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<br />OnderSlepoort J. vet. Res., '6, 21s-.218 (1989)
<br />
<br />/( r Utsser-
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<br />
<br />RESEARCH COMMUNICATION
<br />
<br />SOME OBSERVATIONS ON THE NARCOTIZING ABILITY OF ELECTRIC CURaENTS
<br />ON THE COMMON CARP CIT;~INUS CARPIO .
<br />
<br />I W. T. BARHAM!, H. J. SCHOONBEE2 andJ. G. J. VISSER!
<br />
<br />ABSTRAcr
<br />BARHAM, W. T., SCHOONBEE, H. J. & VISSER, J. G: J., 198~. Some observations on the
<br />narcotizing ability of electric currents on the common carp Cyprmus carpiO. Onderstepoort Journal of
<br />Veterinary Research, 56,215-218 (1989).
<br />Some effects of alternating current electronarcosis and ?f rectified currc:nt electronar~sis on C.
<br />carpio were investigated. In alllOstances recovery from narcosIs was accompamed by convulslv~ spasms.
<br />Haemorrhaging of the gills was also observed to occur. Carp do not appear to be sUitable candIdates for
<br />electronarcosis.
<br />
<br />INTRODUCTION
<br />
<br />The European common carp Cyprinus carpio is
<br />one of the most domesticated freshwater fish used in
<br />aquaculture today. Although the pond production of
<br />tilapia is still on the increase in countries such as
<br />Taiwan and Israel (Schoonbee, personal observa-
<br />tion, 1988) the common ca9' still remains an impor-
<br />tant table fish in the Mediterranean and northern
<br />European countries. Even in Israel where pond pro-
<br />duction of tilapia has increased significantly from.
<br />5 % of the total pond fish yield in 1967 to almost
<br />27 % in 1987 (Sarig, 1987), the common carp still
<br />comprises more than 60 % of the total tonnage of
<br />pond fish produced. For this reason research on its
<br />feeding and reproduction biology is still continuing
<br />(Viola & Arieli, 1983; Siwicki & Studnicka, 1986;
<br />Viola, Arieli & Zohar, 1988).
<br />
<br />C. carpio is known to survive water temperatures
<br />well below 10 oC but can also withstand wann water
<br />conditions exceeding 30 oC (Schoon bee, personal ob-
<br />servation, 1972). It has a tough leathery skin richly
<br />endowed with mucus cells and has been subjected to'
<br />a number of blood PhYSiOlogic. al studies locally (Fer-
<br />reira, 1979, 1982; Smit, 1980).
<br />
<br />Barham Schoonbee & Visser (1987b, 1988, 1989)
<br />reported on the narcotizing effects of electric Cur-
<br />rents on the tilapia Oreochromis mossambicus and
<br />came to the conclusion that alternating current was
<br />the method of choice for that species. The present
<br />study evaluates the use of both alternating and recti-
<br />fied currents on C. carpio as possible alternatives to
<br />chemical anaesthesia.
<br />
<br />MATERIALS AND METHODS
<br />
<br />The materials and methods were those used by
<br />Barham et al. (1987a,b, 1988, 1989). Fish were elec-
<br />tronarcotized individually in a 60 cm long 48 t ca-
<br />pacity aquarium. Water temperature was 20 oC un-
<br />less otherwise indicated. Alternating current electro-
<br />narcosis was induced at a potential of 60 Vnns, ex-
<br />cept in the voltage trials. Rectified current
<br />electronarcosis was induced at a potential of 100 Vp.
<br />Each group consisted of 8 fish.
<br />
<br />RESULTS
<br />
<br />The effects of alternating current electronarcosis
<br />
<br />The effects of voltage
<br />
<br />Although there was a significant difference (P =
<br />0,01) in mean narcosis times between 15 Vnns and
<br />
<br />1 Tilapia Research Unit, University of Zululand, Private Bag
<br />X1001, KwaDlangezwa 3886, Republic of South Africa.
<br />
<br />2 Department of Zoology, Rand Afrikaans University, P.O. Box
<br />524. Johannesburg 2000, Republic of South Africa.
<br />
<br />Received 6 March 1989-Editor
<br />
<br />30 Vnns and highly significant differences (P =
<br />0,001) in the mean narcosis time at 15 Vnns and the
<br />mean times obtained at 60 Vnns and at 90 Vnns, the
<br />mean narcosis times at 30, 60 and 90 Vnns did not
<br />differ significa,ntly from each other (T~ble 1, Fi~. 1).
<br />This pattern 1S remforce~ by narcOSIs co~fficlents
<br />which show clearly that, WIth a m~an narcosIS coeffi-
<br />cient value of 1,2 s cm- , a potenttal of 15 Vnns was
<br />the least effective voltage. Furthe~ore an incr~ase
<br />in the potential beyond 30Vnns dldnot resul~ m a
<br />substantial improvement on 2,1 s cm-!. The higher
<br />voltage also resulted in longer opercular r~covery
<br />times than at the lowest voltage but once agam there
<br />were no significant differences in these times at the
<br />higher voltages. This pattern extended to recovery
<br />times.
<br />At all voltages the fish exhibited erratic opercular
<br />movements shortly after the current was switched off
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<br />FIG. 1 The effect of alternating current electronarcosis at 3 dif-
<br />ferent potentials on mean narcosis time (:!: SE)
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<br />Temperature .C
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<br />FIG. 2 The effect of 100 Vp rectified current electron~rc,?5is at 3
<br />different water temperatures on mean narcosIs time (:!:
<br />SE)
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