Genetic stock structure of commercially important deep sea crab species
Two deep sea crab species crystal crab (Chaceon albus) and champagne crab (Hypothalassia acerba) are captured by both the West Coast Deep Sea Crustacean Managed Fishery (WCDSCMF) and South Coast Crustacean Managed Fishery (SCCMF). The greatest catches of these two species are landed by the WCDSCMF. As part of the MSC certification process for the WCDSCMF, information is required on the stock structure of (PI 1.2.3) and recent surveillance of this fishery identified; "…there is little information on the stock structure of crabs.... and this may weaken a stock assessment". Therefore information on the genetic stock structure will assist in the stock assessment of crystal crab and future MSC re-certification of the WCDSCMF. The information will also aid in the stock assessment and management of the SCCMF crab fisheries. The recent stock assessment of crystal crab in the SCCMF indicated an unacceptable level of stock depletion. Catches in this area have been highly cyclical unlike those on the west coast. This pattern is very similar to that of rock lobster and blue swimmer crab, whereby the main spawning stock resides on the west coast with large and consistent catches, while those on the south coast are sporadic with recruitment e.g. possibly only flowing down in strong Leeuwin Current years. These south coast areas are considered a resource ‘sink’. Irrespective of the similarities, the south coast deep-sea crab fisheries are still managed conservatively under the assumption of self-recruiting (they are not treated as sink populations). Determination of the recruitment linkages between the west and south coast fisheries will have marked implications on the management arrangement required for both fisheries.
