Trans-Atlantic Study of Calanus: Regional and Seasonal Variability of feeding and reproduction

The time series work at weathership "M" and selected stations on cruises will be used for this work. In order to cover a wide geographic range including the open ocean, we will employ a combination of standardized measurements of egg production from live specimens and from preserved samples. To achieve this, an existing method (Runge 1987) will be improved by including histological preparations of the female gonad.

A strong discrepancy has been observed between life-time fecundity of females fed in the laboratory (Hirche 1991) and a fjord population (Diel and Tande 1992), which laid only 20 % of the eggs spawned by laboratory females. We will tackle this problem by studying the effect of female condition, food quantity and quality on egg production. The role of senescence of females will also be investigated.

Grazing, female condition (CN and lipid composition, gonad maturity) egg production (on shipboard and preserved samples), hatching viability, and nauplii survival will be determined.