Life cycles and seasonal distributions of Calanus finmarchicus on the central Scotian Shelf

Abstract

The life cycle of Calanus finmarchicus on and around Western Bank, 1991–1992, was essentially annual; the overwintered generation (G0) produced G1 that developed at temperature-dependent rates and then largely disappeared after June to winter as late copepodids at depth. However, a small fraction of G1 matured to spawn a less rapidly developing G2 that outnumbered G1 in the depths of Emerald Basin in autumn 1990. Estimated mortality on the central Scotian Shelf for G1 from egg to copepodid stage 5 in June was ~4%·day–1 but subsequently for G1 and G2 was nearly constant at ~1%·day–1. Populations on Western Bank mostly derived from reproduction by overwintered G2 on the Scotian Shelf. Larger populations in Emerald Basin in 1987–1988 were augmented from advected animals enabled to diapause there at depth and on Emerald Bank by inputs from beyond the shelf break, ultimately from farther north. Our observations and analyses match the physical circulation in the region.