ASFB Home > 2003 > Biological Invasions: Consequences for Parasites, Pathogens, Emerging Diseases, and Fisheries in the Marine Environment.

Regional scale population structure for snapper in South Australia

Anthony Fowler and Karina Hall

South Australian Research and Development Institute, PO Box 120, Henley Beach 5022, South Australia.
Email: fowler.anthony@saugov.sa.gov.au

In recent years the snapper fishery of South Australia has become a major contributor to the total Australian catch. This State fishery is still managed as a single large stock, despite that regional differences in some population characteristics suggest that a finer scale stock structure may exist. This finding is, however, somewhat inconsistent with the current understanding of the life history of snapper in South Australia, which is thought to involve a complex, age-related migration that would provide significant opportunity for mixing of fish that originate from different regions. These issues constitute the biggest obstacle to determining the best management protocol for this fishery.

This talk and the following one by Dr K. Hall explore the question of whether the South Australian snapper population constitutes a single, large, inter-mixed population or whether it is divisible into numerous smaller, discrete, regional sub-populations. The biological data presented in this talk represent a compilation of regional comparisons for the following parameters: fishery catch statistics; population size structures; length / age relationships; otolith weight / age relationships; and optical characteristics of otoliths. In each case the comparison resulted in a clear regional difference. Clearly, fish collected from different regions must spend substantial parts of their lives occupying different water masses, which is not consistent with the hypothesis of a single, large, inter-mixed population. This hypothesis rejection must be reconciled with the current ‘migration’ life history model, which will be discussed.

Room 3 Thursday 11.30 am