Re-thinking the “ecological envelope” of Eastern Baltic cod (Gadus morhua): conditions for productivity, reproduction, and feeding over time

Henrik Svedäng, Oleg P Savchuk, Anna Villnäs, Alf Norkko, Bo Gustafsson, Sofia A. Wikström, Christoph Humborg

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Hypoxia is presently seen as the principal driver behind the decline of the former dominating Eastern Baltic cod stock (EBC; Gadus morhua). It has been proposed that both worsening conditions for reproduction and lower individual growth, condition, and survival are linked to hypoxia. Here, we elucidate the ecological envelope of EBC in terms of salinity stratification, oxygen content, and benthic animal biomasses, and how it has affected EBC productivity over time. The spawning conditions started deteriorating in the Gotland Deep in the 1950s due to oxygen depletion. In contrast, in the Bornholm Basin, hydrographic conditions have remained unchanged over the last 60 years. Indeed, the current extent of both well-oxygenated areas and the frequency of hypoxia events do not differ substantially from periods with high EBC productivity in the 1970s–1980s. Furthermore, oxygenated and therefore potentially suitable feeding areas are abundant in all parts of the Baltic Sea, and our novel analysis provides no evidence of a reduction in benthic food sources for EBC over the last 30 years. We find that while reproduction failure is intricately linked to hydrographic dynamics, a relationship between the spread of hypoxia and the decline in EBC productivity during the last decades cannot be substantiated.
Original languageEnglish
JournalICES Journal of Marine Science
Volume79
Issue number3
Pages (from-to)689-708
Number of pages20
ISSN1054-3139
DOIs
Publication statusPublished - Apr 2022
MoE publication typeA1 Journal article-refereed

Fields of Science

  • ATLANTIC COD
  • BODY-SIZE
  • DEMERSAL FISH
  • DYNAMICS
  • Eastern Baltic cod
  • HYPOXIA
  • LONG-TERM CHANGES
  • OXYGEN
  • REGIME SHIFTS
  • SEA
  • VARIABILITY
  • benthic biomass
  • hypoxia
  • productivity
  • reproduction volume
  • spatial scales
  • 1181 Ecology, evolutionary biology

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