The effect of ration on the growth of pairs of juvenile sea bass Dicentrarchus labrax fed squid mantle was recorded at four temperatures: 6, 10, 14 and 18 C, covering the range typical of Welsh coastal waters. Initial weight of the fish ranged from 2·8 to 15·9 g. A predictive model for the maximum meal size (M max ) at temperatures between 10 and 18 C, accounted for 95% of the variance in lnM max . Even when offered excess food, bass at 6 C had a low rate of food consumption [0·19% body weight (BW) day 1 ] and lost weight (G= 0·04% day 1 ). Predictive regression models for specific growth rate (G) accounted for 86% of the variance at reduced rations and 70% at maximum meals. The relationship between G (calculated for total biomass per tank) and ration was a decelerating curve. G at maximum meals increased with temperature, at lower rations G decreased with temperature. For a pair of bass with a combined weight of 15 g, predicted maintenance ration ranged between 0·7 and 2·3% BW day 1 and increased with temperature. Maximum meal size was more sensitive to temperature than maintenance ration. At 18 C optimum ration was 7·4% BW day 1 . At lower temperatures, the optimum ration was the maximum meal. The maximum gross growth efficiency was 17·4% at 18 C. Mean absorption efficiency was 94·8%. Ration level had no significant effect on absorption efficiency, which was lowest at 6 C. Condition indices (Fulton condition factor, wet and dry liver-somatic indices and body depth index) increased with meal size at all temperatures except 6 C. An increase in temperature between 10 and 18 C generally resulted in a decrease in condition indices at a given ration. When comparisons were made at a given standard length, gut and carcass weight increased with ration. Visceral fat and gut weight decreased with increased temperature. 1996 The Fisheries Society of the British Isles

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