Review of climate change impacts on marine fisheries in the UK and Ireland

ABSTRACT

1. Commercial fishing is an important socio-economic activity in coastal regions of the UK and Ireland. Ocean–atmospheric changes caused by greenhouse gas emissions are likely to affect future fish and shellfish production, and lead to increasing challenges in ensuring long-term sustainable fisheries management.
2. The paper reviews existing knowledge and understanding of the exposure of marine ecosystems to ocean-atmospheric changes, the consequences of these changes for marine fisheries in the UK and Ireland, and the adaptability of the UK and Irish fisheries sector.
3. Ocean warming is resulting in shifts in the distribution of exploited species and is affecting the productivity of fish stocks and underlying marine ecosystems. In addition, some studies suggest that ocean acidification may have large potential impacts on fisheries resources, in particular shell-forming invertebrates.
4. These changes may lead to loss of productivity, but also the opening of new fishing opportunities, depending on the interactions between climate impacts, fishing grounds and fleet types. They will also affect fishing regulations, the price of fish products and operating costs, which in turn will affect the economic performance of the UK and Irish fleets.
5. Key knowledge gaps exist in our understanding of the implications of climate and ocean chemistry changes for marine fisheries in the UK and Ireland, particularly on the social and economic responses of the fishing sectors to climate change. However, these gaps should not delay climate change mitigation and adaptation policy actions, particularly those measures that clearly have other ‘co-benefits’. Copyright © 2012 John Wiley & Sons, Ltd.

INTRODUCTION

Commercial fishing is an important socio-economic activity in coastal regions of the UK (including England, Scotland, Wales, Northern Ireland, Isle of Man and the Channel Islands) and Republic of Ireland. In 2010, total landings of fish and shellfish into the UK and into Ireland were 606,295 and 245,856 tonnes, respectively, with a first-sale value of £719 million and £208 million respectively (~US$ 1.1 billion and $0.33 billion) (Marine Management Organization, 2011; Sea Fisheries Protection Authority, 2011) (Figure 1). In total, landings into the UK and Ireland contributed only around 1% of global catch but more than 30% of landed value in 2009 (FAO, 2010). Within the UK, the fishing industry is particularly important in Scotland, which contributed about 60% of the total landings by weight and value. This is followed by England (30%), Northern Ireland (5%), Wales (2%) and the Channel Islands/Isle of Man (<1%) (Figure 1). Overall, the UK fishing fleets consist of ~6477 vessels, directly employing 12 703 people, while the processing sector employed an additional ~18 000 people in 2010 (Marine Management Organization, 2011). The dependency on fishing for jobs can be as high as 20% or more in some coastal communities. The fisheries sector (fishing boats and onshore processing) contributed £1192 million Gross Value Added (GVA) to the UK economy in 2009–2010 (Marine Management Organization, 2011). Marine fisheries is also an important sector in Ireland, the most important fishing ports being Killybegs (mostly pelagic fishing vessels), Castletownbere, and An Daingean (mostly demersal vessels). The Irish fishing fleet consisted of ~1700 registered vessels in 2010, the vast majority of which are small, although the Irish fleet also includes some of the largest fishing vessels in the EU (mainly targeting pelagic species) (Sea Fisheries Protection Authority, 2011). In Ireland, around 12000 people are employed directly in fish-related industries (Sea Fisheries Protection Authority, 2011). Of these, 6100 people are employed in the fishing fleet, 4000 in seafood factories, and some 2000 in ancillary employment servicing the industry.

Figure 1. Total landings and first-scale value into the UK (by UK vessels) and Republic of Ireland in 2010 (Marine Management Organization, 2011; Sea Fisheries Protection Authority, 2011). The Islands includes the Channel Islands and Isle of Man.

Many commercially important demersal fish stocks such as Atlantic cod (Gadus morhua), sandeel (Ammodytes marinus) and whiting (Merlangius merlangus) in the UK and Ireland have been over-exploited (ICES, 2009). Total landings into the UK peaked at 1.1 million tonnes in 1930 but dropped to 600,000 tonnes in 2010, while fishing power, particularly trawlers, has increased by an order of magnitude (Engelhard, 2008). Part of this decline in total catch was a consequence of lost fishing opportunities in distant waters (e.g. around Iceland and Norway in the 1970s) (Kerby et al., 2012). There have also been various booms and collapses in fish stocks that are of importance to UK and Irish fisheries, e.g. Atlantic cod and herring (Clupea harengus). Fishing effort of the demersal fishery has declined by about 30% since 2000, and this fishery operates mainly in the North Sea, west of Scotland and in the Irish Sea. It is estimated that only 20–40% of fish stocks around the UK are being fished at a level that would achieve long-term maximum sustainable yield (Charting Progress 2: chartingprogress.defra.gov.uk/fisheries). Fishing competes with other human uses of the ocean, such as marine sand and gravel extraction, waste disposal, shipping, marine renewable energy developments (i.e. wave, wind, and tidal power), aquaculture, recreational activities and oil and gas exploration.

Species that comprised the majority of fisheries catch in the UK and Ireland in 2009 include pelagic and demersal fishes and invertebrates (Marine Management Organization, 2011; Sea Fisheries Protection Authority, 2011) (Figure 2). Atlantic mackerel (Scomber scombrus) contributed the second and largest catches by value and weight, in the UK and Ireland respectively. Other species that are important in value in both the UK and Ireland include scallops (Pecten maximus), monkfish/anglerfish (Lophius spp.), langoustine/scampi (Nephrops norvegicus) and hake (Merluccius merluccius) (Marine Management Organization, 2011; Sea Fisheries Protection Authority, 2011). In the UK, the highest value catch is Nephrops due to its high price, while the species that made up the greatest catch by weight was mackerel. Long-term changes in climate and ocean biogeochemistry have been observed and predicted in the UK shelf seas (Frost et al., 2012), which may have direct and indirect implications for marine ecosystems and fisheries. These changes include warming (both increase in mean temperature and seasonal differences), changes in the frequency of severe weather events or the onset of stratification and mixing of the water column. In addition to changes related to temperature and density of the ocean, the chemistry of sea water is also affected by greenhouse gases, notably through ocean acidification and low oxygen levels (Orr et al., 2005; IPCC, 2007; Brierley and Kingsford, 2009; Cochrane et al., 2009). Temperature changes, ocean acidification and changes in oxygen levels are likely to affect marine ecosystems and their associated fisheries, adding to the challenges of managing fisheries sustainably.

Figure 2. Total values of the top 10 species with the highest value in 2010 and their landings in (a, b) the UK and (c, d) Ireland.

The major biological changes associated with environmental changes that have been observed so far include changes in the physiological performances of marine organisms (Pörtner and Knust, 2007; Pörtner et al., 2008; Pauly, 2010; Pörtner, 2010), shifts in species distribution (Perry et al., 2005; Dulvy et al., 2008), changes in phenology, i.e. the timing of biological events (Edwards and Richardson, 2004; Genner et al., 2010), productivity (Boyce et al., 2010) and community and ecosystem structure (Hiddink and ter Hofstede, 2008; Möllmann et al., 2009; ter Hofstede et al., 2010). These changes in exploited marine populations and ecosystems may affect fishing operations, leading to direct and indirect impacts on local economies and on fisheries management (Allison et al., 2009; Merino et al., 2010; Pinnegar et al., 2010; Sumaila and Cheung, 2010).

This paper reviews existing knowledge with regard to the exposure of UK and Irish fisheries to ocean-atmospheric changes resulting from anthropogenic greenhouse gas emissions. Impact include changes in distribution, productivity and variability of resources, effects on fishing operations and their implications for fisheries management and conservation under climate change. We then discuss how these changes have in the past or are expected in the future to affect the economics of fisheries, including recreational fishing. Finally, we discuss possible measures to mitigate and adapt to these changes and identify major gaps in knowledge that would need to be filled to allow effective management of marine fisheries in the future.

