Northward movement of marine species (CLIM 015) - Assessment published Sep 2008
Climate change (Primary topic)
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CLIM 015
Key policy question: .
- Increases in regional sea temperatures have triggered a major northward movement of warmer-water plankton in the north-east Atlantic and a similar retreat of colder-water plankton to the north. This northerly movement is about 10o latitude (1 100 km) over the past 40 years, and it seems to have accelerated since 2000. This will have an impact on the distribution of fish in the region.
- Many species of fish and plankton have shifted their distributions northward. Sub-tropical species are occurring with increasing frequency in European waters and sub-Arctic species are receding northwards. The rate of northward movement of a particular species, the silvery john dory, has been estimated at about 50 km/year.
- Changes in the geographic distribution of some species of fish have been observed and 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.
Recordings of two tropical fish 1963-1996
Note: Recordings of the migration of the tropical species silvery john dory (Zenopsis conchifer) and rosy dory (Cyttopsis roseus) 1963-1996
Quero, J.-C.; Du Buit, M.-H. and Vayne, J.-J., 1998. Les observations de poissons tropicaux et le rechauffement des eaux dans l'Atlantique européen. Oceanologica Acta 21: 345351.
Northward movement of zooplankton between 1958-2005
Note: The northward movement of zoo-plankton spanning five decades
Beaugrand, G.; Reid, P. C.; Ibañez, F.; Lindley, J. A. and Edwards, M., 2002. Reorganization of North Atlantic marine copepod biodiversity and climate. Science 296: 16921694.
Relative abundance of warm-water to cold-water flatfish species
Note: Data are shown for four different seas and three sections of the North Sea, depending on mean annual SST
Brander, K. M.; Blom, G.; Borges, M. F.; Erzini, K.; Henderson, G.; MacKenzie, B. R.; Mendes, H.; Ribeiro, J.; Santos, A. M. P. and Toresen, R., 2003. Changes in fish distribution in the eastern North Atlantic: Are we seeing a coherent response to changing temperature? ICES Marine Science Symposia 219: 261270.
The increase in regional sea temperatures has triggered a major re-organisation of zooplankton species composition and biodiversity over the entire North Atlantic basin (Beaugrand et al., 2003), shown in Figure 2. During the past 40 years there has been
a northerly movement of warmer-water plankton by 10o latitude (1 100 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.
Marine species generally have a large potential to spread. Ocean currents are able to spread plankton and larvae rapidly over large distances and many species of fish have migration patterns that exceed 100 km each year. Their movement is particularly pronounced along the European continental shelf edge and has been associated with the Shelf Edge Current running north. Consequently the rate of northward movement is faster in the ocean than on land, partly because the marine environment has fewer barriers to dispersal than terrestrial systems; many terrestrial species, for example, are not able to cross water.
Some clear, well-documented examples of fish species shifts are shown in Figure 1. The silvery john dory (Zenopsis conchifer) was first recorded in European waters off the coast of Portugal at 38oN in 1966 and has since been recorded progressively further north, to north of 55oN by the early 1990s (Quero et al., 1998). It is probably transported northward in the continental slope current and the rate of northward shift in distribution of this species is more than 50 km per year. Other species which have become much more common further north, such as sea bass (Dicentrarchus labrax), red mullet (Mullus surmulletus) and European anchovy (Engraulis encrasicolus), are probably now able to overwinter and establish breeding populations there (Brander et al., 2003).
The ratio of catches of two common flatfish species - European plaice (Pleuronectes platessa) and Common sole (Solea solea) can be used as an index of the increase in the relative abundance of a warm-water vs. a cold-water species of flatfish (Figure 3). This change is linked to a steadily increasing temperature trend in the past 25 years, which has caused the sole to plaice ratio to change, particularly in the southern North Sea, the Irish Sea and the northern North Sea. This change is a change in their distribution, as 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 (Brander et al., 2003). Recently it has been shown that a further temperature increase may lead sole to spawn earlier in the season and thus increase the duration of their growing season whereas plaice does not seem to be affected (Teal et al., 2008). 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. In addition, an index based on ratios of catches minimises the influence of fishing when fishing acts on both species in a similar way, as is the case with these flatfish, which are caught in the same kinds of gear and often in the same fishing operations.
Other factors affecting abundance and distribution include fishing pressure, biological interactions, salinity, oxygen, the North Atlantic Oscillation, and pollution. In some cases changes in distribution are probably due to geographic patterns of fishing and not to climate effects.
Scenario projections of future movements of marine species have not yet been made. Uncertainty in making projections of fish distribution changes over the next 20-50 years arise from both the uncertainties in projections of ocean climate and uncertainties of fish community responses to those changes.
Changes in fish distribution in the eastern North Atlantic
provided by International Council for the Exploration of the Sea (ICES)
Recordings of the migration of the tropical fish species silvery john dory (Zenopsis conchifer) and rosy dory (Cyttopsis roseus)
provided by French institute for marine research (IFREMER)
Continuous Plankton Recorder (CPR) survey
provided by Sir Alister Hardy Foundation for Ocean Science (SAHFOS)
More information about this indicator
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