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Research article - Peer-reviewed, 2019

Otolith chemistry indicates recent worsened Baltic cod condition is linked to hypoxia exposure

Limburg, Karin E.; Casini, Michele

Abstract

Deoxygenation worldwide is increasing in aquatic systems with implications for organisms' biology, communities and ecosystems. Eastern Baltic cod has experienced a strong decline in mean body condition (i.e. weight at a specific length) over the past 20 years with effects on the fishery relying on this resource. The decrease in cod condition has been tentatively linked in the literature to increased hypoxic areas potentially affecting habitat range, but also to benthic prey and/or cod physiology directly. To date, no studies have been performed to test these mechanisms. Using otolith trace element microchemistry and hypoxia-responding metrics based on manganese (Mn) and magnesium (Mg), we investigated the relationship between fish body condition at capture and exposure to hypoxia. Cod individuals collected after 2000 with low body condition had a higher level of Mn/Mg in the last year of life, indicating higher exposure to hypoxic waters than cod with high body condition. Moreover, lifetime exposure to hypoxia was even more strongly correlated to body condition, suggesting that condition may reflect long-term hypoxia status. These results were irrespective of fish age or sex. This implies that as Baltic cod visit poor-oxygen waters, perhaps searching for benthic food, they compromise their own performance. This study specifically sheds light on the mechanisms leading to the low condition of cod and generally points to the impact of deoxygenation on ecosystems and fisheries.

Keywords

hypoxia; body condition; Gadus morhua; otoliths; trace element analyses

Published in

Biology Letters
2019, Volume: 15, number: 12, article number: 20190352

      SLU Authors

    • Associated SLU-program

      Coastal and sea areas
      Climate
      Biodiversity

      Sustainable Development Goals

      SDG14 Life below water

      UKÄ Subject classification

      Fish and Aquacultural Science
      Fish and Wildlife Management
      Ecology

      Publication identifier

      DOI: https://doi.org/10.1098/rsbl.2019.0352

      Permanent link to this page (URI)

      https://res.slu.se/id/publ/103276