7133 (2) - Laserfiche WebLink

Home Browse Search

TECHNICAL NOTES Tnet.E 1.-Summary of data for anesthetized goldfish. Each value is an average for 10 fish. Per- Cur- Resis- cent Scrics Maximum rcni in tancc Powcr anes- resistance current fish of fish in fish the- (n) ~ (mA) (mA) (R) (m W) tized 0 Unknown 4.6 2,240 46.2 100 1,000 10 3.0 2,310 2L1 I00 2,000 5 2.3 2,430 12.4 80 4,000 2.5 I.5 2,820 6.0 60 5,000 2.0 1.3 2,870 4.6 50 7,000 l .5 1.0 3,120 3.0 50 10,000 1.0 0.7 4,060 2.1 30 15,000 0.7 0.5 4,570 1.2 0 20,000 0.5 0.4 5,080 0.8 20 The power loss in any fish could also be cal- culated from the value calculated for fish resis- tance and the current measured through the fish. Thus, power in fish = (fish current)z x (fish resistance). Mean values for groups of 10 goldfish indicate that 3 mA or more of electrical current will anes- thetize 100% of the fish and that this percentage decreases to around 20% at 0.5 mA (Table 1; Fig- ure 2). About 20 mW were necessary to anesthe- tize 100% of the goldfish (Figure 2). Although I did not record data according to fish size, it seemed that more current and power were necessary to keep the larger fish immobilized. This possible variation with size could easily be tested with more uniform groups of fish of different sizes. The maximum electrical power dissipated in any goldfish was calculated at 46 mW; this amount of power did not appear to hurl the fish. The fish appeared to recover completely and instanta- neously when returned to their holding tank, and their swimming appeared normal. These obser- vations are consistent with studies in which re- covery. time was measured for immobilized fish (Kynard and Lonsdale 1975; Barham et al. 1987). The fish accepted food immediately after being tested, and no fish were injured or died during the experiment. The resistances were calculated at each mea- sured current, and these data indicate that fish resistance decreased as current increased (Table 1). The calculated resistance for direct currents exceeding 3 mA was less than 2,310 SZ. These re- sistance values represent the net resistance across v m N M t m m c 6 L a LL 0 e 0 v m a 100 B tl' 60 40 20 Power Loss in Fish, mllliwatts 169 FtcuxE 2.-Electrical current and power required to anesthetize fish. the electrodes and are not to be confused with the conductivity or resistivity terms normally used to describe the characteristics offish flesh (Sternin et al. 1972). In conclusion, the results of this experiment provide estimates of electrical current and power levels necessary to anesthetize goldfish of approx- imately 86 mm total length. Further tests to eval- uate the effect of fish size and fish species could determine the applicability of this technique for general use in fish management. References Barham, W. T., H. J. Schoonbee, and J. G. J. Visser. 1987. The use of electronarcosis as anaesthetic in cichlid, Oreochromis mossambicus (Peters). I. Gen- eral experimental procedures and the role of fish length on the narcotizing effects of electric currents. Onderstepoort Journal of Veterinary Research 54: 617-622. Gunstrom, G. K., and M. Bethers. 1985. Electrical anesthesia for handling large salmonids. Progressive Fish-Culturist 47:67-69. Haskell, D. C., J. MacDougal, and D. Geduldig. 1954. Reactions and motion of fish in a direct current electric field. New York Fish and Game Journal 1: 47-64. Kynard, B., and E. I.onsdale. 1975. Experimental study of galvanonarcosis for rainbow trout (Salmo gaird- neri) immobilization. Journal of the Fisheries Re- search Board of Canada 32:300-302. Orsi, J. A., and J. W. Short. 1987. Modifications in electrical anesthesia for salmonids. Progressive Fish- Culturist 49:144-146. Sternin, V. G., I. V. Nikonorov, and Y. K. Bumeister. 1972. Electrical fishing, theory and practice. Trans- lated from Russian: Israel Program for Scientific Translations, Jerusalem. (Available as TT 75-50005 from U.S. Department of Commerce, Springfield, Virginia.) 0 v 1 2 3 4 5 Current in Fish, mllllamps 0 10 20 30 40 50