GAMs of blue crab distribution

In a paper published in Transactions of the American Fisheries Society (Jensen et al 2005), we applied geostatistical techniques to estimate the distribution and abundance of blue crab. Spatial heterogeneity is a striking feature of the blue crab life history and fisheries in Chesapeake Bay. Patterns of sex- and age-specific habitat use have long been documented; however, a quantitative assessment of the spatial distribution of blue crab during winter has been lacking. Here, we apply geostatistical techniques (variogram modeling and kriging) to 13 years of data from a winter dredge survey (WDS) to map patterns of blue crab winter abundance. These maps are then quantified to derive a time-series of baywide abundance and to examine changing patterns of habitat use and aggregation. Geostatistical abundance estimates are higher on average than those calculated from design-based methods and are more highly correlated with fishery catch per unit of effort. Both time series show a large and significant decline in abundance from 1990 - 2002. The latitude of the weighted centroid of blue crab density during winter in Chesapeake Bay varied over the time series. The latitude of the centroid was positively related to Baywide abundance, suggesting density-dependent changes in distribution. The southward shift in winter distribution may increase the vulnerability of blue crab to exploitation in a winter dredge fishery that occurs only in the southern portion of the Bay. Such quantitative and spatially explicit information provides a potentially useful base for constructing population models and evaluating alternative management options

Here we provide graphs, not found in the paper, showing model krigged distributions and the associated error maps for each year. Maps are provided as pdf files.  Select the year of interest.

1990 1991 1992 1993 1994 1995 1996
1997 1998 1999 2000 2001 2002 Average

QuaFEL research areas

Recruitment

Blue crab ecology

Multispecies interactions

Fisheries Oceanography

Elasmobranch ecology

Ecotoxicology

Last revised: 4/3/2015