GROWTH AND CONTENT OF ENERGY RESERVES IN JUVENILE SEA SCALLOPS, PLACOPECTEN-MAGELLANICUS, AS A FUNCTION OF SWIMMING FREQUENCY AND WATER TEMPERATURE IN THE LABORATORY

The effects of swimming frequency and water temperature on shell growt h, tissue mass, and stored energy reserves of juvenile sea scallops, P lacopecten magellanicus Gmelin, were examined in a factorial laborator y experiment spanning six weeks in July and August 1992. Individually tagged scallops of similar initial size (22.5 +/- 0.1 mm shell height, n = 240) were induced to swim to exhaustion at three different swimmi ng frequencies (every day, twice a week, or not at all) in two differe nt water temperature regimes (4 to 7 or 7 to 13 degrees C). The scallo ps were fed an ad libitum mixture of cultured microalgae. At the end o f the experiment, cumulative increase in shell height, dry weight of s oft tissues, condition index of dry adductor muscle (adductor muscle d ry weight/soft tissue dry weight x 100) and total carbohydrate content of dry adductor muscle were measured for each scallop. Scallops at th e higher temperature had significantly greater shell heights, and were in better metabolic condition as evidenced by significantly higher co ndition indices and muscle carbohydrate contents. The dry soft tissue weights did not differ significantly from their low temperature counte rparts, Swimming frequency had no significant effect on shell height, dry tissue weight, or carbohydrate content, but condition index of the adductor muscle increased significantly with swimming frequency. Thes e results show that not only was there no cumulative cost of swimming in terms of shell growth, total soft tissue weight, or carbohydrate co ntent in young scallops, but that condition of adductor muscle tissue was higher in scallops that swam.