Spatial distributions of groundfish in the northern Bering Sea in relation to environmental variation

Abstract

Two bottom trawl surveys of fish were undertaken during the seasonal sea ice retreat in 2006 and 2007 in the northern Bering Sea. For each trawl, we calculated catch per unit area (CPUA) for all fish taxa. Arctic cod Boreogadus saida, Bering flounder Hippoglossoides robustus and snailfish (Liparidae) were the dominant species south of St. Lawrence Island (SLI), whereas Arctic alligatorfish Ulcina olrikii, Arctic staghorn sculpin Gymnocanthus tricuspis and shorthorn sculpin Myoxocephalus scorpius were the dominant fishes north of SLI. Cluster analysis and multidimensional scaling were used to investigate relationships between environmental conditions and fish community structure in the northern Bering Sea. One goal of the study was to assess the importance of environmental variables on groundfish assemblages. The results showed that sediment grain size (an indicator of current speed) was the most important environmental factor explaining fish community structure in both years of the study. Bottom water nutrients (nitrate + nitrite), bottom water chlorophyll a (chl a) (with similar results for total chl a in the water column), sediment grain size, and sediment C/N ratios had stronger relationships with fish distribution in 2006 (cold, pre-bloom conditions), whereas bottom water temperature and sediment grain size were more important in 2007 (warm, bloom conditions) among a total of 14 environmental variables that were analyzed. These findings indicate strong linkages between physical conditions (e.g. water temperature and hydrography as it affects sediment grain size) and biological conditions (e.g. bloom status) in structuring fish communities in the northern Bering Sea.

Ocean Acidification at High Latitudes: The Bellwether

“…However, the rapid retreat of summertime sea ice cover has exposed these waters to the atmosphere, allowing for enhanced air-sea exchange, and increased the sink for atmospheric CO 2 from 24 TgC yr -1 to 66 TgC yr -1 over the past three decades . Furthermore, melting of sea ice reduces the CaCO 3 saturation state of seawater, primarily by reducing alkalinity (Steinacher et al, 2009 Polar marine invertebrates often exhibit low metabolic rates (Bluhm et al, 1998;Peck and Conway, 2000) and very slow development and growth (Pearse et al, 1991;Arntz et al, 1994;Coyle and Highsmith, 1994) are increasing in the north (Grebmeier et al, 2006, Cui et al, 2009), whereas ampeliscid amphipods that are the prey of gray whales are declining (Moore et al, 2003;Coyle et al, 2007). Whether these crustaceans will be impacted by increasing CO 2 levels in bottom waters is unknown.…”

Fluxes, Fins, and Feathers: Relationships Among the Bering, Chukchi, and Beaufort Seas in a Time of Climate Change

“…Farther to the north, there is a profound change in the fauna, as large fish become relatively scarce (Cui et al, 2009;Norcross et al, 2010;Stevenson and Lauth, provision-ally accepted), the benthic community receives more of the production than the pelagic community (Grebmeier and McRoy, 1989), and benthic invertebrates dominate the biomass (Bluhm et al, 2009). Seabirds and marine mammals are abundant in the Bering, Chukchi, and Beaufort Seas; some species migrate between summer and winter feeding grounds.…”

“…With sea ice retreat in April and May, much of the spring primary production of the central and northern Bering Sea is associated with ice algae and with an ice-edge bloom (McRoy and Goering, 1974;Alexander and Niebauer, 1981;Grebmeier and McRoy, 1989;Lovvorn et al, 2005;Jin et al, 2007). This early spring production largely sinks to the bottom and helps support a rich benthic fauna dominated by invertebrates and small epibenthic fishes (Barber et al 1997;Cui et al, 2009;Norcross et al, 2010). Seasonal ice and strong coupling between pelagic and benthic production are characteristic of shallow, ice-dominated systems (Grebmeier et al, 2006b).…”

Resource partitioning among Myoxocephalus sculpins, and their predator–prey relationships with Chionoecetes crabs in the eastern Bering Sea

“…These results are similar to what is reported in the western Bering Sea (Tokranov 1981(Tokranov , 1987. Farther north, sculpins contribute a larger proportion of the fish biomass, with M. jaok and M. scorpius being dominant species (Cui et al 2009, Stevenson & Lauth 2012. M. scorpius was abundant along the central middle shelf, where a 'cold pool' often exists, and in the NBS, where cold bottom temperatures are found (Cui et al 2009, Lauth 2011.…”

“…Reflecting a general trend in fishes, movement of larger fish to deeper waters could be related to the utilization of resources (e.g. larger sized or different prey or predator avoidance) and an increase in longevity (Macpherson & Duarte 1991 (Cui et al 2009, Lauth 2011. These conditions may be more favorable for post-settlement and juvenile M. scorpius.…”