Implications of habitat use and movement of stocked juvenile dusky flathead (Platycephalus fuscus) on stock enhancement release strategies

Abstract

Stocking of marine fish into coastal systems to augment natural recruitment is a growing practice adopted by fisheries managers around the world. Releasing fish directly into well-resourced nursery grounds greatly increases survival and retention of stocked individuals but requires an understanding of juvenile habitat requirements. In eastern Australia, the dusky flathead (Platycephalus fuscus) is a highly regarded recreationally targeted species and the focus of an emerging stock enhancement programme, although little is known of their specific nursery habitat. Using acoustic telemetry, hatchery-reared juveniles were monitored in Lake Macquarie to quantify habitat use and dispersal. Sandy areas adjacent to edges of seagrass beds were favoured, likely as foraging habitat. Within 5 weeks after release, fish were detected 5 km from the release site, but only at locations containing seagrass beds, so stocked fish likely disperse around estuaries to regions with suitable habitat. Future releases of dusky flathead should target areas containing patchy seagrass-sand to optimise stocking outcomes. Beyond fisheries enhancement programmes, our findings highlight the importance of structured habitat, such as seagrass beds, for juvenile fish.