IMPACTS OF CLIMATE AND OCEAN CHANGES ON FISHERIES

Effects of climate and ocean changes driven by greenhouse gas emission on marine fisheries can be divided into effects on: (1) resource availability, (2) fishing operations, (3) fisheries management and conservation measures, and (4) profits from fisheries (balance between price of fish products and fishing costs). A major difficulty in assessing the magnitude of these impacts is to directly attribute observed changes in fisheries to climate and ocean changes rather than other stressors such as intensive fishing pressure. This is mainly because marine ecosystems are characterized by large natural variability in climate and ecosystem processes, and also respond to fishing and other extraction activities. Furthermore, it is now known that fishing can make marine ecosystems more sensitive to climate variability and change (Ottersen et al., 2004) through impoverishment of age structure in fish populations and hence reduced ‘buffering capacity’ to climate-related poor year classes. Here, existing knowledge is used to understand the mechanisms through which climate and ocean change impacts on fisheries, and the interactions between different aspects of marine fisheries in the UK and Ireland, to infer the current and future implications of these changes.

Effects on resource availability

Climate change and ocean acidification could have major consequences for resource availability, and in particular the interaction between fish populations and fishing gears is dependent on the distribution of the resources and productivity of the underlying stock. The observed and projected future changes in resource, in terms of each of these factors, and their implications for UK and Irish fisheries are discussed here.

Distribution shift

Studies have shown that aerobic scope (oxygen availability for metabolism) of marine fishes and invertebrates, and its interactions with temperature, food availability and ocean chemistry, is a major factor determining life history, growth and distribution (Pauly, 2010; Pörtner, 2010). Fishes and invertebrates generally have an optimal environmental temperature that allows maximum aerobic scope, which is reduced as temperature increases or decreases from the optimum. Changes in ocean chemistry, particularly ocean acidification and reduced oxygen level, can also reduce the aerobic scope of the organisms (Pörtner, 2010; Cheung et al., 2011a). Changes in food availability, especially in early life stages, can affect survival and productivity of the exploited populations. These physiological mechanisms have direct implications for the distribution and abundance of fishery resources.

As distributions of marine organisms are generally dependent on optimal environmental conditions (e.g. temperature, oxygen, food availability), long-term changes in temperature and/or other ocean conditions often coincide with observed changes in distribution and fisheries (Sumaila et al. 2011). In an analysis of 50 abundant species in the waters around UK and Ireland, 70% of the species demonstrably responded to warming in the region by changing distribution and abundance (Simpson et al., 2011). Specifically, warm-water species with smaller maximum body size have increased in abundance while cold-water, large-bodied species have decreased in abundance. Such changes are significant and related to changes in water temperature (Simpson et al., 2011) Recent analyses of Scottish and English commercial catch data spanning the period 1913–2007 has revealed that the peak catches of target species such as cod, haddock (Melanogrammus aeglefinus), plaice (Pleuronectes platessa) and sole (Solea solea) shifted latitudinally, albeit not in a consistent way (Engelhard et al., 2011). For example, cod distribution seems to have shifted steadily north-eastward and towards deeper water in the North Sea. Sole seems to have retreated away from the Dutch coast, southwards towards the eastern Channel whereas plaice distribution has moved north-westwards (van Keeken et al., 2007; Engelhard et al., 2011) while southern species such as sea bass (Decentrarchus labra) and red mullet (Mullus barbatus) may be expanding their northern distribution boundary into UK waters, in particular the English Channel and southern North Sea. These changes in commercial catches are likely to be indicative of an underlying climate-driven distribution shift in the exploited population, as shown from the significant correlation between environmental temperature and distribution metrics of these species based on fishery-independent survey data (Perry et al., 2005; Dulvy et al., 2008; Hiddink and ter Hofstede, 2008; Engelhard et al., 2011). However, differential exploitation patterns and ecosystem production trends may also contribute to such observations. International fisheries landings data for the whole north-east Atlantic region (from around 36–80^oN and 42^oW–68.5^oE) demonstrate both northerly and southerly shifts over recent decades. Many more species shifted southwards than northwards between the 1970s and 1980s (a relatively cool period) and vice versa in the 1980s and 1990s (a relatively warm period) (Heath, 2005), clearly illustrating that changes in underlying fish distribution patterns manifest themselves as changes in the distribution of commercial fishery catches, with resulting impacts on profits. These changes also have implications for fisheries management (see discussion below).

Changes in productivity and variability of fisheries resources

Recruitment variability is a key measure of the productivity of a stock, and is defined by the number of juvenile fish that have survived from the annual egg production and become available to the fishery. There are a number of hypotheses proposed to explain the large reduction observed in numbers remaining from the egg to the adult stage in marine fish, but most of them focus on physical processes and the necessity for adequate environmental conditions, e.g. optimal environmental window (Cury and Roy, 1989); Triad hypothesis (Bakun, 1996); oscillating control hypothesis (Hunt et al., 2002), or the provision of adequate food at the right time (e.g. match-mismatch hypothesis Cushing, 1990; Durant et al., 2007). Empirical data on exploited populations and fisheries often show strong relationships between recruitment success, fisheries catches and climatic variables in a number of fish and shellfish stocks that are important to the UK and Ireland. These strong relationships have been demonstrated, for example, for cod, whiting and haddock (Brander and Mohn, 2004; Cook and Heath, 2005), plaice (van der Veer and Witte, 1999), herring (Nash and Dickey-Collas, 2005), Atlantic mackerel (Jansen and Gislason, 2011), sea bass (Pawson, 1992), and scallops (Shephard et al., 2010).

In the case of cod, there is a well-established relationship between recruitment and sea temperature (O'Brien et al., 2000; Beaugrand et al., 2003; Clark et al., 2003), but this relationship differs between the different cod stocks that inhabit the North Atlantic (Planque and Fredou, 1999). For stocks at the northern extremes, warming leads to enhancement of recruitment, while in the North Sea, close to the southern limits of the range, warmer conditions lead to weaker than average year classes. During the late 1960s and early 1970s, cold conditions were correlated with a sequence of positive recruitment years in cod, haddock and whiting (Brander and Mohn, 2004; Cook and Heath, 2005) and subsequently high fisheries catches for a number of years thereafter (Heath and Brander, 2001). For Atlantic mackerel, currently forming the most valuable fishery in Ireland, increases in sea surface temperature are known to affect the timing and magnitude of growth, recruitment and migration with subsequent impacts on permissible levels of exploitation (Jansen and Gislason, 2011). Similarly recruitment in blue whiting (Micromesistius poutassou) also seems to be dependent on prevailing climatic conditions. Hátún et al. (2009) demonstrated that the position of the North Atlantic subpolar gyre west of the British Isles seems to regulate spawning distribution of blue whiting and hence future recruitment patterns in this species. For scallops, data collected from the scallop fishery in the Isle of Man showed that numbers of young scallops each year were, on average, positively related to seawater temperature in the spring when the animals were spawned. The gonads of adult scallops were also larger in warmer years, indicating higher egg production (Shephard et al., 2010). Thus, ocean warming may have opposite effects on the productivity of different exploited fishes and invertebrates, depending on their temperature preference and current environmental conditions.

