Impacts on arctic freshwater and anadromous fisheries

Published: February 9, 2010, 3:32 pm

Updated: May 7, 2012, 4:27 pm

Topics:

Fisheries (main) Water (main) Ecology (main) Climate Change (main)

This is Section 8.5.5 of the Arctic Climate Impact Assessment
Lead Authors: Frederick J.Wrona,Terry D. Prowse, James D. Reist; Contributing Authors: Richard Beamish, John J. Gibson, John Hobbie, Erik Jeppesen, Jackie King, Guenter Koeck, Atte Korhola, Lucie Lévesque, Robie Macdonald, Michael Power,Vladimir Skvortsov,Warwick Vincent; Consulting Authors: Robert Clark, Brian Dempson, David Lean, Hannu Lehtonen, Sofia Perin, Richard Pienitz, Milla Rautio, John Smol, Ross Tallman, Alexander Zhulidov

The potential and realized impacts of changes in climate and UV radiation (Ultraviolet radiation effects on freshwater ecosystems in the Arctic) parameters on arctic fisheries must be viewed in terms of direct impacts upon the fish and fisheries as well as indirect impacts mediated through the aquatic environment. For fisheries, however, the human context is of great importance and must be considered. Fisheries are managed to have a sustainable harvest. Harvests (i.e., quantity) in fisheries affect different species and their life stages differently. Fisheries must also be viewed from the perspective of product quality, which affects its suitability for human consumption as well as its economic value. Finally, success of a fishery implies that the fishers themselves have suitable access to and success in the fishery, typically the result of experience and local knowledge. This also means that fishers are able to return high-quality catch in good condition to points of consumption or transport to market. All these components of fisheries in arctic freshwaters (quantity, quality, and success) are subject to both direct and indirect impacts of climate change and increased UV radiation levels to a greater or lesser extent. Similarly, climate change is very likely to affect aquaculture operations conducted in arctic freshwaters (Freshwater ecosystems in the Arctic). The following sections explore the implications for fisheries conducted in freshwaters, estuarine waters, and nearshore coastal waters.

Nature of fisheries in arctic freshwaters (8.5.5.1)

Fisheries for arctic freshwater and diadromous fish are conducted in all polar countries including Canada, Denmark (Greenland), the Faroe Islands, Finland, Iceland, Norway, Russia, Sweden, and the United States (Alaska). Freshwater fisheries as described here include those for species that live their entire lives in freshwater, such as lake trout, and those for diadromous species such as Atlantic salmon. Chapter 13 (Impacts on arctic freshwater and anadromous fisheries) addresses offshore marine fisheries conducted on anadromous species and the relevant impacts of climate change on these species in marine waters.

Arctic freshwater fisheries generally involve mostly local indigenous peoples, although some may also involve non-indigenous local people as well as visitors to the Arctic. (See Chapter 3 (Impacts on arctic freshwater and anadromous fisheries) for indigenous accounts of changes in fishes and fishing in recent years.) Although details vary locally, at least three types of freshwater fisheries can be distinguished:

• commercial fisheries, where the product is sold commercially either locally or often in markets far removed from the sources;
• recreational fisheries in which non-indigenous people participate primarily for the experience rather than for economic, cultural, or nutritional reasons; and
• domestic or subsistence fisheries conducted by indigenous or local peoples primarily for cultural and sustenance reasons (see also Chapter 12 (Impacts on arctic freshwater and anadromous fisheries)).

Arctic freshwater fisheries can be substantial but generally never achieve the same economic significance that marine fisheries do, in part due to abundances and in part due to the lack of fishery infrastructure (e.g., absence of processing plants in many areas such as the lower Lena River, extremely long distances to markets). For the nine arctic countries, reported commercial catches for northern fishes in 2000 (8 to 350,000 tonnes) represented 0.002 to 32% of total commercial catches for all species within those countries, although about 10% or less of this catch was truly "arctic" as defined herein. Rather, arctic fisheries are diverse, locally widely dispersed, and target a variety of species that are locally abundant. Such fisheries are extremely important in meeting the needs of the local peoples and contribute significantly to the economy and society of northern peoples (see also [[Chapter 12 (Impacts on arctic freshwater and anadromous fisheries)]2]), thus their value must be measured in more than simple economic terms and understood in the context of climate impacts.

