Hatchery-reared fish have less consistent behavioral pattern compared to wild individuals, exemplified by red tilefish studied using video observation and acoustic telemetry tracking

Abstract

The behavior of wild and hatchery-reared red tilefish Branchiostegus japonicus was analyzed using two different methods: video observation and acoustic telemetry tracking. In the laboratory, digging and swimming activity of seven wild and five hatchery-reared fish were recorded for 2–4 days in an experimental aquarium and related to changes in light intensity. The activity of wild individuals increased with light intensity, while hatchery-reared individuals were active during both day and night. In the field, 18 wild and 9 hatchery-reared fish were released and tracked using an acoustic telemetry system during the winter and the summer in Maizuru Bay, Kyoto (Japan). Seven wild and three hatchery-reared fish settled within 2 km of the release point for 21–200 days whilst 11 wild and 6 hatchery-reared fish were detected in the central part of the bay within 13 days. The settled fish demonstrated a diel pattern of behavior; most of them probably stayed outside their burrows in the daytime but inside their burrows during the nighttime. During the winter wild fish tended to stay near the release site for longer periods than the hatchery-reared fish. However, in summer the hatchery-reared fish tended to remain close to the release site for longer than the wild fish. Based on these two experiments, we suggest that the activity of wild red tilefish respond to changes in low levels of light intensity (0–0.1 μmol m −2 s −1 ) at dawn and display a diel behavior. Hatchery-reared fish may differ from wild fish with regard to their behavior, response to water temperature and light conditions.