Ocean acidification may have direct and indirect impacts on the recruitment, growth and survival of exploited species (Fabry et al., 2008) and some species may become more vulnerable to ocean acidification with increases in temperature (Wood et al., 2010; Hale et al., 2011). The impacts are suggested to be particularly apparent for animals with calcium carbonate shells and skeletons such as molluscs, some crustaceans, and echinoderms (Gazeau et al., 2007; Cooley and Doney, 2009; Kroeker et al., 2010), but research shows large variations between and within taxonomic groups. While invertebrates including Nephrops and lobsters are highly valuable fisheries in the UK and Ireland, these species are also shown to be potentially vulnerable to impacts from ocean acidification. For example, under a CO₂ concentration that is equivalent to the high emission scenario in the IPCC AR4 assessment (SRES A1F, 1200 ppm by 2100; IPCC, 2007), European lobster (Homarus gammarus) did not show significant change in carapace length or development, but carapace mass was significantly lower during the final developmental stage of the larvae (Arnold et al., 2009). Also, experiments on larvae of oysters (Crassostrea virginica and C. ariakensis) have shown that pCO₂ within the range projected by the IPCC (up to 1200 ppm by 2100) could lead to 16% decrease in shell area and 42% decrease in calcium carbonate content relative to those kept under the pre-industrial CO₂ level (280 ppm) (Miller et al., 2009). Current evidence on direct impacts of ocean acidification on commercial finfish, however, is limited. It is possible that the physiological functions of some finfish may be impaired (Munday et al., 2010), the development and survival of their early life history stages may be impacted (Munday et al., 2010; Frommel et al., 2012) and the invertebrate food sources of fishes may be affected by ocean acidification (Fabry et al., 2008; Hale et al., 2011). On the other hand, a meta-analysis of vulnerability in various marine taxonomic groups suggests that many marine organisms may be more resistant to ocean acidification than previously thought, and their long-term adaptive capacity is poorly understood (Hendriks et al., 2009).

There is strong consensus and robust evidence in the literature that acidification of the ocean will continue in this century as atmospheric CO₂ concentrations increase. So far, impacts from ocean acidification on UK and Irish fisheries have yet to be detected. Little modelling has yet taken place to scale up from laboratory experiments to populations and to the consequences for fishermen and fleets. A preliminary economic assessment estimated the extent of possible economic losses to the UK shellfish industry under ocean acidification (Pinnegar et al., 2012). Four of the ten most valuable marine fishery species in the UK are calcifying shellfish and the analyses suggested that losses in the mollusc fisheries alone could amount to £55–379 million per year by 2080 depending on the CO₂ emission scenario chosen. In addition, a further £59.8–124.6 million might be lost from the shellfish aquaculture industry assuming future CO₂ concentrations increase from the current level of ~380 ppm to ~740 ppm (pH 7.9–8.0). Thus, there is a clear economic reason to improve our understanding and techniques for modelling the up-scale implications of physiological and behavioural responses to ocean acidification. Such analyses are necessary if we are to understand the magnitude of impacts from ocean acidification on fishing fleets, which would help refine estimates of impacts on the UK and Irish national economies (Le Quesne and Pinnegar, 2011).

Implications for resource availability

Model simulations suggest that distributions of exploited species will continue to shift in the next five decades both globally and in the north-east Atlantic specifically (Cheung et al., 2009, 2010, 2011a; Lindegren et al., 2010). For example, an approach called the Dynamic Bioclimate Envelope Models (DBEMs) has been developed to project future distribution and resource availability under scenarios of climate change (Cheung et al. 2008, 2009, 2010, 2011a). The approach is based on observed species distribution patterns, population dynamics and includes empirical scaling of primary production. An analysis by Cheung et al. (2010) included all major exploited species in the world (1066 species of fish and invertebrates). This study estimated future changes in maximum potential catch (a proxy of maximum sustainable yield) as exploited species shift their distribution and marine primary productivity changes under scenarios of climate and ocean chemistry (SRES A1B,) projected by the NOAA GFDL coupled climate model CM2.1. Cheung et al. (2010) suggest that climate change may lead to large-scale redistribution of global maximum catch potential, with an average of 30–70% increase in yield of high-latitude regions (>50^o N in the northern hemisphere), but a drop of up to 40% in the tropics. Northern European countries such as the UK and Ireland are projected to gain slightly in maximum potential catch (but not as much as countries such as Norway and Iceland). A small gain (<5%) is projected in the North Sea if potential effects of ocean acidification are ignored (Figure 3).

Figure 3. Projected changes in maximum catch potential by 2050 relative to 2005 (10-year average) under the SRES A1B scenario with assumption of no sensitivity (black bar) and high sensitivity (open bar) to ocean acidification. Projections were produced from the dynamic bioclimatic envelope model with physical and biogeochemical outputs from the NOAA's GFDL Earth System Model (TOPAZ) (redrawn from Cheung et al., 2011a).

Subsequently, Cheung et al. (2011a) explicitly accounted for the potential impacts of ocean acidification, low oxygen and changes in size-structure of phytoplankton into the DBEM to predict maximum catch potential in 2050. The results suggest that these additional factors may cause a reduction in the maximum catch potential by up to 30% in the North Sea and other European seas. Any scenario that would result in a 10–25% loss of shellfish landings as a result of ocean acidification will have dramatic impacts on the UK fishing industry in the order of £26–66 million per year and around 1000–3100 potential job losses. In contrast, using a size-structured food web model (Blanchard et al., 2009) to investigate how future temperature and primary production could modulate future fisheries potential in the UK, a 24% increase in potential catch was predicted (Blanchard et al., 2010). Possible reasons for the differences in the projected changes from DBEM (Cheung et al., 2011a) and Blanchard et al. (2010) can be because of the consideration of the assumed negative effects of ocean acidification (admittedly still uncertain) on maximum potential catch by the DBEM that is not included in the Blanchard et al. (2010) analysis. Moreover, the biogeochemical models that were used by the two studies are substantially different. A detailed numerical comparison could be carried out to gain a better understanding of the differences in the projected catch changes from the two models. Overall, these modelling approaches have their own sets of assumptions and uncertainties, including those arising from the biological and ecological components in the impact assessment model and the physical and chemical components of the Earth System Models (Stock et al., 2010). Given these model assumptions and uncertainties, interpretation of the model projections should focus on the general trend instead of the detailed numerical outputs.

Climate change is expected to result in reduction in the potential catch of species with northern distributions, such as cod and plaice because of a shift in distribution and changes in stock productivity. On the other hand, some evidence suggests that warm-water species are moving into UK and Irish seas and offer new fishing opportunities, although detailed scientific analysis is lacking. Notable examples include new and/or expanding fisheries for sea bass, red mullet, John dory (Zeus faber), anchovy (Engraulis encrasicolus) and squid. Biomass estimates for sea bass in the eastern Channel have quadrupled from around 500 t in 1985, to in excess of 2100 t in 2004/2005, with populations also increasing rapidly in the western Channel, North and Irish Seas (Pawson et al., 2007). This has resulted in a dramatic expansion of sea bass fisheries (rising to 2500 vessels in 2004), both within the commercial fisheries sector, but also in the recreational fishing sector, for which sea bass is a key target species. Sea bass are caught by angling on the Scottish east coast, but the northern limit of the commercial bass fishery is around Yorkshire, where trawl-caught fish are increasingly being landed into Scarborough and Whitby. In 2009, 7000 t of sea bass were landed in the UK, compared with 460 t in the mid-1980s. Red mullet is a non-quota species of moderate, but increasing, importance to UK fisheries. From 1990 onwards, international landings from the English Channel in the UK increased strongly, and so have the landings from the North Sea (Engelhard et al., 2010). France is the main country benefiting from this species (contributing around 70% of the landings in France in 2009). However, UK commercial catches have also increased significantly, from only 26 t in 1980 to 392 t in 2009 (Engelhard et al., 2010). Beare et al. (2004) demonstrated that red mullet is one of many species that have become prevalent in North Sea bottom trawl surveys in recent years, rising from near-absence during surveys between 1925 and 1990, to around 0.1–4 fish per hour of trawling between 1994 and 2004. Commercial catches of anchovy increased dramatically around UK coasts in 2007 rising to around 939 t, with the result that several pelagic fishing boats switched to actively targeting this species for the first time. The apparent increase coincided with a gradual spread of anchovy (as indicated by research surveys) northward into the western Channel, southern North Sea and Irish Sea over the past decade and observations of large populations of juveniles in the Thames estuary and along the Dutch coast. A recent ICES report (ICES, 2008) confirmed that the species is now widely distributed over almost 80% of the North Sea, even though only occasional records of anchovy had been made off Britain and in the Skagerrak in the period between 1977 and 1989. Squid numbers are highly uncertain around UK coasts, but there are strong indications that cephalopods (squid, octopus, cuttlefish) generally are also becoming more abundant, possibly in response to a change in environmental conditions (Hastie et al., 2009a). Cephalopod populations are suggested to be responsive to climate change (Hastie et al., 2009a); growth in squid availability in the North Sea is generating considerable interest among policymakers and marine ecologists and has led to the establishment of a new fishery off the Aberdeen coast (Hastie et al., 2009b). Off north-east Scotland, where most of the squid is found, more boats are now trawling for squid than the region's traditional target species, such as haddock and cod (Hastie et al., 2009b).

