viable gametes only o H. rufescens ~H. ~gQ)g during late winter (Leighton, 1972). 3 ot!. f.!!jgQBj DEVELOPMENT AND HATCHING IN EGGS 2 At'14°-16°C (ambientfor LaJolladuring most of the year) eggs ofall species hatched within 18-24 h. Generally, development to hatching appeared normal over a rather broad thermal range. At hatching, however, consequences ofinappropriate incubation temperatures became pronounced as trochophore larvae at and near thermal limits be­ came highly abnormal in appearance and be­ havior and usually succumbed within 48 h, par­ °Sl---.l....--.JIS---2L..O---2.l.S--...l30 ticularly at higher temperatures. Bizarre ciliated TEMPERATURE (Oe) bodies predominated athigh extremes oftempera­ FIGURE 3.-Hatching time for eggs of three species of Haliotis ture while retardation and paralysis occurred at incubated at several temperatures. lowest temperatures. Commonly torsion was in­ complete in larvae held at subnormal tempera­ tures. A consequence ofensuing abnormality and peaks of curves with time to suggest true optima mortality near thermal limits is apparent in the at temperatures about 2°C lower than observed in series ofcurves generated for development during trochophore larvae was found in all species the first several days of larval life. Attrition at studied due to supraoptimum mortality. upper and lower extremes and relatively high Hatching time was strongly dependent on survival and rapid growth at optimal tempera­ temperature and ranged between 10 and 72 h. tures is reflected in the sharply peaked curves for Both H. corrugata and H. fulgens, at tempera­ larval development rate versus temperature. In tures supporting rapid but normal growth (their H. rufescens, for example, eggs developed in an respective thermal optima), reached the point of apparently normal manner over the range hatching sooner than did H. rufescens (Figure 3). 10°-23°C, butlarval growth afterhatchingbecame Strongest contrast in specific development rate is restricted to the comparatively narrow range seen in the stage attained at supraoptimum tem­ 13.5°-20.0°C (Figure 2). The apparent shift ofthe peratures (2°_3°C above optimum). In 2 days: H. 1140 LEIGHTON: INFLUENCE OF TEMPERATURE ON ABALONES rufescens (near 19°C) reached the early (preeye Circular­ 24 days spot) operculate stage, H. corrugata (near 23°C) Shelled had formed eyespots and cephalic tentacle buds, Mid Asymmetric 10 days and H. fulgens (near 25°C) had become mid­ Early cephalic tentacle operculates. In the latter, set­ Asymmetric Crawling tling was observed as early as 3 days after fertili­ (Settling) 5 days zation. Branched .Cephalic Tentacle Mid Cephalic OBSERVATIONS ON Tentacle Incipient TROCHOPHORELARVAE Cephalic Tentacle 3 days Operculate When swimming trochophore larvae rather Veliger Inflate-shell than developing eggs were introduced to the Veliger thermal gradient system, survival was improved. Cap-shell In experiments initiated with fertilized eggs, sur­ Veliger vival beyond 3 days in the 20-ml tubes was low Trachaphare Larva 5 10 15 20 25 30 despite routine addition of dihydrostreptomycin TEMPERATURE (OCI sulfate and sulfanilamide (to final concentration, 10 ppm). Substances within the perivitelline space FIGURE 4.-Development of larvae of Haliotis rufescens at a series of temperatures when introduced to the thermal gradient (including excess sperm) are liberated at rupture as trochophores. of the albumen membrane, frequently promoting fouling. Temperature block studies in which Circular ­ trochophore or veliger larvae were freed of con­ Shelled taminants by repeated transfer and then ad­ Mid Asymmetric 17 days mitted to the tubes showed reduced mortality. Early 8 days Haliotis rufescens larvae settled approximately Asymmetric Crawling 6 days 4 days after fertilization (l8°C). However, after 3 (Settting) wk in the temperature block, only those groups Branched between 14° and 18°C had reached advanced post­ Cephalic Tentacle Mid Cephalic larval stages (Figure 4). Settling occurred in some Tentacle H. corrugata larvae within 3.5 days, but postlar­ Incipient vae did not survive (22°-23°C). Most rapid growth cephalic Tentacle Operculate and best survival in H. corrugata was at 21°-22°C; Veliger the circular-shell postlarval stage was reached in Inflate-shell Veliger 17 days (Figure 5). Settlement began in larvae of Cap-shell H. fulgens at 25.5°C in slightly less than 3 days, Veliger but again, subsequent success was poor. Those at Trachaphare Larva 5 10 15 20 30 22°-23°C, however, settled by the fourth day and TEMPERATURE (OC) progressed to the circular-shell stage in 15 days (Figure 6). There was a close correspondence of FIGURE 5.-8tages attained by larvae ofHaliotis corrugata over curves for development rate vs. temperature ob­ a period of 17 days. Larvae were placed in the thermal gradient at the trochophore stage. tained with progeny from different spawnings and parentage. Optima described graphically for each the lO-liter volume and illumination in theplastic species varied within only 1°C for H. corrugata, rearing containers. In an experiment illustrating 1.5°C for H. fulgens, and 2°C for H. rufescens. the point, H. corrugata eggs, trochophores and Larvae introduced to a thermal gradient as operculate veligers wereplaced inthe gradientfor operculate veligers exhibited tolerance to a 5 days in each case. At 20°-22°C, eggs developed broader temperature range. Subsequent de­ rapidly and early postlarval stages reached in 5 velopmentrate was, however, slowed. The general days. However, operculate veligers had not yet retardation may he a shock response to environ­ reached the crawling stage at an age of 7 days mental change. The greatly reduced volume pro­ (Figure 7). vided in the 20-ml tubes and the totally darkened In temperature block. experiments, survival conditions in the temperature block contrast with through settling usually ranged between 50 and

