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7.2 Knowledge Status

7.2.1 Parameters Needed to Assess Potential Responses of VECs to Environmental Stressors Transport and fate / exposure potential

Models have been developed that adequately address the transport and fate of surface oil spills (e.g. ASA 2011 and McKay 2009).  These models take into account the effects of wind and surface currents and are useful predictions of the movement of oil at the surface and into the water column.  They predict the concentrations of oil within a volume of water which permits the comparison of those exposure values to toxic effects based measurements of adverse effects observed in laboratory studies (Gallaway et al., in review). When oil is released at the surface of the water or at depth it begins to spread, thin and dilute into 2 or 3 dimensions.  For surface spills the oil begins to spread primarily in a horizontal direction based on currents and wind-driven transport with the more soluble components diluting into the third or vertical dimension, which includes the water under the surfaced oil and release of the more volatile components to the atmosphere. Subsurface releases generally have an initial momentum that provides rapid dilution by entrainment of surrounding waters during the initial rise of the fluids from the bottom, driven by any jet turbulence from the simultaneous release of natural gasses and the natural buoyancy of the oil.  This rapid dilution is followed by continued vertical transport based on the specific gravity or density and size of oil droplets created during the initial release including entrained diffusion of the more soluble components into the water column accompanied by horizontal dispersion by subsurface currents.  Other processes that occur and which may influence the bioavailability of oil components include biodegradation processes and physical/chemical changes that may occur due to pressure changes (e.g. clathrate formation) or emulsion formations by incorporation of water into the oil mass.  In addition to the physical contact of organisms with oil (e.g. fouling on birds) organisms also respond to the bioavailable chemical components that are present in water and food.

Another component of the fate evaluation for models is the change in chemical composition and bioavailability of oil that occurs during physical weathering and biological activity, mineralization and biodegradation.  The relative contribution and total concentrations of oil compounds changes through time and the rate of change varies depending on the environmental compartment in which the oil resides.  Surface oil that emulsifies undergoes less efficient biodegradation and appears to be less available for biological uptake into tissues than oil that is dispersed into the water column as small droplets.  Oil that is stranded on beaches or within interstitial waters between grains of sediment also undergoes slower rates of biodegradation as demonstrated by the ‘lingering oil’ effects seen in Prince William Sound decades after its stranding.  These important concepts are further developed in Sections 3 and 5 (fate of oil and biodegradation processes, respectively).

The transport and fate of a released quantity of oil has the potential to affect the population abundance, standing crop/production, increase daily mortality coefficients, and response to stressor exposure within different environmental compartments.  Variation in these attributes for each environmental compartment are expected and assessments can be generated based on assumptions that are meant to provide a maximum level of effect using the most conservative estimates or to best characterize the distinctions between the compartments. Oil toxicity evaluations / sensitivity

The bioavailable fractions of oil derived from the soluble compounds that are present during the initial release of the oil or in locations where oil becomes re-concentrated (e.g. at convergence zones, pycnoclines, shorelines, air/water and ice/water interfaces).  As dilution of these compounds and biodegradation processes occur the relative and total concentrations may be reduced.  Eventually, the concentrations of the soluble compounds decreases to the point that the acute effects may be replaced by more subtle, sublethal doses resulting in longer term exposure to lower but more constant concentrations of the remaining compounds.  Measurements made during accidental and experimental spill events have shown that the higher total petroleum hydrocarbon (TPH) concentrations observed in the upper 3 m of the water column range from ~2 to 37 mg/L for physically dispersed oil and between 36 and 527 mg/L for chemically dispersed oil (Trudel et al., in press; Brandvik et al. 1995).  The chemical dispersants introduced more oil into the water column but the effects based concentrations for measured petroleum compounds were less per unit of oil for the chemical dispersions (Gardiner et al., 2013).  These field evaluations also showed reduced TPH concentrations of 50% within an hour and approximately 2 orders of magnitude differences in concentration within the upper 10 m of the water column for both physically and chemically dispersed oil. 

Empirical studies of the acute toxicity of oil and its components or modeling the effects of complex mixture exposure and uptake are alternative methods for estimating the effects of oil in different compartments.  For acute responses to oil exposure, including mortality and avoidance behaviors toward soluble components, toxicity testing is appropriate.  The exposure regimen for this type of assessment has been developed to emulate field conditions observed during spill events and controlled experimental spill events that were described in the previous paragraph.  The methods employ spiked concentrations of oil followed by dilutions with clean water to simulate the dispersion/dilution processes that occur in the field.  There are a significant number of experiments that have been performed using this protocol and it provides a good characterization of the acute effects that might be expected from dynamic exposure concentration from an oil spill at the surface or a depth (refer to Section 6 on Ecotoxicology for further toxicological information). The longer term, chronic and sublethal responses of organisms can be modeled by using constant exposure to lower concentrations of oil that might occur with organisms drifting with the oil after the initial dispersion or those inhabiting contaminated sediments.  There are also models that have been built to estimate the potential effects of the uptake of the bioavailable components into the tissues of organisms resulting in chronic responses to oil components.  These models are based on the relative narcosis effect of many PAH compounds (Di Toro et al. 2007). Population distributions, stressors, and mortality rates

