Spatio-temporal dynamics and behavioural ecology of a "demersal" fish population as detected using research survey pelagic trawl catches: The Eastern Baltic Sea cod (Gadus morhua)

Cod is usually monitored for scientific purposes using bottom trawl surveys, although its regular pelagic occurrence is well documented. Here we analysed, using Generalized Additive Models, the spatio-temporal changes in the Eastern Baltic cod adult population using pelagic catches from an acoustic survey covering 37 years and the whole central Baltic Sea. Our analysis shows that in the northern areas cod catch per unit effort (CPUE, kg h-1) was high in the early 1980s whereas it dropped and remained very low thereafter. Conversely, in the southernmost area CPUE largely oscillated after the early 1990s. Our model was able to capture key ecological features of the Baltic cod such as preferred depth of occurrence and response to hypoxic conditions. The model also revealed a clear daily cycle of CPUEs, indicating diel vertical migrations at the population level. The temporal trends of pelagic CPUEs generally followed those from the bottom trawl surveys, although differences were observed especially in the recent years with a relative decline in the cod occurring in the pelagic waters. Our results point to the great potential of acoustic survey trawl catches to complement bottom trawl surveys for investigating the spatio-temporal population dynamics and behaviour of the Baltic cod

A Turbulent political history and the legacy of state Socialism in the Baltic countries

This chapter provides a survey of the political, socio-economic and demographic development of the Baltic countries. It is meant to give readers a general understanding of the setting in which large urban housing estates were built from the 1960s to the 1980s. The chapter begins with an account of the history of the Baltic countries, including their emergence as independent nations, their incorporation into the USSR and their reappearance on the world map in 1991. The second section analyses the modernisation of the Baltic economies, the Soviet strategies for industrialisation and their impact on the housing sector. The Baltic region enjoyed somewhat higher living standards and exhibited greater openness to Western influences than other union republics, which made Estonia, Latvia and Lithuania attractive to economic migrants from other parts of the USSR. The analysis also shows that the Baltic countries experienced demographic modernisation earlier than other regions of the USSR. A high demand for labour is driven by Soviet strategies for economic development, and slow population growth in the host countries, particularly in Estonia and Latvia, contributed to the persistence of high levels of immigration throughout the post-war decades. Due to their large numbers, migrant workers significantly transformed the composition of the urban population in the Baltic countries. Through a combination of factors, including the housing allocation mechanism, immigrants gained privileged access to new accommodation, and they became over-represented in the housing estates. This development connects the future of the housing estates with the integration of immigrants who settled in the region during the Soviet era