Ghost fishing by Tanner crab (Chionoecetes bairdi) pots off Kodiak,Alaska: pot density and catch per trap as determined from sidescan sonarand pot recovery data

摘要

Sidescan sonar was used to locate 189 putative lost crab pots in a 4.5 km(2) area of Chiniak Bay, near Kodiak, Alaska. Subsequent observations of 15 such objects by submersible and ROV verified that they were indeed crab pots. In 1995 and 1996, 147 pots were recovered from the surveyed and adjacent nonsurveyed areas by grappling, and their condition and contents were examined. Tanner crabs, Chionoecetes bairdi, were the most abundant organism, with 227 found in 24 pots (16% frequency of occurrence); sun-flower sea stars (Pycnopodia helianthoides) were the most frequent (42%) occupant and second most abundant (189 in 62 pots). Octopuses (Octopus dofleini) were significantly associated with pots containing Tanner crabs. Occurrence of crabs in pots was primarily a function of background crab density and differed between the surveyed and nonsurveyed areas. Recently lost pots (< 1 yr old) had significantly more male crabs, significantly larger male crabs, and contained seven times more total crabs than older pots (those lost two or more years prior to recovery). The proportion of pots with damaged webbing increased with pot age, but holes in pot webbing did not significantly affect catch per pot.