Theme D: Developing optimal release strategies
43. SITE FIDELITY AND MOVEMENT OF HATCHERY-REARED LINGCOD RELEASED INTO PUGET SOUND, WASHINGTON, USA
Jonathan S.F. Lee, Eugene P. Tezak, Barry A. Berejikian
NOAA Fisheries, Manchester Research Station, 7305 Beach Dr E, Port Orchard, WA 98366, USA
Jon.Lee@noaa.gov
Lingcod (Ophiodon elongatus) is a strongly piscivorous species that can exhibit strong site fidelity after recruiting to rocky reef habitats. Lingcod are highly-sought targets of recreational fishermen in Puget Sound, Washington, USA because of their large size and flesh quality. Population declines in lingcod and other species have prompted strong fishing restrictions in Puget Sound and beyond. The release of hatchery-reared lingcod may be a viable means to bolster the wild population. However, development of a stock enhancement program requires a cautious approach that includes releasing small numbers of fish and monitoring their impacts on natural lingcod and other imperiled species.
A Before-After-Control-Impact (BACI) experimental design is planned to quantify the potential costs and benefits of lingcod stock enhancement. Hatchery lingcod will be released at two sites in Puget Sound. To determine the impacts of releases on wild fishes, the abundance and diversity of wild fishes will be monitored at the two release sites, and compared to two control sites where no hatchery lingcod are present. Conducting a valid BACI experiment requires distinct “control” sites with no hatchery-released fish present and “impact” sites with hatchery-released fish present. However it may be difficult to create “impact” sites if released lingcod quickly disperse away from impact sites or to control sites.
To determine the optimal release conditions that would maximize site fidelity, hatchery-reared lingcod were released at different ages, seasons, and habitats. To avoid contamination of future control sites, less than 150 lingcod were released, but each was implanted with an acoustic telemetry tag. A tag-effects study indicated that the telemetry tags do not affect movement behavior. Mobile tracking was conducted to quantify site fidelity and movements away from the release site. The poorest site fidelity was observed in the two youngest release groups (approximately 9 and 11 months post-hatch; Figure 1). Approximately one year after release, 4% and 4% of these two subyearling release groups were detected within three-km of the release site while 17% and 16% were detected further away. Seventeen-month-old lingcod that were released in the summer showed the best site fidelity, with 23% remaining within three-km of the release site one year after release. None of the 17-month-old lingcod were detected further away while mobile tracking approximately one year after release, suggesting that this release age and season may be best suited for the future BACI experiment. We will describe movement patterns of individual fish to provide some insights into the behavioral mechanisms that may cause subyearling and yearling lingcod to differ in distributions one year after release, and also compare these release groups to four-year-old lingcod released at similar sites. Hatchery lingcod behavior will be compared to published studies on wild lingcod behavior.
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