Baltic cod (Gadus morhua callarias) recovery potential under different environment and fishery scenarios

Abstract

The Atlantic cod (Gadus morhua) is one of the most significant fishery targets in northern seas. The cod occurs also in the brackish Baltic Sea, where besides fishing, several abiotic and biotic factors have a strong effect on their population dynamics. All cod stocks have diminished simultaneously due to heavy exploitation. Maintaining a sustainable fishery requires sufficient understanding of the recovery process and adequately tailored management plans. In marine habitats, temporal environmental fluctuations are often positively autocorrelated. Yet the temporal autocorrelation is often disregarded in models estimating fishery stock dynamics. For the Eastern Baltic cod (Gadus morhua callarias), the main environmental factors are water salinity and oxygen concentrations, which determine species distribution and reproductive success. The Baltic Sea's oceanographic characteristics make the ecosystem sensitive and climate change is expected to convert the type and magnitude of environmental fluctuations. This could potentially lead to inaccurate stock estimation and requires reassessment for any management strategy. We analyzed the recovery potential of the Eastern Baltic cod (Gadus morhua callarias) under different fishery and environmental scenarios. Our results illustrate how the unpredictability of stock size, catch, and recovery increase with increasing environmental autocorrelation. Under current environmental conditions and threshold methods fishing is at sustainable level. However, under more radical environmental fluctuations, like global warming, the estimation of cod population recovery becomes more difficult. Moreover, the precautionary fishing methods are important for population recovery by ensuring more sustainable fishing and preventing stock collapses.