VA Sea Grant Research




	About Us News & Events Research Publications Education Seafood Aquaculture Fisheries Coastal Economies & Recreation Contact Us			Funding Instructions Schedule Policies Projects Virginia Sea Grant funded research Quantitative valuation of nursery habitats for the blue crab Rom Lipcius , John Hoenig, Robert Orth, Sebastian Schreiber, Rochelle Seitz, Jacques van Montfrans (Virginia Institute of Marine Science) The major objective of this proposal is to determine the quantitative value of the key primary and secondary nursery habitats for the blue crab population in Chesapeake Bay. The focus will be upon the newly established paradigm of nursery habitats for the blue crab whereby seagrass beds are hypothesized to be the primary nursery (used by the youngest juveniles), while salt-marsh fringed coves and shorelines are believed to be the critical secondary nursery (used by older juveniles). Salt marsh habitats include the unvegetated fringe in the intertidal and subtidal zones bordering the marshes. Thereafter, subadults and adults disperse to deeper habitats. A second objective is to determine the impact of the 2005 mass defoliation of eelgrass upon blue crab population abundance. We expect that our project will produce the necessary empirical and theoretical information for quantitative valuation of the blue crab’s essential nursery habitats, and thereby provide the quantitative foundation upon which decisions concerning habitat protection, restoration, and assessment are made within the framework of ecosystem-based management of the blue crab stock in Chesapeake Bay. Our approach involves a combination of field experiments, field sampling, retrospective analyses of long-term data, and population modeling. Field experiments will establish survival and growth rates of younger and older juveniles in the primary and secondary nursery habitats (i.e. seagrass beds and salt marsh habitats). Field sampling will provide abundance data to test hypotheses concerning size-specific use of the alternative nurseries by younger and older juveniles, and recolonization of eelgrass beds after the mass defoliation. Retrospective analyses of long-term data from the VIMS Trawl Survey, VIMS/MDNR Blue Crab Winter Dredge Survey, and VIMS Submerged Aquatic Vegetation Survey will be used to assess the value of eelgrass to the blue crab population and the impact of the 2005 mass eelgrass defoliation at the population level. Population modeling will be based on stage-structured spatial models that provide a quantitative theoretical framework to assess the impact of varying the availability of the primary and secondary nursery habitats. As such, we expect to produce a standard, quantitative protocol that can be used to estimate the production value of nursery habitats to blue crab populations in Chesapeake Bay and elsewhere. moss at a hFur beds) experienced a mass defoliation in 2005, heretofore observed only once three decades ago (1975). The defoliation occurred throughout the lower Chesapeake Bay during the entire recruitment period (m200eir primary nursery, and had to settle, grow and survive in alternative habitats, such as the secondary nurseries. Despite the blue crab’s economic and ecological impo25-Jan-2008the relative value of its essential nursery habitats at the population level. For instance, we have been unable to ascertain the impact of the 2005 mass defoliation upon the blue crab stock, which was a severe environmental disturbance. Consequently, there is at present no standard quantitative protocol for valuation of the blue crab’s nursery habitats at the population level, which precludes effective ecosystem-based management, restoration efforts, and assessment of the effects of environmental and anthropogenic disturbances. This project seeks to provide this vital information.

Virginia Sea Grant • Virginia Institute of Marine Science
P.O. Box 1346 • Gloucester Point, VA 23062 • 804-684-7164 • 804-684-7161 (fax)

25-Feb-2008