ASFB Home > Potential Changes in Prey Population Structure Following Removal of Predators by Fishing

Is There a Place for Aquatic Protected Areas in the Management of Small Pelagic Fish in Coastal Waters?

Daniel Gaughan

Department of Fisheries Western Australia, NORTH BEACH, AUSTRALIA

Theme: TH1

Sardinops sagax occur in a continuous distribution, but with uneven abundance, along the south coast of Western Australia (SCWA); stocks are very small by global standards and are exploited from three distant ports along the SCWA. Mixing of adult Sardinops along the SCWA is insignificant. The same has not been found for juveniles, whose spatial relationships remain problematic. An ecosystem-level “experiment”, in which the southern Australian population of Sardinops suddenly and dramatically decreased in size by 70% due to mass mortality, permitted otherwise unattainable observations. Recovery of the Sardinops stocks along the SCWA progressed east to west; spatial patterns in timing and magnitude of recovery indicate that the more western locations were seeded with recruits from the eastern regions. Adults breeding in the eastern region were able to contribute to the recovery in all regions because they suffered less-exploitation during the decade preceding the “experiment”. The less exploited part of the continuum of non-mixing adult Sardinops has apparently acted as a reserve-breeding-stock. The combination of small stocks with limited alongshore mixing and areas of coast not accessible to fishing has resulted in a default aquatic protected area (APA) that has already benefited the pelagic ecosystem off southern WA. Examples of exploited stocks for which unfished portions act as default APA need to be identified, catalogued and subjected to meta-data studies so as to search for those similarities that provide an indication of what works (e.g. relevant spatial scales) when planning APAs.