Modeling population responses that can occur as a result of exposure to oil should include a representation of the temporal and spatial distribution of age classes of the VECs.  The spatial evaluation needs to take into account the vertical and horizontal distribution of the abundance of each VEC and its relationship to key environmental components.  Examples of environmental components include river discharges, lagoon occupation, annual and permanent ice, propensity to cluster at zones of convergences (e.g. currents, pycnoclines, upwelling and downwelling) and different types of shorelines and bottom types for each of the VEC age classes.  The populations of VECs undergo different natural stressors within each of these habitats ranging from environmental exposure conditions, inter and intra-annular differences in environmental conditions, differences in spawning success and variable predation rates.  As a result, the influence of an additional stressor will influence populations at different rates.  These natural and ongoing impacts produce natural mortality rates that can be determined.  For fish the daily mortality rates can be determined by examining daily growth rings on otoliths and the relative abundance of individuals at comparable ages.  Invertebrates generally lack these types of structures and their mortality rates are based on the relative abundance of different size classes within a population.  Once the natural mortality rates are estimated, the impact of another stressor can be added to determine what the combined mortality will be. 

For example, a recent assessment of the acute effects of chemically dispersed oil into Arctic pelagic open ocean, ice-free waters on larval Arctic cod (Boreogadus saida) was modeled to determine the adult female equivalents that would be lost as a result of a large oil spill (Gallaway et al., in review).  The fisheries model obtained daily mortality rates from otolith assessments and applied toxicity information obtained by Gardiner et al. (2013) and assumed that a large oil spill would be at the center of the maximum population sizes observed.  Comparing the increased mortality rates of the oil indicated that number of adult female equivalents impacted by the oil were a fraction of the natural range in abundance of this species.  Based on these results the resiliency of the population of Arctic cod would be sufficient to recover during the following spawning year.  Had the oil not been treated with dispersants it would have been transported toward shore where juvenile Arctic cod are present in very large schools numbering in the millions, and the Arctic cod population would be subjected to greater stress. 

The following sections include technical information on copepod, amphipod, and fish population ecology and discuss the types of information necessary to assess the potential population effects of oil on two groups of species, copepods and fish. 

7.2.2 Copepod Population Ecology

Copepods are a subclass of small crustaceans found in marine and freshwater habitats throughout the world, including Arctic and sub-Arctic waters.  Copepods feed on phytoplankton or other zooplankton making them the dominant secondary producer present in the water column.  Their health and abundance can act as a bottom-up control on entire ecosystems, including specific effects on commercially important fisheries such as cod (Beaugrand et al. 2003) as well as populations of marine birds and mammals.  This section presents a broad overview of some aspects of the population ecology of copepods in the Arctic and sub-Arctic including: preferred habitat, life cycle and development, species present, and their respective populations. Each of these descriptions can be used to evaluate the potential impacts to copepod populations after an oil release. Copepod Growth and Development

Copepods are divided into ten orders, but only cyclopoida, poecilostomatoida, and calanoida are common as plankton.  The order calanoida includes some of the most dominant species found in the Arctic in terms of abundance and biomass.  Calanoid copepods all follow the same life stages from egg to adult organism as follows:

  • Egg: Newly laid eggs are small capsules that sink to the bottom and swell until they become spherical.  The number of eggs laid by females of different species is variable.
  • Naupliar stages: The postembryonic development stages are referred to as naupliar stages.  Six such stages (Stages I through VI) exist for calanoid species.  The naupliar stages are characterized by the use of the antennae for swimming and the appearance of a first, unpaired eye.
  • Copepodite stages: A copepodite larva has two pairs of swimming appendages and develops a hind body comprised of the thorax and abdomen.  Five copepodite stages exist (Stages I through V). Molting of the outer exoskeleton marks the transition between each stage.
  • Adult: The adult stage is reached with the development of gonads in males and ovaries in females, with no further molts.

There are common factors such as water temperature and food availability that dictate the growth rate of all copepods.  There are also specific habitat preferences and adaptations that result in varying growth rates for the different species.  Three representative calanoid species, Calanus finmarchicus, Calanus glacialis, and Calanus hyperboreus, are used to illustrate how habitat preferences and seasonal variations in Arctic conditions influence copepod life cycles. Understanding the duration of the copepod life cycle and how their populations shift vertically in the water column in response to food availability can help to inform when a population might be more vulnerable to an oil spill incident.

