Summary

Although the longfinned river eel is the target of a significant trap and fyke net fishery in eastern Australia, no studies have focussed on the differences in sex ratios, age, size and abundance of populations within and between coastal catchments.  In this study, eels were caught from three river systems (Hacking, Hawkesbury and Clarence) in NSW, Australia, between 1999 and 2001.  Catch per unit effort (CPUE) data showed that greater numbers of eels (predominantly female) were captured per trap in upper freshwater areas compared to lower, tidal, marine habitats.  The greatest concentration of males were found in the brackish upper tidal areas in each catchment.  Eels captured in the non-tidal freshwater areas were larger and older than those in the lower tidal areas.  This is due to the increasing proportions of females upstream and their longer residence time in fresh water compared to the earlier outward migration of younger, smaller males from tidal areas.

Differences in size and sex ratios between males and females indicates that habitat refuges and the application of appropriate size at capture restrictions are essential to ensure future male and female reproductive success.  Increasing the minimum size limit to 58cm would be acceptable to conserve male stocks which reside primarily in tidal waters where commercial fishing activity is focused.  It is also important to maintain the current closure of non-tidal flowing freshwaters in NSW to provide refuge for the older, larger and potentially highly productive females.