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- Bekkevold, Dorte, et al.
(author)
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Mixed-stock analysis of Atlantic herring (Clupea harengus) : a tool for identifying management units and complex migration dynamics
- 2023
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In: ICES Journal of Marine Science. - : Oxford University Press. - 1054-3139 .- 1095-9289. ; 80:1, s. 173-184
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Journal article (peer-reviewed)abstract
- We developed and validated a mixed-stock analysis (MSA) method with 59 single-nucleotide polymorphisms selected from genome-wide data to assign individuals to populations in mixed-stock samples of Atlantic herring from the North and Baltic seas. We analysed 3734 herring from spawning locations and scientific catches of mixed feeding stocks to demonstrate a "one-fits-all" tool with unprecedented accuracy for monitoring spatio-temporal dynamics throughout a large geographical range with complex stock mixing. We re-analysed time-series data (2002-2021) and compared inferences about stock composition with estimates from morphological data. We show that contributions from the western Baltic spring-spawning stock complex, which is under management concern, have likely been overestimated. We also show that a genetically distinctive population of western Baltic autumn spawners, ascribed low fisheries importance, contributes non-negligible and potentially temporally increasing proportions to mixed-stock aggregations, calling for a re-evaluation of stock definitions. MSA data can be implemented in stock assessment and in a variety of applications, including marine ecosystem description, impact assessment of specific fleets, and stock-rebuilding plans.
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| 2. |
- Bråte, Inger Lise, et al.
(author)
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Micro-and macro-plastics in marine species from Nordic waters
- 2017
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Reports (other academic/artistic)abstract
- This report summarises the knowledge on plastics in Nordic marine species. Nordic biota interacts with plastic pollution, through entanglement and ingestion. Ingestion has been found in many seabirds and also in stranded mammals. Ingestion of plastics has been documented in 14 fish species, which many of them are of ecology and commercially importance. Microplastics have also been found in blue mussels and preliminary studies found synthetic fibres in marine worms. Comparability between and within studies of plastic ingestion by biota from the Nordic environment and other regions are difficult as there are: few studies and different methods are used. It is important that research is directed towards the knowledge gaps highlighted in this report, to get a better understanding on plastic ingestion and impact on biota from the Nordic marine environment.
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| 3. |
- Lehtiniemi, Maiju, et al.
(author)
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Distribution and reproduction of the Arctic ctenophore Mertensia ovum in the Baltic Sea
- 2013
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In: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 491, s. 111-124
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Journal article (peer-reviewed)abstract
- Species identification based on morphological characteristics has caused misidentifications and led to twisted views of abundances and roles of ctenophores. Based on extensive field studies from 2007 to 2010, the occurrence of the arctic ctenophore Mertensia ovum was genetically verified in the southern, central and northern Baltic Sea, and its egg production, distribution and abundance were studied in relation to physical factors. Genetic analyses indicate that M. ovum is by far the most abundant small ctenophore in the Baltic Sea. Specimens from a 20 yr old ctenophore collection were also genetically identified as M. ovum, contrary to their previous morphological identification as another ctenophore species, Pleurobrachia pileus. Thus, earlier reports on P. pileus in the Baltic Sea may actually refer to M. ovum. The abundance of M. ovum was regulated by both salinity and temperature, with highest abundances found in sea areas and water layers at temperatures <7 degrees C, salinities >5.5 and oxygen levels >4 ml l(-1). During summer, the highest abundances of ctenophores and their eggs were found near the halocline, while the distribution was more uniform throughout the water column during winter. Only ctenophores >3.5 mm (oral-aboral length) produced eggs in the experiments, with an average rate of 2.2 eggs ind.(-1) d(-1). Finally, comparison with published data from the 1980s (assuming that those data refer to M. ovum) indicates that the present-day ctenophore abundance is similar to 80% lower in the north and similar to 55% higher in the southern parts of the Baltic Sea, due to reasons yet to be established.
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