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  • 1
    Publication Date: 2020-01-02
    Description: In the Baltic, the first observation of the round goby (Neogobius melanostomus, Pallas 1814) was made in 1990. Within the past decade the species became invasive and spread rapidly throughout the Baltic Sea. Studies about the fishes potential impacts on resident species promote the need for an increasing knowledge of their basic stock structures such as growth rates, longevity and mortality, which all rely on accurate estimates of age. Former studies on the round goby have used several different age reading techniques. In this study, we compared three standard otolith preparation methods for ageing and present the best procedure for the invasive round goby. The results showed significant differences in age estimates of the same fish between the different preparation methods and between readers. The estimation of the first annulus, the first year, was the most problematic. The overall agreement was lowest when reading the whole otoliths while the best performance was achieved with sectioned and stained preparation method. Depending on method used the growth estimates also differed. The results question comparability between previous studies and highlight the importance of harmonised aging procedures for the round goby for obtaining correct estimates of population parameters such as growth rate, age at maturity, and longevity.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2022-04-26
    Description: The period of larval drift into a suitable nursery area is considered to be of great significance for recruitment variability in flatfish. Here, a hydrodynamic model coupled with a Lagrangian particle tracking technique was utilized to study the drift from the first feeding larval stage until time of settlement of Central and Eastern Baltic flounder (Platichthys flesus), originating from spawning in the Baltic Sea deep basins, the Arkona- and Bornholm basin (central Baltic Sea), and the Gdansk deep and Gotland basin (eastern Baltic Sea). We examined the spatio-temporal dynamics of the probability to settle in preferred nursery habitat by detailed drift model simulations. The study suggests that the majority of larvae (89% and 74% for Central- and Eastern Baltic flounder, respectively) drift towards coastal areas and settle at metamorphosis ≤20 km from a sandy habitat enabling further migration to a preferred nursery area, i.e. larval drift seems not to be a major bottleneck in recruitment of flounder spawning in the Baltic Sea deep basins. The drift model results suggest that Central Baltic flounder utilize nursery areas mainly in the central and western Baltic, and in the Kattegat, whereas Eastern Baltic flounder mainly utilize the coast in the central and eastern Baltic. Thus, the two stock components seem to use different nursery areas following settlement. Further, in accordance with the “nursery size hypothesis”, the model demonstrates that larvae from the Bornholm basin, utilizing areas with extensive distribution of preferred nursery habitat, display the highest relative successful transport to nursery grounds until settling (72% of successfully settled larvae), suggesting that spawning in the Bornholm Basin is of great importance for stock recruitment of deep basin spawning Baltic flounder.
    Type: Article , PeerReviewed
    Format: text
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  • 3
    Publication Date: 2012-06-14
    Description: Andersson, J., Florin, A.-B., and Petersson, E. 2012. Escapement of eel ( Anguilla anguilla ) in coastal areas in Sweden over a 50-year period – ICES Journal of Marine Science, 69: 991–999. The escapement of eel from coastal areas in Sweden during the last 50 years was assessed using data from voluntary fishery journals and fishery-independent coastal fish monitoring programmes. It was evident that the level of escapement, determined as catch per unit of effort in numbers, from the Baltic Sea decreased over time, with the most rapid decline occurring in the 1960s and early 1970s, but also in recent years. There were, however, differences in the temporal variability in escapement between areas. Escapement from the northernmost studied site did not change significantly during the last 50 years, while there was a rapid decline in the southern areas. Escapement remained relatively stable between the late 1970s and 2000 however, and escapement at the Swedish west coast, inferred from yellow eel catch per unit of effort, generally increased during the same time. The loss in numbers has to some extent been compensated by an increase in mean weight of silver eel. Possible explanations for the retained level of escapement during the last decades despite the continued reduction in recruitment are discussed. Favourable environmental conditions in combination with a lower fishing effort are suggested as the most probable reasons why the escapement decline has not been more dramatic, but stocking and density-dependent effects cannot be ruled out.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
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