In Ireland, new fisheries have recently opened up for boarfish Capros aper, a small, previously unimportant species that is converted to fish meal for aquaculture. Landings have grown rapidly from less than 120 t in 2001, to more than 139 000 t in 2010 (ICES, 2011). Both Irish and Danish fishermen have invested in new technologies to successfully catch and land this species, and in addition, Irish fishermen also invested in scientific research to increase knowledge of the biology and dynamics of this resource (White et al., 2011). This fishery is now worth more than €4 million year^-1, yet the fishery only became commercially viable following a sudden expansion of the stock in the early 1990s. Boarfish became increasingly prevalent in French and UK survey catches after 1991 (Pinnegar et al., 2002), and this phenomenon has been reported as occurring simultaneously elsewhere in the North Atlantic including the Bay of Biscay (Farina et al., 1997; Blanchard and Vandermeirsch, 2005), the Gulf of Lion (inside the Mediterranean; Abad and Giráldez, 1990) and on offshore seamounts (Fock et al., 2002). In the past boarfish outbreaks had been linked to storms and variability in offshore climate (Cooper, 1952). Their appearance after 1991 across the whole North Atlantic basin may be linked to a series of strong positive anomalies in the North Atlantic Oscillation (NAO) since positive phases of the NAO tend to be associated with above-average temperatures across northern Europe as well as strong westerly winds.

The impact of changes in resource availability on fisheries and fishing fleets will vary around the UK and Ireland depending on the make-up of the fleet in each fishing port, the species being targeted and distance/proximity to resources in the future. For example, the UK pelagic fleet (mainly targeting herring and mackerel) primarily operates out of Peterhead and Fraserburgh in NE Scotland, in Lerwick (Shetland Islands), as well as Ardglass in Northern Ireland. The fleet may benefit from the increases in abundance of sardine and anchovy in the North Sea that are associated with warming, although it may suffer from a projected decline in mackerel catch potential (Pierre et al., 2012). It should be noted that pelagic fisheries are known to respond dramatically to environmental fluctuations (Barange et al., 2009), leading to temporal closures during periods of low abundance (Arnason, 2006; Barange and Perry, 2009). By contrast, UK beam-trawlers are primarily concentrated in south-west England (Brixham, Plymouth and Newlyn), targeting sole, plaice and cuttlefish while the demersal ‘otter-trawl’ fleet which targets species such as haddock, cod and whiting, is more widely distributed but landings are highest in Peterhead, Aberdeen and Hull. The fishing ports that have probably benefited most from species migrating into UK waters are those in the English Channel, where sea bass, anchovy, red mullet, and John dory have expanded the most. However, the ‘western approaches’, English Channel and southern North Sea are also the regions that have witnessed the greatest declines of ‘traditional’ (often cold-water) target species such as cod, and where future prospects for such species look the most bleak (Drinkwater, 2005). In the UK, pots and trap fisheries comprise 1672 vessels and land high quality shellfish mainly for export to EU countries (12% of total income from European lobster, edible crab and whelk) (Anderson and Guillen, 2009). In Ireland, it is thought that a similar number of inshore vessels use these types of fishing gear although the exact numbers are not known. The valuable crustacean species targeted by this fishing sector are potentially most vulnerable to ocean acidification (although the sensitivity is somewhat unclear), consequently the long-term sustainability of this sector remains highly uncertain.

Effects on fishing operations

Climate change may affect fishing operations directly, potentially through changes in frequency of extreme weather events and the resulting disruption to fishing activities and/or land-based infrastructure. Outputs from Global Climate Models suggest that climate change could result in a north-eastward shift of storm frequency in the North Atlantic, although the change in storm intensity that this implies is not clear (Meehl et al., 2000; Ulbrich et al., 2008). The increase in frequency of storms could reduce the ability of fishing boats to access resources in the future, which may be further constrained if the management tactic is based on limitation of number of fishing days. Storms and severe weather events can also destroy landing sites, boats and static fishing gears (Westlund et al., 2007).

Climate change may also affect fishing indirectly through its effect on behaviour and activity of the exploited animals. There is evidence from experiments suggesting that catchability of some species to fisheries can be positively related to temperature, e.g. trawling for shrimp, crayfish (Cherax tenuimanus) and western rocklobster (Panulirus cygnus) (Chittelborough, 1970; Morgan, 1974; Morrissy and Caputi, 1981; Somers and Stechey, 1986). Experiments using crayfish and lobster traps (Morgan, 1974; Somers and Stechey, 1986; Miller, 1990) and on the catchability of Pacific halibut (Hippoglossus stenolepis) to longline (Stoner et al., 2006) suggest that increases in temperature often result in increases in the consumption rate of fishes and invertebrates, potentially increasing their vulnerability to baited fishing gears. In contrast, there is little evidence for significant changes in catchability of demersal trawl gears as a result of environmental changes, although experiments suggest behavioural adaptation of Atlantic cod related to temperature changes, and this may affect its catchability to bottom trawl gears (Winger, 2004). Thus, so far, available studies do not demonstrate clear and strong indirect effects of ocean and climate changes on demersal fishing operations through changes in catchability of the species to fishing gear.

In contrast, changes in depth of the thermocline may affect the catchability of pelagic gears. In the tropical Pacific, along the west coast of the Americas, strong El Niños, such as the 1982–1983 event, resulted in a deeper thermocline, suppressed upwelling and resultant declines in yellowfin tuna (Thunnus albacores) catches per unit effort – CPUE (Miller, 2007). However, the declines were followed by rapid rebounds in CPUE, suggesting that a strong El Niño may cause temporary horizontal and/or vertical displacement of the stocks and reduce their accessibility to harvesters while there is little evidence of lasting adverse impacts on population abundance (Miller, 2007). In the Indian Ocean, vulnerability of skipjack (Katsuwonus pelamis) and yellowfin tuna to purse seine gears decreased during ENSO events, because of a significant deepening of the thermocline. During the latest very strong ENSO, a collapse of CPUEs in the western Indian Ocean pushed boats to the eastern basin where very good catches were recorded in relation to an abnormal rise of the thermocline induced by the ENSO (Miller, 2007). As climate change is expected to lead to a deepening of the thermocline around the UK and Ireland as well as earlier onset of seasonal stratification (Barange and Perry, 2009), catchability of pelagic fisheries may be affected through mechanisms similar to those described above.

