Effects of climate change on arctic anadromous fish

May 7, 2012, 1:03 pm

This is Section 8.5.4 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


About 30 species within the arctic regions belonging to the families Petromyzontidae, Acipenseridae, Anguillidae, Clupeidae, Osmeridae, Salmonidae, and Gasterosteidae exhibit diadromous behavior (i.e., spend part of their lives in the marine environment and migrate to freshwater to spawn, or the converse). Most arctic diadromous species are actually anadromous (i.e., use estuarine and/or marine environments for feeding and rearing; and freshwater environments for spawning, early life history, and, in the case of most arctic species, overwintering); only freshwater eels (Anguillidae) and some lampreys (Petromyzontidae) are catadromous (i.e., breed at sea and rear in freshwater). Most anadromous species in the Arctic are facultatively anadromous[2] in that many individuals in a population do not necessarily migrate to sea even though it is accessible. Typically, anadromous behavior is most prevalent at northern latitudes[3] because the ocean is more productive than adjacent freshwater habitats in temperate and arctic zones[4]. For a number of facultative anadromous species (e.g., Arctic char, Dolly Varden, brook trout, brown trout, and three-spine stickleback), anadromous behavior declines in frequency or ceases toward the southern portion of the distributional range of the species[5]. Anadromy in Arctic char also declines or ceases towards the extreme northern geographic limits, probably because access to and time at sea, hence benefits, are limited. Facultative anadromous species exhibit anadromy in polar regions to take advantage of marine coastal productivity and escape extreme oligotrophic conditions that typify arctic lake systems. Generally, individuals of a population that exhibit anadromous behavior have a larger maximum size and higher maximum age, indicating some benefit to seaward migration and feeding.

Diadromous fishes will integrate climate change effects on freshwater, estuarine, and marine areas, hence the total impact on these fishes is very likely to be significant[6]. This will have major resulting impacts since these fishes support important fisheries in all arctic regions (section 8.5.5, Chapter 3). The following paragraphs discuss the consequences of climate change for diadromous fishes.

The projected impacts of climate change on arctic lakes suggest that, overall, productivity of these limited systems will very probably increase due to a longer ice-free growing season and higher nutrient loads. Anadromous fish populations will probably benefit initially with increases in survival, abundance, and size of young freshwater life-history stages, which will possibly cascade to older, normally anadromous stages. Thus, facultatively anadromous species will possibly exhibit progressively less anadromous behavior if the benefits of remaining in freshwater systems outweigh the benefits of migrating to coastal areas for summer feeding over time. Nordeng[7] reported that when the freshwater food supply was experimentally increased, the incidence of anadromous migration by Arctic char decreased. However, the increased estuarine production discussed previously will possibly offset any tendency to reduce facultative anadromy in response to increased freshwater production. The exact balance and circumstances of how such scenarios unfold will be ecosystem-specific and will depend on the details of present productivity, accessibility, and ease of migration by fish, as well as the nature and degree of any climate-related effects.

The variability associated with projected changes in productivity is uncertain. Most Arctic anadromous species are typically long-lived (15–50 years) compared to other fish species. Longevity benefits species living in variable environments by ensuring a relatively long reproductive cycle, thus minimizing the risk that prolonged environmentally unfavorable periods (5–15 years) will result in the loss of a spawning stock[8]. Anadromous forms of arctic fish species are relatively long-lived (>10–15 years) and are probably suited to cope with increased variability that will possibly accompany climate change. Initially, as environmental conditions improve, successful spawning episodes are very likely to increase in frequency. Anadromous fish that are short-lived (<10–15 years) are likely to exhibit more variability in abundance trends with increased variability in environmental conditions.

