Feeding activity, energy balance and scope for growth in the juvenile sea scallop Placopecten magellanicus (Gmelin) in Newfoundland

Bacon, Gregory Scott (1994) Feeding activity, energy balance and scope for growth in the juvenile sea scallop Placopecten magellanicus (Gmelin) in Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The physiological responses of juvenile sea scallops (Placopecten maqellanicus) (Gmelin.) exposed to experimental food rations, that varied in concentration and quality, were evaluated using techniques of physiological energetics. This included: 1) the pre-ingestive feeding activity such as clearance rate, pseudofaeces production and preferential selection; 2) energy gained through ingestion and absorption; 3) energy losses associated with respiration and excretion; and 4) the integration of these energy gains and losses to predict scope for growth. -- To accomplish this, scallops were exposed to laboratory experimental diets with qualities (at 12° C) set at 25%, 50%, and 80% particulate organic material (POM) and diet concentrations set at approximately 1, 3, 7, and 14 mg 1⁻¹ using varying proportions of the microalgal diatom Chaetoceros muelleri and inert silica particles (SiO₂) . These conditions mimicked the range of seston conditions this species is exposed to in the natural environment in eastern Newfoundland. -- Juvenile sea scallops exposed to the above conditions were able to regulate ingestion rate by reducing clearance rate and increasing the amount of material rejected in pseudofaeces, all in order to maintain a high absorption efficiency. An increase in scope for growth by this species with particle concentration was facilitated by maintaining relatively constant oxygen consumption and ammonia excretion rates. -- P. maqellanicus showed no relative difference in scope for growth at concentrations greater than 3 mg 1⁻¹ when fed a 50% organic mix of algae and silica when compared to a ration consisting of 80% organic content (i.e. 100% algae). A direct grow out experiment would be required to confirm that scallops could grow as effectively on a 50% diet as on an 80% diet, but these results suggest the cost of rearing algae and the hatchery/nursery stage of culturing this species of scallops could be reduced by supplementing algal food with inorganic particles such as silica.

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