Effects of angling on post-release mortality, gonadal development and somatic condition of Australian bass Macquaria novemaculeata.

This study assessed the protracted effects of two angling treatments (mild and harsh) on the post-release mortality, gonadal development and somatic condition of Australian bass Macquaria novemaculeata in a pond-based experiment. Angled fish were destructively sampled (along with controls) three times: immediately before, and 1 or 4 weeks after release into cages. Compared with the other groups, harshly angled fish had similar, low immediate and short-term mortalities (< or =5%), but significant delayed mortality (25%) and fed only minimally. None of these fish ejected ingested hooks. Forty-six per cent of captive fish (across all groups) and 20% of wild fish had non-ripening gonads (stage I) prior to, or during, the experiment. In females with ripening ovaries (stages II or III), neither angling treatment significantly reduced standardized gonadal mass. The mean per cent of atretic oocytes increased among females in all groups, but was significantly greater in those that were harshly angled. The results demonstrated that the gonadal development of M. novemaculeata could be suppressed or impaired (by angling, handling and confinement), and that further research is warranted. In particular, the timing and severity of angling in relation to the stage of gonadal development could have important implications for the introduction of temporal restrictions to angling.