Hypoxic regions are expected to be modulated by climate change as it alters oceanographic conditions (Stramma et al., 2008; Rabalais et al., 2010). Low oxygen is starting to become an issue of concern for waters around the UK (Weston et al., 2008), potentially affecting the distribution of fisheries resources. For example, in the central North Sea, an area known as the ‘Oyster Grounds’ (part of the Dogger Bank) has witnessed decreasing oxygen levels in recent years (Weston et al., 2008) and hypoxia has been reported for coastal waters around the German Bight. In the Kattegat, the Baltic Sea and the Gulf of St Lawrence, cod completely avoid low oxygen waters (Chabot and Claireaux, 2008). Furthermore, in the Baltic, cod eggs do not survive low oxygen conditions, and years with extensive hypoxia have been related to very poor stock recruitment for this species (Köster et al., 2001).

Effects on fisheries management and conservation

Currently, UK and Irish fisheries are managed under a quota system, which ensures that landings remain substantially lower than is possible for the existing fleet (Anderson and Guillen, 2009). Quota is partly based on scientific advice provided by fisheries research agencies that undertake fish stock assessments. However, most fisheries stock assessment approaches are based on the assumption that biological and environmental conditions are stationary; an assumption that has been challenged by climate variability and the known impact on marine resources (Barange et al., 2010a). Climate change is likely to challenge this assumption further, potentially affecting long-term management and sustainability of some fisheries.For example, Clark et al. (2003) used projections of future North Sea surface temperatures and estimated the likely impact of climate change on the reproductive capacity of the cod stock. Output from the model suggested that the cod population would decline, even without a significant temperature increase. However, even a relatively modest level of climate change (+0.005° C yr^-1), resulted in a more rapid decline in fish biomass and juvenile recruitment. Scenarios with higher rates of temperature increase resulted in faster rates of decline in the cod population. In the analyses of Clark et al. (2003), fishing mortality was assumed to continue at the 1998–2000 average (F = 0.96). This is a relatively high value and does not take into account current efforts to cut fishing pressure. In a re-analysis by Kell et al. (2005), the authors modelled the effect of introducing a cod recovery plan (as being implemented by the European Commission), under which catches were set each year so that stock biomass increased by 30% annually until the cod stock had recovered to around 150 000 tonnes. The length of time taken for the cod stock to recover was not greatly affected by the choice of climate scenario (generally around 5–6 yr). However, overall productivity was affected, and stock biomass (SSB) was predicted to be considerably less than would have been the case assuming no temperature increase (251035 t compared with 286689 t in 2015). The overall message from this study is that in the short term, climate change has little effect on stock recovery, which depends instead upon reducing fishing effort to allow existing year classes to survive to maturity (Merino et al., in press). In the longer term, climate change may have a greater effect on stock status, but higher yields and biomass might equally be expected (perhaps more so) if fishing mortality is further reduced.

Climate and ocean changes affect the distribution of fish resources, with potential implications for the allocation of quotas across international boundaries in the case of shared and straddling fish stocks (Miller and Munro, 2004; Hanesson, 2006). A notable example is the share of North Sea mackerel quota between Norway, Iceland, the Faeroe Islands, and the European Union. Shifts in distribution of North Sea mackerel may require political negotiations between fishing nations that share access to this stock (Sissener and Bjørndal, 2005). In 2009, North Sea mackerel appeared to migrate away from Norwegian waters, creating conflict over the level of permissible catches by Norwegian boats in EU waters. Norwegian vessels were evicted from Scottish waters once they had caught their allotted quota. At the same time, Iceland and the Faeroe Islands unilaterally claimed quota for mackerel, since the species had expanded westwards and achieved a level that would sustain a fishery in their exclusive economic zones. With climate change in the future, we might anticipate more territorial disagreements of this type.

A similar phenomenon is now occurring in the Irish Sea and English Channel region with regard to access to anchovy stocks. Anchovy stocks are currently low in the Bay of Biscay where Spanish and French vessels operate, but are increasing further north along the coasts of Ireland and the UK (and are starting to be targeted by UK pelagic vessels). Detailed political negotiations are underway to determine whether Spanish and French vessels should be allowed to operate in areas where previously they had no quota, and indeed whether the more northerly distributed anchovy represent the same or a genetically different stock to those in the Bay of Biscay.

A pro-active approach to ensure that existing fisheries management measures and agreement are adaptive to climate change should improve the long-term effectiveness of fisheries management and reduce disputes in cross-sectors and/or multi-lateral fisheries agreements. Current scientific knowledge on responses of fisheries resources to climate change allows us to develop scenarios of marine ecosystems and fisheries in the UK and Ireland. In addition to the standard stock assessment, these future scenarios should be developed and, subsequently, all fisheries policies and agreement should be assessed under these scenarios. Through such exercises, policies or agreements that are potentially ill-adapted to climate change could be identified and revised in a timely fashion.

Shifts in species abundance and distributions have compromised the effectiveness of closed areas and other spatial fisheries management measures, such as the southern North Sea ‘Plaice Box’ (van Keeken et al., 2007; Figure 4) in recent years. In the North Sea, juvenile plaice are typically concentrated in shallow inshore waters and move gradually offshore as they grow. Surveys in the Wadden Sea have shown that 1-group plaice are now completely absent from the area where they were once very abundant (Engelhard et al., 2011), probably as a result from changes in the productivity of the region and warming temperatures. Consequently, the ‘Plaice Box’ is now not as effective as a management measure as was the case 10 or 15 years ago.

Figure 4. Areas closed for fishery management purpose in the UK and Ireland, including the Trevose Closure, Mackerel box, Plaice box, Sandeel box and Irish Sea Cod box (Source: UKCP).

The boundaries of and expectations for marine protected areas (MPA) may need to be ‘adaptive’ in the future in the context of climate change, something MPAs are not typically designed to be. For example, fisheries closures in the Bornholm Basin of the Baltic Sea do not account for year-to-year environmental variability and particularly the periodic inflow of water from the North Sea which greatly influences the spawning location and year class strength of species such as cod (Lindegren et al., 2010). In some years the Bornholm closure area is successful in protecting much of the cod stock, but in other years, most of the spawning population is outside the boundaries of the protected area, and hence the MPA offers no protection at all (for a review of Baltic closure areas, see ICES, 1999, 2004). The North Pacific Fishery Management Council has recently decided upon very risk-averse management actions, in light of uncertainty about the effects of warming (and loss of sea ice) in the North Pacific region. The Council has considered whether opportunities for unregulated fishing could result in changes in fish distribution, and has closed the Arctic Ocean to all commercial fishing pending further research (Stram and Evans, 2009). Extensive area closures have been established where fishing with bottom-trawl gear is prohibited, to protect vulnerable crab habitat and to control the northern expansion of the trawl fleet into newly ice-free waters (Stram and Evans, 2009). Thus, for spatial management such as marine protected areas, there is a need to anticipate how climate change would affect the spatial pattern of resources and ecosystems, and to adjust management tactics accordingly. For example, larger and networks of marine protected areas may be needed to ensure effective conservation of spatially shifting and/or more variable resources under climate change.

In UK waters there are a number of closed areas aimed at protecting particular fish stocks, and these include many estuarine sites which will experience dramatic changes in temperature and river flow in the next few decades. It is possible that estuaries where fishery closures are in place, for example to protect juvenile herring or sea bass, may no longer be hospitable for these species in the future, or that estuaries further north, that are currently unprotected, may need to be closed to fishing to accommodate migrating populations. Estimates of future temperature change for fishery closure areas (Figure 4) around the UK and Ireland are included in Table 1 (Stephen Dye, pers. comm.). This analysis suggests that most fishery closure areas established under the EU Common Fisheries Policy will experience between 2 and 3ºC of temperature rise over the next 80–100 years and consequently it is unlikely that the species they are designed to protect will occur in the same numbers as at present, if we assume that the various species have defined temperature tolerances or preferences.

