Seasonal and interannual variations in size, biomass and chemical composition of the eggs of North Sea shrimp, Crangon crangon (Decapoda: Caridea)

In the shrimp Crangon crangon , an important fishery resource and key species in the southern North Sea, we studied temporal variations in size, biomass (dry weight, W ) and chemical composition (C, N, protein and lipid) of eggs in an initial embryonic stage. Data from 2 years, 1996 and 2009, consistently revealed that egg size and biomass varied seasonally, with maxima at the beginning of the reproductive season (January), decreasing values throughout spring, minima in June–July, and a slight increase thereafter. This cyclic pattern explains why “Winter eggs” are on average larger and heavier than “summer eggs”. Using a modelling approach, we estimated the duration of oogenesis in relation to seasonally changing seawater temperatures. According to an additive model of multiple explanatory variables, the C content per newly laid egg showed in both years a highly significant negative relationship with day length ( r ² = 0.38 and 0.40, respectively; P