When in freshwater, anadromous species also inhabit streams or rivers in addition to lakes. Projected climate impacts on arctic hydrology (section 8.4) suggest that runoff is very likely to be driven by increased precipitation and will very probably not be as seasonally variable; winter flows are very likely to be enhanced and summer flows reduced. In addition, warmer conditions are projected to reduce the length of winter, shorten the ice season, and reduce ice-cover thickness. Thus, streams that were previously frozen solid will very probably retain water beneath the ice, benefiting anadromous species that utilize streams for winter habitat (e.g., Dolly Varden). Overwintering habitat is critical for arctic species and is typically limited in capacity[9]. However, the shortened ice season and thinner ice are very likely to reduce ice-jam severity. This will have implications for productive river deltas that require flooding. There are several anadromous species, such as Arctic cisco, that rely on deltas as feeding areas, particularly in spring[10].

Anadromous fish are by definition highly migratory and tolerant of marine conditions. Thus, as limiting environmental factors ameliorate, a number of sub- or low-arctic anadromous species are likely to extend their northern limits of distribution to include areas within the Arctic. Pacific salmon species are likely to colonize northern areas of Region 3. Sockeye salmon (Oncorhynchus nerka) and pink salmon (O. gorbuscha) have already been incidentally recorded outside of their normal distribution range on Banks Island, Northwest Territories, Canada[11]. Similarly, anadromous species such as Atlantic salmon, alewife (Alosa spp.), brown trout, and brook trout will possibly also extend their northern range of distribution in Regions 1 and 4. New anadromous species invading the Arctic are likely to have negative impacts on species already present. However, for many of these subarctic species, climate change is likely to have negative impacts on southern populations, offsetting any positive benefits that will possibly accrue in the north[12]. Catadromous species such as European eel (Anguilla anguilla; Region 3) are primarily warm-water species limited by colder arctic temperatures (e.g., Nordkappe, northern Norway is the present limit[13]). Eastward colonization of Russian areas of Region 2, where the species does not now occur, is possible; additionally, increased abundances are likely in some areas where the European eel presently occurs but where populations are insufficient for fisheries (e.g., Iceland).

Two arctic anadromous species are particularly important in northern fisheries: Arctic char (all regions) and Atlantic salmon (Regions 1 and 4). To indicate the range of possible responses of these species to climate change, they are treated separately in Boxes 8.7 and 8.8, respectively.

Box 8.7. Effects of environmental change on life-history and population characteristics of Labrador Arctic char

Present-day relationships between environmental and biological parameters must be understood to provide the foundation for assessing future climate change effects on fish populations.The general lack of such understanding for most arctic fishes currently precludes in-depth development of comprehensive and accurate qualitative scenarios of impacts, and limits quantification of effects under those scenarios. Development of such understanding requires substantive long-term data that are relatively sparse for most arctic fish; a circumstance that demands redressing. A notable exception is the availability of data for Arctic char.The distribution and life-history patterns of Arctic char are complex, and few attempts have been made to relate fluctuations in abundance, catch rates, and stock characteristics to environmental variables such as temperature and precipitation.The table lists associations between biology and variability in environmental parameters for Arctic char from northern Labrador, Canada.

Environmental associations for Nain Arctic char

Long-term (1977–1997) monitoring of the char fishery at Nain, Labrador (56º 32' N, 61º 41' W) has produced data on both anadromous fish and environmental variables that have been applied in assessing long-term variability in catch biometrics[14]. Climate variability, particularly annual and seasonal, was found to have effects at critical life-history stages, and to affect average stock age, weight, and length characteristics, thus determining the dynamics of exploited Arctic char populations several years later and their eventual spawning success[15].The table also summarizes aspects of climate variability and the probable effects on the population. Mean age-at-catch and weight of Arctic char from the Nain fishery declined significantly, with a lag of four years, in response to high summer precipitation.This precipitation-related change is probably due to fluctuations in river flow and nutrient dynamics during the initial migration of Arctic char to nearshore marine areas. First-time migrants tend to stay in the nearshore areas[16] and are most likely to be immediately affected by changes in nutrient inputs resulting from variability in river flow. High-precipitation years increase nutrient and POC exports from river and lake catchments[17], which increase nutrient inputs to nearshore marine feeding areas and probably increases productivity at all trophic levels.