All species depend on the seasonal production cycle.  The increase of light intensity and melting of sea ice in the Arctic spring produce nutrient rich waters that establish the conditions for a large bloom of phytoplankton.  The carbon fixed by photosynthesis is rapidly stored as lipids by the three Calanus herbivores.  At higher latitudes this cycle of primary production becomes shorter and delayed farther into the summer because of less intense light and differences in ice coverage.  These differences can be significant.  In ice free areas of the SW Barents Sea, the primary production period extends from April through July.  This is followed by continued, but diminished, phytoplankton production into November.  By comparison, the sea ice may not fully melt until July in the in the Kara Sea.  The primary production period extends until mid-September, with reduced production continuing for another month.  Even these time frames are approximations, as there are huge variations in ice cover over time (Falk-Petersen et al. 2009).

Spawning time depends on the species, but occurs before or during the phytoplankton bloom.  Once the eggs have hatched the nauplii rapidly progress through the six stages into copepodites.  For Arctic species the annual bloom ends before copepodites develop into adults.  Copepodites of each species overwinter at depth in a form of hibernation referred to as diapause.  Figure 7-1 presents a summary of the each species response to the spring bloom and corresponding winter diapause.  The transition through the copepodite stages and into adult male and female organisms is marked on the figure.  The following paragraphs detail some species-specific developmental characteristics.

Calanus finmarchicus:  The geographical range of this species is centered in the Norwegian and Labrador Seas as well as in the Barents Sea south of the polar front.  However, it is frequently observed in the Arctic Ocean as an expatriate species (Kosobokova et al. 2011).  C. finmarchicus has a one year life cycle where it spawns at the maximum of the phytoplankton bloom.  Copepodites develop into lipid rich stage V by June-July and then descend to 200 to 1600 meters to undergo diapause.   The stage V copepodites begin to develop into males and females around January.  This process continues through into March when they ascend to the surface waters (Falk-Petersen et al. 2009).

Calanus glacialis:  This is a shelf species that lives in waters that can be ice covered into the summer months.  C glacialis typically has a two year life cycle (Figure 7-1) that begins with spawning during the spring of its third year.  Spawning takes place before or during the Arctic bloom, and likely requires additional energy input from ice algae or fecal pellets of ice dwelling organisms (Sampei et al. 2009). 

Figure 7-1. Upper and lower lines span the depth distribution range. (Source: Falk-Petersen et al. 2009)
Figure 7-1. Upper and lower lines span the depth distribution range. (Source: Falk-Petersen et al. 2009)

Copepodite stage III is reached in the first summer.  Development into stage IV and V and then to adult females require significant lipid reserves and is less likely to occur in the first year.  Instead, the stage III copepodites enter diapause and resume growth with the following bloom.  Once stage V is reached, the copepodites overwinter and develop into females for the following seasons spawning (Falk-Petersen et al. 2009).

Calanus hyperboreus:  These are a large copepod species and one of the Arctic’s key grazers.  Spawning occurs in winter and is fueled by internal lipid reserves.  After the phytoplankton bloom, eggs develop rapidly into stage II and III copepodites.  C. hyperboreus enter diapauses at depths of 800 to 1500 meters as either stage III, IV, or V copepodites.  Over the next two summers, the copepodites grow rapidly through stage IV and into stage V. 

After reaching stage V, the copepodites develop into adults and spawn.  Adult females and stage V copepodites overwinter at different strata.  Females are shallower at 200 to 500 meters where they shed eggs.  Life spans of 1-2 years and 4-6 years have been suggested for C. hyperboreus depending on geographic region and food availability (Falk-Petersen et al. 2009).

In addition to the seasonal migration associated with diapause, copepods can also exhibit a diel migration in an effort to avoid predation.  There is some debate about the extent of this behavior in the Arctic, given both the ice cover and long summer days (Fortier et al. 2001).  However, even when it does occur, the diel migration is not of such a large distance that it significantly changes the vertical position of a copepod population in the water column. Summary of Arctic and Sub-Arctic Copepod Species

Though thousands of copepod species exist throughout the world, relatively few are present in Arctic environments.  Perhaps the best summary of Arctic zooplankton (including copepods) is presented by Kosobokova et al. (2011).  In this study, the authors compiled the results of zooplankton surveys conducted throughout the Arctic Ocean from 1975 through 2007.  A total of 134 locations were sampled at depths ranging from 0 to 3,000 m.  Altogether, 174 different metazoan plankton species were identified from these samples, 91 of which were copepods.  Each species was listed along with their presence or absence in various basins of the Arctic Ocean and their preferred depth range in the water column.  When possible, reproductively active females, eggs, and individuals in the naupliar and copepodite stages were also classified by species.  If some combination of the former were identified, it was considered evidence of a reproducing population in the Arctic.  Species present but not part of reproducing populations were considered expatriates.    Almost 20 percent of Arctic copepods were expatriates.  Six species entered from the Atlantic Ocean, four from the Pacific Ocean, and eight were neritic (Kosobokova et al. 2011).

