Effect of climate on recruitment success of clupeid stocks in the North Atlantic

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Environmental factors have recently been modelled to explain recruitment variability of fish stocks in different sea areas. Among those factors, temperature is often the principal variable investigated since temperature regulates the rate in many ecological and physiological processes. Temperature is assumed to influence recruitment directly, through egg and larval survival, or indirectly via its effects on productivity at lower trophic levels. Although several studies have investigated the effect of temperature on recruitment success of several gadoid species in the North Atlantic, a similar analysis is lacking for pelagic species in the same area. In this study, we explore spawning stock biomass and recruitment data for herring (Clupea harengus), and sprat (Sprattus sprattus) stocks in the North Atlantic in relation to temperature and NAO (North Atlantic Oscillation) variation and their geographic distribution. We used a synthetic approach and argue that including several stocks and areas and long time series of both biotic and abiotic factors are needed to determine generality in biological processes. Our results suggest that recruitment and recruitment success of the Baltic stock-complex are positively related to temperature and NAO while the opposite applies for the North Sea stock-complex. In contrast, recruitment success was not related to temperature in any of the analysed North West Atlantic stocks. Our correlative analysis suggest that recruitment and recruitment success of the North West Atlantic stocks is more dependent on spawning stock biomass then on temperature and NAO compared to North East Atlantic stocks. This implies that the dynamic of North East Atlantic stocks is more dependent to climate shifts than in the North West part of the Atlantic.