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This shellfish continues to be a prime quarry of sport
divers and low tide collectors in California. It has not been the subject
of commercial fisheries since early in the last century such take has
been precluded by California Department of Fish and Game law. Rock scallops,
while locally abundant, would be easily overfished since their habitat
is restricted largely to rocky promontories and reefs at subtidal depths
readily accessible to scuba, hooka, and free divers.
Within the diving community the rock scallop is well-known for its tasty meat. In early studies of rock scallop biology and culture, fresh adductor muscles were compared to commercially available scallop species by a highly objective taste panel evaluation (Leighton and Phleger, 1981). Judged on the basis of flavor, aroma, after-taste and texture, among other criteria, the rock scallop scored high or highest in these tests. The successful rock scallop aquaculturist would find the product commanding top prices.
In general, rock scallops are cultured by methods similar to those applied in culture of oysters, clams, and other bivalves. Specifically, rock scallops present differences in their behavior and physiology which require a special set of conditions for spawning, larval culture, metamorphosis and grow-out. The bulk of this guide is devoted to description of the various steps to be followed in culture of this species. Brood Stock Unlike many other scallop species, sexes are separate in Crassadoma. Southern California populations exhibit a bimodal annual reproductive |
cycle, generally with peaks in late spring
and mid fall. A deep water population off Point Loma, San Diego, was found
to mature about one month later than shallow water populations in the
area. Northern rock scallops appear to have a single peak in early summer
(Leighton, 1991). In captivity, natural peak periods have been extended
(Leighton and Phleger, 1982). In a recent study, adult rock scallops,
collected from the entrance to Mission Bay, San Diego, have been found
sufficiently ripe to release viable gametes upon induction most months
of the year (Leighton, 2003).
Spawn Induction A wide variety of methods to induce spawning were successfully applied to rock scallops (Leighton and Phleger, 1979), including mild heat shock, addition of testis fluid to water containing females, and use of UV-irradiated seawater (Uki and Kikuchi, 1974). Gamete release following injection of the adductor muscle with serotonin (0.2 ml of a 10-3 M solution) was reported by Malakowski (1986) and Rhee and Davis (1998). Our recent two-year study used serotonin injection almost exclusively with good results. During non-peak periods females were less responsive, but males did not fail to produce sperm. We routinely selected five recently-collected adult scallops, scrubbed to remove algae and other fouling organisms, and injected each using a 3 cm gauge 22 hypodermic needle inserted between the valves at either the anterior or posterior commissure directly into the adductor muscle. Scallops were placed immediately in separate pails containing filtered seawater. Males generally released sperm within 15-30 minutes; females within 1-2 hours.
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