Calanus finmarchicus abundance, egg production and growth rates in the Gulf of Maine during winter

E. G. Durbin, M. C. Casas, R. G. Campbell, M. A. Wagner,
J. A. Runge, and B. Niehoff

The Gulf of Maine (GOM) is the major source of Calanus finmarchicus for Georges Bank (GB) during the winter and the timing of onset of reproduction in this region is important for understanding population dynamics on the bank. Abundance and stage distribution, egg production rates, and RNA:DNA ratios of Calanus were measured along a transect from the northern GOM to GB during February, 1999. In Maine coastal waters the spring bloom had not begun with chlorophyll a concentrations <1 µg L-1 and NO3 >10 µM. Across the Central Gulf the spring bloom had begun with chlorophyll a >2 µg L-1 and a slight draw down of nitrate. On GB chlorophyll a concentrations were also >2 µg L-1 but the draw down of NO3 was greater. Most of the resting population of Calanus had molted to the adult stage and reproduction had begun. Egg laying rates were lowest in the Maine coastal waters and high elsewhere. A small cohort of young nauplii was present at all stations in the Gulf, while on Georges Bank the abundance was much greater and the cohort more advanced.