ISSN 10630740, Russian Journal of Marine Biology, 2012, Vol. 38, No. 7, pp. 465–473. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.F. Volkov, 2012, published in Izvestiya TINRO.
Since 2007, alterations of the quantitative and, in
some areas, qualitative characteristics of plankton
communities in the northern Bering Sea have been
manifested as an increase in the biomass of the large
fraction, the significance of its profile groups, as well
as in changes in the ranges of predominant species,
both in the plankton and in the diet of nekton [2–4].
Among these events, the emergence of the hyperiid
in areas where it was absent previ
ously is most notable.
Having the largest size among hyperiids in the
northern Bering Sea and also being widespread even in
the Polar Basin, this species is of great significance as
a forage item for fish and thus it has become a subject
of interest for hydrobiologists and ichthyologists [6–
10, 13, 14, 16, etc.]. No dedicated studies of this spe
cies and its role in the plankton and in the diet of fish
have been conducted in the Bering Sea; meanwhile it
occurs quite frequently in various lists of surveyed spe
the largest species of the genus. Mature individuals
usually grow to 30 mm in length, although females can
sometimes reach 60 mm. This is a circumpolar, cold
water species. The hyperiid inhabits the Central Polar
Basin, where it is observed up to the North Pole area,
as well as marginal Arctic seas. In the Atlantic Ocean,
the species is carried by cold waters along the Ameri
can coast up to the Gulf of St. Lawrence and the island
of Newfoundland; on the eastern side of the ocean, it
has never been found south of Iceland and the North
Cape (Nordkap). In the Pacific Ocean, it is a mass
species of cold waters of the Bering Sea and Sea of
Okhotsk, which are occupied by the “Arctic” plankton
complex. During a cold season, it occurs in small
quantities off the oceanic side of the North Kuril
Islands and also off the eastern Kamchatkan coast.
The major portion of hyperiids is aggregated in the
upper 100meter layer of water, but some individuals
have been recorded far deeper, up to 500 m and even
1000 m. Dunbar [11, 12] supposed that the complete
(in the Canadian Arctic) lasts
for 2 years. Reproduction takes place in the fall and
winter of the second year of life, after this, hyperiids
die. Meanwhile, a part of the individuals can begin
breeding by the end of the first year .
Is the Mass Emergence of
in the Northern Bering
Sea an Invasion or a Bloom?
A. F. Volkov
Pacific Research Fisheries Center (TINRO Center), per. Shevchenko 4, Vladivostok, 690091 Russia
Received December 29, 2011
—The mass occurrence of the large hyperiid
was recorded in both the western and
the eastern Bering Sea within 2007–2011. Those were the years of a relatively long 6year period of cold,
which was caused mainly by the inflow of cold waters from the north; this is confirmed by the distribution of
bottom and surface temperatures and also by the icecover values. This hyperiid became dominant in the diet
of salmon, walleye pollock, herring, and several other nekton fish species.
southward with cold northern waters, finding favorable conditions in “new” areas. Being a rapidly growing
species with a short life cycle, within 1 or 2 years it reaches a high abundance, which then gradually declines
and remains at a mean or low level, as usually occurs with species that were introduced into a new habitat.
After the environmental conditions deteriorate, as a “warm” period arrives with changes in the general cir
culation and a growing inflow of warmed Pacific waters, the southern boundary of the species range moves
back far northward and it completely disappears in the areas where it prevailed in the plankton and was a main
forage item in the diet of many fish species. Taking into account the durations of warm and cold periods from
1980 until 2010, an event like this in the Bering Sea can be expected within 1 or 2 years. In the eastern Bering
Sea, the abundance and dominance of a number of zooplankton species may vary simultaneously. This effect
is more pronounced in
and for this reason the species is considered as a biological indicator of the
described climatic changes in the Bering Sea.
: hyperiid, zooplankton, biomass, cold period, warm period, western Bering Sea, eastern Bering
Sea, salmon, feeding