Long-term seasonal and spatial patterns in mortality and survival of Calanus finmarchicus across the Atlantic Zone Monitoring Program region, Northwest Atlantic

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The Vertical Life Table method was used to estimate stage-specific daily mortality rates and survival from 1999 to 2006 for Calanus finmarchicus sampled in the Canadian Atlantic Zonal Monitoring Program (AZMP), which covers the Newfoundland Shelf (NLS), Gulf of St. Lawrence (GLS) and Scotian Shelf (SS). Stage-specific mortality rates and survival showed significant regional and seasonal differences with the largest signal associated with variations in temperature. Densitydependent mortality, associated with the abundance of C6 females, was the predominant factor affecting mortality in the egg-C1 transition during the period of population growth in spring on the SS and in summer in the GSL and on the NLS. In autumn, mortality in egg-C1 was positively related to temperature and negatively related to phytoplankton biomass, with particularly high mortality rates occurring on the SS. The integration of our results into stage-specific recruitment rates from egg to C5 revealed that C. finmarchicus populations experience their greatest loss (mortality) during the egg-C1 transition. Loss during development to C1 was higher in the GSL than in other regions during the period of population growth, resulting in lower recruitment success in the GSL. In autumn, C. finmarchicus showed low stage-specific daily recruitment rates on the SS at high temperatures and low phytoplankton biomass compared with those in the GSL and on the NLS. Our findings reinforce the necessity of describing regional and seasonal patterns in mortality and survival in order to understand factors controlling the population dynamics of C. finmarchicus.