This is the first time-series study to investigate the gonad maturation and egg production of Calanus glacialis in Svalbard seasonal ice covered fjords, and the first study to investigate the correlation between nutritious status and time of death for Calanus spp. males in the Arctic. There is a significant improvement in reproduction success when the females have access to fresh food. Close to 100% of the fed females spawned compared to only half of the starved females, and both egg production rates and hatching success improved. Females utilized both stored lipids and input of food for reproduction, showing a mixed strategy between capital and income breeding strategy. When food is scarce, the females invest more lipids on fewer eggs as opposed to more eggs, but less lipid per egg when food is abundant. This suggest a life strategy not previously described for Calanus glacialis i.e. when food is absent or low females invest in fewer but more lipid-rich eggs to increase the likelihood for this offspring to survive longer and thus increasing the chances to be present when more favourable food conditions finally appear. The fatty acid composition is more important than total lipid content for the hatching success of the eggs, and 16:0, 18:0, 20:5(n-3) and 22:6(n -3) seems to be particularly important. The fatty acid composition of the females change throughout the winter-spring transition, and the changes seems to be related to where in the reproductive cycle they are. Maturation of the gonads appear to rely mostly on fatty acids the female are capable of synthesizing de novo. The decrease in stored lipids is also evident in the field data where the total lipid level is significantly lower in late April than in early April. Total lipid content of males at the time of death is normally distributed thus, supporting previous suggestions that males die when the stored resources reach a threshold level.