Impacts on quantity and availability of fish (8.5.5.2)

Over the short term, projected productivity increases in arctic freshwater ecosystems, increased summer survival and growth of young fish, and increased overwinter survival of fish will probably result in increased biomass and yields of many fished species. Production shifts will depend upon local conditions such as faunal composition of the fishes and food species, tolerances and reactions of individual species to climate change, and general productivity shifts in aquatic ecosystems. However, there will be much regional and local variation and responses are likely to be primarily species- or ecosystem-specific. Thus, for wholly freshwater species, shifts in productivity are more likely to occur in lakes along the southern fringe of the Arctic, and less likely to be observed in flowing-water ecosystems. For anadromous species, increased summer nearshore productivity will possibly enhance growth rates, hence biomass and potential fishery yields. Furthermore, recent work conducted on Atlantic salmon while in marine waters suggests that warmer sea-surface temperatures (i.e., of 8–10°C) enhance survival in both winter and early summer. Increased growth and survival are very likely to enhance fish returns to freshwaters. Shifts in river flow regimes critical to upstream migrations of anadromous fish, especially in the late summer, will possibly have a negative effect, counterbalancing any positive effects to some degree. Arctic freshwater fisheries production will probably show some increases over the next decade or two. The greatest manifestation of this increase is likely to occur at the southern boundary of the Arctic, and is very likely to involve species that are primarily subarctic (i.e., occurring throughout northern temperate regions and extending into the Arctic). Fisheries yields for such subarctic fish species (i.e., northern pike, lake whitefish, and walleye in eastern North America, and northern pike, European whitefish – Coregonus lavaretus, and percids in northern Europe) have been linked with species-specific (and perhaps region-specific) habitat (Habitat selection) optima. Such yield relationships have been further examined in the context of GCM projections of temperature increase for some areas (e.g., Québec and subarctic Canada). This regional approach suggests that, at least for deeper lakes and perhaps larger rivers, substantial redistribution of fishery potential driven by population productivity as well as by redistribution of species is very likely.

As thermal optima are exceeded locally, and perhaps as ecosystems re-equilibrate and nutrient limitations occur, reductions in biomass and yields are possible. For example, climate change will affect species individually owing to differential colonization, extinction, and productivity rates. This will possibly lead to substantive ecological reorganization. These effects are likely to be most severe for true arctic species such as broad whitefish and Arctic char, which will possibly also be affected by increased competition from more southerly species extending their geographic distributions northward. Thus, in the longer term, the effects of climate change on the yields of arctic fisheries are likely to be negative for true arctic fish species but positive for subarctic and northern temperate species.

As freshwater productivity increases, the frequency of anadromy will possibly decrease within populations that exhibit facultative anadromy (e.g., Arctic char, Dolly Varden, and broad whitefish). Given that anadromy and feeding at sea results in greater size at a given age and larger populations, a switch away from anadromy is likely to result in decreased productivity. To ensure sustainability, this may necessitate lower harvests of native anadromous species; shifts in harvesting of alternate species, if available; and/or a change in location or timing of fisheries (Fisheries and aquaculture). The consequences of these changes in fisheries of local indigenous people who rely on the autumn upstream runs of anadromous fish are very likely to be substantial from economic (i.e., protein replacement and increased costs to travel to new fishing areas for smaller catches), social, and cultural perspectives.

As noted previously, one of the hallmarks of climate change in the Arctic is likely to be increased interannual variability in climate parameters. Although it may be partially lost in the background noise of typically high inherent variability in arctic climate, this in turn will possibly increase the variability of good and poor year-classes in arctic fish. The consequence of this for fisheries will probably be increased variability in fishing success and unstable yields of targeted species. Such increased variability is very likely to exacerbate problems discussed previously that affect the biomass and yields of fisheries. Consequences include those associated with domestic sustenance if the local people rely heavily on the fished species, as well as difficulties with developing stable commercial or recreational fisheries that are economically viable and sustainable. As climate change becomes more pronounced, southern fish species are very likely to colonize newly available areas, enhancing the possibility of negative impacts on arctic fish species from competition. However, they may also represent opportunities for new fisheries. Hence, flexible, adaptive management will be key to the success of future fisheries, particularly in responding to uncertainties associated with available data; an attribute not currently present in many fishery management regimes in the Arctic.

