A peek at rarely seen subarctic marine life!

Snailfish

Snailfish (probably Elassodiscus tremenbundus)

- NOAA cruise to eastern Bering Sea nets midwater samples -

Those acquainted with marine life of the eastern Bering Sea are quite familiar with names like king crab, walleye pollock, Pacific halibut, Dall's porpoise, northern fur seal, Steller sea lion, puffin, murre, kittiwake, and gray whale.  But ask a porpoise or a fur seal what it is familiar with, and you would get a far different list!

Mesopelagic fishes and squids live in the mid depths of the open ocean. They are critical components in the diet of apex predators that are the marine mammals, birds, and near-bottom dwelling fishes in the eastern Bering Sea. Despite the importance of mesopelagic fishes and squids in the food chain, very few studies have been conducted in this region. We know quite a bit about mesopelagic fishes and squids of the western Bering Sea from 25 years of Russian surveys.  Many of our expectations of what to find in the eastern Bering Sea are based on these Russian surveys.  A recent study in the eastern Bering Sea, based on bycatch data from commercial fishing, indicated relatively high abundance of mesopelagic fishes within the Green Belt, an area of enhanced productivity that traces the continental slope. This area also has historically high densities of marine mammals, many now endangered or depleted, most of which prey upon mesopelagic fishes and squids.

A pilot study was designed to identify mesopelagic fishes and squids that occur at different depths in the southeastern Bering Sea Green Belt, to characterize their habitat and predators (marine mammals and birds), and to describe the physical mechanisms that define that habitat.  The study was mounted with support from the National Oceanic and Atmospheric Administration (NOAA) through  Fisheries-Oceanography Coordinated Investigations (FOCI) and the Cooperative Institute for Arctic Research, a joint institute of NOAA and the University of Alaska Fairbanks.

In May 1999, marine mammologists and biologists from NOAA's Alaska Fisheries Science Center and physical oceanographers from NOAA's Pacific Marine Environmental Laboratory undertook a nine-day cruise aboard the NOAA ship Miller Freeman (Fig. 1). Specific cruise instructions are available at http://www.pmel.noaa.gov/foci/operations/instructions/1999/MF9907F.html.  Cruise scientists completed 15 midwater trawls, 45 vertical soundings of ocean temperature and density (CTDs), deployed four satellite-tracked drifters, and conducted visual observations of marine mammals from the ship's flying bridge while underway between fishing stations.  Figure 2 is a map of the ship's operations.

Back deck of Miller Freeman
Figure 1. The research ship -Looking aft toward the trawl ramp aboard the NOAA Ship Miller Freeman.  The mountains in the background are the Aleutian Islands.
 

Map of cruise operations

Figure 2. Map of cruise -The area sampled during the May 1999 cruise was north of the Aleutian Islands over the southeastern part of the Bering Sea basin.  Trawl locations are indicated by red lines with numbered labels.  CTD locations are marked by x's.


The physical and biological data are still in preliminary stages of analysis, but some general trends stand out.

The cruise was a very successful effort from the standpoint of the volume and quality of physical and biological samples obtained, nearly all of which will be fully utilized for genetics, diet and energetics studies, and museum reference collections. However, the most valuable aspect of this pilot study is the window it provides into trophic interactions in the Bering Sea, particularly in light of recent environmental perturbations and extreme species declines in the area.  Plans are to repeat the cruise in the spring of 2000, with a greater number of trawls and more emphasis on community structure and habitat differences.  For more information, contact Beth Sinclair, National Marine Mammal Laboratory, or Phyllis Stabeno, Pacific Marine Environmental Laboratory.
 
 

Further reading

Sinclair, E.H., A.A. Balanov, T. Kubodera, V.I. Radchenko, and Y.A. Fedorets. 1999. Distribution and ecology of mesopelagic fishes and cephalopods. In: Loughlin, T.R. and K. Ohtani (eds.), Dynamics of the Bering Sea. University of Alaska Sea Grant, Fairbanks, Alaska  99775-5040, pp. 485-508.

Stabeno, P.J., J.D. Schumacher, and K. Ohtani. 1999.  The physical oceanography of the Bering Sea.  In: Loughlin, T.R. and K. Ohtani (eds.), Dynamics of the Bering Sea. University of Alaska Sea Grant, Fairbanks, Alaska  99775-5040, pp. 1-28.
 
 


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