Deoxygenation impacts on Baltic Sea cod: Dramatic declines in ecosystem services of an iconic keystone predator

AbstractThe intensified expansion of the Baltic Sea’s hypoxic zone has been proposed as one reason for the current poor status of cod (Gadus morhua) in the Baltic Sea, with repercussions throughout the food web and on ecosystem services. We examined the links between increased hypoxic areas and the decline in maximum length of Baltic cod, a demographic proxy for services generation. We analysed the effect of different predictors on maximum length of Baltic cod during 1978–2014 using a generalized additive model. The extent of minimally suitable areas for cod (oxygen concentration ≥ 1 ml l−1) is the most important predictor of decreased cod maximum length. We also show, with simulations, the potential for Baltic cod to increase its maximum length if hypoxic areal extent is reduced to levels comparable to the beginning of the 1990s. We discuss our findings in relation to ecosystem services affected by the decrease of cod maximum length.

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Oceanographic influences on the distribution of Baltic cod, Gadus morhua , during spawning in the Bornholm Basin of the Baltic Sea

Fisheries Oceanography ◽

10.1046/j.1365-2419.1998.00051.x ◽

1998 ◽

Vol 7 (1) ◽

pp. 48-62 ◽

Cited By ~ 41

Author(s):

JONNA TOMKIEWICZ ◽

KLAUS M. LEHMANN ◽

MICHAEL A. ST. JOHN

Keyword(s):

Baltic Sea ◽

Gadus Morhua ◽

Bornholm Basin ◽

The Baltic Sea ◽

The Baltic ◽

Baltic Cod

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Climate-driven long-term trends in Baltic Sea oxygen concentrations and the potential consequences for eastern Baltic cod (Gadus morhua)

ICES Journal of Marine Science ◽

10.1093/icesjms/fsr145 ◽

2011 ◽

Vol 68 (10) ◽

pp. 2019-2028 ◽

Cited By ~ 25

Author(s):

Hans-Harald Hinrichsen ◽

Bastian Huwer ◽

Andrejs Makarchouk ◽

Christoph Petereit ◽

Matthias Schaber ◽

...

Keyword(s):

Baltic Sea ◽

Field Data ◽

Gadus Morhua ◽

The Baltic Sea ◽

Oxygen Conditions ◽

Long Term Trends ◽

The Baltic ◽

Eastern Baltic ◽

Baltic Cod

Abstract Hinrichsen, H-H., Huwer, B., Makarchouk, A., Petereit, C., Schaber, M., and Voss, R. 2011. Climate-driven long-term trends in Baltic Sea oxygen concentrations and the potential consequences for eastern Baltic cod (Gadus morhua). – ICES Journal of Marine Science, 68: 2019–2028. Variations in oxygen conditions in the Baltic are influenced by several mechanisms. Generally, the frequency and magnitude of major inflows have been identified as the most crucial process for the renewal of oxygen-depleted water masses in the Baltic Sea. Furthermore, enhanced degradation of suspended organic matter by bacteria over the past few decades has increased oxygen consumption. Finally, the effects of large-scale climate warming are causing long-term variations in oxygen content and saturation as an observed increase in temperature has led to a general decrease in oxygen solubility of water masses. Oxygen-dependent relationships based on field data and laboratory experiments were used to analyse the impact of the observed decrease in oxygen content on eastern Baltic cod (Gadus morhua) stock-specific processes (e.g. survival rates of eggs, settlement probability of juveniles, habitat utilization of spawning fish, age structure of successful spawners, food consumption rates of adult fish). The observed long-term decline in oxygen conditions in the Baltic Sea has had a seemingly generally negative impact on oxygen-related processes for the different life stages of eastern Baltic cod. Experimentally derived results of oxygen-driven processes were validated by field data.

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Variation in egg buoyancy of Baltic cod Gadus morhua and its implications for egg survival in prevailing conditions in the Baltic Sea

Marine Ecology Progress Series ◽

10.3354/meps110067 ◽

1994 ◽

Vol 110 ◽

pp. 67-74 ◽

Cited By ~ 90

Author(s):

A Nissling ◽

H Kryvi ◽

L Vallin

Keyword(s):

Baltic Sea ◽

Gadus Morhua ◽

The Baltic Sea ◽

Egg Survival ◽

The Baltic ◽

Baltic Cod

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An ecosystem model of food web and fisheries interactions in the Baltic Sea

ICES Journal of Marine Science ◽

10.1016/s1054-3139(03)00098-5 ◽

2003 ◽

Vol 60 (5) ◽

pp. 939-950 ◽

Cited By ~ 89

Author(s):

Chris J Harvey ◽

Sean P Cox ◽

Timothy E Essington ◽

Sture Hansson ◽

James F Kitchell

Keyword(s):

Baltic Sea ◽

Food Web ◽

Species Interactions ◽

Gadus Morhua ◽

Population Analysis ◽

Clupea Harengus ◽

Trophic Relationships ◽

The Baltic Sea ◽

Management Actions ◽

The Baltic

Abstract Because fisheries operate within a complex array of species interactions, scientists increasingly recommend multispecies approaches to fisheries management. We created a food web model for the Baltic Sea proper, using the Ecopath with Ecosim software, to evaluate interactions between fisheries and the food web from 1974 to 2000. The model was based largely on values generated by multispecies virtual population analysis (MSVPA). Ecosim outputs closely reproduced MSVPA biomass estimates and catch data for sprat (Sprattus sprattus), herring (Clupea harengus), and cod (Gadus morhua), but only after making adjustments to cod recruitment, to vulnerability to predation of specific species, and to foraging times. Among the necessary adjustments were divergent trophic relationships between cod and clupeids: cod exhibited top-down control on sprat biomass, but had little influence on herring. Fishing, the chief source of mortality for cod and herring, and cod reproduction, as driven by oceanographic conditions as well as unexplained variability, were also key structuring forces. The model generated many hypotheses about relationships between key biota in the Baltic Sea food web and may ultimately provide a basis for estimating community responses to management actions.

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