Atmospheric forcing drives recruitment variation in the Dungeness crab (Cancer magister), revisited

Abstract For 12 yr (1997–2001, 2006–2012) daily abundance of C ancer magister megalopae was measured in C oos B ay, O regon. Before 2007 from 2000 to 80 000 megalopae were caught annually. In 2007, catch jumped and has since varied from 164 000 to 2.3 million. The step change in catch size appears related to a shift to negative P acific D ecadal O scillation ( PDO ) values. Late season catches, which cannot be due to local spawning, are negatively correlated to the PDO , suggesting that these megalopae derive from north of the C alifornia Current. During periods of lower and higher catches, annual returns of megalopae were significantly negatively correlated to the day of the year of the spring transition and positively correlated to the amount of upwelling during the settlement season. The size of the O regon commercial catch lagged 4 yr to allow for growth of recruits into the fishery is set by the number of returning megalopae; the relationship is parabolic. At lower returns, the population is recruitment limited, but at higher returns, density‐dependent effects predominate and set the commercial catch. Lagged commercial catches in W ashington and N orthern and Central C alifornia were also related to the number of megalopae returning to C oos B ay, suggesting that the forces causing variation in larval success are coast wide. If high return rates are due to a PDO regime shift, then for years to decades the commercial catch may be set by density‐dependent effects following settlement and the huge numbers of returning megalopae may impact benthic community structure.