Table 1. Predicted change in the near sea bed temperature (ºC) at five fishery closure areas around the UK and Ireland (under the EU Common Fisheries Policy), assuming a medium emissions scenario for the years 2080–2099 (based on UKCP09 data)

	Near sea bed temperature (^oC)
	Winter	Spring	Summer	Autumn
Celtic Sea Mackerel Box	2.4 (SD = 0.1)	2.5 (SD = 0.07)	2.5 (SD = 0.07)	2.7 (SD = 0.45)
North Sea Plaice Box	3.1 (SD = 0.23)	3.0 (SD = 0.14)	2.8 (SD = 0.14)	3.2 (SD = 0.21)
Firth of Forth Sandeel Box	2.5 (SD = 0.05)	2.5 (SD = 0.1)	2.2 (SD = 0.1)	2.3 (SD = 0.14)
Trevose Cod Box	2.4 (SD = 0.07)	2.5 (SD = 0.02)	2.3 (SD = 0.09)	2.5 (SD = 0.38)
Irish Sea Cod Box	2.5 (SD = 0.05)	2.6 (SD = 0.02)	2.4 (SD = 0.09)	2.7 (SD = 0.16)

Effects on fishing profits

The price of fish and cost of fishing may respond to ocean and climate changes differently depending on the particular species and fishing sectors. In the UK, the relative distribution of fish market prices has changed significantly from the 1980s, with high trophic level species experiencing greater price rises than lower trophic level species (Pinnegar et al., 2002). Such changes are suggested to be related to the decrease in supply of high trophic level species because of overfishing and the subsequent substitution by lower trophic level species (Pinnegar et al., 2002). Similarly, changes in supply of fisheries products because of climate change are expected to affect their market prices. For example, the price of high-value finfish, crustaceans and molluscs is expected to increase in the future (Delgado et al., 2003). This may provide benefits in terms of the revenue potential of demersal fishing fleets that target these species. On the other hand, demersal trawl/seine fleets are likely to be affected by the shifting distribution of demersal fisheries resources and associated increases in fishing cost. A shift in the location of fishing grounds will affect fuel usage and hence the cost of fishing. Demersal trawling, in particular, is a fuel intensive means of catching fish (especially beam trawling) and is therefore economically vulnerable to changes in fuel cost (Abernethy et al., 2010). Currently, demersal trawl/seine fleets in the UK consist of around 1467 active vessels and are responsible for ~45% of total income mostly from cod, haddock, anglerfish (Lophius piscatorius), scallops, Nephrops, and shrimp. In Ireland, there are around 195 active fishing vessels using towed demersal gears. Thus, any impacts from climate change on the demersal sectors may have a large overall effect on the profitability of the industry as a whole. Some projections suggest that certain commercial species will shift distribution towards the UK (e.g. plaice and red mullet in the North Sea), thereby reducing necessary fuel costs, whereas other species (such as cod) may move further away.

The economic consequence for the pelagic fisheries under climate change may be particularly uncertain given the observed and projected increases in certain species (e.g. anchoveta and sardine) and decreases in others (e.g. mackerel) that are thought to be linked to changes in ocean conditions. Revenues and profits will depend on the ability of the pelagic fisheries to capitalize on the changes in pelagic resources that are also strongly affected by the balance between human consumption and industrial use, the latter a result of the price and demand for fishmeal. In the UK, blue whiting, sprat, sandeels and herring have been used to produce fishmeal and oil. The processing of other species into fishmeal may be a possibility (e.g. boarfish), particularly if the price of fishmeal continues to rise faster than the availability of fresh fish (Delgado et al., 2003; Merino et al., 2010). There is considerable uncertainty regarding the most sustainable course of action to optimally manage small pelagic fisheries (Arnason, 2006; Merino et al., 2010), especially where these resources naturally exhibit fluctuations as a consequence of climate variability. Fish meal and oil are globally traded commodities and so shortcomings in local supply (e.g. North Sea sandeel) will usually be made up by additional imports from further afield, (e.g. Peruvian anchovita). Conversely, climate variability in the Pacific is known to have a significant impact on the price of fishmeal in the North Sea (Merino et al., 2010). A more thorough assessment of global fisheries economics is needed in order to provide the context for detailed local studies on fisheries responses to climate change.

Fuel price has increased more rapidly than fish prices in the last 10 years and its volatility has threatened the viability of UK industries and fishing communities (Abernethy et al., 2010). How these drivers may unfold in the coming decades will determine the future of UK and Irish fishing fleets in a world of global climate and ocean changes.

Overall, climate change will produce winners and losers. It is already resulting in closures and contractions in some fleet segments, but also opportunities for development of new fisheries as described in this paper and others (Pinnegar et al., 2010). What seems clear is that fleets will need to adapt to incoming farmed seafood and rising fuel prices (caused by dwindling supplies and taxes aimed at lowering carbon emissions) by increasing their efficiency and reducing their environmental impacts. To date, very little economic analysis has been performed looking at the circumstances under which operators choose to enter or exit a fishery. ‘Adaptive capacity’ may be limited in some fleets and it is possible that some fishermen may choose to leave the industry rather than follow their traditional target species northwards (see discussion in Tidd et al., 2011).

Effects on recreational fishing

Managers of marine fisheries in Europe have thus far paid little attention to recreational fisheries, though recreational fishing constitutes a considerable social and economic activity. Total expenditure on recreational fishing across Europe is believed to exceed €25 billion a year (Dillon, 2004), by comparison the 2007 value of commercial landings in the 27 EU member states was estimated at €6.2 billion. In the UK, it is estimated that £1 billion is spent annually by anglers on marine recreational fishing (PMSU, 2004). This highlights the importance of recreational fishing as an economic sector and the need to understand how this sector will be affected by climate change.

A number of fish species that are heavily targeted by the recreational fishing sector throughout Europe are also anticipated to be affected by future climate change, e.g. sea bass (Pawson et al., 2007). Many recreational fishermen in the UK and Ireland target salmon (Salmo salar) or sea trout (Salmo trutta). These species are known to be particularly sensitive to environmental changes (Ottersen et al., 2004; Jonsson and Jonsson, 2009). Climate change will probably affect the migration, embryonic development, hatching, emergence and growth (both in the sea and in rivers), and increase the virulence of some diseases (Jonsson and Jonsson, 2009). Salmon depend on environmental variables as migratory cues (Friedland et al., 2003). Whalen et al. (1999) reported that peak migration of salmon smolts occurs later in spring for tributaries with lower temperature. Also, annual variation in the timing of peak migration of Atlantic salmon is related to variation in annual water temperatures (McCormick et al., 1998). Changes in precipitation patterns under future climate change scenarios, may influence the ability of smolts to successfully migrate from rivers to the sea. Conversely, low water flow in rivers can have a negative effect on upstream migration of adult salmon returning from the sea to rivers to spawn (Solomon and Sambrook, 2004). The resultant changes in distribution, productivity and seasonality may directly affect recreational fishing opportunities.

