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Casini M.,Institute of Marine Research | Kornilovs G.,Institute of Food Safety | Cardinale M.,Institute of Marine Research | Mollmann C.,University of Hamburg | And 5 more authors.
Population Ecology | Year: 2011

For the first time an international acoustic survey dataset covering three decades was used to investigate the factors shaping the spatial and temporal patterns in the condition of sprat and herring in the Baltic Proper. Generalized additive models showed that the spatial and temporal fluctuations in sprat density have been the main drivers of the spatio-temporal changes of both sprat and herring condition, evidencing intra- and inter-specific density dependence mediated by the size and distribution of the sprat population. Salinity was also an important predictor of herring condition, whereas temperature explained only a minor part of sprat model deviance. Herring density was an additional albeit weak significant predictor for herring condition, evidencing also intra-specific density dependence within the herring population. For both species, condition was high and similar in all areas of the Baltic Proper until the early 1990s, coincident with low sprat densities. Afterwards, a drop in condition occurred and a clear south-north pattern emerged. The drop in condition after the early 1990s was stronger in the northern areas, where sprat population increased the most. We suggest that the increase in sprat density in the northern areas, and the consequent spatial differentiation in clupeid condition, have been triggered by the almost total disappearance of the predator cod from the northern Baltic Proper. This study provides a step forward in understanding clupeid condition in the Baltic Sea, presenting evidence that density-dependent mechanisms also operate at the spatial scale within stock units. This stresses the importance of spatio-temporal considerations in the management of exploited fish. © 2011 The Society of Population Ecology and Springer.

Semionova S.,Atlantic Scientific Research Institute of Marine Fisheries and Oceanography AtlantNIRO | Smyslov V.,Atlantic Scientific Research Institute of Marine Fisheries and Oceanography AtlantNIRO
2006 IEEE US/EU Baltic International Symposium, BALTIC 2006 | Year: 2016

Long-term researches of phytocene, chlorophyll "a" an hydrochemical water composition made in the Russian (southern) part of Curonian Lagoon on the eve of 20th and 21st centuries (1989-2001), revealed significant changes occurred in the community condition under the impact of anthropogenic eutrophication and global climate warming, observed in 1930s, 1950s, 1970s and 1980s. The structural reorganization was manifested in the remarkable increase of species diversity, including toxic species, caused by appearance of the species more tolerant to unfavorable environment conditions. The Shannon's index of species diversity increased, active vegetation of Cryptophyta was observed and Cyanophyta occupied the leading position. Partial replacement of dominating species and biomass indices increase were observed. The summer maximum amplitude became higher than that of spring. The third autumn peak, never observed in 1979s, appeared in October. The extension of phytoplankton vegetative period was found. The Lagoon waters are classified as poly-hypertrophic, and in anomalous years - as poly-trophic, while in 1970s they were eutrophic. The water quality is considered as satisfactory (Class III). © 2006 IEEE.

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