Bulletin of the Sea Fisheries Institute 2 (156) 2002 - CEEMaR

46 K. FORMICKI, A. KORZELECKA-ORKISZ, M. BONIS£AWSKA, A. TAÑSKI, W. WAWRZYNIAK and A. WINNICKI
The literature on herring is rich and investigations date back over hundred years (Brook
1885; Blaxter 1960; Holliday and Blaxter 1960; Galkina 1968; Kosior and Strzy¿ewska 1979;
Wawrzyniak 1987); this is principally due to the fact that these fish are commercially important
and they are very palatable and nutritional. However, there are few reports dedicated to the
early stages of their embryonic development. Mainly, variations in oxygen demand during
embryonic development are addressed (Volodin 1956). Later, detailed studies of Atlantic herring
include a detailed description of the embryogenesis of this species whose habitation conditions
and, more importantly, reproduction conditions, namely increased water salinity, are
different from those of Baltic herring. This may have an impact on the differences of egg size
and the rate of developmental processes (Ojaveer 1981, Griffin at al. 1998, Hill and Johnston
1997).
As shown by the literature, the spring herring in the temperate zone begins spawning in
warm seasons, predominantly in late May/early June, at ambient temperatures of 5–14°C. Herring
lay significant numbers of eggs, up to 65,000, covered by an adhesive, gelatinous substance
which helps the spawn to stick to solid elements such as rocks, rubble or underwater
plants (Kupfer 1878, Kryzhanovski 1956a, Kosior and Strzy¿ewska 1979, Wawrzyniak 1987).
The eggs that are laid are unfertilized, small (φ = 0.86-1.01 mm – Volodin 1956, 1.2-1.5
mm – Kryzhanovski 1956a) and of a regular spherical shape. Their size increases by 40-50%
from the moment of activation as it absorbs water (Kryzhanovski 1956a, Volodin 1956).
Kryzhanovski (1956b) reported that Baltic herring eggs that were activated in waters with a
five-fold higher salinity increase their volume identically to spawn incubated at 5‰. It is known
that the hatching larvae are well developed, relatively large versus egg size and mobile due to
the small-sized, longitudinal yolk sac.
The external features of morphogenesis are roughly known and do not differ from other
teleost fish; however, the internal features which characterize the structure of the egg, the spatial
distribution of the internal structures and the dynamics of morphological changes which
comprise the whole of embryogenesis have not been very well recognized.
In this context, the findings reported by Hill and Johnston (1997) on microstructural
changes during Pacific herring embryonic development, by Griffin et al. (1998) on the embryogenesis
of the Baltic herring at different salinities and by Ojaveer (1981) on the temperature
and salinity effects on Baltic herring embryonic development are all particularly elucidating.
These findings allowed the relatively adequate identification and interpretation of a series
of phenomena that take place during embryogenesis, such as, e.g., microscale structural processes,
although these are not wholly indicative of causal relationships between the habitat and
morphomechanics of embryogenesis in the full dynamics of the latter.
Earlier, long-term, studies of over a dozen species of freshwater teleost fish have shown
that there were differences in both the spatial structure of eggs and the structural variations of
embryonic development. These differences were revealed during the analyses of the transformations
and morphomechanic phenomena during embryonic development, despite the abovementioned
characteristic identity of different species. These differences are usually more significant
and noticeable among distantly related taxa, however, they also occur among closely
related species (Winnicki and Korzelecka 1997, Winnicki et al. 1998, Bonis³awska et al. 1999,
Tañski et al. 2000). Therefore, it was of interest to follow the embryogenesis of herring, which
is a marine fish, and to compare its development with observations of the development of
freshwater fish. The principal aim was to try to find an explanation for the reasons for the
morphophysiological differences which may occur, with a special focus on one ecological factor
that differed from those of the freshwater fish, i.e. water salinity.