Availability of fish species to fisheries will probably change as a result of several factors. For example, most fished arctic species are salmonids that tend to prefer cool or cold thermal regimes especially as adults (e.g., lake trout), thus they seek summer refuge in colder waters below thermoclines in lakes. As thermocline depths deepen, the availability of these species to fisheries will possibly change because deeper waters are more difficult to fish. This is very likely to occur in larger, deeper arctic lakes (e.g., Great Slave Lake in Canada) and will possibly necessitate gear changes for fisheries and/or retraining of fishers in new techniques. Questions as to how this might occur and how costs can be covered are currently not being addressed. In addition, the optimal temperature [[habitat (Habitat selection)]s (Habitat selection)] of salmonids (e.g., European whitefish and brown trout) are very likely to change in northern Europe and summer temperatures in shallow arctic lakes will possibly become too high for these species, with consequent effects on local fisheries.

Impacts on quality of fish (8.5.5.3)

Quality of fish captured in a fishery refers to its suitability for marketing (e.g., locally or distantly by trade, cultural exchange, and/or sale) and for consumption by humans. This suitability is affected by factors inherent in the fish resulting from environmental conditions experienced prior to capture, as well as factors that affect the fish product after capture. Factors influencing fish quality before capture include "fish condition" (typically an index of weight and length that measures fatness or nutritional state or "well being"); flesh firmness, which is typically influenced by water temperatures immediately prior to capture (i.e., warmer waters generally result in poorer-quality flesh); general appearance (e.g., color and lack of imperfections) of both the fish itself and key consumed organs such as livers; parasite loads and disease; and contaminant burdens. Factors influencing fish quality after capture include preservation (e.g., cooling or freezing), and the ease, conditions, and time associated with transport to the consumption site, market, or processing facility. As for all other impacts of change in climate parameters or UV radiation levels, both direct and indirect impacts will influence fish quality.

Indirect and direct impacts on quality of fish before capture are primarily those considered in previous sections. For example, impacts on ecosystem structure and trophic pathways are very likely to affect food availability (both amount and quality) to the fish, influencing fat levels and condition; impacts on migratory patterns or access are very likely to influence growth and condition; and impacts such as higher late-season water [[temperature]s] will possibly decrease flesh firmness of cold- and cool-water fishes such as salmonids, reducing either perceived or real quality. There is evidence that the color, size, and firmness of livers and flesh in some species is affected by nutritional state, for example, burbot (Lota lota) livers appear to be affected by fat content and presumably nutritional state. This appears to relate in part to seasonal variance in nutrition rather than specifically to environmental impacts such as contamination. Thus, climate change impacts that affect nutrition of fished species are very likely to have consequent effects on fish quality, but these may be difficult to distinguish from ongoing typical seasonal effects.

Some additional potential impacts are worth noting or emphasizing. In general, climate change is very likely to result in increased contaminant burdens in fish flesh, with a concomitant decrease in fish quality and acceptability for human consumption; these contaminant burdens will possibly exceed safe consumption limits. This will possibly be particularly acute for some contaminants such as heavy metals (e.g., mercury) and in some areas of the Arctic. Thus, cautions and caveats associated with arctic contaminants as discussed in the Arctic Monitoring Assessment Programme report will possibly become more relevant as climate change occurs (see also Section 8.7 (Impacts on arctic freshwater and anadromous fisheries)).

Furthermore, the potential impacts of climate change on fish parasites and hence on fish quality have been poorly addressed but appear to represent major higher-order impacts. Potential direct impacts on aquatic parasites include many of the same ones noted for fish species, for example, both biological challenges and opportunities associated with parasite physiology either as a direct effect of the environment on the parasite (e.g., higher [[temperature]s] and/or shorter durations of low temperatures accelerating development) or as mediated through the host fish (e.g., shifts in fish feeding affecting parasite development). Higher parasite developmental rates suggest increased burdens upon fish hosts, which are very likely to result in decreased productivity of the population and/or poorer condition of individuals. A further potential impact of parasites on arctic freshwater fishes is the introduction of new parasites to new host species or new areas (i.e., those not presently colonized) via host colonization of such areas through range extension. This will be complicated by a tendency toward higher levels of eutrophication in arctic water bodies associated with a general increase in temperature, resulting in changes in the species composition of both parasite and fish communities. In addition, disruption of normal developmental synchronicities between parasites and host fish, such as seasonal migrations within a water body, will possibly result in shifts in transmission rates to various hosts necessary to the life cycle of the parasite, but will possibly also result in switching to different hosts. Thus, parasites typically found in temperate fishes will possibly switch to arctic fishes, affecting the latter both biologically and from the perspective of quality. Shifts in thermal regimes that result in increased local densities of hosts, especially intermediate ones such as planktonic or benthic invertebrates, are also very likely to increase parasite species diversity. Conversely, activities such as fishing (which reduce the density of larger and older fish in relatively pristine fish populations, increasing the density of younger and smaller fish) can result in the "repackaging" of parasites and a net overall increase in parasite density within individual fish. This reduces fish quality and marketability. The nature and timing of water delivery and potential shifts in overall amounts of precipitation may also affect parasite levels: a general increase in parasites and associated problems is likely to accompany a general decrease in water levels. Although poorly studied at present, the potential impact of fish diseases must also be addressed. Climate change is likely to result in increased incidence and spread of diseases, and perhaps increased intensity locally as fish populations are stressed. Furthermore, effects such as those associated with parasites, disease, and contaminants are part of the cumulative effects on local populations and must be considered when addressing issues of impacts on fish quality.

