Suitability of saltmarsh creeks as release locations for stocked Mulloway (Argyrosomus japonicus)

Abstract

Enhancing local marine fish population through stocking programs is widely undertaken around the world. The family Sciaenidae is particularly well represented in marine stocking programs where they are released to enhance both commercial and recreational fisheries. In Australia, a stocking program of the sciaenid Mulloway (Argyrosomus japonicus) is currently underway with fingerlings being released into deep water habitat within estuaries. However, many estuaries also contain fringing saltmarsh and mangrove creeks which may provide resource-rich release habitat locations. To examine the suitability of marsh creeks as stocking sites, we used acoustic telemetry and monitored the habitat use and movement of 30 hatchery reared fish, released into wetlands of the Hunter River estuary. After initially rapidly dispersing the region covered by the array due to high salinities, some fish returned when physicochemical conditions improved. Despite being detected within the array almost daily for four months, none of the returned fish ever re-entered the marsh creeks. This study confirms releases of juvenile Mulloway should continue to focus on deeper waters which appears to be provide nursery habitat for this species. More broadly, this shows stocked fish will seek out better resourced habitats, and an understanding of these requirements which informs release strategies that place fish as close to these habitats as logistically possible would optimise stocking outcomes.