Factors influencing the growth rate of juvenile rock lobsters, Jasus lalandii

Environmental conditions for juvenile spiny lobsters can vary spatially, interannually, and seasonally. We examined both field and aquarium data to elucidate some of the most important factors influencing somatic growth rates of juvenile Jasus lalandii. Growth increments of juveniles were determined at two sites in Table Bay, South Africa. Premoult individuals were captured and held in aquaria until they moulted. In addition, growth rates of small, medium, and large juvenile lobsters were monitored in aquaria under approximately ambient conditions for nine months. A separate aquarium experiment addressed effects of temperature. Moult increments at the two field sites varied significantly with season (highest in winter, lowest in spring), and month and site interacted. Temperature and diet affected grow-out significantly. Tagging and limb regeneration slowed grow-out. The 10degreesC and the 15degreesC experimental groups did not differ significantly in mean moult increment, but intermoult period at 15degreesC was 50% shorter, so lobsters at 15degreesC grew faster. Temperature affects intermoult period but, provided food is not limiting, does not appear to affect moult increment (within normal temperature range). In the wild, however, moult increments can vary up to twofold with season, probably at least in part because of seasonal temperature variation.