1141 FISHERY BULLETIN, VOL. 72, NO.4 quently oxygen depletion was not a cause ofmor­ Circular ­ Shelled tality. Mid A$ymmelric Early THERMAL TOLERANCE OF Asymmetric POSTLARVAE Cra'flling (Sefllingl Branched Postlarvae ranging in age from 1 to 2 mo were Cephalic Tentacle placed (2-5/tube) in the thermal gradient block Mid Cephalic Tentacle and provided each 3-4 days a mixture of three Incipien' species of diatoms (Nitzschia spp.). Tubes were cephalic Tentacle checkedfor survival and growth ofpostlarvaeover Operculate Veliger periods of2 wk. Survivalwas good in all species at Inflate-shell colder temperatures, but those at 10°_12°C invari­ Veliger Cop-shell ably were lethargic and could not right them­ Ve/iger selves once overturned. Haliotis rufescens Trochophore survived over the range lOo_19.5°C. Haliotis cor­ larva 5 10 15 20 25 30 rugata and H. fulgens were tolerant to the same TEMPERATURE (Oe) lower temperatures but had different upper FlGUnE 6.-Stagesattainedby Haliotis{ulgens larvae incubated limits, 23.5° and 26.0°C, respectively. Typically at several temperatures for 15 days. The experiment was ini­ tiated with trochophore larvae. survival was nearly lO(Y}0 over a broad inter­ mediate range of temperatures, but declined sharply within 2° of the extremes. Circulor­ Shelled Mid Asymmetric POSTLARVAL AND JUVENILE Early GROWTH Asymmetric Crawling (Settling) Specific differences in growth rate ofboth post­ Branched Cephalic Tentocle larvae and juveniles under laboratory conditions Mid Cephalic were measured. When its postlarvae were pro­ Tentacle vided near optimal thermal and feeding environ­ Incipien' Cephalic Ten,ocle ments, H. fulgens formed thefirst respiratorypore Opercula'e Veliger o S days, in as Zygotes in about half the time required by the other Inflate-she" A 6 days, in as Trachaphares species. As the pore is formed, a notch is first seen Vefiger o 7 days, in as Operculates on the anterior right shell margin. The feature is Cop-shell Veliger conspicuous and serves as a convenient point of Trachaphore comparison. The "notch stage" was reached in larva S 10 15 20 25 30 some rapid-growing H. fulgens at an age of 30 TEMPERATURE (OCI days (Table 1). FIGURE 7.-Comparison of development rate and tolerated Variability in growth rate was marked. Groups thermal range in larvae of Haliotis corrugata placed in the ofjuveniles ofidentical parentage, age, and rear­ temperature block at 1, 20, and 48 h after fertilization. ing environment sampled periodically for shell length distribution reflected a broad range and 8