Many of these effects are most likely to occur, and present major problems for fish quality, in areas of the southern Arctic that presently have both reasonably high levels of exploitation and large southern catchments that flow north to the Arctic Ocean (Section 8.2.3 (Impacts on arctic freshwater and anadromous fisheries)). Thus, problems that may be small at present and confined marginally to the southern Arctic will possibly increase in intensity and spatial distribution as climate change becomes more pronounced throughout the Arctic.

The impacts of increased UV radiation levels on some fish parasites will possibly be beneficial for fish by slowing infection rates and/or inhibiting the spread of some parasites. However, immunosuppression resulting from increased UV radiation exposure will possibly exacerbate the effects of parasitism, disease, and contaminant loading on individual fish. This will possibly lower population productivity by decreasing survival. In addition, any obvious physical damage such as lesions or growths resulting from increased UV radiation exposure is very likely to decrease fish condition and quality.

Impacts on access to and success of fisheries (8.5.5.4)

From the perspective of the fishers, climate change is very likely to have substantive impacts on how, when, and where fisheries may be conducted. Climate change will very probably affect access to and from fishing sites, and local knowledge associated with fish presence, migratory timing, and species composition. The success of the fisheries, especially as measured by transportation of high-quality product to market or point of consumption, is very likely to be similarly affected. Section 16.3 (Impacts on arctic freshwater and anadromous fisheries) addresses some aspects of the latter impacts, such as transportation and infrastructure issues. Most arctic freshwater fisheries are small in scale, conducted locally and seasonally, and often use limited and relatively simple gear. Climate change impacts that fishers will very probably have to accommodate include increased frequency of extreme events such as high-intensity storms, and increased winter precipitation and stronger water flows that will possibly imperil the fishers, restrict their access to fishing sites, or result in the loss of fishing gear (hence economic burden). Generally, arctic freshwaters have long winter periods during which ice provides a stable platform for transportation across lakes and rivers and for deploying some types of fishing gear such as gill nets. Decreased length of the ice season, concomitant increases in the duration of freeze-up and breakup, and increased ice roughness from storms are very likely to result in substantive changes in timing, duration, and methods by which fisheries are conducted in the future. [[Chapter 3 (Impacts on arctic freshwater and anadromous fisheries)]2] documents indigenous observations of changes in ice, including declines in ice duration, thickness, stability, and predictability, which not only alter the timing and safety of ice travel, but also limit and reduce the success of traditional and subsistence activities such as ice fishing (e.g., Sections 3.4.1 and 3.4.9 (Impacts on arctic freshwater and anadromous fisheries)).

Success of fisheries often depends upon the experience of the fishers, and for domestic fisheries is intimately connected with traditional knowledge of where and when to fish for particular species. The predictability associated with this will possibly decrease as climate change impacts occur. The timing of migratory runs, the typical keystone event in many northern domestic fisheries, is very likely to exhibit increased variability and decrease the ability of the fishers to know when best to begin fishing. Such circumstances will possibly result in decreased success of fisheries. Furthermore, such variability is likely to become the norm as [[ecosystem]s] undergo shifts, at least until new equilibriums are established. Because the changes wrought by climate change are likely to be protracted and depend in large part upon local ecological circumstances and the nature of the biota present, new equilibriums are unlikely to be quickly established. Thus, fishers will possibly have to tolerate highly variable and unstable conditions in freshwater and coastal ecosystems. This is very likely to result in highly variable successes in freshwater and anadromous fisheries, at least over longer timeframes.

