Effects of temperature on growth of juvenile snow crabs, Chionoecetes opilio, in the laboratory

Abstract

The effect of water temperature on the growth of juvenile snow crabs Chionoecetes opilio (Fabricius, 1788) was investigated in laboratory culture experiments. Laboratory-born juveniles were cultured from instar I to VIII at four temperatures (approximately 1, 3, 5 and |$8^\circ {\rm{C}}$|⁠). The growth indices (size increments at moulting in mm and in % of premoult carapace width) were significantly higher in crabs reared at |$5^\circ {\rm{C}}$| than in those reared at other temperatures. The relationship between the mean temperature |$(T)$| and intermoult period |$(D)$| of each instar was described by the heat summation theory equation: |$D = K / \left( {T - \alpha } \right)$|⁠. The thermal constant |$K$| is the summation of the effective temperature for development (above the threshold temperature, |$\alpha $|⁠) up to a selected biological end point. The thermal constant tended to increase and the threshold temperature tended to decrease with increasing mean premoult carapace width of each instar, reaching asymptotes of 1573 day-degrees and |$ - 4.7^\circ {\rm{C}}$|⁠, respectively. Size- and temperature-dependent growth models were developed for snow crab juveniles.