FISHERY BULLETIN: VOL. 87. NO. 3. 1989 



1977, 1985). Some culturists employ chemical re- 

 laxants (such as Benzocaine at 100 ppm) to facili- 

 tate transfer, but associated losses may be high. 

 The latter method becomes necessary when orig- 

 inal culture tanks are large and immovable. 



Japanese methods for abalone culture, out- 

 hned by several researchers (Kan-no 1975; Ino 

 1980; Grant 1981; Uki 1981), almost universally 

 employ elongate rectangular "raceway" tanks 

 holding vertically suspended coiTugated plastic 

 panels for culture of postlarvae and juveniles. 

 Larvae are allowed to settle directly on the plas- 

 tic substrates in special tanks prior to transfer to 

 the raceways. Young abalone are reared to 1-2 

 cm under those conditions. While some hatcher- 

 ies release the juveniles in the sea for fishery 

 enhancement at that point, others retain the 

 abalone in mesh-bottom drums held upright in 

 larger tanks or supported by rafts in protected 

 marine areas for growth to 3-5 cm (Kan-no 

 1975). 



In the two principal hatcheries for red abalone 

 in California (The Abalone Farm and Ab Lab), 

 culture through early juvenile stages is achieved 

 employing similar systems. However, these 

 groups differ markedly in their approaches for 

 rearing young abalone to market size (4-10 cm). 

 The Abalone Farm practices raceway culture in 

 which juveniles are reared in a series of concrete 

 troughs through which seawater cascades from 

 upper to lower members. Vigorous aeration is 

 supplied intermittently and seawater flow rates 

 vary from to 200 L/min, depending on the 

 pumping schedule. The kelp, Macrocystis 

 pyrifera, is the principal food provided, although 

 many species of red, gi'een, and brown algae are 

 available locally in large quantity and are sup- 

 phed supplementally. Ab Lab transfers juvenile 

 red abalone at about 1 cm to containment struc- 

 tures held in the channel at the entrance to Port 

 Hueneme Harbor. Large polyethylene drums 

 (ca. 55 gal capacity) with plastic or stainless steel 

 mesh capped ends are secured in a horizontal 

 position to braces in racks, all immersed to a 

 depth of a few feet beneath a pier. Each drum 

 receives several thousand individuals initially. 

 Macrocystis forms the majority of the diet. Thin- 

 ned with growth, the young abalone are reared 

 to a size of 4-5 cm and sold live to specialty 

 seafood dealers in the Los Angeles area (Hamil- 

 ton 1988). 



The relatively slow growth rate typical of aba- 

 lones (ca. 2.5 cm/yr) has been limiting to com- 

 mercial production by mariculture. However, 

 some species exhibit accelerated development 



and grow1;h at water temperatures higher than 

 normally experienced in nature. The Pacific aba- 

 lone has been reared in thermal effluent sea- 

 water from an electric power plant in Japan dur- 

 ing the cold season (McBeth 1972). Grovrth rate 

 of the California green abalone was almost 

 doubled when reared at 24°-28°C in power plant 

 effluent in an extensive 4-yr study (Leighton et 

 al. 1981; Leighton 1985). Two new programs in 

 abalone mariculture are being estabhshed to uti- 

 lize thermal energy from coastal power facilities 

 in Southern California for commercial production 

 of this valuable species (see Future Prospects). 



ALTERNATIVES FOR GROW-OUT 



High costs of grow-out in most land-based sys- 

 tems make methods to rear abalone from juve- 

 niles to marketable adult stages in the sea at- 

 tractive. As discussed earlier, emphasis in Japan 

 has been placed on the design and testing of a 

 diversity of artificial habitats for environmental 

 improvement and partial containment for aba- 

 lone in the ocean. In that country the largely 

 government-supported hatcheries supply seed 

 abalone to members of fishery cooperatives for 

 planting on improved and controlled areas of sea 

 bottom (Saito 1984; Sheehy and Vik 1981). The 

 introduced abalone are allowed to mature for a 

 period of 2—4 years before final harvest. Much 

 attention has been given means for enhancing 

 survival and growth of these crops by increasing 

 production of kelps and other seaweeds as well 

 as expanding the substrate necessary for concen- 

 trated "farming" of abalone. Yields of market- 

 able abalone have been increased appreciably in 

 some areas as these two approaches are coupled 

 with measures to harvest or otherwise reduce 

 numbers of predatory fish and invertebrates 

 (Ino 1980; Uki 1981). 



In the mid-1960s, significant advances were 

 made in the United States toward kelp habitat 

 improvement (North 1976). Areas of rocky bot- 

 tom maintained in minimal algal productivity by 

 large concentrations of sea urchins are often 

 those with the highest potential for algal produc- 

 tion and abalone recruitment. A valuable tool for 

 restoration of ecological balance resulted from 

 the finding by Leighton that calcium oxide effec- 

 tively reduced numbers of overgrazing echi- 

 noids, fostering the return of Macrocystis and 

 other vegetation with subsequent repopulation 

 by diverse fauna (Leighton et al. 1966; Leighton 

 1971). Red and pink abalone populations re- 

 turned to the Point Loma Shelf (San Diego) with 



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