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- Neuenfeldt, Stefan, et al.
(författare)
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Feeding and growth of Atlantic cod (Gadus morhua L.) in the eastern Baltic Sea under environmental change
- 2020
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 77:2, s. 624-632
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Tidskriftsartikel (refereegranskat)abstract
- Five decades of stomach content data allowed insight into the development of consumption, diet composition, and resulting somatic growth of Gadus morhua (Atlantic cod) in the eastern Baltic Sea. We show a recent reversal in feeding level over body length. Present feeding levels of small cod indicate severe growth limitation and increased starvation-related mortality. For young cod, the low growth rate and the high mortality rate are manifested through a reduction in size-at-age. The low feeding levels are likely the result of a decrease in benthic prey abundance due to increased hypoxic areas, while decreasing abundances of pelagic species in the area of cod distribution have prevented a compensatory shift in diet. Our study emphasizes that environmental forcing and the decline in pelagic prey caused changes in consumption and growth rates of small cod. The food reduction is amplified by stunted growth leading to high densities of cod of smaller size competing for the scarce resources. The average growth rate is negative, and only individuals with feeding levels well above average will survive, though growing slowly. These results suggest that the relation between consumption rate, somatic growth and predatorprey population densities is strongly environmentally mediated.
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| 2. |
- Neuenfeldt, Stefan, et al.
(författare)
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Review of trophic models for the Baltic Sea
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This review aims to be a representative overview over the available types of trophic models in order to investigate, if their output can be used to quantify existing food-web indicators for the EU Marine Strategy Framework Directive (MSFD) . The goal is to obtain a comprehensive picture of the applicability of various model approaches to contribute to achieving MSFD objectives. The work will feed into XWEBS Task 3.3 on ’ Evaluation of the model application potential’. In total we have identified 27 food-web related models with different application areas in the Baltic Sea. We highlight the specific purpose for which each model was designed and the key assumptions underlying each model.The assessment of model applicability here is focused on strengths and gaps of the models to realistically depict size and dynamics of functional groups in the Baltic Sea food web. Based on the latter, we illustrate existing gaps in the models, and assess the extent to which the models can be applied to represent status and dynamics of the Baltic Sea food webs. For the future, we recommend to use an ensemble approach where possible to determine guild biomasses as indicators for food web status. Spatial heterogeneity should be accounted for. This issue should be initiated by collecting all relevant processes in the Baltic Sea, such as source-sinks or coastal-offshore connectivity. The spatial and temporal scale of ecosystem models and potential food web indicators should be aligned as far as possible, and following functional criteria, such as topographic differences and known separated community structures. This way, one can avoid erroneous conclusions that are based on limited data projected over the whole Baltic.
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