McDonald, P.S., T.E. Essington, J.P. Davis, A.W.E. Galloway, B.C. Stevick, G.C. Jensen, G.R. VanBlaricom, and D.A. Armstrong. 2015. Distribution, abundance, and habitat associations of a large bivalve (Panopea generosa) in a eutrophic, fjord estuary. Journal of Shellfish Research 34: 137-145.
Marine bivalves are important ecosystem constituents and frequently support valuable fisheries. In many nearshore areas, human disturbance including declining habitat and water quality, can affect the distribution and abundance of bivalve populations, and complicate ecosystem and fishery management assessments. Infaunal bivalves, in particular, are frequently cryptic and difficult to detect; thus assessing potential impacts to their populations requires suitable, scalable methods for estimating abundance and distribution. Here population size of a common benthic bivalve (geoduck clams, Panopea generosa) is estimated with a Bayesian habitat-based model fit to SCUBA and tethered camera data in Hood Canal, a fjord basin in Washington State, USA. Densities declined over two orders of magnitude along a north-south gradient concomitant with patterns of deep-water dissolved oxygen and intensity and duration of seasonal hypoxia. Across the basin, geoducks were most abundant in loose, unconsolidated, sand substrate. The present study demonstrates the utility of using SCUBA, tethered video, and habitat models to estimate the abundance and distribution of a large infaunal bivalve at a regional (385 km2) scale.