Stock structure of Australian herring ( Arripis georgiana) in southwestern Australia

Abstract

Arripis georgiana is a commercially and recreationally important nearshore pelagic fish distributed along southern Australia. Presently, the fisheries in each state are managed independently and stand to benefit from improved understanding of the biological stock structure of this species. Three stock delineation techniques were used to examine the stock structure, mark/recapture, allozyme electrophoresis and stable isotope analysis of otolith carbonate. Tag recaptures revealed that adult fish tagged on the western south coast of Western Australia in autumn, predominantly migrate to the west while fish tagged along the lower west coast of Western Australia were all recaptured locally. Electrophoretic results indicated negligible genetic differentiation between populations covering over 4800 km of coastline (overall F st=−0.0007). Oxygen isotope ratios of the otolith carbonate revealed that, in general, the fish had not spent their entire life in the waters where they were captured. These results support the single stock hypothesis and provide evidence that Australian herring is a migratory species, with a westward migration along southern Australia to the lower west coast of Western Australia prior to spawning. Management of this species should be considered in a cooperative interstate framework.