1142 LEIGHTON: INFLUENCE OF TEMPERATURE ON ABALONES

length at 1 yr of age in four species reared in the TABLE 2.-Variation in size of juvenile Haliotis of identical laboratory varied over a range greaterthan 10mm parentage, age, and growing environment. (Table 3). Shell length (mm) Age Species (months) Number Mean Range SO INFLUENCE OF TEMPERATURE ON H. rufescens 3.7 18 4.4 2.6-6.1 1.06 H. corrugata 5.0 27 9.2 6.8·14.1 2.42 GROWTH RATE OF JUVENILES H.lulgens 4.7 70 7.1 3.6·12.0 2.00 H. sorenseni 3.3 19 4.3 3.0·5.6 0.64 Several growth experiments were conducted with juveniles of the three species of abalones to gain comparative data and to establish respective TABLE 3.-Size of Haliotis at completion offirst year growth in temperatures ofmaximum growth rate. Juveniles the laboratory. were reared for month-long periods in 10-liter Shell length (mm) plastic containers held at six temperatures be­ Species Mean Range Number tween 12° and 30°C. Both H. corrugata and H. H. rulescens 15.6 9.9·20.0 50 H. corrugata 18.3 12.2·26.4 18 fulgens displayed enhanced growth rate above H.lulgens 32.8 30.5·38.9 '3 20°C. Haliotis rufescens, however, grew best H. sorensen; 13.4 8.0·21.0 19 below 20°C and, in fact, grew but slightly less at 'Recent observations on growth of over 100 juvenile H. lulgens suggest the three Individuals represented here were exceptionally rapid growers. the coldest temperature, 12.5°C (Table 4, Figure Projection of growth of juveniles presently 8 rna old suggest the mean size 8). H. fulgens again showed a superior growth at 1 yr under laboratory conditions may fall closer to 25 mm. rate. While a mean daily shell growth approach­ tertidal to depths over 35 m. Depth distribution is ing 90 J1 was observed at its temperature of maximum growth rate (26°C), some individuals stratified specifically, although in certain areas (i.e., in the presence oflocalized upwelling) over­ increased in shell length as much as 130 J1 per lapping does occur. Vertical and latitudinal dis­ day. tribution appears most closely related to tempera­ DISCUSSION ture. The Point Lorna (San Diego) shelf from 0 to 35 m supports all California abalone species Seven species of Haliotis occur in southern (Table 5). Colder water species may be found in­ California waters ranging vertically from the in- tertidally in northern California (H. rufescens, H.

\ TABLE 4.-Daily shell elongation rate for groups ofjuvenile Haliotis reared for month·long periods at different temperatures (microns/day).