The significance of increased winter precipitation is related to events occurring in the first critical winter of life for char. Heavier, more frequent snowfalls in Labrador maintain ice cover in an isothermal state and limit ice thickness[18]. Deeper snowpack maintains taliks, or unfrozen areas, in lake and river beds[19], improving winter refugia conducive to fish survival[20].

The possible effects of temperature on Arctic char are complex. Mean fish length increased with rising summer temperatures and the persistence of optimal growth temperatures (12–16 ºC) over a longer period of time[21]. High spring temperatures and accelerated ice breakup, however, can have negative effects on populations migrating with ice breakup[22]. In the Fraser River (Labrador), breakup typically occurs in late April or early May[23] and would be well advanced, as would seaward migration, in years experiencing above-normal May temperatures. Although temperature increases can advance preparatory adaptations for marine residency (i.e., smoltification), they also result in a more rapid loss of salinity tolerances and a shortening of the period for successful downstream migration[24]. Rapid increases in temperatures are likely to impinge on the development of hypo-osmoregulatory capabilities in migrants and decrease growth due to the increased energetic costs of osmoregulatory stress, increase the probability of death during migrations to the sea, and decrease average growth by reducing the average duration of marine residence.

Several conclusions arise from this study:

  • Long-term, comprehensive biological and environmental datasets are critical to assess and monitor climate change impacts on fish populations.
  • Climate variables are very important in understanding year-to-year variability in stock characteristics.
  • Causative relationships appear to exist between life history and environment but precise roles played, timing of the effect, and limits to the effect need more thorough investigation.
  • For long-lived arctic fish, the effects of particular environmental conditions are often lagged by many years, with cascading effects on fishery production and management.
  • Environmental effects are manifested in the fish population in the same way that other effects such as exploitation are (e.g., in terms of individual growth that translates into survival, fitness, reproduction, and ultimately into population-dynamic parameters such as abundance), thus distinguishing specific effects of climate change from other proximate drivers may be problematic.
  • Particular environmental effects tended to reinforce each other with respect to their effect on the fish; although generally positive in this study, effects from several environmental parameters could presumably act antagonistically resulting in no net effect, or could synergistically act in a negative fashion to substantially impact the population.


 Box 8.8. Projecting stock-specific effects of climate change on Atlantic salmon

Differences in stock characteristics, local geography, and interannual variations in spawning escapement of Atlantic salmon confound attempts to apply the results of specific field studies[25] in projecting the effects of climate change[26]. Further complications arise from the ongoing debate regarding whether environmental variation and population effects are greatest in fresh or marine waters[27], and how these act to determine survival of various life stages and population abundance. Knowledge of Atlantic salmon biology, however, is sufficient to describe the range of temperature conditions required for optimal growth and reproductive success, and thus to allow inferences of climate change effects. Atlantic salmon life-history stages all occur within optimal temperature ranges[28]. However, variation in the required range of optimal temperatures for salmon at different life stages makes projecting the effects of climate change difficult.To date, three approaches to tackling the problem have been proposed in the scientific literature (see section 8.5.2).

In the first approach, regional climate scenarios and projections are coupled directly to knowledge of the physiological limits within which salmon operate. For example, winter discharges and associated overwintering habitat will respond to precipitation changes[29]. Low summer discharge on the east coast of Newfoundland and in southern Québec, which limits parr (young salmonid with parr-marks before migration to the sea) territory and hampers upstream adult migration, is also very likely to change, affecting population abundances in many rivers[30]. Problems with this approach include uncertainty in precipitation and extreme events forecasts, and coupling of regional climate models with ocean circulation models.


caption Table for Box 8.8. Results of modeling experiments projecting the possible effects of climate change on different populations of Atlantic salmon[1].


