Reproductive bioenergetics within the summer and winter generations of Euchaeta norvegica (Copepoda)

The predatory copepod Euchaeta norvegica from Korsfjorden, western Norway, has a half-year life cycle. Egg sacs produced by the winter generation are heavier on average than those produced by the summer generation. This is probably determined by the supply of food during the breeding period rather than by the average weight of mature females at the beginning of the breeding period. Measurements on individuals from a Swedish fjord show that the respiratory rate is relatively low and stable over the year. Bioenergetic budgets for the period prior to and during breeding reveal pronounced differences between individuals from the summer and winter generation, the latter being the more efficient at converting energy from a lower trophic level. It is suggested that the most important environmental factor governing this is the abundance of prey organisms.