LEIGHTON: ABALONE MARICULTURE 



All California species have now been cultured 

 experimentally, but the red abalone remains as 

 the principal species for mariculture. This cold- 

 water abalone has been the focus of attention 

 chiefly because it thrives along the central Cah- 

 fornia coast where early mariculture operations 

 were most effectively established. Furthermore, 

 most biological information was available for the 

 red abalone and the species was most attractive 

 from the mariculture standpoint, being the 

 largest member of the genus and having the 

 strongest commercial history. It has proved, for- 

 tunately, to be the most easily cultured Cali- 

 fornia abalone (Leighton 1987). 



The gi'een abalone has shown special potential 

 for mariculture in systems utilizing thermal ef- 

 fluent (Leighton 1974, 1985; Leighton et al. 1981) 

 and other means to provide temperatures in the 

 range 20°-28°C (e.g., thermal enhancement in 

 passive solar or geothermal systems). In the late 

 1970s, Leighton transported larval and juvenile 

 gi'een abalone to mariculture facilities in Hawaii 

 and Florida, finding survival and gi-owth to be 

 exceptional in those tropical regions (Leighton 

 1987). The green abalone is especially attractive 

 since its gi'owth rate is significantly increased at 

 higher water temperatures; young adults gain 

 nearly 5 cm/yr in shell diameter (Leighton 1974, 

 1985; Leighton et al. 1981). 



Pink and white abalones have been cultured 

 on a small scale (Leighton 1972, 1974). The 

 black abalone, a shallow-water species of lower 

 commercial gi-ade, is broadly tolerant of tem- 

 perature in adult stages, but larvae from Cah- 

 fornia races have thermal Hmits similar to that 

 of the cold-water red abalone. Black abalone 

 have been reared from laboratory-spawned 

 eggs (Leighton 1974, unpubl. data). Flat, H. 

 walallensis, and threaded, H. kamtschatkana 

 assimilis, abalones have also been cultured in 

 research projects in Southern California. The 

 pinto abalone, H. k. kamtschatkana, is receiv- 

 ing attention as a mariculture subject in Wash- 

 ington and British Columbia (Fletcher 1987). 

 All species of eastern North Pacific abalones 

 have been found to hybridize in the laboratory 

 with varying degrees of success. In most cases 

 larvae and subsequent stages are fully viable 

 and young adults fertile (Owen and Meyer 1972 

 [fn. 3]; Leighton and Lewis 1982). Some hybrids 

 exhibit features which promise to be advan- 

 tageous to mariculture, including environmental 

 adaptability, improved growth rate and hardi- 

 ness, and possibly refinements in quality of 

 flesh (Leighton 1987). 



AMERICAN ABALONE CULTURE 

 TECHNOLOGY 



As stated earher, methods to culture abalone 

 in California were developed quite indepen- 

 dently from those practiced in Japan. Generally, 

 the emphasis by U.S. culturists has been on pro- 

 duction of crop animals of small adult size di- 

 rectly marketable in the domestic trade. Aba- 

 lone are reared to sizes of 7-10 cm either within 

 specialized tanks on shore or in containments 

 held in protected ocean waters. In Japan, how- 

 ever, young abalone are usually released to the 

 natural environment at a size of 2-5 cm for con- 

 tinued growth over periods of 2-4 years until a 

 marketable size (7-10 cm) is reached (Saito 

 1984). Few attempts have been made in that 

 country to rear abalone to adults under the con- 

 trolled environmental conditions afforded by 

 appropriate tank systems. However, highly 

 elaborate concrete and plastic structures of 

 many designs to provide protective substrate 

 and improved foraging are now being appHed to 

 abalone gi'ow-out in the sea (Sheehy and Vik 

 1981). Coupled with habitat improvement (i.e., 

 algal afforestation and predator control), these 

 in-sea approaches to increase abalone production 

 are gaining success (see Alternatives for Grow- 

 Out). The economic and other risks associated 

 with such measui'es have constrained develop- 

 ment by private enterprise in the United States. 



Hatchery Methods 



The requirement of North American species of 

 abalones for rapidly moving, well-aerated sea- 

 water led to the early development of culture 

 tanks which provided full circulation. Circular 

 tanks proved most effective, and Leighton (1977) 

 introduced such a tank in which rotary flow was 

 easily maintained by air-lift with minimum 

 energy input. Self-cleaning features accompany 

 the vortical drive, airlift return design (Fig. 3). 

 Originally devised for culture of relatively ses- 

 sile marine invertebrates, the tank allows maxi- 

 mum control, a rapid circulation, and foam frac- 

 tionation via the return line. These features are 

 effective for culture of swimming larvae and 

 early settled stages. Following use by us (Cali- 

 fornia Marine Associates), new entrants adopted 

 similar tank designs for postlarval and juvenile 

 culture. Now typical of U.S. hatchery tank ar- 

 rays, round tanks stand in marked contrast to 

 the "raceways" and immersed plastic panels em- 

 ployed in Japan and elsewhere. 



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