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Freshwater Crayfish 12(1): 935-936 (1999)

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Biological principles of artificial propigation of freshwater crayfish Pontastacus leptodactylus in the lower River Volga

Kalmikov E  e-mail link

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Abstract

A decline in the stock of crayfish in the lower River Volga has stimulated investigations into their artificial propagation. Experimental studies have been performed since 1988. Various techniques for larvae production have been tried: under rearing pond conditions, in the Vace apparatus, in various incubators, in flow-through water, recirculating water system and enclosed cycle of water supply. A series of experiments was carried out at optimum conditions of incubation and larval rearing. It was shown that the maximum number (80%) of eggs hatched at a temperature of 25.0 ± 1°C. The best results were obtained in the enclosed cycle of water supply at the following environmental parameters: O2 7.5–9.4 mg/l; pH 7.7-8.4; NH4 0.12-0.15 mg/l; NO 0.02 mg/l; NO3 0.5 mg/l; CO2 0.4-2.2 mg/l. Eggs hatched during different time periods depending on regulation of the incubation temperature. Growth rates were very close to each other in all age groups. Experimental studies of the fertility of females of different age groups showed that for rearing purposes specimens of 12.0-14.0 cm in length should be preferred as they produce more numerous progeny with better size and weight characteristics. Results of rearing young crayfish at different stocking densities indicate that the number of crayfish ought not exceed 25 specimens per m2. In experiments on thermal resistance of young crayfish the upper and lower shock and lethal temperatures were determined. The study showed that young specimens of larger size in the same age group exhibited a higher tolerance for temperature changes. Crayfish adapted to 26.0°C can tolerate a sharp drop in water temperature to 15°C and also a temperature rise up to 35.8°C. Water temperatures from 20.0°C to 30.0°C may be considered optimal since no lethal disfunctions are observed within these temperatures. Salt tolerance of crayfish living in fresh and sea water was studied. The data obtained suggest that young Caspian crayfish are euryhaline within 0-12‰. One-summer old freshwater crayfish are less salt tolerant and prefer fresh water areas where they are found to concentrate (72%). A biotechnique of artificial propagation of crayfish in the lower River Volga has been developed and introduced based on the results of these studies.

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Kalmikov E. (1999). Biological principles of artificial propigation of freshwater crayfish Pontastacus leptodactylus in the lower River Volga. Freshwater Crayfish 12(1):935-936. doi:

 

 

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