Arctic copepods were also sorted by their geographic home ranges as a means of determining which species were endemic.  This geographic breakdown is presented in Figure7- 2. Thirty one percent of the identified species were endemic to the Arctic Ocean, including the cryopelagic and newly described Arctic copepods.  The cryopelagic copepods were Jaschnovia tolli, J. brevis, and Eurytemora richingsi.  These three species are most abundant in association with the ice, but occurred with enough frequency at stations where ice was absent for them to be counted as pelagic transients (Kosobokova et al. 2011).

Nineteen percent of the Arctic copepod species could also be found in the North Atlantic compared to only one percent from the North Pacific.  A larger percent of species were present in the North Atlantic and the North Pacific (10 percent) as well as species that were more widely distributed throughout the globe (28 percent). 

The shared distributions of species from the North Atlantic and North Pacific, as well as the presence of expatriate species, are important because it demonstrates the large scale movement of copepods into the Arctic Ocean.  Pacific copepods can enter the Chukchi Sea through an influx of species via the shallow Bering Strait.  In the Atlantic, transport occurs from the Norwegian and Greenland Seas through the Fram Strait, over the shelf of the Barents Sea, and into the Arctic Ocean (Kosobokova et al. 2011).  Although there may be shifts in specific species, copepods in general serve a functional role in the Arctic trophic web (Figure 7-2).

Figure 7-2. Percent of copepods from various geographical ranges out of a total of 91 species. AO = Arctic Ocean, NA = North Atlantic, NP = North Pacific [Source: Kosobokova et al. 2011]
Figure 7-2. Percent of copepods from various geographical ranges out of a total of 91 species. AO = Arctic Ocean, NA = North Atlantic, NP = North Pacific [Source: Kosobokova et al. 2011]

7.2.3 Copepod Populations

The Kosobokova et al. 2011 species summary does not include the abundance of individual copepod species or a spatial distribution of copepod abundance throughout the Arctic Ocean.  A rough estimate from their study implies an abundance of ~1,100 individuals per m3 in the surface layer (0-25 m).  The overall abundance of zooplankton declined exponentially with depth from the surface layer down to the deepest layer (2000-3000 m).  Species diversity, as measured by Margalef’s richness, continually increased to a depth interval of 500-1000 m, and remained elevated to the deepest layer.

Community sampling conducted off Franz Josef Land (FJL) found a similar abundance of copepods at 1,300 individuals/m3 (Table 7-2; Dvoretsky and Dvoretsky 2011).  FJL is typically covered by ice year round, but recent warming trends in Arctic waters had made this region periodically accessible.  Two particularly warm years were 2006 and 2007.  Copepod sampling was carried out in each of these years with the intent to measure both abundance and biomass (as total carbon).  Differences in these measurements between the years were statistically evaluated and explained by inter-annual variations in salinity and temperature.  

Table 7‑2. Mean abundance and biomass with standard error of the six most represented copepod species caught off Franz Josef Land in 2006 and 2007.

SpeciesGeographic Range1AbundanceBiomass
(Individuals/m3)(mg Carbon/m3)

Calanus glacialis

Abundant on Arctic shelf areas deeper than 50 m.

740 (± 190)

150 (± 38)

46 (± 11)

7.4 (± 1.6)

Calanus finmarchicus

North Atlantic species; expatriate to Arctic.

17 ( ± 5)

4.4 (± 1)

0.82 (± 0.23)

0.23 (± 0.045)

Calanus hyperboreus

Abundant in Arctic central basins.

2 (± 1)

7.7 (± 2)

1.4 (± 0.45)

4.7 (± 0.6)

Pseudocalanus minutus

Shelf species of boreal and Arctic waters.

160 (± 38)

65 (± 19)

0.71 (± 0.18)

0.2 (± 0.068)

Metridia longa

North Atlantic/Arctic species present on deep shelf areas

75 (± 27)

58 (± 32)

1.2 (± 0.45)

1.2 (± 0.59)

Microcalanus pygmaeus

Widely distributed species

33 (± 6)

29 ± (8.6)


0.068 (± 0.023)

Oithona similis

Abundant throughout Arctic; bipolar species.

