Radio-tagging and tracking of translocated trout cod (Maccullochella macquariensis: Percichthyidae) in an upland river

Abstract

Radio-tracking provides an effective means of studying the spatial ecology of threatened fishes where almost inaccessible habitats and species rarity render conventional mark–recapture methods impractical. Initially, validation of an effective radio-tagging method is required; in the present study, an aquaria trial based on nine hatchery-reared, adult male Maccullochella maquariensis (Percichthyidae) was conducted. Fish resumed feeding within days of being internally implanted with a radio-tag, and tag rejection was not observed (0%, n = 9) based on a 2-month observational period. Following release into an upland stream, individual-specific movements resulted in upstream (n = 1) and downstream (n = 6) dispersal as well as fidelity to the release site (n = 2) at the completion of the study. Individuals established small home-ranges (mean length of river used by an individual per diel period ranged from 47 to 292 m) and were most active in the early morning and evening (n = 6). Complete survivorship of individuals bearing active radio-transmitters (n = 8) was recorded up until 4 months after release. However, an estimated zero or one individual was alive when the last active radio-tag expired 11 months after release (n = 8). The present study highlights the use of radio-tracking in monitoring the dispersal and survivorship of small numbers of hatchery-reared threatened fish released into natural habitats as part of species re-introduction programs.