MAIN GOALS AND TASKS

Ecology of organisms and communities

Professor M.I. Shatunovsky

The Onego Lake, the sig, 2004.
Professor Yu.S. Reshetnikov

Professor G.V. Nikolsky

Geographic variation of morphological features, species structure, distribution, peculiarities of growth, feeding, spawning and population structure of Siberian sturgeon were studied within its natural range. Revision of the sturgeon species structure as well as evaluation of the state of different sturgeon populations were carried out. The complex of specific adaptations of Siberian sturgeon determining its ecological plasticity and acclimatization in a wide range including Arctic regions were revealed.

Gametogenesis abnormalities were studied for the acipenserids of Siberia and the Volga basin (Siberian sturgeon, sterlet, beluga, Russian sturgeon and stellate sturgeon). The ranges of abnormalities and their dynamics of occurrence were determined, and a comparative evaluation of the state of spawning parts of these species was given. Long-term dynamics of teratogenesis in the young acipenserids, bred in the Volga fish-hatcheries, was analyzed.

Complex analysis of the data on the acipenserids numbers in the Volga-Caspian basin was carried out, the main trends in their change after regulation of the Volga stream were revealed, the complex of factors influencing this process was determined including truncation of migration routes. The main patterns and intraspecific differences of the seasonal and long-term changes of acipenserids distribution in the Caspian Sea were revealed, the maps of distribution of these species were created.

Monitoring studies of the Moskva-River ichthyofauna within the metropolis area allowed to identify some factors that indicate successional character of the changes in the ecosystem of this river reach . In catches, the eurybiontic background species were prevalent more often (roach, perch, gudgeon), while the numbers of other species individuals decreased (bream, European chub), and individuals of some species disappeared from the catches (undermouth, rasorfish).

A method of complex assessment of ecological state of small rivers was developed. The method includes the study of fishes, aquatic invertebrates and their habitats, bottom sediments, aquatic vegetation and water. In fishes, their abundance is studied, biotopes are described, complete biological analysis is carried out, the gonads and the character of feeding and spawning are studied, the age is determined, the analysis of toxicants loading (heavy metals, oil products, phenols) are undertaken. The same analysis is carried out also for invertebrates. The toxicants concentration is studied in bottom sediments, water and higher aquatic vegetation.

A trophic-dynamical simulation model of the ecosystem of Lake Syamozero (Karelia) was developed. The model reproduces the dynamics of 17 trophic groups of hydrobionts on the basis of numerical solution of the system of differential equations of the Lotka-Volterra's type.

A generalization was made on the ichthyofauna of fresh-water waterbodies of Russia in the form of the Atlas of Freshwater Fishes of Russia in two volumes. The Atlas contains description of 293 species, referring to 13 orders, 33 families and 138 genera. In the outlines for each species, Latin and Russian names of the species is given, a picture of the fish, a short systematic description with the indication of characteristic features and species structure, a refined range with the map of distribution is given, a short description of living conditions of the species with the indication of its commercial value and protective status.

An individually-based model of forading behavior of fish fry was created, which takes into consideration the effects of feeding selectivity. The model simulates spatial-temporal dynamics of the population of consumer (young fish) under conditions of non-depletable food resource. Food organisms are represented by two size categories: big and small ones. The purpose of simulation experiments lies in determination of evolutionary stable strategies of survival under conditions of different spatial distribution of the forage (homogenous, random, aggregated), food-searching behavior of young fish (algorithms of food-searching behavior include random walk, directional search and localized search) and initial distribution of the fish. The modeling results indicate that in conditions of random homogenous distribution of the forage particles the natural selection doesn't promote the formation of selective feeding.

The method for determination of fish production losses as a result of human activity on waterbodies was developed. Estimation procedures of the method are based on the equations of the model of dynamic pool, implying an equilibrium state of the system "fish stock - fishery". Developed algorithms for calculation of losses to fishery allow to obtain the quantitative measures of impact of antropogenous factors in situations when the pulse increase of young fish mortality takes place, when the impact has a prolonged character and influences both juveniles and adults, when the impact leads to decrease in food resource and, as a consequence, to the decrease in fish growth rate.

Collecting an icthyological material
on Blue Nile

On the basis of analysis of inhouse and literary data a conclusion was made that the process of global eutrophication of European freshwater waterbodies, observed in 60s-80s years of the last century had not only ended, but the reverse process - the reduction in their trophic ability (reoligotrophization) had been detected. For the Russian waterbodies this was shown on the rivers of Kaluga, Moscow, Yaroslavl, Vologda, Arkhangelsk Regions, on the rivers and lakes of Karelia. The process of oligotrophication of the waterbodies of Russia is connected with the decrease in volumes of industrial and agricultural effluents.

For the first time on the actual material a 'basic hypothesis' of reticulate speciation was grounded and by that a principle possibility of a complete cycle of this way of speciation in vertebrates was proved. In accordance with the 'basic hypothesis', under hybridization of triploid clonal forms with diploid bisexual species, tetraploid species can originate, but now with renewed bisexuality. As a result, the cycle of reticulate speciation turns out to be completed, i.e. a transition from usual bisexual species by means of hybridization, clonal propagation and triploidy to tetraploid bisexual species takes place.

A balance trophic model of the aquatic community of the Northern Caspian Sea was developed. The community is represented in the model by 14 trophic groups, combining populations with similar food range and position in the trophic chain. From the analysis of modeling results, it follows that production possibilities of the ecosystem provides definite reserves of biological product, at present being not utilized sufficiently. An advantage of the model developed is the ability for searching of optimal fishery strategies considering trophic structure of communities.

On the basis of modern methods of taxonomic studies a complex description of ichthyofauna of Ethiopia was given. For the first time the patterns of fish distribution in freshwater waterbodies of this country depending on paleohistory of separate water basins and their modern condition were determined. The position of Ethiopian ichthyofauna in the general scheme of ichthyofaunistic zoning of African continent was analyzed; the patterns of fish evolution in conditions of faunistic depletion of fish population in mountain waterbodies were defined. Recommendations on organization of rational fishery of freshwater fishes of Ethiopia were given.

A revision of freshwater ichthyofauna of Vietnam was carried out. Geographic distribution of some species was analyzed, their habitats were described, and evaluation of their commercial usage was given.

On the basis of analysis of extensive inhouse and literary materials on fish reproduction, distinct mechanisms of its regulation were identified and systematized, which acted at four levels of organization (cell, organ, organism and population). Obviously, the first three groups of mechanisms work during the ontogeny of an individual, are interconnected and can be united into the group of ontogenic mechanisms. They determine the age of attaining sexual maturity and spawning periodicity. Such reproduction indices as

• changes in age characteristics of the spawning part of population (a medium age of attaining sexual maturity, the number and ratio of age groups of spawners)
• changes in sex ratio
• change in the continuance of spawning (at the expense of asynchrony of breeding of individuals of different ages and different parts of generations - slowly and rapidly growing ones)
• formation of the dwarf forms, - are population mechanisms of reproduction regulation in fishes.