ADAPTATION OF UK AND IRISH FISHERIES TO OCEAN–ATMOSPHERIC CHANGES

Adaptability of the fishing sectors

There are a number of studies that set out to investigate the vulnerability and adaptive capacity of the fisheries sector in response to climate change at a global scale (McClanahan et al., 2008; Allison et al., 2009). However, until recently there has been little directed analysis at the local scale of how climate variability and change will affect the lives and livelihoods of those involved in UK and Irish fishing and fish processing sectors. Fishery resources will be more robust to climate change if the compounding stresses from overfishing, habitat degradation, pollution and other anthropogenic factors are minimized. Sustainable management will be achieved not through the pursuit of complex biophysical modelling, but by developing and applying simple mechanisms that result in effective adaptive management. In this context fisheries that have been successfully managed to achieve resource sustainability will probably be much better positioned in the long term to respond to the vagaries of climate change.

Allison et al. (2009) provided an assessment of the vulnerability of 132 national economies to climate change impacts on their capture fisheries using an indicator-based approach. Vulnerability to climate change depends upon three key elements: exposure to physical effects of climate change, the degree of intrinsic sensitivity of the natural resource system or dependence of the national economy upon social and economic returns from that sector, and the extent to which adaptive capacity enables these potential impacts to be offset. Based on this study, the UK and Ireland are ranked as ‘very low’ in terms of vulnerability to climate change, with good adaptive capacity and a relatively small anticipated impact. A follow-up analysis as part of the UK NERC-GSI programme ranked the UK as 215th out of 225 countries and territories in terms of climate change vulnerability, the Republic of Ireland was ranked 223, the Channel Islands were ranked 208 and the Isle of Man was ranked 218 (Cefas, unpublished data).

Some estimates of the potential costs of adaptation to climate change to fisheries have already been made. Sumaila and Cheung (2010) attempted to establish the costs of adaptation in the fisheries sector worldwide. The analysis began by detailing the likely impact of climate change on the productivity of marine fisheries (more than 1000 species) and, through that, on landed catch values and household incomes. Adaptation costs were then estimated, based on the expenditure needed to restore revenue losses that would have prevailed in the absence of climate change. The impact of climate change on marine fisheries was assumed to primarily occur through changes in primary productivity, shifts in species distribution, and through acidification of the oceans (Cheung et al., 2011a). Climate change was predicted to lead to losses in gross fisheries revenues world-wide of $10–31 billion by 2050. Governments have implemented various measures to manage fisheries, both to conserve fish stocks and to help communities that depend on fishery resources adapt to changes caused by overfishing and other factors. Measures include buy-backs, transferable quotas and investments in alternative sources of employment and income. Adaptation to climate change is likely to involve an extension of such policies, with a focus on providing alternative sources of income in fishing communities to lessen the dependence on fishery resources. In Europe the estimated annual cost of adaptation was between $30 and 15 million. To estimate adaptation cost specifically for the UK and Ireland, projections for the potential loss in their fisheries values are needed.

Adaptability of the wider seafood industry and markets

It is anticipated that climate change and ocean acidification will not only have an impact on fleets and fishermen within Europe but will have significant consequences for fish production over the world. Fish and seafood are globally traded commodities. Countries that traditionally export seafood products to Europe (e.g. countries of West Africa) will probably face shortages of fish protein in the future (Cheung et al., 2010; Lam et al., in press), or increased internal demand in the face of falling agricultural yields on land. Consequently trade flows will undoubtedly change in the future and this will affect prices and markets.

The wider seafood industry in the UK and Ireland comprises the trade of marine commodities including production from indigenous marine catch and aquaculture, import/export of marine products from overseas as well as retailing and processing. Total purchases of seafood in the UK exceeded £5 billion in 2008. A large proportion of the UK seafood production is exported due to the high value of species such as langoustine (Nephrops), crab, and mackerel. Domestic consumption typically focuses on cod, haddock and salmon (the latter from fishfarms). In 2009, 473 300 tonnes of seafood were exported from the UK mostly to the EU and USA; this accrued around £1.16 billion. Conversely, 718 000 tonnes of white fish, prawns and tuna worth £2.16 billion were imported. A Fisheries Partnership Agreement concluded between the European Community and Greenland covers the period 2007–2012 and represents an investment of €15.8 million, mainly for capelin and/or cod quotas. This fisheries agreement allows vessels from Germany, Denmark, UK, Spain and Portugal to fish in Greenland waters and is the only bilateral trade agreement concluded with a non-developing nation State. As suggested by Arnason (2006), but also Cheung et al. (2009), Greenland is one of the few countries where fisheries are anticipated to benefit significantly as a result of future climate change (in particular landings of cod). Consequently, it is possible that access agreements, as well as imports of fish caught by indigenous fisheries in northern countries, will become increasingly important to markets and consumers throughout Europe, most notably in the UK and Ireland in the future.

The UK and Irish seafood sectors will have to adapt to changing production and consumption patterns both at local and international levels. With local consumption expected to grow very moderately, future trade of seafood in the UK and Ireland could be determined by consumption preferences in the wider European Union (EU) and in the USA (Failler, 2007). As the EU population expands and there is increased demand for seafood, specifically for salmon and trout, UK and Irish aquaculture will face expansion opportunities. However, fish farms will have to adapt to demand by producing more fish with less environmental impact (Naylor et al., 2000, 2009). When relating to species such as salmon, which consume high amounts of marine fish to produce a unit of farmed product, adaptation means reducing their reliance on fishmeal and oil by replacement with alternative protein sources. Fishmeal price has grown in parallel to its utilization in aquaculture (Merino et al., 2010) and a reduction in use will allow increasing salmon production by reducing costs of production, hence increasing competitiveness in international markets and export opportunities. Recent reduction in the use of fishmeal in fish farming suggests that adaptation to the changing face of the seafood trade is already occurring. In salmon farming, for example, 7.5 units of small pelagic fish (typically sandeels or anchovita) were required to produce a unit of salmon in 1995, while currently, less than 4 units of marine fish are required. It is expected that the conversion ratio of marine fish to produce a unit of farmed fish will be reduced further to levels below 2 in the coming decade (Tacon and Metian, 2008).

In the retail sector, adaptation is happening through a shift in consumer preferences and buying habits. In 1986, 51% of the fresh fish purchases were made from independent fishmongers and 15% at supermarkets, and these fish were largely supplied through the domestic fishing industry (vessels operating in nearshore or distant waters). By contrast, those numbers were reduced to less than 30% for fishmongers and increased to more than 50% for supermarkets in the UK, with fish now obtained from suppliers all over the world because of dwindling local supplies and to achieve consistency of supply (Failler, 2007). In 2008, supermarkets in the UK took 87% of all money spent on fish products, a trade that is now sustained by the increasing use of new species from abroad, and through the creation of retailer associations (Failler, 2007).

While the productivity of many EU fish stocks has decreased, overall fish consumption in most countries continues to increase. In the UK, fish consumption amounts to around 20.6 kg per person, per year (and the current population is 62 million) (DEFRA, 2010). In Ireland consumption is slightly higher at 22.5 kg per person, per year (and the population is 4.5 million). By 2050 the population of the UK is projected to reach ~71.2 million and the Republic of Ireland to grow to 6.2 million people. This equates to an increase in the demand for fish products from 1.3 million tonnes in 2010 to more than 1.6 million tonnes in 2050, which could be increasingly difficult to satisfy given predicted impacts of climate change.

