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12-th International Symposium.August 3-9,1998,Augsburg/Germany.(Abstracts) Alexandrova, Elena .Pontastacus leptodactylus: cultivation and restoration of stocks in Central Russia Pontastacus leptodactylus (=Astacus leptodactylus) is one of the most wide-spread crayfish species in Russia/ In Central Russia one can find the subspecies Pontastacus leptodactylus boreoorientalis (Birstein et Winogradow, 1934) in the Kama river basin which is of no particular harvesting value. Not long ago Pontastacus leptodactylus leptodactylus inhabited many water bodies in Central Russia and their resources were of harvesting value. Presently the harvesting population of Pontastacus leptodactylus leptodactylus occur mainly in the North-West and North-East parts of the region. In 1990-1997 there were selected placed suitable for crayfish farming activities including production of stocking materials, and restoration and rational utilization of crayfish resources. Geographical and economical factors influencing the conditions for crayfish farming in Central russia were investigated. Demand for crayfish production within the region and the present value of Pontastacus leptodactylus leptodactylus resources were analysed. The area of the crayfish water bodies including those which can be stoced with crayfish was determined. Local Pontastacus leptodactylus leptodactylus populations were characterised with respect to the most important problems of cultivations and acclimatization. Experiment in crayfish fry breeding and pond-rearing were carried out.
CHERKASHINA, NINA Pontastacus pachyus Rathke, its biology and places of occurrence Pontastacus pachypus, a bright-colored representative of the Astacidae, inhabits the Caspian Sea, the Don River and the Dnieper-Bug lagoons of the Azov-Black Sea Basin. It prefers stone-covered bottom at the depths of 5-50 m, water with asalinity of 12-14%o, temperature of 8-21 degree C and oxygen content not less than 6.1 mg/l (86% saturation). The rate of oxygen demand amounts to 0.043 ml/g/h. Animal food prevails in the crayfish ration amounting to 92% and 865 OF THE TOTAL CONSUMED IN THE SEA AND THE Don, resp., and includes Mytilaster )41%), Nereis (27) in the sea Anodonta 927%) and Amphipoda (31%) in the river. The highest coefficien of the filling of stomach (2.77%) has been observed in the sea. The biotopes of Pontastacus pachypus an confined to areas with high biomass of benthos 9500-1,000 g/m2 in the sea and 200 g/m2 in the Don). The crayfisf mature in the third year of life. 16% and 92.3% of roed females are among specimens of 5.1-6 cm and 7.1-8 cm, resp. The female fertility amounted to 70, 110 and 239 egg cells in the sea, the Don and the lagoonswhile the number of eggs was 15, 50 and 36, resp. The survival of larvae averaged 55,5%. The larvae at stage III have a length of 11.39 mm and a weight of 26.3 mg, while the corresponding data for fry are 3.75 cm and 3.2 g. The population consists of 8 or 9 age-groups. The 7.1-9 cm long are predominant in the sea (54.12%). In the Don they represent 28%; the river contains more fry (33%). Pontastacus pachypus are not large (with a length of 9.6 cm and weight of 32.4 g), however, the weight of the claws amounts to 47% and 54% of the total biomass of females and males, resp. In the sea a higher abundance of the crayfish was observed every 3 years and ranged from 14 min speciment (productive years) to 1.5 mln during nonproductive years. USHIVTSEV, Vladimir.Astacofauna of the present Caspian Sae (distribution, stock dynamics, behaviour, projects of fishery) Astacidae of the Caspian Sea are represented by Astacus leptodactylus eichwaldi Bott and Astacus pachypus Rathke crayfishes. A major portion of Astacidae stock is distributed along the Caspian eastern shelf. In the period of Caspian transgression, considerable changes in crayfish biotopes of the littoral shelf caused by a rise in sea level of 2.4 metres or more are recorded. High Astacidae stock dynamics are observed under twochanging environmental conditions: I. Changing population species composition; 2. Trophic relations in biocenosis. In some areas crayfish stock numbers have increased 16 times. In our studies on Caspian crayfish behaviour we discovered their regular positive reaction to underwater light sources. The studies on photo-reaction allowed us to indentify the optimum light source, concentrating crayfishes at 20-25 per square metre. The tjtal number of crayfish in the light zone is about 1,500. Experimental field research on the trap supplied with this light source made it possible to catch more than 30 kg (up to 1,500 speciments) of crayfish per sampling night.
