Spatial and temporal variability in environmental factors can exert major influences on survival and growth of livlng organisms. However, in many key areas of fisheries sclence (e.g. growth, survival and recruitment determination), environmental heterogeneity is usually ignored because of insufficient environmental or fisheries data or lack of evidence that such heterogene~ty impacts response variables. For the eastern Baltic Sea (ICES Subdivisions 25 to 321, we evaluated spatial and temporal differences in conditions affecting the sunrival of cod Gadus morhua L. eggs at survival on four distinct spawning sites within the assessment area. We intercalibrated ways of quantifying the volume of water ('reproductive volume') at each site where salinity, oxygen and temperature conditions permitted successful egg development. We have developed and compared a time series (1952 to 1996) of reproductive volumes among the areas to identlfy spatial differences. The results of 2 independent volume-estimation methods are comparable, indicating that highly significant differences exist among the sites, and that the westernmost spawning ground, Bornholm Basin, has on average the highest reproductive volume and the lowest variability among the 4 sites. These findings may be useful in evaluating how spatial and temporal variability in environmental conditions affect egg hatchng success and possibly recruitment in the Baltic stock.

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The aim of this article: assess the impact of abiotic conditions on aquatic biological resources (sprat, herring, cod) of the Baltic Sea. The need for this study is due to the pronounced climate variability in the modern period. There is an increased role of the impact of environmental conditions on commercial fish species and, often, unfavorable for their spawning, survival of offspring, feeding, etc.   Methods used: carried out an integrated ecosystem analysis using the method of principal components in the R software environment. To detect statistically significant levels of changes in the time series of principal components, the STARS program, represented by an Excel add-in, was used. For the analysis of abiotic conditions, long-term series of air temperature, data from regular oceanological observations at a monitoring station were used. Since the stocks of commercial fish species in the Baltic Sea are transboundary, the values of their spawning biomass and biological parameters of populations were analyzed according to the data ofthe ICES Working Groups.   Novelty: this is the first time that such an analysis for a 30-year period adapted to the Russian water area in SD ICES 26 has been carried out.   Result: an integrated analysis of the abiotic and biotic components of the sea over the past three decades showed «mesoscale» shifts in 2002 and 2013. The direct and indirect impact of climate on the fish stocks of the Baltic Sea was an important unfavorable factor determining the current state, size and weight parameters, reproductive capacity and stocks dynamics. The most pronounced negative impact of environmental factors was noted for the stock of cod.   Practical significance: the results of the analysis carried out are necessary when predicting the catch of aquatic biological resources in the Baltic Sea for the short and long term, for making management decisions on the regulation of fishing in terms of understanding the risks in the current conditions of climate change.