Effects of habitat complexity and relative larval supply on the establishment of early benthic phase red king crab (Paralithodes camtschaticus Tilesius, 1815) populations in Auke Bay, Alaska

Between September 1996 and May 1998, the influence of habitat complexity an d larval supply on the establishment of early post-settlement populations o f red king crab (Paralithodes camtschaticus) was studied in situ in Auke Ba y, southeast Alaska. Dive transects and suction dredge surveys conducted du ring fall 1996 and spring 1998 indicated that late age 0 to 1+ red king cra bs were located only in the most complex habitat. This pattern was similar to patterns observed for early age 0 crabs, using settlement pails, during the summer of 1997. Early instars recruited into settlement pails containin g ambient sediment at both the rocky cobble and shell-hash sites, but no se ttlement could be detected in muddy habitat. Population density of benthic age 0 + crab peaked in mid-July, then dropped throughout the summer, and gr eater densities were always observed in rocky cobble than in shell-hash. Si multaneous use of passive larval collectors ruled out the possibility that these patterns were simply a reflection of larval supply. Rather, the highe st levels of larval supply were associated with the muddy site at which no settlement could be detected. The availability of complex habitat, defined simply as substrate rich in available crevice space that is scaled to the b ody size of the crab instars, appeared to be the primary determinant of the value of nursery habitat, and it is likely to be the critical factor deter mining early post-settlement survivorship within the population. Such consi derations are vital to management of red king crab fisheries where complex nursery habitat is likely to be relatively rare and where conflicts with tr awl fisheries and other anthropogenic disturbances to bottom habitat are a potential concern. (C) 2000 Elsevier Science B.V. All rights reserved.