For a fish as prevalent and important as the West Australian Dhufish, its offspring have remained under the research radar for a remarkably long time.
Endemic to Western Australia, the Dhufish (Glaucosoma hebraicum) is a favourite of recreational and commercial fishers. But, until recently, little was known about its eggs or larvae, which had not been found in the wild.
Now, a groundbreaking study has combined the techniques of hydrodynamic modelling, plankton sampling and near realtime DNA-based identification to locate, identify and assess the biomass of Dhufish eggs and larvae at two sites off the coast of south-west Australia.
Researchers hope that improved understanding of the biomass and movement of Dhufish eggs and larvae, and their recruitment into adult fish stocks, will enable sustainable management of Dhufish fisheries.
Together with snapper, Dhufish account for about half the commercial catch from the West Coast Demersal Scalefish (Interim) Managed Fishery, with a commercial value estimated at more than $2.4 million.
Evidence is emerging that Dhufish stocks are not as healthy as they once were. Both commercial and recreational fishers are having to move further offshore to catch Dhufish, suggesting that populations have decreased in shallower waters. The fish that are being caught tend to be younger, indicating that the proportion of older fish is decreasing. Data also suggests that fishing mortality in Dhufish populations is outstripping natural mortality, raising concerns about the long-term sustainability
of the fishery, which has led to recent changes to demersal species fishing regulations.
With these factors in mind, a team of researchers from CSIRO Marine and Atmospheric Research (CMAR) and the Western Australian Department of Fisheries set out to find the eggs and larvae of West
Australian Dhufish in the wild for the first time. Read more here (pdf file, article begins on page 20).