130 (± 20)

530 (± 190)





1300 (± 270)

1300 (± 320)

51 (± 12)

14 (± 2.4)

Notes:  Statistical significant (P<0.05) differences between 2006 and 2007 are bolded.  1Arctic Ocean Diversity Database [Population Data Source: Dvoretsky and Dvoretsky 2011]

The five species with the highest abundance and the five species with the highest biomass are presented above.  A brief summary of the geographic range of these species is also included for reference. Seven species are actually listed because of the extreme differences in size between the copepods.  Even though Oithona similis was the second most abundant copepod, it contributed little to the total biomass.  Conversely, few Calanus hyperboreus were observed, but their larger size ranked them in the top five for total biomass.

There were significant differences in copepod abundance between the two years for several of the species, ranging up to a factor of five difference for Calanus glacialis.  Even with the difference in annual abundance, C. glacialis was the largest contributor to total biomass.  It comprised 91 percent and 53 percent of total copepod biomass in 2006 and 2007, respectively.  Total abundance was similar for both years, but there were statistically significant differences in total biomass due to the reduced abundance of the large C. glacialis and increased abundance of the smaller species, O. similis.

Interannual variability in copepod populations of this magnitude is not uncommon.  Long term monitoring of two species in the Gulf of Maine demonstrated that copepod abundance can vary by up to a factor of eight between years (Ji et al. 2012).  Frequent swings in abundance may impact food availability for the VECs relying on copepods as food source and these should be taken into account when modeling population impacts from oil spills.

7.2.4 Arctic Fish Population Ecology

Arctic waters are home to a variety of fish species, yet relatively little is known about their total diversity and abundance across the polar region.  In Canadian Arctic waters alone, 189 species representing 115 genera and 48 families have been documented.  An additional 83 species are known in Arctic waters adjacent to Canada (Coad and Reist 2004).   Taken together, this represents about 270 species, which compares well with other estimates (Mecklenburg and Mecklenburg 2009; Mecklenburg et al. 2011).

While there are several factors unique to the Arctic Ocean that contribute to these population uncertainties, the primary reason is the regions inaccessibility.  The seasonal and even continuous ice cover makes it difficult for scientists to employ standard sampling techniques, such as trawling.  The same limitation has prevented commercial fisherman from targeting the Arctic, resulting in no harvest records or by-catch data that could otherwise provide a rough characterization of fish stocks.  What is known is that the fish are a key component of the Arctic ecosystem, serving as consumers of the secondary production of zooplankton, and in turn becoming an important source of prey for marine birds and mammals.  Commercial fisheries exist in Barents Sea, which is warmer and more productive than higher latitude waters.  Even at these higher latitudes, Arctic fish have been harvested by humans. This fishing was historically conducted on a local scale at rates greater than the catches that were reported to the respective governments of the region (Zeller et al. 2011).  However, the overall removal rates from human fishery pressures were still low and fish stocks in Arctic coastal waters are thought to be relatively intact.

Climate change combined with increased anthropogenic presence and the additional associated environmental stresses in the region adds to the existing uncertainty in predicting the response of Arctic fish populations to a potential oil release.  The following section provides details on the population abundance, life cycle, and development of fish species that are of particular importance to the Arctic.  Additional details on the most representative species including geographic range, life span, and age at spawning are provided in Table 7-3. 

Table 7-3. Representative fish species of the Arctic Ocean.

Common NameScientific NameFamilyGeographic RangeSizeBiology

Arctic cod

Boreogadus saida


Arctic, circumpolar

40 cm

  • Cryopelagic or demersal down to 1383m
  • Occasionally occurs in large schools which attract predators; key food source for marine mammals and birds
  • Main consumer of offshore plankton
  • Mature at 2-6 years, spawns once per lifetime averaging 12,000 egg per female

Arctic cisco

Coregonus autumnalis


Alaska, Atlantic, Eurasia

64 cm

  • Nerito/pelagic
  • Anadromous
  • Eats invertebrates and small fishes
  • Locally important fisheries and commercial fisheries

Arctic char

Salvelinus alpines


Alaska, Atlantic, Eurasia

101.6 cm

  • Nerito/pelagic
  • Anadromous
  • Eats crustaceans and fishes
  • Important in native food fisheries, as well as commercial and sport fisheries

Greenland halibut

Reinhardtius hippoglossoides



120 cm

  • Epibenthic, occasionally pelagic. Surface to deep waters down to 2000m
  • Eats crustaceans, fishes, and squid
  • Increasingly important as a commercial fishery in the Eastern Arctic


Mallotus villosus


Circumpolar, Arctic but not present at high latitudes

25 cm

  • Nerito/pelagic shallows to 725m
  • Eats plankton, worms, and small fishes
  • Commercially important in areas
  • Major source of prey for Pacific cod, marine birds, and mammals
  • Mature at 2-6 years, high mortality rate after spawning

