Temperature effects on the molting, growth, and lipid composition of newly-settled red king crab

Abstract

Red king crab (RKC) ( Paralithodes camtschaticus Tilesius, 1815) is one of the most important fishery resource species in Alaska. It is threatened by heavy fishing pressure and changing climate conditions, yet little is known about the species' first year of post-settlement life. This study was undertaken to explore how temperature mediates growth and energy allocation in newly metamorphosed juveniles. RKC were reared using four temperature treatments ranging from 1.5° to 12 °C for a period of 60 days, both individually and in low-density populations. Temperature had no significant effect on survival of RKC, and there was no consistent difference in survival between individually cultured crabs and those in populations. Growth was very slow at 1.5 °C, and increased rapidly with temperature with both a contracted intermolt period and small increase in growth increment. Twenty percent of the crabs held at 1.5 °C never molted, while more than 90% of the crabs in 12 °C reached juvenile stage 4 or higher. Overall growth increased as an exponential function of temperature, with slightly higher growth rates observed in populations than for isolated individuals. Growth records for individuals revealed an inverse exponential relationship between water temperature and intermolt period. There was also a small increase in growth increment from juvenile stage 1 to stage 2 with increasing temperature that appeared to be linear. Lipid class analysis revealed a trend towards higher proportions of storage lipids in larger crabs cultured at 12 °C than in crabs cultured at low temperatures. High proportions of essential fatty acids in all crab groups coupled with elevated levels of triacylglycerols in 12 °C animals, indicate that rapid growth does not negatively affect condition in juvenile RKC. Data provided by this study will help to model temperature-dependent growth and survival in the field, and assist in designing the best possible temperatures and diets for hatchery production of seed stock intended for enhancement of depleted RKC stocks.