Eastern Baltic cod recruitment revisited—dynamics and impacting factors

Fritz Köster, Bastian Huwer, Hans-Harald Hinrichsen, Viola Neumann, Andrei Makarchouk, Margit Eero, Burkhard V. Dewitz, Karin Hüssy, Jonna Tomkiewicz, Piotr Margonski, Axel Temming, Jens-Peter Hermann, Daniel Oesterwind, Jan Dierking, Paul Kotterba, Maris Plikshs

Research output: Contribution to journalReviewResearchpeer-review

Abstract

The Eastern Baltic cod abundance started rapidly to increase in the mid-2000s as evidenced by analytical stock assessments, due to increased
recruitment and declining fishing mortality. Since 2014, the analytical stock assessment is not available, leaving the present stock status unclear and casting doubts about the magnitude of the recent increase in recruitment. Earlier studies identified main factors impacting on cod reproductive success to be related to the loss of two out of three spawning areas in the 1980s caused by lack of major Baltic inflows with a concurrent reduction in salinity and oxygen. Other important factors include prey availability for first-feeding larvae, egg predation by sprat and herring and cannibalism on juveniles, all in one way or the other related to the prevailing hydrographic conditions. These factors cannot explain increased reproductive success in the last decade, as the period was characterized by an absence of large-scale Baltic inflows since
2003 and persistent anoxic conditions in the bottom water of the deep Baltic basins. This questions the perception of the increased recruitment in later years and challenges our present understanding of cod recruitment dynamics in the Baltic Sea. In this contribution, we review evidence from the recent literature supplemented by information from latest research cruises to elucidate whether cod reproductive success indeed has increased during the last decade, and we suggest the key processes responsible for the recent dynamics in cod recruitment and outline directions for future research.
Original languageEnglish
JournalICES Journal of Marine Science
Volume74
Issue number1
Pages (from-to)3-19
ISSN1054-3139
DOIs
Publication statusPublished - 2017

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