Nearshore Fish Assemblages in the Chukchi Sea Near Barrow, Alaska
Figure 3. Capturing nearshore fishes along the Chukchi Sea using a beach seine. Photo by Scott Johnson.
The Arctic is one of the most rapidly changing ecosystems in the world, yet a large void exists in information on essential fish habitats and what species and life stages use these habitats.
Rapid change in the Arctic ecosystem is well documented: the year 2007 was the warmest on record for the Arctic, and the minimum extent of sea ice in 2009 was the third lowest since the start of satellite measurements in 1979. Loss of sea ice from global warming threatens marine life and habitat (e.g., increased coastal erosion) and has the potential to open up formerly inaccessible areas to oil and gas exploration, vessel traffic, mining, and commercial fishing.
Increased human activity translates into increased risk to fish and habitat from development and oil spills. Recent increases in domestic energy costs have increased the demand for oil and gas exploration and development in the Arctic. The U.S. Minerals Management Service estimates that the Beaufort Sea, Chukchi Sea, and North Aleutian Basin have recoverable resources ranging from 2.8 to 65.8 billion barrels of oil and 11.4 to 305 trillion cubic feet of natural gas.
Because information is nonexistent or outdated for fishes in the Arctic, ABL with support from the North Slope Borough sampled nearshore fish assemblages at six sites in the Chukchi Sea in August 2007, 2008, and 2009, and September 2009.
At each site, fish were captured with a beach seine (<5 m deep) (Fig. 3) and with a small bottom trawl at two depths (5 m and 8 m; < 1.5 km from shore). In addition, baseline hydrocarbon samples were collected with passive samplers and sediment collections.
A total of 15,030 fishes representing 20 species were captured in 24 beach seine hauls, and 3,221 fishes representing 23 species were captured in 48 trawl tows. Species composition and catch differed dramatically by gear type and time of sampling (i.e., among years and within 2009).
Total seine catch was dominated by capelin (75%), whereas total trawl catch was dominated by Arctic cod (48%). Among years (August only), capelin accounted for 96%, 4%, and 27% of the total catch for both gear types, whereas Arctic cod accounted for <1%, 46%, and <1% of the total catch. Other fish captured that are important forage or subsistence species were Pacific sand lance, saffron cod, and rainbow smelt.
In 2009, catch and species richness was much greater in September (7,861 fishes, 20 species) than in August (2,633 fishes, 13 species). Differences in catch and species composition may be attributed to differences in habitat use, environmental conditions among years, and time of sampling. For example, Arctic cod dominated the total catch in August 2008 compared to August 2007 and 2009; ice persisted longer in 2008 (about mid-August) and water temperature (mean = 1.8°C) was much cooler than in 2007 (mean = 9.1°C) or 2009 (mean = 6.2°C).
Sites established in this study will provide a long-term and large-scale baseline in an area under rapid change. The Arctic is probably the world's fastest changing and least understood ocean. Continued monitoring of nearshore fish populations in the Arctic is warranted; a reorganization of community structure is likely as new fish species are expected to migrate to the Arctic with unknown consequences to existing stocks and food webs.
The nearshore must be included in any research effort in the Arctic; several species that are important forage fish or subsistence species (e.g., capelin, rainbow smelt) are found almost entirely in nearshore waters. As with other areas of concern in the Arctic (e.g., offshore fish assessments, marine mammals, loss of sea ice), nearshore fish assemblages and habitat needs a continuum of study, perhaps decades, to begin to be understood.
