Finding their way in the world: Using acoustic telemetry to evaluate relative movement patterns of hatchery-reared fish in the period following release

Abstract

Patterns in space use and activity were compared for wild and hatchery-reared Mulloway (Argyrosomus japonicus) using acoustic telemetry. Acoustic tags were implanted in four wild (42±2cm; mean±SE), and four hatchery-reared (42±1cm; mean±SE) Mulloway, and movements were simultaneously monitored for up to 288h in an 11km section of river. Across all fish, space utilisation contours developed from weighted kernel density estimates ranged between 2–51ha (90% or total area) and 1–28ha (50% or core area), and contained up to 99% optimal habitat area. Hatchery-reared fish used significantly larger total and core areas, and activity rates of hatchery-reared fish were consistently higher than wild fish. A period of settlement or acclimation appeared to occur during the first 5days following release for hatchery-reared fish, and their movement tended to contract back to within the habitat patch into which they were released from the 6–12th day following release. The movement ranges of wild fish were largely invariant between the two periods. The relevance of this research to understanding broader ecological processes is discussed. Acoustic telemetry presents a useful approach for studying post-release dynamics of hatchery-reared fish and their wild counterparts.