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Stock and Fishery Dynamics of Coregonus Lavaretus of Lake Sevan, Armenia
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Datum
2002
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IGU/ISEP
Zusammenfassung
Reduction in water level of Lake Sevan brought about by hydroconstruction and abstraction of water for irrigation has essentially changed the lake’s ecological regime. Changes of the lake's ecosystem have resulted in considerable disturbance of habitats of fish affecting mostly their natural reproduction and food provision conditions (Rubenian 1997, 6). Recent years due to secondary eutrophication of the lake and intensified illegal fishing, populations of all commercial type fish have been depressed (Gabrielyan 1998, 3). In the present paper, the trends of the dynamics of Coregonus lavaretus stock from 1979-1998 are revealed and an attempt is made to give short-term forecast of catch of this species in Lake Sevan. For choosing the most appropriate stock estimation method retrospective analyses are done for two types of fishing gears purse seine net and gillnet. Analysis of the obtained data has shown that in 1990s a tendency in the population toward rejuvenation is observed in parallel with depletion of its stock. It should be noted that in the preceding period the main regulating factor having impact on the stock was change of water quality caused by the changes of the reservoir's regime, while for recent years the main factor is the fishing pressure caused by uncontrolled overfishing. Drastic reduction of stock of C. lavaretus as a result of fishery may result in misbalance of its food base, accumulation of excessive organic matter in the lake and therefore, aggravation of eutrophication processes there.