Development of large copepods during spring in the Gulf of Alaska

Development rate in Neocalanus plumchrus at Station P (50°N, 145°W) in the Gulf of Alaska was estimated from changing copepodite stage proportions. Apparent duration of the third copepodite stage (C3) was 13.4 days. The error imposed on this estimate by differential mortality was modelled numerically. If mortality rate declines with age, C3 duration as short as 11.7 days is compatible with the data. If it accelerates with age, durations up to 16.2 days are reasonable. These estimates are shorter than those made previously for May 1984. Dry weight and lipid-free dry weight estimates show that Neocalanus flemingeri C5 with full lipid loading were smaller in 1988 (270μg DW, 170μg LFDW) than in 1987 (400μg DW, 225μg LFDS). Resting stage N. flemingeri females from 1988 were smaller than those of any recorded year, while those of 1987 were of average size. Nutrient, floristic, and microbial conditions were unusual in May 1988, all possibly shifted by a late season storm in mid-April. This could have caused the poor growth of N. flemingeri and a delay in development of N. plumchrus of two weeks compared to 1984.