Table 8.2. Summary of possible, likely, and very likely effects of changes in climate or UV radiation levels on quantity of fish in arctic freshwater and anadromous fisheries.
Climate change or UV radiation effect	Potential impact on fisheries	Consequences/comments
Increased productivity at lower trophic levels is very likely to result in increased growth, recruitment, and survival of freshwater species	Biomass and yields increased	Short-term management for increased fishery yields, especially for temperate species in the southern Arctic
Increased productivity at lower trophic levels is likely to result in increased growth in early years for facultatively anadromous species that promotes a shift to wholly freshwater life histories	Shifts in balance of anadromy versus non-anadromy decreases yields overall (i.e., smaller fish and perhaps more fish)	Long-term management for change in type and location of fisheries, and for decreased fishery yields
Local water temperature increases will at some point exceed thermal optima for individuals, possibly decreasing growth	Biomass and yields decreased	Especially true for arctic species and for coolwater species in the southern Arctic; population declines and local extirpation; synergistic effects from other factors such as competition from southern taxa; management issues associated with declining fishery yields
Reduced ice-cover duration on arctic lakes especially in northern arctic areas, increased and more rapid stratification, earlier and increased primary production, and decreased oxygenation at depth will possibly result in a reduction in the quality and quantity of habitat for species such as lake trout	Survival, biomass, and ultimately yields of preferred species generally decreased	Management for decreased fishery yields; potential management for declining fisheries and loss of populations
Improved quality of winter habitat will possibly result in increased survival (but this would also be affected by summer conditions, stratification, and overturns)	Biomass and yields increased	Short-term management for increased fishery yields; long-term implications unknown
Increased water temperatures generally and seasonally, but ultimately a decrease in summer habitat (e.g., deeper thermoclines in lakes, shrunken hypolimnia in lakes, reduced colder waters in rivers) are likely to reduce available habitat and decrease fish productivity, resulting in fish movements to deeper areas and/or fatal stresses on some fish species (e.g.,Arctic grayling)	Short-term increase in biomass and yields (several to tens of years) Long-term decrease in biomass and yields (greater than tens of years) Decreased availability of traditionally targeted species and/or loss of key populations	Short-term management for increased fishery yields (e.g., limit growth of fishery) Long-term decrease in traditional fisheries, switch to alternative fisheries if available Long-term relocation of fisheries to new areas such as deeper portions of lakes, possible cost issues to support this relocation
Southern arctic and subarctic fish species very likely to extend distribution ranges northward, which is likely to result in some significant negative effects on native species	Decreased availability or local loss of native species; increased opportunity to fish new species (especially in southern arctic areas)	Management issues for emerging fisheries, i.e., manage to allow increase in populations and successful colonization of arctic areas; retooling and education in new ways of fishing if needed
Northern (wholly arctic) species are very likely to experience range contraction and/or local extirpation	Decreased availability of arctic species to local fisheries, potential for replacement by other species low or uncertain	Management issues for declining fisheries, and ultimately addressing rare or endangered species; in Canada this also has implications under land claim legislation for basic needs provisions
Decreased water flow in summer is likely to decrease habitat availability and possibly deny or shift access for migrating fish	Decreased biomass and yields Decreased availability due to changes in migratory runs	Management issues for declining fisheries Replacement of protein and potential social issues for peoples that heavily rely on traditional fishing; switch to other wildlife
Increased UV radiation levels in surface waters are likely to disrupt development and/or cause damage to young fish consequently decreasing survival, or forcing fish deeper thus slowing growth	Decreased biomass and yields	Management for declining fishery yields
Increased interannual variability in climate, aquatic habitats, productivity, and fish growth and production characteristics are very likely	Unknown: some arctic species are relatively long-lived indicating an ability to withstand prolonged periods of poor year-class success Increased frequency of good and poor year classes	Variability in fishing success; conservative management for median (at best) or low-yield year classes to ensure sustainability; management for highly unpredictable fisheries Instability in yields of targeted species results in uncertainty of product for fisheries
Increased water flows in winter, increased runoff in winter, and decreased spring floods	Changes in migratory runs; possible decreased biomass and yields	Revised management needs for relocated or declining fisheries

Another aspect that deserves consideration is shifts in species composition as new species colonize an area. If the new colonizer is similar to existing species (e.g., Pacific salmon as another salmonid present in an area), the existing experience and interest of fishers is likely to be applicable. Alternatively, if the new species represents an unfamiliar taxon, fishers will possibly have to build the experience base for capture and marketing, assuming the species is desirable. Undesirable species (defined by local needs and wants such as, for example, spiny-rayed species) will possibly prove to be pests by clogging nets and reducing capture efficiency. Such species may also be considered substandard for local use based upon either tradition or physical characteristics. Although highly adaptable, northern peoples will still require time and experience to modify existing practices and develop necessary adaptations for continuing successful fisheries.

