Historical analysis of Dungeness crab abundance and the contribution of estuarine habitats to fisheries harvest

Dungeness crab (Cancer magister) are an important ecosystem good for coastal communities, particularly for provision of economically valuable commercial and recreational fisheries. Historical surveys (1998-2000) of Dungeness crab, conducted as part of the Pacific Northwest Coastal Ecosystems Regional Study (PNCERS), showed that estuarine juvenile Dungeness populations contributed recruits to coastal populations targeted by commercial fisheries. We conducted summertime surveys of nekton and adjacent intertidal estuarine habitats within four small Oregon estuaries (Tillamook, Yaquina, Alsea, and Coos) to assess whether habitat type was a good predictor of juvenile Dungeness crab density (see Lewis & DeWitt, CERF 2019). Here, we compare the resulting crab-habitat relationships to those from PNCERS and discuss the effect of interannual variability on juvenile crab density and the correspondence with adult Dungeness crab landings. Preliminary analyses highlight the importance of lower side channel habitat to juvenile Dungeness crab populations within the estuaries. Connecting these data with crab fisheries economic data may allow us to provide a partial estimate of the dollar value of specific estuarine habitat types to Dungeness fisheries. In addition, these data provide us the opportunity to re-examine the contribution that Oregon estuaries provide to coastal Dungeness fisheries.

Impact/Purpose

Scientists from EPA’s Pacific Coastal Ecology Branch in Newport, OR conducted surveys of juvenile Dungeness crab (Cancer magister) and adjacent intertidal habitats in four Oregon estuaries (Tillamook, Yaquina, Alsea, and Coos). These data were analyzed to determine the relationships between juvenile Dungeness crab and specific intertidal habitats within and across estuaries. The resulting relationships were then compared to results from the Pacific Northwest Coastal Ecosystems Regional Study (PNCERS) to examine interannual variability on juvenile Dungeness crab density and the correspondence to regional Dungeness landings. Results from both studies show that the lower side channels of intertidal flats support the highest densities of juvenile crabs. These findings and the specific relationships, coupled with fisheries economic data, offer researchers the potential to estimate the dollar value contribution of specific habitat types to Dungeness fisheries. This study offers resource managers insight into the differential importance of estuarine habitat types on Dungeness crab, which are highly sought in recreational and commercial fisheries. Understanding the contribution of these intertidal habitats to the Dungeness fisheries can allow managers and stakeholders to make more informed decisions about habitat restoration, conservation, and management to increase the abundance of this valuable species.

Citation

Dewitt, T. AND N. Lewis. Historical analysis of Dungeness crab abundance and the contribution of estuarine habitats to fisheries harvest. CERF, Mobile, AL, November 03 - 07, 2019.