Gulf of Alaska | Fishes and Fish Habitats
Maximizing success of red king crab stock enhancement in Kodiak, Alaska Presenter: Chris Long , chris.long@noaa.gov, NOAA Alaska Fishery Science Center Peter Cummiskey , kayakampers@gmail.com Eric Munk , emunk@gci.net Ben Daly , ben.daly@alaska.gov
Red king crab, Paralithodes camtschaticus , was commercially important around Kodiak, Alaska, USA in the 1960s and 1970s; however, the stock crashed in the late 1970s and has failed to recover despite the commercial fishery being closed since 1973. The use of hatchery-reared juveniles has been considered to help bolster the wild population. In two different release experiments, both performed in Trident Basin, Kodiak, we examined factors that may contribute to enhancement success. In the first experiment, we examined the effects of release density on in situ survival of hatchery- reared red king. Juveniles were released at three densities, 25, 50, and 75 m-2. In the second experiment, we examined the effects of release season and size. Juveniles were released at three times, June, August, and September with the size at release increasing from June to September. We monitored densities inside and outside of release plots after release using quadrat counts to determine loss and emigration rates. Relative predation risk was determined using tethering experiments repeated 3 times after release, and predator densities were quantified using quadrat counts and predator transect counts in both experiments. In the first experiment, initial mortality over the first 24 h was approximately 68%. Loss rates after the initial mortality did not differ among density treatments and were a combination of mortality and emigration. Relative predation risk of tethered crabs decreased with time from release, but did not vary among density treatments. Predator density did not vary over time or with density treatment. In the second experiment, initial mortality over the first 24 h was 53%. Mortality rates decreased from the June to the September releases and migration rates increased. Similar to the first year, predator density did not differ among release treatments and predation risk decreased after August. Although mortality decreased with release season, including mortality from laboratory holding suggests that earlier release timings are the best strategy to minimize overall mortality. Estimates suggest mortality rates of hatchery-reared juveniles are variable, but similar to that of wild individuals in a commercially harvested population in southeast Alaska, indicating that stock-enhancement may be ecologically viable, at least during the early benthic phase of the crab’s life-history. Future work should focus on ways to reduce initial release mortality.
Alaska Marine Science Symposium 2023 20
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