Determining biological characteristics of the champagne crab (Hypothalassia armata) for management purposes
Since the commercial catches of the champagne crab Hypothalassia armata are rising sharply, there is an urgent need to ensure that appropriate management arrangements are set in place for this fishery. The information required as the basis for this management is biological data on such features as growth, size composition, size at first maturity, fecundity and yield and egg (or mature biomass) per recruit relationships. There is thus clearly a crucial need to determine the biological characteristics listed below under Objectives (B4).
Final report
During recent years, commercial trap fisheries have developed for the champagne and crystal crabs in deep waters off the lower west and south coasts of Western Australia. Thus, data on crucial aspects of the biology of these species were required to enable plans to be developed for conserving their stocks. No such biological data were previously available.
Commercial catches of champagne crabs in south-western Australia rose from negligible levels in 1990 to peak at ~73 000 kg in 1998 and then declined progressively to ~17 300 kg in 2003, due mainly to fishers on the west coast shifting their effort towards crystal crabs. The catches of champagne crabs underwent a progressive seasonal change, particularly on the south coast where they reflected a decline in fishing effort during the inclement late autumn to middle spring months. Commercial catches of crystal crabs in south-western Australia, which came almost entirely from the lower coast, rose from very low levels in 1997 to reach ~222 000 kg in 2001 and then remained close to this level in 2002 and 2003. Catches and catch per unit effort of crystal crabs remained similar throughout the year. For the fisheries for both champagne and crystal crabs, the mean carapace lengths and catch rates were greater for males than females. Enclosure of traps in fine mesh did not lead to the capture of a relatively greater number of small crabs.