18.104.22.168 Marine fisheries and aquaculture
An assessment of the vulnerability of the north-east Atlantic marine ecoregion concluded that climate change is very likely to produce significant impacts on selected marine fish and shellfish (Baker, 2005). Temperature increase has a major effect on fisheries production in the North Atlantic, causing changes in species distribution, increased recruitment and production in northern waters and a marked decrease at the southern edge of current ranges (Clark et al., 2003; Dutil and Brander, 2003; Hiscock et al., 2004; Perry et al., 2005). High fishing pressure is likely to exacerbate the threat to fisheries, e.g., for Northern cod (Brander, 2005). Sea-surface temperature changes as low as 0.9°C over the 45 years to 2002 have affected the North Sea phytoplankton communities, and have led to mismatches between trophic levels (see Glossary) throughout the community and the seasonal cycle (Edwards and Richardson, 2004). Together with fishing pressure, these changes are expected to influence most regional fisheries operating at trophic levels close to changes in zooplankton production (Anadón et al., 2005; Heath, 2005). Long-term climate variability is an important determinant of fisheries production at the regional scale (see Klyashtorin, 2001; Sharp, 2003), with multiple negative and positive effects on ecosystems and livelihoods (Hamilton et al., 2000; Eide and Heen, 2002; Roessig et al., 2004). Our ability to assess biodiversity impacts, ecosystem effects and socio-economic costs of climate change in coastal and marine ecosystems is still limited but is likely to be substantial for some highly dependent communities and enterprises (Gitay et al., 2002; Pinnegar et al., 2002; Robinson and Frid, 2003; Anadón et al, 2005; Boelens, et al., 2005). The overall interactions and cumulative impacts on the marine biota of sea-level rise (coastal squeeze with losses of nursery and spawning habitats), increased storminess, changes in the NAO, changing salinity, acidification of coastal waters, and other stressors such as pollutants, are likely but little known.
Marine and freshwater fish and shellfish aquaculture represented 33% of the total EU fishery production value and 17% of its volume in 2002 (EC, 2004). Warmer sea temperatures have increased growing seasons, growth rates, feed conversion and primary productivity (Beaugrand et al., 2002; Edwards et al., 2006), all of which will benefit shellfish production. Opportunities for new species will arise from expanded geographic distribution and range (Beaugrand and Reid, 2003), but increased temperatures will increase stress and susceptibility to pathogens (Anadón et al., 2005). Ecosystem changes with new invasive or non-native species such as gelatinous zooplankton and medusa, toxic algal blooms, increased fouling and decreased dissolved oxygen events, will increase operation costs. Increased storm-induced damage to equipment and facilities will increase capital costs. Aquaculture has its own local environmental impacts derived from particulate organic wastes and the spread of pathogens to wild populations, which are likely to compound climate-induced ecosystem stress (SECRU, 2002; Boelens et al., 2005).