Temperature (OC ± 1.5") Species and date 12 15 18 21 24 27 30

H. rulescens

Oct. 1971 91 61 90 45 32 (') Jan. 1972 36 41 68 61 29 Mar. 1972 70 64 84 79 35 Dec. 1972 46 92 67 95 13

Mean 60.9 64.5 77.3 70.0 27.3

H. corrugata

Jun. 1972 26 29 30 46 53 May 1973 57 55 62 54 60 28 Jun. 1973 45 72 91 63 68 14

Mean 41.5 43.0 54.7 63.7 58.7 48.0 14.0

H.lulgens

Mar. 1973 23 29 63 77 119 84 May 1973 21 21 55 74 88 114 Jun. 1973 21 56 60 50 86 54

Mean 22.0 23.7 58.0 70.3 85.8 88.0 54.0

'H. rulescens did not survive in the 27°C containers. These data are averages for groups of 8 to 15 Individuals reared in each of six 1O·liter plastic drums. In the case of H. corrugata and H. lulgens, temperatures were raised throughout for the third experiment to cover the supraoptimal range. Juveniles used in these experiments ranged from 5 to 20 mm.

1143 FISHERY BULLETIN: VOL. 72, NO. 4

100 likely dependent on their remaining within a !i. !!!!g~ ----CI. water mass of appropriate temperature and _.0' \ further, settling in areas over which temperature -" \ t!,. rufescens ~ ;>1(- \ \ change will not be extreme. Recruitment to mar­ ~ / '. \ ginal environments may rely on the timely influx "-' t:...... A/ \ :{i 60 of advanced veliger larvae. The situation is com­ "-'a:: / b u plicated, no doubt, by acclimation of mature ~ I I I adults near distribution limits...... :x: 40 I Japan, H. discus han­ "-':x: nai. Its broad thermal tolerance (approximately f/) 50 _30°C) and relatively rapid growth at elevated 0L--'ZL-----l----J..'S---:2L.'---:24:--"""-:!:Z7;----::30 15 temperatures have attracted the interest of °C (! 1.5°) mariculturists. The species exhibits rapid larval development, settling in 3 days at 25°C and reach­ FIGURE 8.--Growth rate ofjuvenile abalone held for month-long periods atdifferent temperatures. Pointsare averages for groups ing the notch stage in 42 days (Kan-no and of 8 to 15 individuals (see Table 4). Kikuchi, 1962). When reared at five temperatures between 5° and 25°C, juvenile H. d. hannai TABLE 5.-Approximatedepth distribution ofHaliotis species off displayed daily increments in shell length of 1, Point Lorna (San Diego, Calif.). 2,32,68, and 95j.t, respectively, according to the

Depth range same report. During winter months when sea Species (m) temperatures at the coastal hatchery drop below H. cracherodii 0-2 10°C, culturedjuvenile abalone are transferred to H. fulgens 0-5 H. corrugata 1-20 a site adjacent the Yogasaki Electric Generating H. rufescens 10-25 Plant using 26°C water detoured from the effluent H. k. assimi/is 10-30 H. sorenseni 15-35 stream (Kan-no, pers. commun., McBeth, 1972). H. wa/al/ensis 1515 Thermal tolerance and growth characteristics oflarvae andjuveniles ofthe Japanese species are similar to that observed in the present study in H. kamtschatkana, and H. walallensis together with fulgens. Ofthe American species considered here, the generally shallow water and intertidal H. only H. fulgens could be recommended for heated cracherodii).Haliotis sorenseni, H. corrugata, and effluent mariculture. H. fulgens range from Pt. Conception to central First year growth measured in this study is not Baja California. Haliotis cracherodii andH. rufes­ considered to approximate growth in nature. cens oCCur throughout California and northern Artificial lighting, synthetic materials in rearing Baja California, while H. k. assimilis replaces H. tanks, and other factors may have influenced kamtschatkana in southern California (McLean, growth, and the growth rate estimates are likely 1966). conservative. The general observation of rapid, This study has shown that the thermal re­ moderate, and slow growth in H. fulgens, H. quirements, particularly for eggs and early lar­ rufescens and H. corrugata, respectively, is con­ vae, are exacting. Field distribution of juvenile cluded to reflect specific differences in growth and adult members of each species correspond potential. with the thermal tolerance range observed in lar­ vae in the laboratory. The range of tolerance in­ LITERATURE CITED creased with larval age. Larvae of H. corrugata BOOLOOTIAN, R. A., A. FARMANFARMAIAN, AND A. C. GIESE. placed in the thermal gradient as operculate veli­ 1962. On the reproductive cycle and breeding habits oftwo gers survived a range of 18° (from 8° to 26°C), western species of Haliotis. BioI. Bull. (Woods Hole) while those resulting from eggsplaced inthe same 122:183-193. situation were tolerant ofa range ofonly 8° (from IMAI, T. 1967. Mass production ofmolluscs by means of rearing the 15° to 23°C). The observation is not new nor lim­ larvae intanks. [In EngI.,Jap. summ.] Venus 25:159-167. ited to Haliotis (Loosanoff and Davis, 1963). IND, T. Thus, survival of larvae dispersed in nature is 1952. Biological studies on the propagation of Japanese

