Scale loss and mortality in angled-and-released eastern sea garfish (Hyporhamphus australis)

The eastern sea garfish (Hyporhamphus australis) is an endemic Australian marine teleost that is angled in large numbers throughout its distribution. Most fish are retained, although some are released, mainly because of size-grading in response to bag limits. Owing to their fragility, there are concerns that few released fish survive. To investigate this assumption, 185 angled and 90 control eastern sea garfish were released in groups of five into holding cages, then monitored for up to 24 h. One control and 93 angled fish died, providing an adjusted angled mortality rate of 49.2%. All fish that ingested their hooks (n=7) subsequently died. Generalized linear mixed models for the remaining mouth-hooked garfish revealed that mortalities were mainly caused by scale loss (p<0.01) and air exposure (p<0.05). Further analyses revealed that scale loss most likely occurred when fish were held with dry bare hands (p<0.05), dropped (p<0.05) and exposed to air (p<0.01), or confined in 20-l buckets (p<0.05) for long periods. Air exposure was not significantly affected by any of the variables. Magnetic resonance imaging of 10 live and 5 dead angled-and-released fish revealed no significant differences in dermal damage, although the fatalities typically had greater abrasions than the survivors. The results demonstrate that the fate of eastern sea garfish can be improved significantly if they are released quickly, without physical contact. This protocol could have similar utility among other released species with deciduous scales.