A second approach to understanding the possible impacts of climate change on Atlantic salmon is to apply what is known about relationships between weather and salmon population dynamics. For example, historical records from the salmon fisheries in the Ungava region of northern Québec show a correlation between ice conditions, the late arrival of salmon, and poor catches.This relationship suggests that an improvement in salmon abundances will possibly occur in the future associated with a climate-induced reduction in the extent and duration of sea-ice cover[31].The correlation between stock characteristics and latitude[32] suggests that mean smolt (young salmonid which has developed silvery coloring on its sides, obscuring the parr marks, and which is about to migrate or has just migrated into the sea) ages are likely to decrease in association with increases in average temperatures and growing-season length.The modeling results of Power M. and Power[33] projected that temperature increases and decreases will have varying effects on populations at different latitudes (see table). Where present-day temperatures are at the upper end of the optimal temperature range for growth, increases in temperature reduced growth, increased average riverine residency and associated riverine mortalities, decreased smolt production, and increased parr densities.The reverse (increased smolt production and decreased parr densities) occurred when temperatures at the lower end of the temperature range optimal for growth were raised. Modest changes in precipitation, and thus available habitat, had no significant direct effect or interactive effect with changes in temperature on either smolt production or parr density under any of the considered temperature scenarios.Thus, depending upon the exact location and characteristics of the salmon population, the precise impact of a given environmental change under a future climate scenario may be positive or negative relative to present conditions.This makes regional differences in fish biology, present-day local climate, and climate change scenarios extremely important in projecting future situations.

A third approach to projecting the effects of climate change involves attempting to shift ecological zones into more appropriate geographic locations to reflect probable future climate regimes and the known physiology of potentially affected species. The present distribution of many fish is limited by the position of the summer isotherms that limit the fish either directly due to thermal relationships or indirectly through effects on critical resources such as food[34]. Use of this approach suggests that Atlantic salmon will possibly disappear from much of their traditional southern range in both Europe and North America as temperatures rise, and find more suitable habitat in cold rivers that experience warming. In the eastern Atlantic, the overall area occupied by salmon is likely to shrink due to a lack of landmasses to the north with potentially suitable environments. In the western Atlantic, rivers in the Ungava Bay area will possibly become more productive and are likely to experience increases in the numbers of salmon (e.g., the Koroc and Arnaux Rivers). Rivers that currently have large salmon runs are also likely to become more productive (e.g., the George, Koksoak, and Whale Rivers) and experience associated increases in salmon abundances[35].There are also rivers on Baffin Island and Greenland that will possibly become warm enough for Atlantic salmon to colonize. Such colonization, however, is likely to come at the expense of Arctic char populations that currently inhabit the rivers because of competition between the two species. Constraints on redistribution northward with climate change include reductions in the availability of spawning substrate with increased sediment loading of rivers, changes in stream and river hydrology, and delay in the establishment of more diverse and abundant terrestrial vegetation and trees known to be important for the allochthonous inputs that provide important sources of carbon for salmon[36].



Chapter 8: Freshwater Ecosystems and Fisheries
8.1. Introduction
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