Fishing as an industry carries relatively high inherent risks associated with the environment and with the tools employed. These include loss of equipment (i.e., fishing gear and boats) and injury and death of the fishers. Along with the projected changes and increased variability in climate systems, and thus decreased predictability associated with forecasts and environmental conditions, the incidence and severity of catastrophic climatic events such as severe storms are very likely to increase. Such circumstances will imperil fishers exposed to the elements. For example, protracted breakup or freeze-up periods will make ice conditions more unpredictable. Travel over ice is essential to arctic life and especially to early winter fisheries conducted through the ice; the choice facing fishers will be increased risk or decreased fishing time, hence decreased catch.

This general summary of the impacts of changes in climate and UV radiation levels on arctic freshwater and anadromous fisheries is by no means comprehensive. Tables 8.2, 8.3, and 8.4 summarize numerous additional potential impacts.

Detailed regional and local analyses of particular types of fisheries (e.g., commercial, recreational, or domestic) and of specific arctic freshwater and anadromous fisheries are required to more fully elucidate all impacts, understand their consequences for local fisheries, and stimulate the development of appropriate short- and long-term adaptive responses by fishery managers and related constituents of the fishery infrastructure. Failure to address these issues in a timely fashion will undermine coherent and comprehensive preparedness to meet challenges that changes in climate and UV radiation levels present for arctic freshwater and anadromous fisheries.

Table 8.3. Summary of possible, likely, and very likely effects of changes in climate or UV radiation levels on quality of fish in arctic freshwater and anadromous fisheries.
Climate change or UV radiation effect	Potential impact on fisheries	Consequences/comments
If water temperatures increase, thermal optima for individual growth are likely to be exceeded, resulting in negative effects on individuals	Individual fish condition reduced, thus quality is lower Biomass and yields are reduced	Especially true for arctic species and arctic-adapted cool-water species requiring thermal refugia; value of individual fish and total amount landed are reduced
If water temperatures increase, flesh firmness will possibly decrease due to capture in warmer waters	Flesh quality reduced	Value is reduced; preservation compromised
If air temperatures increase, fisheries may occur under warmer conditions, which is very likely to increase problems of preserving and transporting the product	Problems with immediate preservation increased (e.g., on-board refrigerators required) Transportation costs increased (i.e., faster method or more return trips to fish plants) or impossible Quality of product decreased Costs of production increased	Low-value marginal fisheries will not be economically viable; northern fishery development compromised; and some fisheries may be abandoned if transportation is not possible Consumption of lower-quality or poorly preserved product may increase human health risks
Changes in climate and/or UV radiation levels will possibly result in physical disfiguration of fish (e.g., discolorations, lesions, growths, etc.)	Perceived and real quality and value of fish decreased	Increased concern voiced by local peoples requiring appropriate investigation and response from management agencies, e.g., ruling out potential proximate causes other than changes in climate or UV radiation levels Increased inspection and addressing of real and perceived health concerns required
Changes in climate and/or UV radiation levels will possibly result in increased parasitism, and new parasites and/or diseases in traditionally fished arctic species	Decreased interest in fisheries especially those based upon high-quality fish (e.g., recreational fisheries)	Economic development compromised
Persistent contaminants mobilized from natural sources (e.g., mercury liberated by permafrost thawing or flooding), or fluxes from anthropogenic sources to arctic ecosystems increase, which is likely to result in higher body burdens in arctic fish and cascade effects on other higher trophic levels	Real and perceived quality of fish decreased Compromised fish health reduces growth, decreases biomass and fishery yield	Increased inspection and monitoring required Health concerns about fish consumption, especially for domestic fisheries that typically are not routinely monitored

