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Is Anguilla reinhardtii Really a Freshwater Eel?

Bruce Pease, David Booth and Chris Walsh

NSW Fisheries, CRONULLA, AUSTRALIA

THEME: ASFB

As a member of the family Anguillidae, Anguilla reinhardtii is generally referred to as the catadromous Australian longfinned freshwater eel. We have been conducting biological and ecological studies of this species within coastal catchments in New South Wales since 1998. Fishery dependent and independent sampling programs in the Clarence River, Hawkesbury River and Hacking River catchments reveal significant differences in size structure, age structure and sex ratios between populations from freshwater and estuarine habitats. Sonic tagging studies in the Georges River show that individuals are capable of making short-term movements between fresh and brackish waters. Laser ablation inductively coupled plasma mass spectrometry (ICPMS) analysis of Sr/Ca ratios in otoliths from eels sampled in a wide variety of habitats verifies that some eels move back and forth between freshwater and estuarine habitats during their long period of residence (up to 50 years) in coastal catchments. Others reside in estuarine habitats for many years and may never enter fresh water. Despite the fact that some proportion of the population may reside for long periods of time in fresh water, we conclude that Anguilla reinhardtii is not an obligate catadromous freshwater species. We suggest that terminology such as, 'facultative catadromous river eels', more accurately describes the life-history characteristics of this species.