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.

Sources: Coad and Reist 2004; Mecklenburg and Mecklenburg 2009

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).

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).