Table 8.4. Summary of possible, likely, and very likely effects of changes in climate or UV radiation levels on the success of arctic freshwater and anadromous fisheries.
Climate change or UV radiation effect	Potential impact on fisheries	Consequences/comments
Increased climate variability and frequency of extreme events (e.g., storms affecting fishing, catastrophic winter fish kills) will possibly result in biological consequences for fish populations, consequent synergistic effects on biotic systems (e.g., parasites), and synergistic effects from other impacts (e.g., local industrialization)	Increased unpredictability in places, times, and amounts of fish present in an area, and amounts captured and transported to processing, distribution, or consumption points Increased risk of gear and boat loss Increased personal risk to fishers	Extreme unpredictability in fish volumes has significant consequences for local peoples relying on fish for sustenance, for infrastructure development to support fisheries (e.g., fishing supplies, fish processing plants, transportation), and for development of markets for products from commercial and sport fisheries Loss of gear decreases success, economic viability, and persistence of fishery Need for search and rescue increased; fishing as an occupation falls from favor with a societal cost
Shifted environmental regimes are likely to affect time and difficulty of transportation to fishing sites and of product from sites to distribution or consumption points	Decreased economic value (or increased cost) of many arctic fisheries remote from communities or without permanent access Costs associated with fishing are increased	Marginal fisheries not economically viable, fishery development compromised; increased reliance on local easily accessible domestic fisheries raises the probability of over-exploitation with consequent sustainability and management issues As/if domestic fisheries fail, issues with protein replacement from other sources increase
Changes in the distribution and abundance of traditionally harvested fishes will cause traditional fishing sites to have fewer fish available	Decreased harvests and fewer fish available for communities	Indigenous fishers are tied to location and particular species by tradition and adaptation may be difficult

Impacts on specific fishery sectors (8.5.5.5)

In addition to the general impacts discussed previously, climate change will have impacts specific to the various types of fisheries conducted in the Arctic.

Commercial fisheries

Perhaps the most significant challenge facing commercial fisheries will be development of appropriate adaptive management strategies that deal with the complex, synergistic, and cumulative effects of climate change on fish populations and their environment, particularly in the context of sustainable use and long-term conservation.

For example, the conundrums of how to manage both declining and increasing populations of two fishable species in a particular location, how to understand and integrate climate change impacts through functional ecosystem pathways to project future states, and how to balance the needs of local peoples and competing demands all represent real problems for northern fishery management. Clearly, some sort of adaptive or heuristic approach that incorporates elements of both fishery and ecosystem management is required. Generally this is either unavailable or not being applied at present, a situation that must be rectified in order to adapt to climate change as it unfolds in the north.

Furthermore, the research necessary to both underpin management approaches and to elucidate ecosystem linkages to fisheries must be undertaken in the north to fill gaps in understanding. The best approach would be to leave sufficient resilience and compensatory capacity within fished populations and their supporting ecosystems to account for all impacts, and to provide sufficient buffers for increased variability and surprises associated with climate change. Current management practices incorporate such buffers in a limited way, especially in the Arctic. The development and application of such buffers (e.g., through risk analysis or other techniques) need to be extended. This presents a significant challenge in terms of developing or modifying appropriate tools for use in arctic fisheries.

Domestic fisheries

The subsistence sector in the arctic portion of the Canadian northern economy is estimated to be approximately CAN$ 15,000 per year per household. This represents one-quarter to one-half of the total local economy, and this proportion may be growing. Similar values are likely for domestic fisheries in other arctic countries, especially in more remote regions where the proportion of the total economy, hence value, may be even higher. Furthermore, replacement of this sector by wage or industrial economies is generally unlikely. Fisheries, which in the Canadian Arctic include marine mammals in coastal areas, comprise as much as 20% of the overall subsistence harvest in some areas. Thus, climate-mediated impacts on fish habitat, individual fish, and fish populations are very likely to have significant effects on the availability, use, and sustainability of domestic fisheries. In addition to those discussed previously, the following effects are likely to occur within domestic fisheries.

Climate change will possibly compromise traditional ecological knowledge developed over hundreds or thousands of years of direct environmental contact, with more pronounced impacts in particular areas where climate change effects are acute. Extreme events, which are unpredictable, are likely to exacerbate these impacts. Thus, increased climate variability and concomitant unpredictability of environmental conditions will possibly be more significant than will change in the trends of such conditions. As noted previously, this will possibly alter access to traditional fishing areas, increase risk associated with travel on the land or ice, and change fishery success. Loss of a significant portion of fish from the household economy is very likely to require replacement with some other means – perhaps increased reliance on food transported from the south and/or on other local northern foods (e.g., terrestrial mammals), further stressing those populations. The former solution (i.e., a dietary shift to southern transported foods) will possibly contribute to dietary problems and increased health costs. Increased transportation costs for such foods are likely to be covered in some manner by subsidies from southern portions of the national economies, but this feedback from the north would increase the economic impact of climate change in southern areas. The availability of new fish species in some areas will possibly mitigate these problems but may not provide immediate solutions.

