Известия ТИНРО (Sep 2014)
Formation and modern state of ecosystem in Tolmachevskoye reservoir (Kamchatka) and the acclimatized there population of kokanee ( <i>Oncorhynchus nerka kennerlyi</i>)
Abstract
Evolution of local ecosystem in Tolmachevskoye reservoir and changes in its artificial population of kokanee salmon are traced on the data of authors’ observations in 2009-2013 and previous archival and cited data. Decreasing of inorganic phosphorous, nitrogen, and bioavailable iron is detected in the water against a background of water warming. As the result, phytoplankton production and abundance decrease, its species composition becomes simpler, chlorophyll а concentration becomes lower. Zooplankton abundance is stable (1-2 g/m3), as before the reservoir appearance, but species structure of plankton crustaceans is changed, and the copepods Cyclops scutifer , small cladocerans Holopedium gibberum, Bosmina longirostris , and Daphnia ( Daphnia ) cristata group prevail recently. The salmon food spectrum is wide and includes a lot of unedible fractions as wood chips and plant detritus; coefficient of consumption is high - these factors indicate a deficiency of forage resources for fish. The fish condition indicates a chronic malnutrition. The state of female gonads is satisfactory, without any visible pathology, as in 2003-2007, but the oocytes resorption goes concurrently with maturation of gonads that is a sign of hard competition for the food within the kokanee population. The current stable state of the population differs from preceded stages of its development by lower stock add smaller size of fish, the age of spawning is now 4-7 years. Among other freshwater fish, the kokanee salmon is distinguished by high content of ω-3 polyunsaturated fatty acids. Artificial populations in Kamchatka could be considered as a resource for both amateur or sport fishing and commercial aquaculture.
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