LEIGHTON: ABALONE MARICULTURE 



unusually heavy recruitment following treat- 

 ment in 1963-65 of the area with quickhme to 

 reduce sea urchin numbers (Leighton 1968). 

 Interest is gaining in Japan to reclaim vast areas 

 of potentially productive sea bottom limited by 

 sea urchins (e.g., the "isoyake", or "pink rock", 

 coralline algae/echinoid-dominated bottom) for 

 increased abalone production using several ap- 

 proaches of physical habitat improvement, 

 chemical treatment, and algal afforestation (Uki 

 1986*). 



Several groups holding leases to areas of off- 

 shore California land are engaging in "sea-floor 

 ranching" of abalone. In 1984, a total of about 50 

 acres had been leased for this pui'pose in south- 

 ern California (Leighton 1984^). One individual 

 (D. Gilbert, San Diego Mariculture) has hber- 

 ated many milhons of late-stage larvae onto rock 

 bottom within boundaries of his lease holdings. 

 Increases in population densities of seeded 

 species are reported in preliminary surveys. 

 Larval seedings often fail for a number of 

 reasons, including "temporary settlement" 

 (chnging while retaining the ability to swim once 

 again; Leighton 1987), micropredation, and vari- 

 able viability of different larval stocks. A suc- 

 cessful field plant of larval H. iris in New 

 Zealand has been reported (Tong et al. 1987). In 

 that experiment, localized recruitment occurred, 

 likely because larvae were released at an ad- 

 vanced age (13 days, Tong 1987^'^^'), thus reducing 

 the opportunity for emigration. 



It appears success of larval and juvenile plant- 

 ings is dependent on a variety of factors (see 

 Problem Areas). Extremely high losses of red 

 abalone juveniles were reported soon after re- 

 lease off the California coast by Department of 

 Fish and Game biologists (Tegner and Butler 

 1985). Introduction of young abalone to the mar- 

 ine environment is, however, quite unlike releas- 

 ing trout fiy in freshwater lakes and streams. 

 Using "temporary protective habitats", 

 Leighton (1985, 1987) found gi'eatly improved 

 survival of green abalone through reduced 

 handling duiing transport and minimized preda- 

 tion during the critical 1-2 days following plants. 



*N. Uki, National Research Institute of Aquaculture, 

 Nansei, Mie 516-01, Japan, pers. commun. 1986. 



'Leighton, D. L. 1984. Recent developments advanc- 

 ing aquaculture of abalone Ln southern CaUfomia. Paper 

 presented to Marine Aquaeulture-Southem California, 1984 

 Symposium. Annual Meeting, Southern California Academy 

 of Sciences, May 12, 1984, Los Angeles. 



"'L. Tong, Ministrj' of Aquaculture and Fisheries, Fisher- 

 ies Research Center, P.O. Box 297, Wellington, New- 

 Zealand, pers. common. 1987. 



This highly effective and low cost method uses 

 shelters consisting of stacked corrugated PVC 

 sheet (Fig. 4) which allow high density contain- 

 ment during transport and initial protection at 

 the planting site, virtually eliminating "planting 

 mortality". Survival one year after release, 

 based on live recoveries, has been at least 20%; a 

 highly conservative estimate since the planting 

 areas w-ere sampled without destructive ap- 

 proaches to open crevices or upturn large rocks 

 (Leighton 1985, 1987). Likely a combination of 

 controlled planting, habitat improvement, algal 

 afforestation, and predator reduction will prove 

 most effective for the success of seafloor ranch- 

 ing of abalone in California. 



Experimental U.S. progi-ams in containment 

 culture carried out by private interests have 

 included buoyed cages (Pacific Ocean Farms, 

 Monterey), cylindrical modular habitats (At- 

 lantic-Richfield Company/California Marine 

 Associates, Santa Barbara), and bottom-secured 

 concrete pipe sections. Containment cultm-e in 

 the sea presents advantages for concentration 

 and protection not inherent in the more exten- 

 sive approach of seafloor ranching. Under ap- 

 propriate routines for feeding and maintenance, 

 abalone may be reared at high densities, greatly 

 simplifying the harvesting process. However, 

 containment culture has, to date, proven expen- 

 sive, not enth'ely free of predation problems (as 

 young stages of crabs, seastars, etc. enter 

 cages), and subject to destruction by heavy 

 surge and entanglement by drifting kelp. Groups 

 conducting studies in California have not solved 

 all these problems. New designs of containment 

 structures, which incorporate effective feeding 

 systems, are simply monitored and are less 

 susceptable to damage by physical forces are 

 needed to advance technology in this area. 



PROBLEM AREAS 



The major technological impediments to full 

 development of efficient abalone mariculture in 

 North America appear to fall into three cate- 

 gories: 1) Yields of juveniles under hatchery 

 conditions generally represent less than 10% of 

 the larval stock; 2) conditions for optimization of 

 the culture environment to promote maximum 

 health and growth still require definition for 

 each of the principal species cultivated; and 3) 

 cost-effective methods and associated materials 

 for gi'ow-out, especially in the ocean, remain to 

 be tested and applied on a commercial scale. 



Abalone culture technology advanced rapidly 



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