Data from: Spatio-temporal dynamics of a fish predator: density-dependent and hydrographic effects on Baltic Sea cod population

Understanding the mechanisms of spatial population dynamics is crucial for
the successful management of exploited species and ecosystems. However,
the underlying mechanisms of spatial distribution are generally complex
due to the concurrent forcing of both density-dependent species
interactions and density-independent environmental factors. Despite the
high economic value and central ecological importance of cod in the Baltic
Sea, the drivers of its spatio-temporal population dynamics have not been
analytically investigated so far. In this paper, we used an extensive
trawl survey dataset in combination with environmental data to investigate
the spatial dynamics of the distribution of the Eastern Baltic cod during
the past three decades using Generalized Additive Models. The results
showed that adult cod distribution was mainly affected by cod population
size, and to a minor degree by small-scale hydrological factors and the
extent of suitable reproductive areas. As population size decreases, the
cod population concentrates to the southern part of the Baltic Sea, where
the preferred more marine environment conditions are encountered. Using
the fitted models, we predicted the Baltic cod distribution back to the
1970s and a temporal index of cod spatial occupation was developed. Our
study will contribute to the management and conservation of this important
resource and of the ecosystem where it occurs, by showing the forces
shaping its spatial distribution and therefore the potential response of
the population to future exploitation and environmental changes.