  1. ^ Craig, P.C., 1989. An introduction to anadromous fishes in the Alaskan Arctic. In: D.W. Norton (ed.). Research Advances on Anadromous Fish in Arctic Alaska and Canada. Biological Papers of the University of Alaska, 24:27–54.
  2. ^ McDowall, R.M., 1987. Evolution and the importance of diadromy: the occurrence and distribution of diadromy among fishes. American Fisheries Society Symposium, 1:1–13.
  3. ^ Gross, M.R., R.M. Coleman and R.M. McDowall, 1988. Aquatic productivity and the evolution of diadromous fish migration. Science, 239:1291–1293.
  4. ^ McDowall, R.M., 1987. Evolution and the importance of diadromy: the occurrence and distribution of diadromy among fishes. American Fisheries Society Symposium, 1:1–13.
  5. ^ Fleming, I.A. and A.J. Jensen, 2002. Fisheries: effects of climate change on the life cycles of salmon. In: I. Douglas (ed.). Encyclopedia of Global Environmental Change, Vol. 3, Causes and Consequences of Global Environmental Change, pp. 309–312. John Wiley and Sons.
    –Friedland, K.D., 1998. Ocean climate influences on critical Atlantic salmon (Salmo salar) life history events. Canadian Journal of Fisheries and Aquatic Sciences, 55(S1):119–130.
  6. ^ Nordeng, H., 1983. Solution to the "char problem" based on Arctic char (Salvelinus alpinus) in Norway. Canadian Journal of Fisheries and Aquatic Sciences, 40:1372–1387.
  7. ^ Leaman, B.M. and R.J. Beamish, 1981. Ecological and management implication of longevity in some northeast Pacific groundfish. Bulletin of the International North Pacific Fisheries Commission, 42:85–97.
  8. ^ Craig, P.C., 1989. An introduction to anadromous fishes in the Alaskan Arctic. In: D.W. Norton (ed.). Research Advances on Anadromous Fish in Arctic Alaska and Canada. Biological Papers of the University of Alaska, 24:27–54.
  9. ^ Craig, P.C., 1989. An introduction to anadromous fishes in the Alaskan Arctic. In: D.W. Norton (ed.). Research Advances on Anadromous Fish in Arctic Alaska and Canada. Biological Papers of the University of Alaska, 24:27–54.
  10. ^ Babaluk, J.A., J.D. Reist, J.D. Johnson and L. Johnson, 2000. First records of sockeye (Onchorhynchus nerka) and pink salmon (O. gorbuscha) from Banks Island and other records of Pacific salmon in Northwest Territories, Canada. Arctic, 53:161–164.
  11. ^ Welch, D.W., Y. Ishida and K. Nagasawa, 1998.Thermal limits and ocean migrations of sockeye salmon (Onchorynchus nerka): Long-term consequences of global warming. Canadian Journal of Fisheries and Aquatic Sciences, 55:937–948.
  12. ^ Dekker, W., 2003. On the distribution of the European eel (Anguilla anguilla) and its fisheries. Canadian Journal of Fisheries and Aquatic Sciences, 60:787–799.
  13. ^Power, M., J.B. Dempson, G. Power and J.D. Reist, 2000. Environmental influences on an exploited anadromous Arctic charr stock in Labrador. Journal of Fish Biology, 57:82–98.
  14. ^Ibid.
  15. ^Berg, O.K., 1995. Downstream migration of anadromous Arctic charr (Salvelinus alpinus (L.)) in the Vardnes River, northern Norway. Nordic Journal of Freshwater Research, 71:157–162.
    -- Bouillon, D.R. and J.B. Dempson, 1989. Metazoan parasite infections in landlocked and anadromous Arctic charr (Salvelinus alpinus Linneaus), and their use as indicators of movement to sea in young anadromous charr. Canadian Journal of Zoology, 67:2478–2485.
  16. ^ Allan, J.D., 1995. Stream Ecology: Structure and Function of Running Waters. Chapman & Hall, 400pp.;
    Meyer and Likens, 1979
  17. ^ Gerard, R., 1990. Hydrology of floating ice. In:T.D. Prowse and C.S.L. Ommanney (eds.). Northern Hydrology: Canadian Perspectives. National Hydrology Research Institute, Saskatoon, Scientific Report No. 1, pp. 103–134.
  18. ^ Allan, 1995,Op. cit.;
    -- Prowse,T.D., 1990. Northern hydrology: an overview. In:T.D. Prowse and C.S.L. Ommanney (eds.). Northern Hydrology: Canadian Perspectives. National Hydrology Research Institute, Saskatoon, Scientific Report No. 1, pp. 1–36.
