Динамика и сравнительный анализ паразитофауны речного судака (Stizostedion lucioperca L.) в современных экологических условиях бассейна реки Куры в пределах Азербайджана

Abstract

Every year, the Kura River is polluted intensely with industrial, domestic and agricultural waste, which is discharged by Georgia (260 million / l), Armenia (300 million / l), and Azerbaijan (25 million / l). The hydrobiological and ichthyologic studies of recent years in the basin of the Kura River within Azerbaijan have shown significant changes in the composition of the fishes and the fodder invertebrates. So, the study of the parasitic fauna of valuable commercial fish species, including river pike-perch (zander) in modern ecological conditions has considerable scientific interest. In the course of our research (1999-2015), 19 species of parasites were observed in the sander (pike-perch). There are Monogenea – 1 species, Cestoda – 1 species, Trematoda – 7 species, Nematoda – 5 species, Acanthocephala – 1 species, Mollusca – 1 species, Crustacean – 3 species. The greater number of species of parasites (14 species) was recorded in the mouth of the Kura River. Among the most frequent parasites are Monogenea – A. paradoxus and Cestoda – P. percae that noted in all the sites studied. Both of these parasites are narrowly specific for zander (pike-perch) and therefore their widespread is not surprising. Nematode – R. acus, a characteristic parasite for predatory fish, was present at all sites except Varnavinsky reservoir. Crustacean – E. sieboldi was not found only in the Kazakh section of the Kura River and in the Shamkir reservoir. Trematode – B. polymorphus and nematode – E. exisus were observed in 4 sectors. Trematode – D. paracaudum, nematode – C. truncatus, mollusca – Glochidium sp. and crustacean – A. foliaceus have been found in 3 sites investigated. Trematoda – R. campanula, D. mergi, D. chromatophorum and nematoda – P. reticulatum were recorded in 2 sites. All other parasites were met once. Of the parasites found, narrowly specific for pike-perch is only the Monogenean – A. paradoxus. Cestoda – P. percae, trematodes – B. polymorphus and R. campanula, nematoda – R. acus are specific for predatory fish. An interesting fact is the significant infection of the pike-perch with chinks of the truly marine species of nematodes – A. schupakovi, E. exisus, P. reticulatum, which, apparently, is infected in the coastal zones of the Caspian Sea. In order to clarify the degree of changes in the pike-perch fauna during the last 60 years, we turned to the research data of T.K. Mikailov (1975), which were conducted in the 50s of last century, i.e. before changing the factors that influenced the testimony of our research. This work, like ours, was carried out almost simultaneously and covers the entire Kura River basin within the country. T.K. Mikailov noted 21 species of parasites at the pike-perch (zander), and in our studies 19 species. The total number of species of parasites over this period remained almost stable, however the species composition has changed. We observed the several categories of parasites -narrowly specific, typical predators, widespread in the parasitic fauna of the pike-perch (zander). Some parasites, such as E. crassum, B. luciopercae, D. spathaceum, T. clavata, A. coleostoma, P. geometra, C. lacustris and A. persarum was not noted in our studies. On the contrary, parasites such as A. tincae, D. mergi, D. pracaudum, D. chromatophorum, A. schupakovi, and L. esocina were not observed in the studies of the 1950s. But nematodes – Eustrongylide sp., was found in the studies of T.K. Mikailov, in all probability, corresponds to the E. exisus we have noted. The fauna of trematode was predominant in previous and in our studies. At the same time, enrichment of the nematode fauna and depletion of the fauna of cestodes and crustaceans are observed in our studies. We also observed the disappearance of leeches. The significant differences in the species composition were observed in two groups of parasites: trematodes and crustaceans. Some parasites (larvae of Anisakis, A. foliaceus, etc.) have great practical importance. The parasites that found in pike-perch and pathogenic for humans are larvae – A. schupakovi, C. complanatum, E. exisus, P. reticulatum. Recently, the numerous cases of infection of humans with Anisakis larvae has noted in the literature, which led to fatal outcome. And E. sieboldi and A. foliaceus cause considerable damage to pond fish farms in the country.