Spatial distribution of juvenile and adult female Tanner crabs (Chionoecetes bairdi) in a glacial fjord ecosystem: implications for recruitment processes

Abstract

Nielsen, J. K., Taggart, S. J., Shirley, T. C., and Mondragon, J. 2007. Spatial distribution of juvenile and adult female Tanner crabs (Chionoecetes bairdi) in a glacial fjord ecosystem: implications for recruitment processes. – ICES Journal of Marine Science, 64: 1772–1784. A systematic pot survey in Glacier Bay, Alaska, was conducted to characterize the spatial distribution of juvenile and adult female Tanner crabs, and their association with depth and temperature. The information was used to infer important recruitment processes for Tanner crabs in glaciated ecosystems. High-catch areas for juvenile and adult female Tanner crabs were identified using local autocorrelation statistics. Spatial segregation by size class corresponded to features in the glacial landscape: high-catch areas for juveniles were located at the distal ends of two narrow glacial fjords, and high-catch areas for adults were located in the open waters of the central Bay. Juvenile female Tanner crabs were found at nearly all sampled depths (15–439 m) and temperatures (4–8°C), but the biggest catches were at depths <150 m where adults were scarce. Because adults may prey on or compete with juveniles, the distribution of juveniles could be influenced by the distribution of adults. Areas where adults or predators are scarce, such as glacially influenced fjords, could serve as refuges for juvenile Tanner crabs.

Depth distribution, habitat associations, and differential growth of newly settled southern Tanner crab (Chionoecetes bairdi) in embayments around Kodiak Island, Alaska

“…Further, we encountered few individuals larger than the C7 molt stage (carapace widths of 20-26 mm), indicating that crabs older than 2 or 3 years of age are found in different, perhaps, deeper habitats. In Glacier Bay, Alaska, Tanner crabs are segregated by ontogenetic stage; smaller, or juvenile, crabs are located at the heads of fjords, near glaciers, and adult, or larger crabs are more centrally located in fjords and in inlet areas (Nielsen et al, 2007). However, this segregation did not appear to be depth related, and the authors speculated that cannibalism, competition, predation, or differences in substrate preferences might be responsible.…”

Spatial patterns and movements of red king and Tanner crabs: implications for the design of marine protected areas

“…Red king crabs were not spatially segregated by sex (Cramer-von Mises = 2.11, p = 0.488); male and female Tanner crabs also did not demonstrate spatial segregation by sex (Cramer-von Mises = 0.57, p = 0.266; but see Nielsen et al 2007 for additional analysis on segregation by size).…”

Spatiotemporal overlap of spiny dogfish (Squalus acanthias) and commercial fisheries in the northeast U.S. shelf large marine ecosystem

“…where n = the number of observations, x i and x j are the attribute values (CPUE ≥0) at points i and j; x = the mean CPUE; w ij = the weighting function (w ij =1 if points are within d, otherwise w ij =0) (Nielsen et al, 2007); and Σ ij = the sum over i and j with i≠j.…”