Assessment of shallow-water clam resources: case study of razor clams, Eastern Cook Inlet, Alaska

Beaches along eastern Cook Inlet in Alaska currently support a large sport fishery of over one million razor clams annually. A study commenced in 1987 to provide absolute estimates of abundance and sustainable yield of razor clams for selected beach areas. Harvest and age composition data on razor clams are available for some beaches since 1969, but management has been based mainly on a relative measure of population abundance, catch-per-unit-effort (c.p.u.e.), which has varied little over time and may not be a sensitive indicator of trends in abundance. A three-stage sampling design (transects, beach levels, and replicates) was implemented to sample beach areas. The sampling unit is a circular area of 0.5 m2 and all clams are removed to a depth of about 1 m. Estimates of abundance from the survey are precise for Clam Gulch, an area of fairly uniform clam density. Survey estimates do not correlate highly with estimates of c.p.u.e., suggesting that c.p.u.e. is not a useful indicator. Currently, harvest is low compared to sustainable yield in Clam Gulch. We envision that future assessments will use survey estimates to tune catch-age analyses in different management areas