Decadal changes in recruitment of the geoduck clam (Panopea abrupta) in the Pacific NW

J.L. VALERO; C. HAND; J.M. ORENSANZ; A.M. PARMA; D.A. ARMSTRONG; R. HILBORN

Vancouver, Canada

Congreso; Fourth World Fisheries Congress; 2004

American Fisheries Society

Geoducks are conspicuous because of their size (largest infaunal bivalve, up to 5kg and 25 cm shell length), longevity (oldest record 168 yr) and growth pattern (fast growing during the first 7-12 years, no growth afterwards). Geoduck stocks are structured as metapopulations, collections of subpopulations of sedentary adults connected with each other by dispersing meroplanktonic larvae. Back-calculation of relative recruitment based on age-frequency distributions (AFDs) compiled in 1979-1983 indicates that by 1975 recruitment had been declining for decades at a large geographic scale, from British Columbia (BC, Canada) to Puget Sound (PS, Washington State, USA).Pre- and post-harvest data in PS suggested a rebound in several areas during the 1980s and 1990s. However, no significant age data became available during 1983-2002 and concerns arose regarding the sustainability of the fishery, one of the most profitable of the NE Pacific and virtually the sole supplier to the world´s geoduck market. Analysis of AFDs collected between 1993 and 2000 all over BC show a decadal recruitment decline reaching a minimum ca. 1975, followed by a rebound. This recruitment trend is positively correlated with recruitment of other NE Pacific species (most notably clams) and with environmental indices that capture conditions in the coastal zone, such as river discharges (negatively correlated) and coastal sea surface temperature (positively correlated).We discuss the consequences of long-term changes in recruitment in the context of population dynamics and management of the fishery.