Results of research (Reshetnikov, 2001) show that the presence of rotans in small water bodies results in an essential decline of diversity of species and abundance of larvae of amphibians and invertebrates feeding on these larvae. However different species of amphibians are to a varied extent susceptible to the action of P. glenii
. In water bodies colonized by rotan tritons Тriturus cristatus
, Т. vulgaris
, frogs Rana temporaria
, R. arvalis
and R. lessonae
as a rule cannot reproduce successfully. Rotans can disturb normal development of spawning behaviour of tritons of both species, consume adult Т. vulgaris
and larvae of both species. Frogs of three species do not avoid spawning in water bodies colonized by rotan, but their larvae are actively eaten by rotans and in the majority of cases are eliminated by them completely before the beginning of metamorphosis. Toads В. bufo reproduce successfully in water bodies inhabited by rotan. Larvae of this species of amphibian are relatively not fit for P. glenii and in their mass reach the stage of metamorphosis in such water bodies. Possibly conditions of development of larvae of В. bufo even improve after colonization of water bodies by rotans (Reshetnikov, 2001). In small water bodies inhabited by rotan the author noted 0 to 2 species of amphibian, whereas in water bodies without rotans this index varied from 0 to 5. Significant negative correlation has been revealed between presence of rotans and diversity of species (N=22; r = - 0.4619; p = 0.03) and also abundance.(N=22; r = - 0.4455; p=0.038) of amphibians in 1997.
Similar results were obtained during analysis of relationship between abundance of rotans and diversity (r = - 0.4969) and abundance of (r = - 0.4792) amphibians.
In a number of water bodies rotan may completely eliminate larvae of tritons (Reshetnikov, Manteifel, 1997).
According to the observations of other authors for the basin of the Danube T. dobrogicus no longer occurs in some water bodies in the vicinity of Chop, Batevo and Mukachevo after appearance of this species of fish in them. In 1996 rotan had not appeared yet, in 2000 it was already numerous (Litvinchuk, Borkin, 2000).
Negative correlation was revealed between the presence or rotans in water bodies and diversity of species of invertebrates (r = -0.5528; N= 18; р - 0.017) (Reshetnikov, 2001). In water bodies inhabited by rotan adult beetles of the fam. Dytiscidae and their larvae, beetles Hydrous sp., larvae of dragon flies Aeschna cyanea, Somatochlora aenea and Erythromma viridulum, spiders Dolomedes sp., and leeches Haemopis sanguisuga did not occur or were rare. These species were noted in some other water bodies that are not inhabited by rotan. However клопы-гладыши Notonecta glauca are abundant in a water body with с P. glenii. Of molluscs in a water body inhabited by rotan large прудовики Lymnea stagnalis are numerous. Pronin (1982) thinks that invasion of rotan, [элодеи канадской, рипуса, пеляди] in Baikal and ichthyoparasites brought with acclimatized species should be regarded as biological pollution of the lake. Biological pollution of large water bodies is nearly not restricted in time. The intentionally of unintentionally acclimatized species will evolve with the ecosystem.
In another publication dealing with rotan in Baikal Litvinov и O'Gorman, 1996 analyzed relations between rotan and other fishes. Siberian roach and Siberian dace are commercially important in many areas of Lake Baikal and together they accounted for about 50% (by weight) of the commercial harvest in the Barguzin commercial area during 1980-1989 (records of the Ust-Barguzinsky Inspector and Protector of fish). But these two valuable fishes must now share food resources with the rotan. Thus, the establishment of the rotan may eventually lead to reductions in the populations of Siberian roach and Siberian dace through competition for food. Consumption of fish eggs and young fish by rotan, however, is perhaps a more serious threat to the native fish community. Most species of native fishes spawn in deltas, in rivers, or in the few shallow, marshy areas around the lake. Establishment of dense populations of rotan in these areas could diminish recruitment of many fishes and eventually lead to large-scale population declines. In the Great Lakes, the exotic alewife appears to have contributed to the collapse of endemic fish populations by eating young fish (Eck and Wells 1987).
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