Glacial Eelpout (representative of eelpout)

Lycodes frigidus


Arctic Basins

69 cm

  • Endemic to Arctic
  • Deep-sea species, endemic to Arctic basins from 475 to 3,000m
  • Eats fishes, cephalopods, mollusks, and other abyssal fauna
  • Spawning likely occurs at great depths, fall or winter spawning likely

Arctic staghorn sculpin

Gymnocanthus tricuspis


Arctic, circumpolar

30 cm

  • Benthic, shallow water close to shore down to 450m
  • Eats polychaetes, gastropods, euphausiids, amphipods
  • Prey for other fishes including Arctic and Atlantic cod
  • Matures at 5-6 years, spawns in late autumn to winter
  • Females produce 2,000-5,500 eggs

Arctic alligatorfish

Ulcina olrikii


Alaska, Atlantic, Eurasia (not present in Barents Sea)

8.6 cm

  • Benthic, at depths of 7-520m
  • Eats amphipods, polychaete and nemertine worms, ostracods
  • Prey for halibut and other bottom fishes

Sources: Coad and Reist 2004; Mecklenburg and Mecklenburg 2009 Arctic Fish Species Diversity

The most representative fish species are those with the widest geographic range and greatest abundance.  In many cases the geographic range is better understood than abundance for Arctic fish.  Determining the relative size of fish populations from the literature can be a difficult task.  First, there is not a lot of data available.  Second, when data is available, there are often inconsistencies between studies in how the absolute numbers of fish are reported and what the numbers represent.    For example, catch records indicate the tonnage of fish caught are very different from those converted to Catch Per Unit Effort (CPUE), which in turn are different from studies that simply report the total number of individuals caught.   Given these discrepancies, the fish species mentioned in this section were selected based on qualitative and quantitative data available from the reviewed literature. 

The most comprehensive list of Arctic fish species reviewed was the “Annotated List of the Arctic Marine Fishes of Canada” by Coad and Reist (2004).  This document was a preparatory step towards a book describing the Arctic marine fish species of Canada.  The geographic area covered by this document is extensive, encompassing nearly all types of Arctic marine habitat. This document was the product of an extensive compilation of published and unpublished literature as well as museum collections and field studies.  All species present in this report were ranked by number as a means of determining the relative prevalence of a given fish in the Arctic.  The numbers do not represent counts of fish, but rather the number locations where a species has been observed.  Rankings extend from rare (1-2 records) to abundant (500+ records) and very abundant (2,000+ records). 

For the purposes of this review, the most abundant fish species are the most relevant, since they are most likely to be impacted by an oil release.   A total of fourteen species were listed as abundant, while only four were considered very abundant.  The species are listed below.

  • Abundant: Pacific herring (Clupea pallasii), Capelin (Mallotus villosus), Rainbow smelt (Osmerus mordax), Cisco (Coregonus artedi), Arctic cisco (Coregonus autumnalis), Lake whitefish (Coregonus clupeaformis), Least cisco (Coregonus sardinella), Roughhead grenadier (Macrourus berglax), Greenland cod (Gadus ogac), Arctic staghorn sculpin (Gymnocanthus tricuspis), Shorthorn sculpin (Myoxochphalus scorpius), Arctic alligatorfish (Ulcina olrikii), Gelatinous snailfish (Liparis fabricii), Arctic flounder (Pleuronectes glacialis)
  • Very Abundant:  Arctic char (Salvelinus alpines), Arctic cod (Boreogadus saida), Fourhorn sculpin (Myoxocephalus quadricornis), Greenland halibut (Reinhardtius hippoglossoides)

While Coad and Reist (2004) was very comprehensive and provides a sufficient list of representative species, the following paragraphs highlight studies conducted in areas outside the Canadian Arctic and provide additional background about Arctic fish populations. 

Historical fish harvests in the Arctic have been limited to small scale fisheries.  The fish caught typically went towards feeding indigenous peoples or sled dogs prior to the advent and adaptation of snowmobiles.  Zeller et al. 2011 reconstructed catch data for fishing communities throughout coastal areas of the Arctic for the years 1950 through 2006.  Their goal was to create a more accurate record of fish catches than was available from government reported data.  As such, this study is biased towards shallow and nearshore areas and the anadromous fish that inhabit these areas. 

Reconstructed catch records were reported for Russia, the United States, and Canada.  Russia was the largest harvester of fish during the selected period.  Areas surveyed in Russia included the Kara, Laptev, and East Siberian Seas.  Within these seas, the reported tonnage of the sardine cisco and Arctic cisco dominated the totals, with additional contribution from other Coregonus spp.  Catches of the long lived and slow growing Siberian sturgeon (Acipenser baeri) were recorded early in the survey timeline for the Kara Sea, but declined by the late 1960’s (Zeller et al. 2011).

