Effect of temperature and ration on growth and condition of king scallop ( Pecten maximus) spat

Abstract

Hatchery-reared king scallop ( Pecten maximus L.) spat (5–14 mm shell height) were held in mesh-based Perspex cylinders suspended in 2.5 l beakers of seawater. This seawater was maintained at eight temperatures (5°C–23°C inclusive), and various rations (0.012–0.492 g (organic weight of algae) g −1 (live weight of spat) week −1) of a diet consisting of a mixture of Pavlova lutheri (Droop) Green and Chaetoceros ceratosporum Ostenfeld were fed. Size of the animals was estimated weekly by computer analysis of video images taken of the scallops in the cylinders while in seawater. The relationship between temperature and food ration was evaluated. As temperature increased, the scallops consumed a bigger ration, and the highest ration that they consumed efficiently determined their maximum growth rate. This ration, and the corresponding growth rate, both increased with temperature. At the end of each 3–4 week experiment, the condition (ratio of dry meat weight to dry shell weight) of the spat was estimated. Condition was greatest between 10°C–17°C and least below 8.0°C. Condition decreased with lower rations at all temperatures above 10°C. Comparison of results with preliminary observations made at commercial scallop cultivation sites suggest that temperature rather than food is the factor most often limiting for growth in the sea.