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

Limburg, Karin E.; Casini, Michele

Sammanfattning

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.

Nyckelord

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

Publicerad i

Biology Letters
2019, Volym: 15, nummer: 12, artikelnummer: 20190352

      SLU författare

      • Associerade SLU-program

      Kust och hav
      Klimat
      Biologisk mångfald

      Globala målen

      SDG14 Hav och marina resurser

      UKÄ forskningsämne

      Fisk- och akvakulturforskning
      Vilt- och fiskeförvaltning
      Ekologi

      Publikationens identifierare

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

      Permanent länk till denna sida (URI)

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