Stock enhancement programs of the spotted halibut (Verasper variegatus) have been ongoing in Japan for its rarity and commercial value. Acoustic telemetry was used to estimate the post-release movement and predation of hatchery-reared juveniles, which is known to be critical for successful stocking. From 2023 to 2025, a total of 160 hatchery-reared juveniles (95–108 mm in total length) were tagged with V5D acoustic transmitters (Innovasea, USA), which can detect predation events involving tagged fish. Each year, 40–80 tagged fish were released together with 6,500–10,000 untagged fish, in a harbor located midway of a channel between a lagoon and the Pacific Ocean. The tagged fish were tracked with stationary VR2W receivers (Innovasea, USA). We monitored the dispersal of the tagged fish from the location of release, and their subsequent movement into the lagoon or the sea. We also evaluated the predation rates of tagged fish by three predator types: piscivorous fish, birds, and crustaceans, based on detected predation events and movement patterns. This study highlights the need for the monitoring and avoidance of post-release predation on stocked fish by multiple predator types in marine stock enhancement programs.
Sumino et al. (Wed,) studied this question.