Distribution and species-specific egg production of Pseudocalanus in the Gulf of Alaska

Pseudocalanus species are important contributors to the secondary production of the northern hemisphere mid- to high-latitude oceans. In the coastal Gulf of Alaska, Pseudocalanus are present year round and are represented by three species. In 2001, Pseudocalanus mimus was the dominant Pseudocalanus species on the shelf during spring and summer, comprising 30–100% of the total, while Pseudocalanus newmani dominated in Prince William Sound (10–90%). Pseudocalanus minutus were only abundant in Prince William Sound during early spring. Egg production (by number and volume) was a function of female prosome length and decreased from spring to summer; however, significant variability was attributable to regional influences that were independent of size. For the same sized female, P. newmani produced more eggs per clutch than P. mimus. Pseudocalanus mimus, however, tended to have a larger mean egg size than P. newmani. Consequently, clutch volumes of the two species were indistinguishable. Pseudocalanus egg production rates (EPRs) (eggs female−1 day−1) were lower in July and August (ca. 2–4) than April and May (ca. 1–9), but total egg production by the population (eggs day−1) was nearly equivalent for the two time periods due to higher female concentrations in summer.