ESTIMATING OPTIMAL POPULATION DENSITY FOR INTERMEDIATE CULTURE OF SCALLOPS IN SPAT COLLECTOR BAGS

M. Fréchette, M. Gaudet, S. Vigneau-2000

Aquaculture, 183 (1-2): 105-124
Abstract:

In a scallop restocking project in Îles-de-la-Madeleine, Québec, we investigated the spat growing within the collector bags, instead of using the usual pearl net method. To estimate optimal population density in the collector bags, we studied yield as a function of spat population density (B-N curves) at three depths in the water column (10, 20, 30 m) and in a nearby lagoon. The B-N curves suggest that for 1-year-old spat, biomass at 10 m depth was maximum at ca. 1900 individual spat per bag. At higher population density, self-thinning occurred and yield decreased. The B-N curve for 20 m did not reach a maximum at the population densities encountered in the experiment. At population density ca. 2000 ind/bag, yield of individuals >/= 2 cm shell height was greater at 20 m than at 10 m, apparently because of higher food availability at 20 m and presence of interspecific competitors at 10 m depth. Yields in the lagoon and at 30 m depth were not satisfactory. Intermediate culture should be done at 20 m depth, with at least 2000 ind/bag. The upper limit to this estimate could not be determined experimentally.

(Institut Maurice-Lamontagne, Ministère des Pêches et des Océans, 850 route de la Mer, C.P. 1000, , Mont Joli, Quebec, Canada G5H 3Z4)

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