Lebedeva O.V., Mitskevich O.I.

State Research Institute of Lake and River Fisheries, 199053, Makarova Embankment, 26, St. Petersburg, Russia

Freshwater crayfish Astacus astacus L. – one of the most important cultivated inverterbrates – is a stenobiont organism. Large significance for the reproduction of its natural stocks, replenishment and stabilization of yields has the working out of the methods of cultivation. The incubation of eggs, hatching and breeding of juveniles are the most responsible stages of freshwater crayfish cultivation. The basic task on the incubation of juveniles and their breeding is the enhancement of survival rate on all stages of ontogenesis, which is ensured by the creation of optimal abiotic and biotic conditions. All that is necessary for reception of qualitative and viable planting stock. Water pH is one of the most important parameters during cultivation of the freshwater crayfish. A. astacus L. laboratory studies have subsequently shown that low pH may result in disturbance of osmoregulation and acid-base status of crayfish (Malley, 1980; Appelberg, 1985; Wood and Rogano, 1986). Early life history stages were shown to be more sensitive to low pH then later stages (Appelberg, 1984).One of the major indicators of the physiological state of an organism in connection with the conditions of environment is respiratory metabolism. The intensity of the resting metabolism varying under the influence of external factors acts on growth rate. The indicator of this process is the rate of oxygen consumption. A question about the influence of pH on the intensity of oxygen consumption of early life history stages of the crayfish has been little studied.We have investigated the intensity of oxygen consumption by the A. astacus L larvae (stages I, II) at various values of hydrogen ion concentration (pH=5.8, 6.0, 6.3-6.5, 8.2-8.5, 9.25). As a result is ascertained that at drift pH in both parties from the neutral reaction the tendency of the reduction of the respiration intensity is watched. Stage I stronger reacts on modification. Thus at drift into acidic side the intensity of respiration decreased on 47%, and in alkalized up to 80%. The character of modification of oxygen consumption intensity by the II stage larvae by increasing and lowering of pH carried akin nature – in acid water the limit of fluctuation composed 6-32%, in alkalized – 4-30%. In our experiments the influence of negative pH was short-time and the first organism response on the modification of conditions was the inhibition of the metabolism processes, what was reflected on the oxygen consumption intensity. We also have investigated the breeding of A. astacus juveniles in water with pH=7.3-7.5 and pH=8.0-8.2. By the breeding in water with pH=7.3-7.5 the I stage larvae had sizes 8±0.15mm and mass 21.42±2.41mg. The II stage larvae – 11.2±0.03mm and mass 36.23±0.26mg correspondingly. Whereat actual growth rate composed Cw=0.059, Cl=0.035. By the breeding of crayfish in water with pH=8.0-8.2 actual growth rate composed Cw=0.031, Cl=0.01. So in water with the concentration of hydrogen ion 8.0-8.2 lower growth rate is noted.

Thus the rate of oxygen consumption as the marker of the physiological state of an organism determines the growth rate of early juveniles of A. astacus L.

References

Appelberg M. 1984. Early development of the crayfish Astacus astacus L. in acid water. Rept. Inst. Freshw. Res. Drottningholm. №61: 48-50.

Appelberg M. 1985. Changes in haemolymph in concentration of Astacus astacus L. and Pasifastacus leniusculus (Dana) after exposure to the low pH and aluminium. Hidrobiology. V.121. №1: 19-25.

Malley D.F. 1980. Decreased survival and calcium uptake by the crayfish Orconectes virilis in low pH. Can. J. Fish. Aquat. Sc. V.37: 364-372.