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Horbowy J.,Polish National Marine Fisheries Research Institute
Fisheries Research | Year: 2011

Management strategy evaluation (MSE) was used to test the assessment and management performance of three assessment methods in combination with harvest control rules. The assessment procedures considered were: the eXtended Survivors Analysis (XSA), the Schaefer production model, and the difference model. Four HCRs were considered: first, fishing mortality was set on the basis of the relationship between the current biomass and a reference biomass; second, fishing mortality was gradually reduced (or increased) until it reached a required target; and the third and the fourth HCRs were similar to the first and second but with imposed TAC constraints. The stock that was generated in the operating model (OM) resembled the eastern Baltic cod stock. For the XSA assessment, two options were used: XSA with default shrinkage of terminal fishing mortality to the average of the estimates, and XSA with low shrinkage. The simulations showed that for stock assessment, the XSA models performed much better than the difference and Schaefer models. However, for the data tested, the difference and Schaefer models performed somewhat better in terms of management performance than the XSA models, especially the XSA model with default shrinkage. © 2010 Elsevier B.V. Source

Polak-Juszczak L.,Polish National Marine Fisheries Research Institute
Food Control | Year: 2015

Background: Mercury content in fish poses risks to the fish and to those who consume them. The aim of the current study was to verify the protective role of selenium against toxic mercury in Baltic fish. The assessment criteria were the Se:Hg molar ratio, its variability depending on species and tissue, and correlations among Se:Hg ratios, mercury concentration, and specimen length. Assays were performed in muscle and liver tissues of Baltic Sea commercial fish species, i.e., cod, herring, sprat, plaice, and turbot. Results: Mercury concentrations in fish from the Baltic Sea are at low level. The values of the Se:Hg molar ratio were higher than 1 (with the exception of a few cod specimens), with ranges in muscle tissues as follows: cod 0.75-28.2; herring 2.0-50.3; sprat 14.2-56.2; flatfish 1.5-35.1; and in livers as follows: cod 10.9-268.2; herring 10.7-87.1; flatfish 10.2-232. The values of the Se:Hg ratio in muscle and liver tissues were negatively correlated with mercury content and specimen length. Conclusion: Mercury concentrations in commercial fish from the Baltic Sea are low and do not pose risks to consumers. The high values of the Se:Hg molar ratio confirm that mercury levels are safe, and also that selenium might offer protection against methylmercury toxicity, which could increase the safety of fish consumption. The values of the Se:Hg molar ratio could be an additional criterion, in addition to measuring Hg concentrations, for evaluating the risk of mercury exposure in fish from the Baltic Sea. © 2014 Elsevier Ltd. Source

Polak-Juszczak L.,Polish National Marine Fisheries Research Institute
Environmental Monitoring and Assessment | Year: 2013

This paper presents and discusses the levels and temporal trends of concentrations of Cd, Pb, Hg, Cu, Zn, and As in livers and Hg in the muscle tissues of cod (Gadus morhua L) from the Baltic Sea during the period 1994-2010. Concentrations of Pb, Hg, and Cd exhibited significant downward trends. Cu and Zn concentrations exhibited upward trends in the period 1994 to 2010. No trends were detected for concentrations of As. The temporal trends identified in heavy metal concentrations in cod livers corresponded to the directions of changes in concentrations of these elements introduced into the Baltic Sea via river runoff and atmospheric emission, and those in surface and deep waters of the Baltic. Downward trends in the concentrations of toxic metals in cod livers suggest that advantageous changes are occurring in concentrations of heavy metals in the environment of the southern Baltic Sea. © 2012 Springer Science+Business Media B.V. Source

Sokolowska E.,Polish Academy of Sciences | Fey D.P.,Polish National Marine Fisheries Research Institute
Journal of Fish Biology | Year: 2011

The ages of 8 to 23.5 cm total length (LT) round goby Neogobius melanostomus collected monthly during 2006 and 2007 in the Gulf of Gdańsk (Baltic Sea) ranged from 2 to 6 years, with age class 4+ years dominant. Males were larger at age than females. The fastest growth occurred in the first 2 years of life in both sexes. Females were heavier at a given LT than males, but only for fish > c. 15 cm. A strong relationship between N. melanostomus otolith size and fish size was found, with no difference between males and females, and a significant relationship between fish growth rate and otolith growth rate, which enabled backcalculation of growth rates. Marginal increment width analysis confirmed the periodicity of annual ring formation in otoliths and showed that the most intense opaque zone formation occurs in July to August, while hyaline zone formation starts as early as September to October. It was concluded that the N. melanostomus that have colonized the southern Baltic Sea exhibit the largest size and longest life span ever recorded for this species. © 2011 The Authors. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles. Source

Polak-Juszczak L.,Polish National Marine Fisheries Research Institute
Environmental Science and Pollution Research | Year: 2013

Trace metals were examined in the muscle tissue of flatfish species of flounder, Platichthys flesus (Linnaeus, 1758), sediments from two southern Baltic Sea sites (Gdańsk Bay and Ustecko-Łebskie as a reference) and in two areas of the Portuguese Atlantic coast (Douro River estuary and Atlantic fishing ground as a reference) to evaluate spatial differences in trace metals. Additionally, the accumulation of trace metals in flounder of different length classes was assessed. Flounder from the Gdańsk Bay area contained twofold more cupper (Cu), lead (Pb) and mercury (Hg) than did flounder from the Douro River estuary, but zinc (Zn) and cadmium (Cd) were at similar concentrations. The sediments from Gdańsk Bay contained significantly more Zn and threefold more Cd, while concentrations of Cu and Pb were twofold lower. The concentrations of metals in the sediments did not correlate with those in the flounder. Spatial differences were noted in metal concentrations in flounder from the southern Baltic Sea and the Portuguese Atlantic coast as well as within these regions, with higher concentrations in the flounder from the Baltic Sea Gdańsk Bay. The flounder in length class 25-30 cm from Gdańsk Bay contained metal concentrations comparable to those of class 40-45 cm specimens from the Atlantic coast. The accumulation of metals in flounder length classes differed in the two regions. © 2013 Springer-Verlag Berlin Heidelberg. Source

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