Kolmikov, Evgeni VBiological principles of artificial propagation of river crayfish in the lower Volga river. A decline in the stock of crayfish in the lower Volga river 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 on 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 degree 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 show that for rearing specimens of 12.0-14.0 cm in length should be preferred as they produce more numerous progeny with better size and weight characteristics.Result of rearing young crayfish at different stocking densities indicate that the number of crayfish ought not exceed 25 speciment 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 speciment of larger size in the same age group exhibited a higher tolerance for temperature changes. Crayfish adapted to 26.0 degree C can tolerate a shrp drop in water temperature to 15 degree C and also a temperature rise up to 35.8 degree C. Water temperatures from 20.0 C to 30.0 degree 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 curyhaline within 0-12o/oo. One-summer old freshwater crayfish are less salt tolerant and prefer fresh water areas where they are found to concentrate (72%0. A biotechnigue of artificial propagation of crayfish in the lower Volga river has been developed and introduced based on the result of these studies. MIKOUIZA, Andre-Serge, SOKOLWSKY, Arcadi, USHIVTSEV, Vladimir and KOLMIKOV, Evgeny.Biogeography of crayfish populations (Crustacea, Decapoda, Astacidae) in the Volga-Caspian region The southern part of the crayfish area 9Volga-Caspian region) extends from the north to the south for more than 1500 km.Astacus leptodactylus leptodactylus Eschholz, Astacus leptodactylus eichwaldi Bott and Astacus pachypus Rathke crayfishes inhabit different climate zoones and have specific features. The object of this paper was to study the crayfish distribution in the Volga-Caspian region, their stock dynamics and factors that influence it.Investigations were conducted in waterbodies of the Volga-Akhtubian flood-lands, in the delta and delta-front of the Volga river, and on the Eastern shelf of the Caspian Sea in 1991-1995. The research methods were based on the use of light diving facilities, underwater video-survey, and estimation of crayfish stocks in the biotope.The results of these investigations showed that the status of freshwater crayfish populations depends to a great extent on anthropogenic factors (crayfish hunting, the regulated flow of the Volga river, pollution). The abundance and distribution of sea crayfishes depend mainly on environmental conditions changing in the period of transgression.Popular scientific video films “The Eastern Caspian Sea“ and “On the Verge” were made on the base of vidcosurvey materials.
SOKOLWSKY, Arcadi, Mikouiza, Andre-Serge and Kolmikov, Evgeny.Biological particularities of the frsshwater crayfish Astacus leptodactylus leptodactylus Eschholz in the Volgo-Caspian region In the delta of the river Volga there are two subspecies of Astacus leptodactylus: A.L.eichwaldi Bott, and A.l. morpha angulosus Rathke. Biometric analysis of this type of crayfish shows an average length of 117.18+2.44 mm. The length of rostrum is 16.43 + 0.29 mm. The length and width of the upper part and length of the abdomen and appendage is 31.68 +0.74, 63.09 + 1.37, 19.68 +0.38 and 15.34 +0.35 mm, respectively. Comparing our data with the results of research carried out by Rumiantsev (1974) we can conclude that the morphometric characteristics of our frshwater crayfish has not changed in the last 20 years. Analysis of the relationship between the length (Y, cm) and weight of the body (X, gr) of female crayfish allowed us to establish an equation between these parameters: Y=A+Bx+Cx, where A= 5.79 , B =0.19 and C = -0.0015. The coefficient of correlation between the above mentioned parameters is equel to 0.89. For male freshwater crayfish a relation between length and weight was not found.Growth of crayfish during the first year in the delta of the river Volga is relatively rapid. At the end of August 2 months-old male crayfish have attained lengths up to 43 mm and weights up to 2.42 g and females have attained lengths up to 44 mm and weigths of 2.5 g. At the end of August of the third year males have reached a length of 110.0 mm and a weigth of 46.71 g and females of 9.18 mm and 34.55 g respectively.The spectrum of feed of young crayfish under natural conditions is wide. In quantity Ostracoda (48%), Chironomidae (29%) anddd Trichoptera (7%) dominate.The main feeding periods are at 10-11 pm and 6-8 am.The distribution of crayfish in the delta is not homogeneous. The biggest stock is found in the Volga-Akhtubink region with approximately 50-70 tons, another habitat is on the western flat – type water reservoirs with 30 –051 tons. In the estuary zone of the delta where there is no catching the stock is more than 70 – 110 tons. In the entire Astrakhan region there is the possibility to catch 40 tons/year. However due to poor organization of catching not even a catch of 20 tons is reached.
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