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

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-water species, H. fulgens, increased in shell length at an average rate of 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 aspects of the biology and culture of the abalone Haliotis (e.g., Sakai, 1962; Oba, 1964; Tamura, 1966; Imai, 1967; Tanaka, 1969; Shibui, 1971a; and McBeth, 1972, which succeeded the pioneering studies ofMurayama, 1935, and Ino, 1952). In these studies little attention was directed to problems of larval development, and essentially no information has been obtained on the limitations imposed by temperature on growth and survival of larvae and postlarvae with the single exception of the observations on H. sorenseni, reported by Leighton (1972). In 1962, Kan-no and Kikuchi related results of a 3-wk experiment in which juvenile H. discus hannai were reared at five different temperatures, but most investigators have merely reported the range oftemperature prevailing during observations (e.g., Oba, 1964; Shibui, 1971b). This paper describes results of experiments in which groups of larvae, postlarvae, and juveniles were reared at a series oftemperatures encompassing the natural range to examine the influence of these factors on development and survival. Larvae were obtained from three American west coast species spawned in the laboratory: The red abalone, H. rufescens, the pink abalone, H. corrugata, and the green abalone, H. fulgens. 'This work is a result ofresearch sponsored by NOAA Office of Sea Grant U.S. Department ofCommerce, under Grant # UCSD 2·35208 with the Institute of Marine Resources in cooperation with California Marine AsSQciates, Cayucos, Calif. The study was carried out in the aquarium laboratory of the Southwest Fisheries Center, National Marine Fisheries Service, NOAA, La Jolla. Calif. 2Scripps Institution ofOceanography, Universi ty ofCalifornia at San Diego, La Jolla, CA 92037; present address: California Marine Associates, P.O. Box 136, Cayucos, CA 93430. Manuscript accepted December 1973. FISHERY BULLETIN: VOL. 72, NO.4, 1974. MATERIAL AND METHODS Ripe abalone were collected off southern California by diving. In transportation to the laboratory, care was taken to avoid subjecting the animals to desiccation or other physical shock which might have induced premature release of gametes. Adult abalone were allowed a laboratory "conditioning period" of about 2 wk before attempts were made to induce spawning. Water temperature in tanks containing abalone of both sexes was raised approximately 5°·8°C above ambient, following the thermal shock method of Ino (1952) and Oba (1964); a procedure which was only occasionally successful. Most productive spawnings in terms of quantity and viability were those which occurred spontaneously in the laboratory. Natural cues and events associated with "mass spawnings" are not well understood (Owen and Meyer, in press) and were not investigated in this study. Fertilized eggs were collected as soon as possible after their release. The eggs, which settle rather rapidly, were siphoned or pipetted into freshly filtered seawater (Cuno filter unit,3 ca. 5 J.1) at the same temperature as that of the spawning environment. Repetition of the process several times, each time using freshly filtered seawater, was usually sufficient to wash eggs free of excess sperm and debris. Incubation was carried out at ambient temperatures and larvae treated as described elsewhere (Leighton, 1972). While some experiments were performed with eggs at early cleavage stages, most observations 'Reference to trade names doos not imply endorsement by the National Marine Fisheries Service, NOAA.