Temperature-dependent metabolic response of juvenile Dungeness crab Cancer magister Dana: ecological implications for estuarine and coastal populations

Abstract

Oxygen consumption ( Q o 2) of juvenile Dungeness crab Cancer magister Dana in two age groups, 0 + crab [6–16 mm carapace width (CW), 8–116 mg AFDW] and 1 + (35–104 mm CW, 1.03–21.50 g AFDW) was measured at four temperatures of 6, 10, 14 and 18 °C which span seasonal and geographical ranges measured in the Grays Harbor estuary and along the nearshore open coast. Metabolic rate of 0 + crab was significantly higher than Q o 2 of 1 + crab at all temperatures except 18 °C. The pattern of change in Q o 2 of 0 + crab was an increase from 6 to 14 °C but no change from 14 to 18 °C, which is consistent with estuarine residence on intertidal flats where temperatures can be toward the high end of the range. Q o 2 of 1 + crab was more stable at low temperatures ( Q 10 6–10 ° C ≈1) and is consistent with emigration from the estuary to colder coastal water as animals approach a size near sexual maturity. The pattern of increased Q o 2 with temperature is in accord with a marked difference in growth rate of 0 + crab of the same year class that settle during June in estuaries or along the coast and are ≈35 and 14 mm CW, respectively, in September. Metabolic rate of 0 + was not weight-dependent but that of 1 + crab was best described by the quadratic equation: log e Q O 2 − aT 2 − bT log c W − cT + d. Predicted metabolic rates over the range of 6–18 °C showed that, even within the same age class, smaller crab (2 g) have much higher Q O 2 than larger animals (16 g) by 18 °C.