Dynamics of coexisting Calanus finmarchicus, Calanus glacialis and Calanus hyperboreus populations in a high-Arctic fjord

We studied the population dynamics of Calanus. nmarchicus, Calanus glacialis and Calanus hyperboreus in Billefjorden, Svalbard ( 78 degrees 40' N). All three species reproduced in the fjord with different timing. The maximum abundance of Calanus spp. copepodite stages peaked on the 11th of July ( 29,000 ind m(-2)). C. glacialis was the dominant species accounting for 60 - 80% of the total Calanus abundance. C.. nmarchicus appear to thrive in the fjord despite the low temperatures ( - 1.86 degrees C to 5 degrees C) and accounted for 20 - 30% of the total population. C. hyperboreus contributed less to the total abundance ( 5 - 20%). A 1-year life cycle is suggested for C. finmarchicus and C. hyperboreus in the fjord, C. glacialis has a 1- to 2-year life cycle. Highest mortality rates were observed for copepodite stage CV in C. finmarchicus and C. glacialis (0.09 and 0.075 d(-1), respectively) and for females in C. hyperboreus (0.149 d(-1)). Mortality of copepodite stages was substantially lower in C. glacialis than in the other species. This is particularly obvious in the early and numerous copepodite stages (CI + CII) during the period of recruitment to these stages. This suggests that differences in secondary production in Arctic pelagic ecosystems are controlled partly by population loss rates.