Articles | Volume 13, issue 2
Research article
21 Jan 2016
Research article |  | 21 Jan 2016

Potential future fisheries yields in shelf waters: a model study of the effects of climate change and ocean acidification

S. M. van Leeuwen, W. F. Le Quesne, and E. R. Parker

Abstract. We applied a coupled marine water column model to three sites in the North Sea. The three sites represent different hydrodynamic regimes and are thus representative of a wider area. The model consists of a hydro-biogeochemical model (GOTM-ERSEM-BFM) coupled one way upwards to a size-structured model representing pelagic predators and detritivores (Blanchard et al., 2009). Thus, bottom-up pressures like changing abiotic environment (climate change, chemical cycling) will have an impact on fish biomass across the size spectrum. Here, we studied three different impacts of future conditions on fish yield: climatic impacts (medium emission scenario), abiotic ocean acidification impacts (reduced pelagic nitrification), and biotic ocean acidification impacts (reduced detritivore growth rate). The three impacts were studied separately and combined, and results showed that sites within different hydrodynamic regimes can respond very differently. The seasonally stratified site showed an increase in fish yields (occurring in winter and spring), with acidification effects of the same order of magnitude as climatic effects. The permanently mixed site also showed an increase in fish yield (increase in summer, decrease in winter), due to climatic effects moderated by acidification impacts. The third site, which is characterised by large inter-annual variability in thermal stratification duration, showed a decline in fish yields (occurring in winter) due to decline in the benthic system which forms an important carbon pathway at this site. All sites displayed a shift towards a more pelagic-oriented system.

Short summary
– Effects of ocean acidification in shelf waters on fish yield can be of the same order of magnitude as climatic impacts. – Local differences in response within one shelf sea due to different governing hydrodynamic regimes and variation in importance of benthic food web. – Future fish yields in the North Sea: seasonally stratified areas show increased yield, transitional waters show decreased yield and permanently mixed waters show increased yield moderated by acidification impacts.
Final-revised paper