Recreational fisheries

Impacts similar to those outlined previously will also affect sport or recreational fisheries. In addition, management demands and economics associated with such fisheries will possibly alter. For example, recreational fishing for Atlantic salmon in eastern North America is regulated in part through river closures driven by higher [[temperature]s] and low water levels. The rationale is that such conditions stress fish, and catch-and-release angling (the norm for the area) would further stress individuals and affect populations. Between 1975 and 1999, about 28% of 158 rivers on average were closed annually, with up to 70% affected in some years. This resulted in a 35 to 65% loss of potential fishing days with the warmest period (1995–1999) most affected. In part, this stress was the result of increased upstream migratory energy demands associated with lower water levels and higher water temperatures. Although this study was conducted in Newfoundland, it represents a possible future situation for arctic sport fisheries based upon riverine migrating fishes such as Atlantic salmon and Arctic char. Such fishes support significant local tourist economies in many areas of the Arctic, hence climate change impacts on recreational fisheries will possibly result in substantive economic impacts by increasing the frequency and duration of closures.

Impacts on aquaculture (8.5.5.6)

Aquaculture of fish in northern areas of arctic countries tends to focus upon cold-water species with high economic value such as Atlantic salmon and Arctic char. In general, such culture is presently located in areas south of the Arctic as defined herein, but this is likely to change as demand and opportunity increase. Aquaculture can be conducted wholly in freshwater using locally available or exotic species either indoors or out, or in protected nearshore marine areas primarily using anadromous species (see also [[Chapter 13 (Impacts on arctic freshwater and anadromous fisheries)]2]). Climate change is very likely to result in a number of possible shifts in this industry, however, similar to those described previously for fisheries dependent upon wild populations, these will possibly be complex and interactive with both positive and negative consequences. The details will be specific to the local situations. Possible changes include production increases, especially in northern locations, due to temperature-driven increased growth rates of cultured fish and also decreased times necessary for culture to marketable sizes, but this is likely to increase food requirements. Increased production will depend upon other factors not becoming limiting, especially available volumes of freshwater needed for inland operations. Knowledge of projected shifts in precipitation and evaporation with concomitant impacts on groundwater levels will be important to the viability of such endeavors. Production increases will possibly be offset by increased costs associated with oxygenating warmer waters, especially those for summer use, and increased loss to disease or costs associated with prevention.

As warmer conditions extend northward, the areas in which aquaculture is economically viable (i.e., revenue exceeds costs) will possibly increase, opening new areas for this activity. However, increased climate variability and frequency of extreme events will possibly also increase engineering costs. New aquaculture efforts will present economic opportunities, but also have potential negative impacts on local native species, especially if the cultured species is exotic (e.g., a non-native southern species). As climate change effects are realized, the suite of southern species potentially viable for aquaculture will probably increase and present new economic opportunities. This will increase the need for regulatory scrutiny of such development, especially if the risk of escape and naturalization of such species is high. A related issue is very likely to be an increased risk of intentional but unauthorized introductions of exotic species into natural systems already affected to some degree by climate change. Escape and naturalization of Atlantic salmon along the Pacific Coast of North America serves as a valuable model of potential negative effects. Appropriate management and control of such activities will be required; such activities will possibly add significant additional stress to native fish populations already highly stressed by climate change. Strategies to deal with such possibilities are presently lacking or extremely limited, especially for potential transfers within countries.

Chapter 8: Freshwater Ecosystems and Fisheries
8.1. Introduction (Impacts on arctic freshwater and anadromous fisheries) ]
8.2. Freshwater ecosystems in the Arctic
8.3. Historical changes in freshwater ecosystems
8.4. Climate change effects
8.4.1. Broad-scale effects on freshwater systems
8.4.2. Effects on hydro-ecology of contributing basins
8.4.3. Effects on general hydro-ecology
8.4.4. Changes in aquatic biota and ecosystem structure and function
8.5. Climate change effects on arctic fish, fisheries, and aquatic wildlife
8.5.1. Information required to project responses of arctic fish
8.5.2. Approaches to projecting climate change effects on arctic fish populations
8.5.3. Climate change effects on arctic freshwater fish populations
8.5.4. Effects of climate change on arctic anadromous fish
8.5.5. Impacts on arctic freshwater and anadromous fisheries
8.5.6. Impacts on aquatic birds and mammals
8.6. Ultraviolet radiation effects on freshwater ecosystems
8.7. Global change and contaminants
8.8. Key findings, science gaps, and recommendations

References

Citation

Committee, I. (2012). Impacts on arctic freshwater and anadromous fisheries. Retrieved from http://editors.eol.org/eoearth/wiki/Impacts_on_arctic_freshwater_and_anadromous_fisheries