| Abstrakt: |
The development of the ecosystem of Lake Kezenoi-Am (Eisenam) over the past hundred years is described based on literature data and original materials. The ecosystem underwent a catastrophic transformation as a result of the introduction of the chub (Squalius cephalus orientalis Linnaeus, 1758) in the middle of the 20th century and the European perch (Perca fluviatilis Linnaeus, 1758) in 2013–2014. According to our studies and collected survey data, the endemic subspecies the Kezenoi-Am trout (Salmo trutta ezenami Berg, 1948), which was previously represented by two sympatric forms spawning in the lake and in brooks, has almost completely disappeared. The multifold increase in the intensity of net fishing is an additional factor promoting the degradation of the ecosystem. At present, the European perch predominates in the reservoir, and the chub is a subdominant species. Native fish species are currently inhabiting the ecosystem periphery. The Caspian gudgeon (Gobio holurus Fowler, 1976) is found only in the lower reaches of the tributaries. The Kezenoi-Am trout has completely disappeared in the lake basin and currently is found presumably only in the upper reaches of the tributaries. Based on an analysis of the literature data on the transformation of similar ecosystems, we argue that the consequences of the degradation of Lake Kezenoi-Am fauna are irreversible; thus, the Kezenoi-Am trout, which is listed in the Red Book, will disappear totally in the coming years. Urgent measures are required to preserve this endemic species, including artificial trout breeding and reclamation measures to reduce the number of introduced species. [ABSTRACT FROM AUTHOR] |
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