Use of existing hydrographic infrastructure to forecast the environmental spawning conditions for Eastern Baltic cod.

von Dewitz, Burkhard, Tamm, Susanne, Höflich, Katharina, Voss, Rüdiger and Hinrichsen, Hans-Harald (2018) Use of existing hydrographic infrastructure to forecast the environmental spawning conditions for Eastern Baltic cod. Open Access PLoS ONE, 13 (5). e0196477. DOI 10.1371/journal.pone.0196477.

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Abstract

The semi-enclosed nature and estuarine characteristics, together with its strongly alternating bathymetry, make the Baltic Sea prone to much stronger interannual variations in the abiotic environment, than other spawning habitats of Atlantic cod (Gadus morhua). Processes determining salinity and oxygen conditions in the basins are influenced both by long term gradual climate change, e.g. global warming, but also by short-term meteorological variations and events. Specifically one main factor influencing cod spawning conditions, the advection of highly saline and well-oxygenated water masses from the North Sea, is observed in irregular frequencies and causes strong interannual variations in stock productivity. This study investigates the possibility to use the available hydrographic process knowledge to predict the annual spawning conditions for Eastern Baltic cod in its most important spawning ground, the Bornholm Basin, only by salinity measurements from a specific location in the western Baltic. Such a prediction could serve as an environmental early warning indicator to inform stock assessment and management. Here we used a hydrodynamic model to hindcast hydrographic property fields for the last 40+ years. High and significant correlations were found for months early in the year between the 33m salinity level in the Arkona Basin and the oxygen-dependent cod spawning environment in the Bornholm Basin. Direct prediction of the Eastern Baltic cod egg survival in the Bornholm Basin based on salinity values in the Arkona Basin at the 33 m depth level is shown to be possible for eggs spawned by mid-age and young females, which currently predominate the stock structure. We recommend to routinely perform short-term predictions of the Eastern Baltic cod spawning environment, in order to generate environmental information highly relevant for stock dynamics. Our statistical approach offers the opportunity to make best use of permanently existing infrastructure in the western Baltic to timely provide scientific knowledge on the spawning conditions of Eastern Baltic cod. Furthermore it could be a tool to assist ecosystem-based fisheries management with a cost-effective implementation by including the short term predictions as a simple indicator in the annual assessments.

Document Type: Article
Keywords: Oxygen; salinity; spawning; Baltic Sea; Buoyancy; Hydrodynamics; Cod; Fisheries
Research affiliation: Kiel University > Kiel Marine Science
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EV Evolutionary Ecology of Marine Fishes
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
Kiel University
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.1371/journal.pone.0196477
ISSN: 1932-6203
Projects: INSPIRE, BONUS BIO-C3, DEMO, Future Ocean
Date Deposited: 12 Jun 2018 10:05
Last Modified: 17 Dec 2018 08:20
URI: http://oceanrep.geomar.de/id/eprint/43315

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