ABSTRACT: To determine characteristics which may reflect the behavioral quality of red tilefish Branchiostegus japonicus after release, five wild and four hatchery-reared fish were observed in a laboratory and in the sea. The diel activity of the fish was recorded on video tape for 2 days in a tank, where the light condition was regulated to vary periodically over 24 h. The individuals were then released in Maizuru Bay and tracked using acoustic telemetry. Four wild individuals became most active at dawn during a day in the tank, and settled near the release area to stay for 28–104 days after release in Maizuru Bay. In contrast, one wild and four hatchery-reared individuals were not active at dawn, and then did not settle in Maizuru Bay after release. Among the four settled wild individuals, the more active a fish had been in the tank, the more distant the individual moved from the release point until its settlement. The diel activity pattern should be a factor deciding whether red tilefish would settle nearby after release, and the relative amount of activity during rearing is probably related to the degree of dispersion within the release area.
Fisheries Science 06/2007; 73(3):500 - 511. · 0.94 Impact Factor
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 2–4days 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 2km of the release point for 21–200days whilst 11 wild and 6 hatchery-reared fish were detected in the
central part of the bay within 13days. 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 (0–0.1μmolm−2s−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.
Hydrobiologia 04/2007; 582(1):109-120. · 1.78 Impact Factor
ABSTRACT: In order to establish techniques for the stock enhancement of red tilefish Branchiostegus japonicus, it is important to understand the behavioral characteristic of both hatchery-reared and wild fish. Four hatchery-reared and six wild fish were released and tracked using acoustic biotelemetry in Maizuru Bay, Kyoto, Japan, from August 2003 to February 2004. Data for the four wild fish released and tracked from January 2003 to May 2003 were also referred to for analysis. The released fish moved around in relatively large areas within about 10 days after the release, and then three hatchery-reared and two wild fish settled and stayed within limited areas. Fish of both origins showed strong site fidelity and diel activity patterns, i.e. they were detectable in the day but not at night, probably due to hiding behavior in their burrows at night. However, some discrepancies between fish of both origins were detected by comparing their track terms and activity patterns in detail. These discrepancies are probably attributable to the differences in environmental conditions that the fish had experienced before release.
Fisheries Science 06/2006; 72(3):520 - 529. · 0.94 Impact Factor