ISSN 10630740, Russian Journal of Marine Biology, 2013, Vol. 39, No. 5, pp. 350–356. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © E.M. Karaseva, F.A. Patokina, N.A. Kalinina, 2013, published in Biologiya Morya.
Fish eggs and larvae are characterized by high mor
tality; one of the reasons of this is their sensitivity to
unfavorable environmental effects . Egg and larvae
consumption by predators can be considered as a
manifestation of adverse biotic influence on offspring
survival. Mass consumption of cod
Gadus morhua cal
eggs by herring and sprat has been observed in
the central Baltic Sea (Bornholm basin) . In
southeastern areas of the Baltic Sea, which differ from
the Bornholm basin in the environmental conditions,
the consumption by planktivores of the early ontogeny
stages of fish has not been studied so far. The aim of the
present work is to study the species composition of fish
eggs and larvae in the diet of herring and sprat in the
southeastern Baltic and to estimate their daily con
sumption by herring.
MATERIALS AND METHODS
Sampling and processing of data for the study of
herring predation on fish eggs and larvae was per
formed according to the generally accepted methodi
cal approaches [10, 11, 20]. The study area was situ
ated in the Russian economic zone covering the deep
water Gdansk Deep and the adjacent area of the
southeastern Baltic. Samples of sprat and herring were
collected in 1995–2008 during annual trawling surveys
in February–March, May–June, and August, as well
as at daily stations (Fig. 1). Trawling in most cases was
accompanied by complex environmental research.
Before conducting a daily ichthyoplankton station,
one trawl haul was made.
The total material collected in February–March
consisted of 5864 specimens of herring (of these,
49.8% with food in the stomach) and 3930 specimens
of sprat (50.2% with food); in the spring and summer
seasons, these figures were 20 744 specimens of her
ring (64.5% with food) and 16 648 specimens of sprat
(63.1% with food). The species and developmental
stage of the eggs from the fish stomachs were deter
mined . Fish larvae were identified to the species
and measured to the nearest 1 mm; the weight of fish
eggs and larvae (mg) was measured on VLTE150 and
AX200 electronic balances.
The prey occurrence frequency was taken to be the
percentage ratio of the number of fish that consumed
eggs and larvae to their total number (herring or sprat)
caught during the indicated months in 1995–2008.
The consumption of fish eggs and larvae was esti
mated by calculating their average number
(“prey number/stomach”) and average weight (“prey
weight/stomach”) per predator. These indices corre
spond to the number/stomach and weight/stomach
indices used by foreign investigators [16, 20]. The daily
feeding rhythm was analyzed at an interval of 1 h in
May and 4 h in August. The daily rations and feeding
Fish Eggs and Larvae in the Diet of Herring
Linnaeus, 1758 and the Sprat
Sprattus sprattus balticus
(Schneider, 1904) (Clupeidae) in the Southeastern Baltic Sea
E. M. Karaseva, F. A. Patokina, and N. A. Kalinina
Atlantic Research Institute of Marine Fisheries and Oceanography, Kaliningrad, 236022 Russia
Received January 24, 2013
—The qualitative and quantitative composition of fish eggs and larvae in the stomach contents of
Baltic herring and sprat was examined. The occurrence of fish eggs and larvae in the diet of herring was mark
edly higher, compared to sprat. Eggs of four and larvae of nine fish species were found in the herring stomachs.
The prey species composition of the herring and sprat diets was related to the ichthyoplankton composition
and to the degree of overlapping of the prey and predator distributions. Sprat eggs were the predominant prey
in the herring diet in May and sprat larvae prevailed in August. The daily ration estimates indicate that the
sprat larvae consumption by herring in August exceeded the sprat egg consumption in May by many times.
Cod eggs in the herring stomachs were only found at the optimal oxygen content and salinity for the cod eggs
in the nearbottom water layer.
: fish eggs and larvae, predation, herring, sprat, Gdansk Deep, Baltic Sea