Development of larval culture techniques for the shore crab, Carcinus maenas (L)

The shore crab Carcinus maenas is a commercially important species, utilised as sea angling bait as well as supporting a European-wide fishery. Hatchery production could provide an alternative source of bait crabs, alleviating potential competition between these sectors and environmental concerns regarding bait collection practices. A series of experiments were carried to investigate the potential for hatchery production, focusing on effects of dietary regimes and stocking densities through the zoeal stages and the influence of tank substrates and stocking density during the megalopa stage. Inclusion of the rotifer Brachionus plicatilis as live food for early larval stages conveyed no advantage in terms of survival or rate of development compared to a diet of Artemia nauplii. Increasing zoea stocking densities (from 94 to 557 l(-1)) had a significantly negative effect upon survival to the megalopa stage (from 75% down to 47%), although this was off-set by a significant increase in production, with 260 megalopae(-1) produced from an initial density of 557 zoeae l(-1). The inclusion of substrates for megalopa stages had no impact on production or development rate, compared to tanks with no substrate. The completely benthic behaviour of megalopae indicates that tank floor area will be a limiting factor for crab production. Increasing stocking density of megalopae was found to significantly and negatively influence survival, although above 10,000 megalopae m(-2) the rate of decline in survival stabilised and maximum production (3,114 juveniles m(-2)) of juvenile crabs could be achieved at the highest stocking densities tested (40,000 m(-2)).