Fish catches were also evaluated for Alaska and Canada.  The primary species caught along Canada’s Arctic archipelago and into Hudson Bay was the Arctic char, which accounted for around 90 percent of the total catch for both areas.  Within the Beaufort Sea, combined Alaskan and Canadian catches were dominated by Coregonus spp. and Dolly varden (Salvelinus malma).  Alaskan catches in the Chukchi Sea were primarily chum salmon (Oncorhynchus keta) with contributions from sheefish (Stenodus leucichthys) and Dolly varden (Zeller et al. 2011).

A demersal trawling survey conducted in 2008 in the U.S. portion of the Beaufort Sea offers a broader look at some of the species present in the Arctic (Rand and Logerwell 2011).  This was the first such study in the Beaufort Sea since 1977.  Twenty two successful trawls were completed at bottom depths ranging from 40 to 470 meters.  Overall, fish represented six percent of the total weight captured in the trawls, with the remainder consisting of invertebrates.  Arctic cod was the dominant fish species, comprising 92 percent of the total number of fish and 80 percent of the total weight.  The CPUE was in the range of 25.8 to 58.6 kg/ha across the longitudinal range of the deeper water survey area, indicating consistent density of this species.

The next most abundant demersal fishes of the Beaufort Sea included the eelpouts (Lycodes spp.), Bering flounder (Hippoglossoides robustus), and walleye pollock (Theragra chalcogramma).  The presence of walleye pollock and to a lesser extent Pacific cod (Gadus macrocephalus) suggests a possible extension of the known range of these species.  However, it should be noted that fish of spawning age or size were not found in this survey.  Both are commercially valuable species more commonly associated with the Bering Sea to the south.  While it is possible that their range is expanding, the limited time series of data available for the region was not sufficient to make this determination.

The Barents Sea is the southernmost extension of the Arctic Ocean.  Its southern location, geomorphology, and relatively warmer water inputs from the Atlantic Ocean have resulted in populations of commercially and ecologically valuable species not present in the high Arctic.  These species include haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), Atlantic cod (Gadus morhua), Atlantic herring (Clupea harengus), and capelin.  The Barents Sea contains habitat for all life stages of these species, including spawning, nursery areas for larvae and juveniles, and feeding grounds for adults (Olsen et al. 2009).

A series of 257 demersal trawls conducted in the year 2000 reveal that while Atlantic cod, saithe, and haddock were the most abundant species in the Barents Sea, a wide diversity of non-commercial fish were also present (Byrkjedal and Hoines 2007).  A total of 58 species were identified in the trawls and grouped by family and species.  Excluding the cod in family Gadidae, species from Scorpaenidae, Cottidae, Stichaeidae, and Zoaridae were among the most abundant.  Representative members from these three families include the deep water redfish (Sebastes mentella), mustache sculpin (Triglops murrayi), snake blenny (Lumpenus lampretaeformis), and eelpout (Lycodes spp.), respectively.

Using statistical analysis, Byrkjedal and Hoines 2007 evaluated the geographical observations of the identified species against salinity and temperature.  Not surprisingly, they found that the distribution of most species was related to the location of the polar front, the zone where warm water from the south meets subzero polar water.  Gadidae and Scorpaenidae were found in warmer waters, while Cottidae, Zoaridae, and Stichaeidae species were found from the polar front northwards (Byrkjedal and Hoines 2007). Representative Fish Species

Selection of representative Arctic fish species is based on a variety of factors including importance as commercial species, importance to the Arctic ecosystem, and overall abundance.  However, inclusion in the list presented in Table 7-3 does not necessarily mean the species is suitable for population effects modeling of an oil release.  Not all of the listed species would be equally affected by an oil release.  Nor would a population decline of some of the species have the same effect on the higher levels of the Arctic ecosystem.  The best species to use in a population effects model should meet a series of criteria:

  • The species should be abundant in the Arctic and be present over a wide geographic range.
  • The species should have an important position in the Arctic food web as both a main consumer of plankton and a major food source for marine birds and mammals.
  • The species would preferably occupy various zones of the water column.
  • The species should spawn and develop in the Arctic Ocean, where the more sensitive and less mobile eggs and larvae are exposed to oil.

Of the species listed in Table 7-3, Arctic cod best meets these criteria for use in modeling.  Capelin are similar to Arctic cod in many respects in that they have a wide circumpolar distribution and similar life history, but are not present at the high Arctic latitudes.   Anadromous species are only present in the Arctic as adults, and could more easily avoid contaminated habitat.  The remainder of the species are mostly demersal, and aren’t as important of a food source to marine birds and mammals.  In addition to these environmental factors, a large body of oil and dispersant toxicity data is available for Arctic cod, making them a frequent key species in models (Gallaway et al. in press). 

