Monitoring by telemetry reveals differences in movement and survival following hatchery or wild rearing of an endangered fish

Abstract

Species reintroduction is a management strategy used to conserve endemic fish biodiversity. The present study investigated stocking on-grown endangered trout cod (Maccullochella macquariensis) in the Murrumbidgee River, Australia. The hypothesis that post-juvenile dispersal underpins the long-term scarcity of adults recorded at fingerling stocking locationswas also tested. Radio-trackingwas used to quantify dispersal of stocked sub-adults (2-year old hatchery fish, n=27) compared with fish originally stocked as fingerlings (unknown-age wild fish, n=31), but we encountered poor survivorship of the former group (survivorship=9% and 95%, respectively, at 13 months post release). The hatchery group exhibited both limited dispersal and large-scale dispersal (up to 55 km) downstream from the release site. Wild fish exhibited limited net dispersal, occupying home-ranges within a 13-km reach and occasionally undertook large-scale excursions (10–70 km). It is concluded that (1) re-establishment of cod populations based on release of on-grown fish is not straightforward, and (2) adults of this species have an ability to disperse away from stocking sites. The study demonstrates the benefit of using radio-tracking to monitor the movement and survivorship of stocked threatened fish and indicates a need to consider the effects of hatchery rearing when conducting fish reintroductions.