ASFB Home > The effects of spatial and temporal factors on the abundance of seven key finfish species along south-western Australia.

Dynamics in 0+ recruitment and early life-history for snapper (Pagrus auratus) in South Australia.

Anthony Fowler and P R Jennings

SARDI Aquatic Sciences, HENLEY BEACH, AUSTRALIA

THEME: ASFB

The temporal dynamics of the snapper fishery of South Australia are driven largely by recruitment of occasional strong year classes to the population, and when they become available for capture. In recent years, record fishery catches in Spencer Gulf relate to the superabundant year class that recruited as 0+ fish in 1991. Management of this fishery would benefit hugely from an understanding of the biological and or physical processes that influence the variability in recruitment. This general aim has been addressed by; describing the spatial and temporal patterns in recruitment of 0+ fish, and elucidating aspects of the early life-history and larval and juvenile ecology. In April of 2000, 2001 and 2002 annual recruitment surveys were done in Northern Spencer Gulf, that involved night-time 10 minute otter trawl shots at > 100 stations. Catch rates of 0+ fish varied between years, 67 in 2000, 164 in 2001 and only 8 fish in the last. However, the dispersion of fish was consistent, being found in northern areas that support fine, muddy substratum rather than coarser substrate. Early life-history characteristics were described through interpretation of otolith microstructure of captured specimens, and varied considerably between years. Pre-settlement duration was shorter and growth rate faster in 2000 and 2001 compared with the low recruitment year of 2002. The annual difference may relate to 2002 being the coldest summer on record in South Australia.