Abstract-Ghost fishing, the capture and killing of marine organisms by lost or abandoned fishing gear, is a serious ecological and economic problem confronting fisheries. In this study, we quantify the rate of ghost fishing on the population of red king crab (Paralithodes camtschaticus) in Womens Bay, Kodiak Island, Alaska. From 1991 to 2008, crabs with carapace lengths (CLs) from 42 to 162 mm were tagged with acoustic tags and tracked both from a boat at the surface and by divers. Diver observations were used to determine whether a crab molted or died and, in many cases, to determine the cause of death. Of 192 crabs tracked during this study in association with other projects, 13 were killed in ghostfishing gear (12 in ghost crab pots and 1 in a ghost gill net) and 20 were captured in ghost pots and released alive by divers. An additional 13 died of other causes, including predation by sea otters and an octopus and poaching by humans. We estimate that between 16% and 37% of the population of red king crab with CLs >60 mm in Womens Bay were killed by ghost fishing per year during the period of this study, making ghost fishing a substantial source of mortality. These results indicate that steps to reduce ghost fishing in Womens Bay are warranted.
Stock enhancement of red king crab (Paralithodes camtschaticus (Tilesius, 1815)) could increase the crab population near Kodiak, Alaska, which collapsed in the 1980s and has not recovered. We conducted a field experiment examining the effect of juvenile red king crab density on enhancement success. Hatchery-reared crabs were released in plots near Kodiak at three densities: 25, 50, and 75 m−2. Crab densities were monitored for 6 months after release. Predation risk was measured via tethering experiments and predator density via quadrat and transect surveys. Neither migration nor mortality changed with crab density, but mortality rates decreased over time. Crab density did not affect predator density or predation risk, although predation risk decreased with time. Excluding the high initial mortality rate of 67.5%, the predicted survival after 6 months was 34%, which is better than the survival observed in a wild population. This suggests that red king crab enhancement is not predation limited and can occur at high densities. Further, processes affecting juvenile red king crab may not be strongly density dependent, at least at the scales and habitats tested.
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