|A new type of nursery for rearing bivalve postlarvae: construction, equipment and preliminary results|
Lucas, A. (1976). A new type of nursery for rearing bivalve postlarvae: construction, equipment and preliminary results, in: Persoone, G. et al. (Ed.) Proceedings of the 10th European Symposium on Marine Biology, Ostend, Belgium, Sept. 17-23, 1975: 1. Research in mariculture at laboratory- and pilot scale. pp. 257-269
In: Persoone, G.; Jaspers, E. (Ed.) (1976). Proceedings of the 10th European Symposium on Marine Biology, Ostend, Belgium, Sept. 17-23, 1975: 1. Research in mariculture at laboratory- and pilot scale. IZWO: Wetteren. ISBN 90-6281-001-2. 620 pp., more
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|Document type: Conference paper|
The nursery used consisted of a polyethylene greenhouse of 165 m² floor surface. Seawater was pumped into large indoor reservoirs, which supply 12 raceways (3 m³ each) by gravity flow. Algal culture (Phaeodactylum, Dunaliella, Tetraselmis and induced blooms of natural phytoplankton) provided an important nutrient supplement for the reared bivalve postlarvae (about 72 % of the total quantity of food). The increase in seawater temperature in the greenhouse, was small in winter (+1.7 °C in February 1975) and slightly greater in spring (+ 3.7 °C in May 1975). To date, three species of bivalve postlarvae (Venerupis semidecussata, Crassostrea gigas and Mercenaria mercenaria) have been grown in the nursery. The growth rate was closely related to the culturing technique used. The following have been tried out: 1) floating trays without air-lifts, 2) floating trays under the tap, 3) floating trays with air-lifts, 4) suspended "lanterns" without air-lifts, 6) compartmented raceways, consisting of three compartments (seawater upwelling through each) with mollucs held on horizontally placed framed-screens. The best growth rate obtained by methods 5 and 6 due to a better water circulation. Greenhouse culture seemed to have definitive advantages over natural conditions for growing postlarvae during winter and spring, but not during summer. In the nursery it is economically feasible to rear bivalve postlarvae of 2-10 mm size, but not larger ones. The nursery is therefore to be considered as an advantageous transitional step between the hatchery and the wild.