Tagging investigations with small estuarine-associated fish: tag evaluation, capture methodologies and assessment of capture stress and survival in yellow-eyed mullet Aldrichetta forsteri

Abstract

Estuarine ecosystems present a dynamic and often biologically challenging marine environment. Resident and migratory fish occupying these environments must cope with a multitude of variations associated with physiochemical characteristics, interspecies interactions, environmental degradation and variable feed availability. Using the yellow-eyed mullet Aldrichetta forsteri as an exemplar of many other small-bodied, estuarine-inhabiting fish, we sought to assess the suitability of an array of different tag types in tank-based experiments. The survival consequences of wild capture, handling and tagging procedures were then investigated using condition and reflex impairment criteria and simulated release. It was determined that T-bar and passive integrated transponder tags were suitable tag types, but that tagging fish smaller than 50g (~170mm) was detrimental to survival. Using a ‘low-impact’ trap design improved post-capture tagging and survival compared with an alternative capture method. In combination, the possibility of using small-bodied fish for tag–recapture studies is demonstrated and the utilisation of comparable fish for investigations into estuarine population dynamics and ecosystem interactions is advocated.