FISHERY BULLETIN: VOL. 72, NO. 4 



lOOr 



80 



<x 



en 

 o 





60 



40 



20 



H. fulgens 

 q 



H, corru goto 



1 



_L 



18 21 24 



"Cdl.S") 



27 



30 



Figure 8. — Growth rate of juvenile abalone held for month-long 

 periods at different temperatures. Points are averages for groups 

 of 8 to 15 individuals (see Table 4). 



Table 5. — Approximate depth distribution oiHaliotis species off 

 Point Loma (San Diego, Calif). 



Species 



Depth range 

 (m) 



H. cracherodii 

 H. fulgens 

 H. corrugata 

 H. rufescens 

 H. k. assimilis 

 H. sorenseni 

 H. walallensis 



0-2 

 0-5 

 1-20 

 10-25 

 10-30 

 15-35 

 15 35 



kamtschatkana, and H. walallensis together with 

 the generally shallow water and intertidal H. 

 cracherodii). Haliotis sorenseni, H. corrugata, and 

 H. fulgens range from Pt. Conception to central 

 Baja California. Haliotis cracherodii and//, rufes- 

 cens occur throughout California and northern 

 Baja California, while//, k. assimilis replaces //. 

 kamtschatkana in southern California (McLean, 

 1966). 



This study has shown that the thermal re- 

 quirements, particularly for eggs and early lar- 

 vae, are exacting. Field distribution of juvenile 

 and adult members of each species correspond 

 with the thermal tolerance range observed in lar- 

 vae in the laboratory. The range of tolerance in- 

 creased with larval age. Larvae of //. corrugata 

 placed in the thermal gradient as operculate veli- 

 gers survived a range of 18° (from 8° to 26°C), 

 while those resulting from eggs placed in the same 

 situation were tolerant of a range of only 8° (from 

 15° to 23°C). The observation is not new nor lim- 

 ited to Haliotis (Loosanoff and Davis, 1963). 

 Thus, survival of larvae dispersed in nature is 



likely dependent on their remaining within a 

 water mass of appropriate temperature and 

 further, settling in areas over which temperature 

 change will not be extreme. Recruitment to mar- 

 ginal environments may rely on the timely influx 

 of advanced veliger larvae. The situation is com- 

 plicated, no doubt, by acclimation of mature 

 adults near distribution limits. 



Most studies in abalone culture have been con- 

 ducted by Japanese workers concentrating on the 

 species native to northern Japan, //. discus han- 

 nai. Its broad thermal tolerance (approximately 

 5°-30°C) and relatively rapid growth at elevated 

 temperatures have attracted the interest of 

 mariculturists. The species exhibits rapid larval 

 development, settling in 3 days at 25°C and reach- 

 ing the notch stage in 42 days (Kan-no and 

 Kikuchi, 1962). When reared at five temperatures 

 between 5° and 25°C, juvenile //. d. hannai 

 displayed daily increments in shell length of 1, 

 2, 32, 68, and 95 m , respectively, according to the 

 same report. During winter months when sea 

 temperatures at the coastal hatchery drop below 

 10°C, cultured juvenile abalone are transferred to 

 a site adjacent the Yogasaki Electric Generating 

 Plant using 26°C water detoured from the effluent 

 stream (Kan-no, pers. commun., McBeth, 1972). 



Thermal tolerance and growth characteristics 

 of larvae and juveniles of the Japanese species are 

 similar to that observed in the present study in //. 

 fulgens. Of the American species considered here, 

 only //. fulgens could be recommended for heated 

 effluent mariculture. 



First year growth measured in this study is not 

 considered to approximate growth in nature. 

 Artificial lighting, synthetic materials in rearing 

 tanks, and other factors may have infiuenced 

 growth, and the growth rate estimates are likely 

 conservative. The general observation of rapid, 

 moderate, and slow growth in //. fulgens, H. 

 rufescens and //. corrugata, respectively, is con- 

 cluded to reflect specific differences in growd:h 

 potential. 



LITERATURE CITED 



BooLOOTiAN, R. A., A. Farmanfarmaian, and a. C. Giese. 

 1962. On the reproductive cycle and breeding habits of two 

 western species of Haliotis. Biol. Bull. (Woods Hole) 

 122:183-193. 

 Imai, T. 



1967. Mass production of molluscs by means of rearing the 

 larvae in tanks. [In Engl., Jap. summ.] Venus 25: 159-167. 

 Ino, T. 



1952. Biological studies on the propagation of Japanese 



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