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A study on the utility of log piling structures as artificial habitats for red king crabs and other fauna
  • Published Date:
    2002
Filetype[PDF - 2.36 MB]


Details:
  • Corporate Authors:
    Alaska Fisheries Science Center (U.S.)
  • Series:
    AFSC processed report ; 2002-03
  • Document Type:
  • Description:
    During construction of a new breakwater at St. Herman Harbor in Kodiak, AK, a large area of underwater habitat was buried beneath tons of extraneous rock. Red king crabs were among the potential inhabitants of this altered habitat. Previous observations suggest that juvenile king crabs use wooden dock pilings as habitats. In order to test the hypothesis that pilings could be used to mitigate for loss of natural habitat, six piling and beam structures were constructed from untreated spruce and placed in pairs at 3 different locations in ocean bays near Kodiak, AK. Divers from the Kodiak facility of the Alaska Fisheries Science Center conducted a year long study of faunal recruitment to the piling structures, by making quarterly surveys to count organisms on the pilings and adjacent seafloor areas. Abundance of juvenile (age 0 to 1+) king crabs increased steadily from July 1997 through March 1998 as crabs recruited to the structures, then declined in June 1998. Crab abundance was significantly higher on piling structures than on the adjacent substratum. Site, season, and their interaction had significant effects on abundance. Abundance was higher at more exposed sites than at more sheltered sites (i.e., abundance was proportional to exposure or proximity to open ocean) but this was not a significant effect. Red king crabs were associated with the presence of green urchins, decorator crabs, leather stars, and sculpins. Each of the three sites could be discriminated by their unique community of inhabitants. Pilings do indeed attract juvenile king crabs, but the reason is unknown. Pilings are inefficient habitats because they do not provide much surface area per volume, and do not persist in the environment. For these reasons, we do not recommend their use as artificial habitats to mitigate for the loss of natural habitat.