fact sheets - GEMFISH
HSI has nominated gemfish for listing as a threatened species under the Commonwealth Environment Protection and Biodiversity Conservation Act, and also under the NSW Fisheries Act. We expect a decision from the Federal Environment Minister on listing by the end of 2003.
Gemfish Rexea solandri, also known as hake, king couta, or kingfish, live in relatively deep water (300-600m) on the upper continental slope off southern Australia and New Zealand.
They are large, predatory species, which grow to about 1.2m in length and a weight of about 12kg. They mature at 4-6 years of age (60-70cm in length), and the majority of fish in the breeding population range from 4 to about 8 years of age.
Four separate populations of gemfish are recognised. Two populations occur in Australian waters, an eastern stock ranging from Tasmania to northern NSW and a western stock in the Great Australian Bight and WA waters. There are also two populations in New Zealand waters. Fish from each stock, spawn in a short, well defined season each year, and the four stocks are considered to be distinct breeding populations.
Each mature female gemfish is capable of producing between 0.5 and 6 million eggs in a spawning season. Little is known of the breeding biology of gemfish, or the environmental factors influencing spawning success and larval survival. Despite their high reproductive capability, three of the four stocks appear to have suffered major declines due overfishing and their failure to produce sufficient numbers of young fish.
There has been a steady and significant reduction of the Eastern Gemfish stock in NSW. The cause for this decline has been unsustainable levels of commercial fishing in both Commonwealth and NSW managed fisheries
Years of targeted fishing of the eastern gemfish have resulted in the significant reduction in the eastern stock. An assessment suggests that the spawning biomass was less than 40% of the 1979 level. All scenarios indicate that the biomass of the mature eastern gemfish is still declining, as trawlers continue to catch large quantities of juvenile fish as bycatch, before they are able to mature and contribute to the spawning population.
Eastern gemfish are particularly vulnerable to over fishing as the majority of the catch is taken during their northward migration to the spawning grounds. During this migration, the fish form a narrow band, the so-called gemfish run, which is easily targeted. Targeted fishing for eastern gemfish commenced in about 1970, when trawlers began fishing new grounds along the continental slope. Fishers saw high catch rates as indicative of high fish abundance rather than of high vulnerability to fishing.
Recreational and charter boats are also responsible for fishing gemfish on certain grounds.
Quantities of gemfish continue to be caught incidentally as bycatch in commercial fisheries.
Unless the factors threatening the species are removed, the stock is unlikely to recover. The very restricted spawning period and location makes the species vulnerable to environmental variability, which a large robust population would be able to withstand.
Current management arrangements are not allowing the Eastern Gemfish stock to recover. HSI believes that the species needs to be listed as endangered and a Recovery Plan formulated to protect the eastern gemfish from reaching levels beyond which it will never recover.