7.2.5 Application of Population Models

This section provides several examples of population models that have been used to predict population level effects combining life history and toxicity data. 

The effects of oil releases on Barents Sea stocks of Atlantic cod were evaluated (Johansen et al. 2003; Hjermann et al. 2007).  Atlantic cod have eggs and larvae that are concentrated in the upper 10 m.  Population mortality was estimated based on oil spill simulations for different scenarios and different toxicities of the dissolved oil. Mortalities were predicted for 4 km2 grids or cells over a portion of the Barents Sea using oceanographic and spill simulation data and life history data for the respective cells, as well as no effects concentrations for the eggs and larvae of 900 ppb based on a review of laboratory studies of fish, invertebrates and larvae.  Johansen et al. (2003) also used a safety factor of 10, to set the PNEC at 90 ppb.  Based on simulations, Johansen et al. (2003) predicted losses in the region of 5 %, and in some cases up to 15 %, for a blowout lasting less than 2 weeks, while very long-lasting blowouts could give losses of eggs and larvae in excess of 25 %.  A 20 % loss in recruitment to the cod population is estimated to cause a 15 % loss in the cod spawning biomass and to take approximately eight years to recover fully. The population impact is to a large degree dependent on whether high oil concentrations in the water column were coincident with high egg and larvae concentrations, which are generally only be concentrated at the surface during calm seas over a period of weeks or months.  Hjermann et al. (2007) further evaluated the life history of the Barents Sea fish populations and oceanographic models to refine effects estimates using Monte Carlo simulations.  Data for Barents Sea stocks of Atlantic cod, herring and capelin were used, as well as data on the variation of oceanographic and ecological conditions.  Hjermann et al. (2007) found that the variability within the system overwhelmed the models ability to predict long-term effects.

For the Beaufort and Chukchi systems, population models were coupled with field-collected data on the distribution, abundance, natural mortality and fecundity of Arctic cod (B. saida) to predict population level effects associated with modeled exposure concentrations (Gallaway et al. in prep).  Exposures were simulated using the Integrated Oil Spill Impact Model System (SIMAP) to allow for different spill and response scenarios to be evaluated.  Toxicity data from laboratory exposures of Arctic cod to WAF and CEWAF, field collected data from the western Beaufort Sea, and the SIMAP model simulations to predict potential population effects from physically and chemically treated oil in open water. A simulated release of 100,000-ton of Alaska North Slope oil (ANS) treated with dispersants resulted in a release of oil into the pelagic waters, creating a toxic volume of 266 million m3 as opposed to a volume of 71 million m3 for a 100,000 ton spill of ANS when not treated with dispersants. Dispersants rapidly transports large quantities of the oil from the surface into the water column. A 100,000-ton spill treated with dispersants resulted in estimated losses of about 2 million Arctic cod larvae. On the order of 87 million eggs would have been required to produce 2 million juveniles. This level of egg production represents the reproductive output of about 7,300 adult females. The population of Arctic cod age 1+ has been estimated to range between 2 and 4 billion fish. These and other data presented herein suggest that the abundance of adult Arctic cod (age 3) in the Alaska Beaufort number in the 10’s to 100’s of millions. For the time and place evaluated (mid-shelf Alaska Beaufort Sea, mid-August) even a large spill dispersed within the maximum concentrations of larval cod appeared unlikely to have the potential for major impacts on Arctic cod populations.

Integrated modeling systems allow life history and effects data from multiple trophic levels to be incorporated into predictions of population effects.  The SYMBIOSES model is an example of a complex predictive system connecting seven individual models into a computational framework contained within a supercomputer (  It is designed to simulate marine ecosystem components in three dimensional space and time and to predict impacts from selected combinations of sea based activities, i.e. fisheries and petroleum operations. The SYMBIOSES modeling system targets selected marine ecosystem components and maritime activities and allows prediction of population level changes in key commercial fish species linked to the Lofoten/Barents Sea region off of Norway. Ecological models are used to simulate the distribution and behavior of different life stages of important commercial fish, zooplankton, zooplankton prey, and phytoplankton species. Ecotoxicology models simulate chemical uptake and effects on growth, mortality, and reproduction of marine organisms. An oil transport and fate model is used to trace chemicals in the marine environment and a physical model simulates the hydrodynamic features of the region. The SYMBIOSES aim is to become a vital aid to impact and risk analysis, management, decision-making and stakeholder communication for the Lofoten/Barents Sea region.