1144 LEIGHTON: INFLUENCE OF TEMPERATURE ON ABALONES

abalone (genus Haliotis). [In Jap., Engl. summ.] Bull. OWEN, B., AND R. MEYER. Tokai Reg. Fish. Res. Lab. 5, 102 p. In press. Laboratory hybridization of California abalone KAN-NO, H., AND S. KIKUCHI. (Haliotis). 1962. On the rearing of Anadara broughtonii (Schrenk) SAKAI, S. and Haliotis discus hannai Ino. Bull. Mar. Stn. Asamushi 1962. Ecological studies on the abalone, Haliotis discus 11(2):71-76. hannai Ina-IV. Studies on the growth. [In Jap., Engl. LEIGHTON, D. L. synop.] Bull. Jap. Soc. Sci. Fish. 28:899-904. 1972. Laboratory observations on the early growth of the SHiBUI, T. abalone, Haliotis sorenseni, and the effect oftemperature . 1971a. Experimental studies on the predatory animals of on larval development and settling succeBB. Fish. Bull., young abalones. [In Jap., Engl. summ.] Bull. Jap. Soc. Sci. U.S. 70:373-381. Fish. 37:1173-1176. LooSANOFF, V. L., AND H. C. DAVIS. 1971b. Studieson the transplantation ofred abalone andits 1963. Rearing ofbivalve mollusks. Adv. Mar. BioI. 1:1-136. growth and development. [In Jap., Engl. summ.] Bull. McBETH, J. W. Jap. Soc. Sci. Fish. 37:1168-1172. 1972. The growth and survival of the California red TAMURA, T. abalone in Japan. [In Engl., Jap. summ.] Venus 1966. Marine aquaculture. [Transl. by M. I. Watanabe]. 31:122-126. Natl. Tech. Inf. Serv., Springfield, Va., 1052 p. McLEAN, J. H. TANAKA, Y. 1966. West American prosobranch gastropoda: Super­ 1969. Studies on reducing mortalityoflarvae andjuveniles families Patellacea, Pleurotomariacea and Fissurellacea. in the course of the mass-production of seed abalone-I. Ph.D. Thesis, Stanford Univ., 272 p. Satisfactory result with streptomycin to reduce intensive MURAYAMA, S. mortality. [In Jap., Engl. summ.] Bull. Tokai Reg. Fish. 1935. On the development of the Japanese abalone, Res. Lab. Haliotis gigantea. J. ColI. Agric., Tokyo Imp. Univ. THOMAS, W. H., H. L. SCOTTEN, AND J. S. BRADSHAW. 13:227-233. 1963. Thermal gradient incubators for small aquatic or­ OBA, T. ganisms. Limnol. Oceanogr. 8:357-360. 1964. Studies on the propagation of an abalone, Haliotis YOUNG, J. S., AND J. D. DEMARTINI. diversicolor supertexta Lischke-II. On the development. 1970. The reproductive cycle, gonadal histology, and [In Jap., Engl. synop.] Bull. Jap. Soc. Sci. Fish. gametogenesis of the red abalone, Haliotis rufescens 30:809-819. (Swainson). Calif. Fish Game 56:298-308.

1145