Bight redfish (Centroberyx gerrardi) and deepwater flathead (Neoplatycephalus conatus) are the two principle commercial species captured along the continental shelf of the Commonwealth managed Great Australian Bight Trawl Fishery worth an estimated $7 million per annum.
Current assessments, based on available data, indicate that Bight redfish fishing mortality is rising and likely to reduce the biomass to below the trigger biological reference point. The outcomes of stock assessments are highly sensitive to the shape of the maturity ogive and fecundity-length/age relationships. Given the current high uncertainty about the validity of existing Bight redfish and deepwater maturity and fecundity relationships, GABFAG has recommended that these be determined with high priority. More scientifically defensible maturity ogives and fecundity-length and fecundity-age relationships will markedly reduce uncertainty in the stock assessments.
This project addressed some of the important information gaps identified during assessment workshops for Bight redfish and deepwater flathead. Improved stock assessments, which incorporate the latest biological parameters (size-at-maturity, fecundity and sex ratio), has lead to the setting of accurate Bight redfish and deepwater flathead TACs. Gear regulations have been proposed that include minimum mesh sizes and T90 extensions, which along with reducing discard species, allow small deepwater flathead to escape capture, and thereby increasing reproductive capacity of the flathead population.
This information has been provided to Great Australian Bight Fisheries Assessment Group (GABFAG) as part of formal and informal reporting arrangements. It has also been distributed to the public via media releases.
Keywords: Bight redfish, Centroberyx gerrardi, deepwater flathead, Neoplatycephalus conatus, eggs per recruit, fecundity, reproduction, size- and age-at-maturity, spawning