Life history strategy and impacts of environmental variability on early life stages of two marine fishes in the North Sea: an individual-based modelling approach

We employed a suite of coupled models to estimate the influence of environmental variability in the North Sea on early life stages of sprat (Sprattus sprattus), a small pelagic clupeid, and Atlantic cod (Gadus morhua), a demersal gadoid. Environmentally driven changes in bottom-up processes were projected to impact the survival and growth of eggs and larvae of these marine fish species in markedly different ways. We utilized a spatially explicit, individual-based model (IBM) to estimate larval fish survival and a 3D ecosystem model (ECOSMO) to provide variable prey fields. The model was applied to each of 3 years (1990, 1992, 1996) specifically characterized by interannual differences in water temperature in late winter and spring. Our results indicated that an important mechanism connecting environmental factors to larval fish survival was the match-mismatch dynamics of first-feeding larvae and their prey, which was species-specific because of (i) differences in the timing and locations of spawning, (ii) the duration of endogenously feeding life stages, and (iii) prey thresholds required for larval survival. Differences in transport processes also played an important role for the potential survival of larvae of both species.