ISSN 1063-0740, Russian Journal of Marine Biology, 2008, Vol. 34, No. 7, pp. 461–467. © Pleiades Publishing, Ltd., 2008.
The gelatinous zooplankton, including medusae,
ctenophors, siphonophors, and salps are a substantial
component of plankton communities. According to
A.A. Shushkina et al. , in the epipelagic of the
Northwest Paciﬁc and at some stations in the Bering
Sea the proportion of these organisms in the meso- and
macroplankton reaches 99% by raw weight and 78% by
carbon percentage. Other data  show that in the
Bering Sea jelly-like organisms amount nearly to half
(by raw weight) of the total biomass of macroplankton
and micronecton in the 0–180 m water layer.
As was shown in previous studies by the TINRO-
Center, the gelatinous zooplankton make up a consider-
able part of trawl catches performed to estimate nekton
[2, 6]. But it is relevant to note that there it is repre-
sented with mainly large medusae having bodies ﬁrm
enough to stay within nets during trawling. The greatest
part of the smaller medusae, as well as ctenophors and
other gelatinous organisms, squeeze through trawl nets.
From 2002 through 2006 six complex trawl surveys
were carried out in the Western Bering Sea. The uni-
form technique, level of trawling, trawling gears and
similar patterns of stations provided good comparabil-
ity of data obtained during these surveys. In this paper
the annual and seasonal dynamics of the distribution
and abundance of jellyﬁsh in the Bering Sea during the
summer–fall seasons of 2002–2006 are discussed and
the results of investigations of their diet in 2006 are pre-
MATERIAL AND METHODS
This work was based on the materials from complex
trawl surveys conducted by the TINRO-Center in the
upper epipelagic of the Western Bering Sea in the sum-
mers and falls of 2002–2006 in the framework of the
Bering–Aleutian Salmon International Survey
(BASIS). The surveys occurred as follows: June 22–
July 21, 2005; July 17–August 24, 2003; August 24–
October 4 2006; September 2–October 9, 2002; Sep-
tember 23–October 25, 2003, and September 26–Octo-
ber 23, 2004. In this list and hereafter in the ﬁgures and
tables the surveys are arranged in the order of increase
of the seasonal time they were conducted. In all years,
except 2006, surveys passed northward, beginning
from the Commander Islands and ﬁnishing in the Gulf
of Anadyr. In 2006 surveys were carried out in the
opposite direction, i.e., southward.
Trawling went on for twenty-four hours each day.
The top line of the trawl was held in the 0 m horizon.
The vertical opening varied from 31 to 41 m. The aver-
age speed was kept at 4.6 knots.
The biomass and abundance of jellyﬁsh was calcu-
lated by multiplying the area of the studied region by
the relative abundance in a unit of area. The relative
biomass (abundance) was found from the formula:
is biomass of the species, kg/km
dance of the species, individuals/km
is actual mass
of the species in the catch, kg;
is the actual number of
species representatives in catch, individuals;
Distribution, Quantitative Composition, and Feeding of Jellyfish
in the Western Bering Sea in Summer and Fall
A. V. Zavolokin, I. I. Glebov, and N. S. Kosenok
Paciﬁc Research Fisheries Center (TINRO-Center), Vladivostok, 690950 Russia
Accepted November 21, 2007
—Materials from six complex trawl surveys conducted by the TINRO-Center in the upper epipelagic
zone of the Western Bering Sea during the summer–fall seasons from 2002 through 2006 were used as the basis
of this paper. The overall biomass (and abundance) of jellyﬁsh increased from 0.6–0.8 million t (1.1–1.8 billion
individuals) in the summer up to 0.9–1.7 million t (4.4–4.8 billion individuals) in fall. Scyphomedusa
and the Hydromedusa
made up the major part of the jellyﬁsh biom-
ass (67–97%). Their distribution varied signiﬁcantly.
aggregated mainly in the deepwater part of
the Bering Sea.
was widely dispersed across the entire area of the investigations and formed the
most considerable aggregations in the Anadyr–Navarin area. In the fall of 2006 the diet of jellyﬁsh generally
consisted of plankton organisms (copepods, euphausiids, amphipods, pteropods, chaetognaths, ostracods, and
larval decapods). However,
had a greater portion of ﬁsh and larval squid in its diet.