Arnason (2007) attempted to estimate the economic impact of climate change on fisheries and on the national economies of Iceland and Greenland. The author assumed that fisheries yields would increase by around 20% for the most important fish stocks (in particular cod and Atlanto-Scandian herring) in Iceland and up to 200% in Greenland over the next 50 years (based on projections from ACIA, 2005). The analysis then used econometric techniques to estimate the role of the future fisheries sector in the wider economy of each country. Somewhat surprisingly the dramatic increase in fisheries yields assumed for Iceland resulted in only miniscule increases in national GDP, despite the fishing industry currently accounting for around 10% of GDP and 40% of export earnings. In the UK and Ireland a slight increase in fisheries yield is also anticipated in the future, by around 1–2% (Cheung et al., 2010). Such change might be insignificant when uncertainties of the prediction are considered. Also, given the very small contribution that fisheries make towards national GDP in these two countries it seems highly unlikely (based on the work of Arnason, 2007) that such changes in fisheries profitability will have significant consequences for the national economy, although there could be minor benefits for highly dependent regions such as the Highlands and Islands in Scotland and around the northern and south-west coasts of Ireland.

Overall, the adaptive capacity of the seafood industry and market in the UK appears to be high. Responses to recent changes in resource supply, demand and regulations suggest that they could respond and adjust quickly. Extrapolating this to changes driven by climate change may suggest a similarly high level of adaptive capacity in the industry and market. To further ensure that the industry is adaptive to climate change, the industry would benefit from tailored advice on implications for their businesses specifically and any anticipated changes in fisheries management policies in response to these changes. Simultaneously, improved consumer education regarding anticipated changes will also facilitate a more rapid response of the market to future changes in supply of fisheries products from local waters.

KEY FINDINGS, GAPS, FUTURE DIRECTIONS AND RECOMMENDATIONS

An important question that this paper aims to address is: given our current knowledge, what will happen to fisheries in the UK and Ireland in the next 50 years under climate change? There is strong evidence suggesting that climate and ocean changes will alter the distribution and productivity of resources that are available to UK and Irish fisheries, affecting the economics of the fishing industry and associated sectors. Specifically, commercially important cold-water associated (Boreal) species such as cod, haddock, halibut (Hippoglossus hippoglossus), ling, plaice, pollack, saithe (Pollachius pollachius) and sandeels are expected to respond by shifting their distribution northward under warming (Perry et al., 2005; Cheung et al., 2011a; Simpson et al., 2011). In contrast, warm-water associated (Lusitanian) species such as sea bass, anchovy, brill (Scophthalmus rhombus), boarfish, hake and monkfish are expected to increase in abundance under warming. However, the rate and direction of shift will vary between species and regions. Interactions between climate change and other human disturbances render detection and attribution of climate change effects on fisheries difficult. Ocean acidification may negatively affect exploited shellfish fisheries while the impacts on finfish fisheries are more uncertain. These changes may lead to loss in fisheries potential as well as emergence of new fishing opportunities in the UK and Ireland. The degree of impacts of these changes on society will largely depend on how society and the fishing industry mitigate and adapt to these changes. Although the fisheries industry and markets appear to be relatively robust to changes in catch composition, it is important to constantly educate and update the fishing sectors regarding the implications of climate change on their business to facilitate adaptive measures. In contrast, fisheries management measures and international fisheries agreements have not fully considered the implications of climate change, potentially threatening the effectiveness of these measures and agreements.

To improve our ability to project the implications of climate change for marine fisheries in the UK and Ireland, key biophysical, social and economic knowledge gaps need to be addressed. First, we are less certain about the finer scale physical and biogeochemical changes anticipated in the waters around the British Isles. Global Climate Models such as those used by the IPCC perform poorly at regional and sub-regional scales, and there is a need to improve such models, and their coupling with the dynamics of shelf seas, where most of the fisheries originate (Holt et al., 2009). Second, we need to understand better the transfer of primary productivity to fish and fisheries (Chassot et al., 2010; Stock et al., 2010), and the potential impacts of climate change on the productivity of a range of marine ecosystems (Barange et al., 2010a, b, c), including the UK shelf seas. Third, we must improve our understanding with regard to evolutionary adaptation and behavioural responses to changed climatic conditions, and the indirect effects on the interactions between species in marine food webs. Fourth, on the human side, we need better understanding with regard to response and adaptation capacity of fishing fleets and fishers to the physical and biological changes. At the moment, there have been few, if any, studies that have specifically looked at the socio-economics of UK and Irish fishing fleets in relation to climate change. Exploring the synergistic dual exposure of marine ecosystems to climate change and human activity appears essential for effective adaptation and mitigation options to be developed (Barange et al., 2010a, b, c). It is also important to understand how different fishery sectors may respond to proposed mitigation and adaptation measures. This might include, for example, the implementation of renewable energy schemes, coastal power stations with large water intake structures, or actions that increase the marginal costs of fishing, such as fuel prices (e.g. through environmental taxes). At a larger scale, UK and Irish fishing and seafood industries are linked directly and indirectly to the globalized ecological, social and economic systems. We need to understand better the interactions between changes within the UK, Ireland and those elsewhere in the world, and between fishing and other sectors (Merino et al., 2010). Addressing these knowledge gaps will clearly require both within-discipline studies and interdisciplinary efforts.

Gaps in scientific knowledge should not delay climate change mitigation and adaptation policy actions. We already know that reducing greenhouse gas emissions would limit the potential impacts of climate change on fisheries and other sectors. We also know that the long-term changes in ocean conditions will continue for decades even if the current rate of greenhouse gas emissions is reduced significantly and immediately. Thus, it is important to develop adaptation policies for the fishing sector, which could be updated and adapted as new knowledge emerges.

There are various ‘no-regret’ policies which have large co-benefits for other ecosystem services. There is a general concensus among scientists that human impacts on marine ecosystems through overfishing, habitat destruction, pollution, etc. reduce adaptive capacity of the ecosystems and organisms to climate and other environmental changes. In the UK, the percentage of fish stocks that are considered to be harvested sustainably is between 25% and 38% during the 2002 and 2009 period (DEFRA, 2009). Fishing threatens some of the unassessed stocks, particularly species that are vulnerable to exploitation such as rays and skates (Dulvy and Reynolds, 2002). The UK and Ireland waters are also used intensively by other human activities such as aggregate extraction, renewable energy, shipping and aquaculture (Foden et al., 2011). Recovery of depleted fisheries stocks depends largely upon reducing fishing effort to allow existing year classes to survive to maturity. By rebuilding over-exploited fish populations and ecosystems, and improving habitat quality for marine organisms, society and the fishing industry would gain from more productive fish stocks, higher biodiversity and higher resilience and adaptive capacity to climate change. In particular, spatial management measures such as marine protected areas and no-take zones have the added advantages of acting as control sites for long-term monitoring programmes that would enable the attribution of observed biological responses to climate change from other human disturbances such as fishing (Cheung et al., 2011b). Second, the fishing sector should also contribute to reducing greenhouse gas emissions. This could be done by reducing fuel consumption through more efficient engines and adjustment in fishing behaviour. For example, during years of high fuel price, it has been shown that some fishers in south-western England were able to reduce fishing cost such as their fishing locations and behaviour, for example, through reducing steaming time by use of alternative fishing gears (Abernethy et al., 2010). This reduces both fuel consumption (and thus greenhouse gas emissions) and fishing costs. Third, improving education and communication within the fishing industry about climate change could be important for effective implementation of climate change mitigation and adaptation policies. For example, the Marine Climate Change Impacts Partnership (MCCIP) programme provides a conduit through which the fishing industry can obtain the latest scientific information about marine climate change in the UK and Ireland. Such measures would allow the fisheries industry to develop capacity and to respond effectively to threats or opportunities posed by climate change.

ACKNOWLEDGEMENTS

This paper is initiated through the UK Marine Climate Change Impact Partnership programme (MCCIP). W. Cheung is supported by Seedcorn funding from Cefas, J. Pinnegar and M.C. Jones are supported by the Defra project E5102 ACME (Adapting to Future Climate Change in the Marine Environment). We thank J. Foden for help in preparing the map and Table 1.