  19. ^Allan, 1995, Op. cit.;
    -- Power, G. and D.R. Barton, 1987. Some effects of physiographic and biotic factors on the distribution of anadromous Arctic char (Salvelinus alpinus) in Ungava Bay, Canada. Arctic, 40:198–203.;
    -- Power, G., R.S. Brown and J.G. Imhof, 1999. Groundwater and fish –insights from northern North America. Hydrological Processes, 13:401–422.
  20. ^ Baker, R., 1983.The effects of temperature, ration and size on the growth of Arctic charr (Salvelinus alpinus L.). M.Sc.Thesis, University of Manitoba, 227pp.;
    -- Johnson, L., 1980.The Arctic charr, Salvelinus alpinus. In: E.K. Balon (ed.). Salmonid Fishes of the Genus Salvelinus, pp. 15–98. Dr.W. Junk Publishers.
  21. ^ Nilssen, K.J., O.A. Gulseth, M. Iversen and R. Kjol, 1997. Summer osmoregulatory capacity of the world’s northernmost living salmonid. American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, 272:R743–R749.
  22. ^ Dempson, J.B. and J.M. Green, 1985. Life history of anadromous arctic charr, Salvelinus alpinus, in the Fraser River, northern Labrador. Canadian Journal of Zoology, 63:315–324.
  23. ^McCormick, S.D., J.M. Shrimpton, J.D. Zydlewski, C.M.Wood and D.G. McDonald, 1997.Temperature effects on osmoregulatory physiology of juvenile anadromous fish. In: C.M.Wood and D.G. McDonald (eds.). Global Warming: Implications for Freshwater and Marine Fish. Society for Experimental Biology Seminar Series, 61:279–301.
  24. ^e.g., Buck, R.J.G. and D.W. Hay, 1984.The relation between stock size and progeny of Atlantic salmon, Salmo salar L., in a Scottish stream. Journal of Fish Biology, 23:1–11.;
    -- Chadwick, E.M.P., 1987. Causes of variable recruitment in a small Atlantic salmon stock.American Fisheries Society Symposium, 1:390–401.;
    -- Egglishaw, H.J. and P.E. Shackley, 1977. Growth, survival and production of juvenile salmon and trout in a Scottish stream, 1966–75. Journal of Fish Biology, 11:647–672.
    -- Egglishaw, H.J. and P.E. Shackley, 1985. Factors governing the production of juvenile Atlantic salmon in a Scottish stream. Journal of Fish Biology, 27(Suppl. A):27–33.
  25. ^Power, M. and G. Power, 1994. Modeling the dynamics of smolt production in Atlantic salmon.Transactions of the American Fisheries Society, 123:535–548.
  26. ^ Friedland, K.D., 1998. Ocean climate influences on critical Atlantic salmon (Salmo salar) life history events. Canadian Journal of Fisheries and Aquatic Sciences, 55(S1):119–130.
  27. ^ Dwyer,W.P. and R.G. Piper, 1987. Atlantic salmon growth efficiency as affected by temperature.The Progressive Fish Culturist, 49:57–59.;
    -- Peterson R. and Martin-Robichaud, 1989;
    -- Power, G., 1990a.Warming rivers (or a changing climate for Atlantic salmon). Atlantic Salmon Journal, 39(4):40–42.;
    -- Wankowski, J.W.J. and J.E.Thorpe, 1979.The role of food particle size in the growth of juvenile Atlantic salmon (Salmo salar L.). Journal of Fish Biology, 14:351–370.
  28. ^Power, G., 1981. Stock characteristics and catches of Atlantic salmon (Salmo salar) in Québec, and Newfoundland and Labrador in relation to environmental variables. Canadian Journal of Fisheries and Aquatic Sciences, 38:1601–1611.
  29. ^Ibid.
  30. ^ Power M. and Power, 1994, Op. cit.
  31. ^Power, G., 1976. History of the Hudson’s Bay Company salmon fisheries in the Ungava Bay region. Polar Record, 18:151–161.;
    Power, G., M. Power, R. Dumas and A. Gordon, 1987. Marine migrations of Atlantic salmon from rivers in Ungava Bay, Québec.American Fisheries Society Symposium, 1:364–376.
  32. ^ Power G., 1981, Op. cit.






Committee, I. (2012). Effects of climate change on arctic anadromous fish. Retrieved from http://www.eoearth.org/view/article/152366


To add a comment, please Log In.