The Role Of Modern Concepts Of Fish Digestion In Aquaculture

V.V. Kuz'mina, M.M. Shishin
Institute of Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia

Abstract

It is known that heavy metals exert an effect on fish behaviour. A poisoning of fish by heavy metals cause high locomotor activity, reflex contract of gill ("cough"), suppression of taste sensitivity. Also it is known about the change of fish behaviour under influence of environment negative factors causing stress. In aquaculture the concentration of heavy metals in water can increase due to their intensive elimination from intestine in a case, when their concentration in food is too considerable. The high (superfluous) contents of heavy metals in water increase of fish density in ponds etc. can cause stress which not only change some physiological and biochemical parameters, but also change some behaviour reactions.
The purpose of this work is to research separate and combine (in a combination with adrenalin, simulating stress) influence of cooper and zinc on carp Cyprinus carpio L. speed feeding reaction (latent time of a feeding - LTF, s). Five groups of fish are investigated: to 1. fish living in clean water, was injected 0.1 ml of Ringer solution (control group), 2. fish living in water with addition of 1mcM ZnSO4 solution (0.28 mg of metals/l), was injected 0.1 ml Ringer solution, 3. fish living in water with addition 1mc? of a solution CuSO4 (0.25 mg of metals/l), was injected 0.1 ml Ringer solution, 4. fish living in water with addition 1mc? ZnSO4 solution (0.28 mg of metals/l), was injected 0.1 ml 0.1 % adrenalin solution, 5. fish living in water with addition 1mc? CuSO4 solution (0.25 mg of metals/l), was injected 0.1 ml 0.1 % adrenalin solution.
The researches have shown, that in the presence of zinc and cooper (2 and 3 groups of fish) the speed of carp feeding reaction decreases (LTF is increased). The norm is restored through 48 and 24 hours accordingly. In the presence of zinc the maximal distinctions between expiremental and control fish (2 and 1 groups of fish) is observed through 1 and 24 hours, when LTF is increased by 87 and 62 % - from 0.7±0.03 up to 1.0±0.1 and 1.1±0.1 s accordingly. At the injection of adrenalin to fish (4 group of fish) the value of LTF comes back to norm in 3 hours. The reliable distinctions between LTF values of 2 and 4 groups of fish in the first terms of observation (0.25 and 0.5 hours) are absent. A gradual decrease of the parameter is marked in 1 hour after hormone injection.
In the presence cooper (3 group of fish) the speed of carp feeding reaction changes in a similar way, however observable effect is a slightly lower, than those of experiment with zinc. The maximal increase of LTF values is registered in 6 hours, when distinction between experiment and control (1 group of fish) makes up 74 %. At the injection of adrenalin to fish (5 group of fish) the LTF values comes back to norm in 1 hour. The significant distinctions between LTF values of 3 and 5 groups of fish in the first terms of observation are also absent. These results testify that the solutions of salts of the studied heavy metals increase latent time of carp feeding. The basic distinctions in character of influence of zinc and cooper on carp speed feeding reaction are absent. The comparison of the combined effect of adrenalin and metals with their separate influence on speed feeding reaction of a carp testify to reduction of negative influence of the studied heavy metals.
This work was carried out at support of Russian Fund of Basic Research (grant N 01-04-49120).