Many species of plankton and fish have shifted their distribution northward and sub‑tropical species are occurring with increasing frequency in European waters, changing the composition of local and regional marine ecosystems in a major way (1,6). Recent studies have shown that the northward movement of southerly species has caused species richness in the North Sea to increase (2). This may have negative ecological and socio‑economic effects: the three large species that have decreased their range the most in the North Sea are all commercially relevant, while only one of the five most increasing species and less than half of the all the species that expanded their range are of commercial value. A climate change-induced shift from large to smaller species is thus likely to reduce the value of North Sea fisheries (2).
During the past 40 years there has been a northerly movement of warmer‑water plankton by 10° latitude (1100 km) in the north‑east Atlantic and a similar retreat of colder‑water plankton to the north. This northerly movement has continued over the past few years and appears to have accelerated since 2000. Sole and other warm‑water species have become relatively more abundant in northerly areas, while plaice and other cold‑water species have become rare in southerly areas (5). Climate is only one of many factors which affect distribution and abundance, but the consistency of the response of this particular index to temperature, both within particular areas (i.e. time trend) and across all areas (i.e. geographic trend) suggest that the causal relationship is quite strong. Scenario projections of future movements of marine species have not yet been made (3).
The kinds of fish which are available for human consumption are not necessarily affected by the distribution changes shown above, because fish are often transported long distances from where they are caught to where they are marketed, but the prices of fish may change if certain species that are common today become less common. People eating locally caught fish may notice changes in the species they catch or buy. Changes in distribution may affect the management of fisheries. Fisheries regulations in the EU include allocations of quotas based on historic catch patterns, and these may need to be revised (3). In general it is not possible to predict whether northward shifts in distribution will have a positive or a negative effect on total fisheries production (4).
The Mediterranean Sea is warming in both shallow and deep waters (8). This warming is part of global climate trends and not a regional phenomenon (7). Fisheries landings fluctuations of the seven Mediterranean EU member states (Spain, France, Italy, Slovenia, Greece, Malta and Cyprus) during 1985-2008 were examined for the most abundant commercial species (59 species) and showed significant year-to-year correlations with temperature for nearly 60 % of the cases (7). From these, the majority (~70 %) were negatively related and showed a reduction of 44 % on average. Increasing trends were found, mainly in the landings of species with short life spans, which seem to have benefited from the increase in water temperature. These results indicate that climate should be examined together with fisheries as a factor shaping stock fluctuations (7). The reason why the landings of some species have increased or decreased with temperature oscillations may be related to stock spawning periods (7). An indirect effect of warming could also be related to food availability (potential modification of fish abundance by climate change through fluctuations in plankton abundance (9).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for France.
- Brander et al. (2003); Beare et al. (2004); Beare et al. (2005); Perry et al. (2005); Stebbing et al. (2002), in: EEA, JRC and WHO (2008)
- Hiddink and Hofstede (2008), in: EEA, JRC and WHO (2008)
- EEA, JRC and WHO (2008)
- Brander (2007), in: EEA, JRC and WHO (2008)
- Brander et al., 2003, in: EEA, JRC and WHO (2008)
- Nicolas et al. (2011)
- Tzanatos et al. (2014)
- Vargas-Yáñez et al. (2008); Nykjaer (2009); Raitsos et al. (2010), all in: Tzanatos et al. (2014)
- Blanchard et al. (2012); Woodworth-Jefcoats et al. (2013), both in: Tzanatos et al. (2014)