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Some Peculiarities of the Effect of an Electric
<br />-Field on Fish
<br />e
<br />V.N. Mel'nikov and E.T. Prel'
<br />Astrakhan Fisheries Technical Institute
<br />Characteristics of the evaluation of the effectiveness of
<br />the action of electric'fields on fish are studied by means of
<br />the actual tension in the body of fish. Methods of determin-
<br />ing this indicator by means of the distortion factor of an
<br />electric field by the body of fish and the conditioned stress.
<br />in the fish body are presented.
<br />The'influence of current density, water temperature, and
<br />size of the aquarium on the threshold values'of conditioned
<br />stress in the fish body is. investigated and the dependence of
<br />threshold values on 'the body length of the fish is presented
<br />in the.form of a logistic curve. Corresponding theoretical
<br />conclusions are confirmed by experimental data.
<br />Patterns of the effect of an electric current on fish are studied for the -
<br />elucidation and-forecasting of their behavior in electric fields, and for-the
<br />development of technical means ensuring the necessary regulating effect and
<br />measures to protect the fish fauna form the harmful action of electric fields,
<br />etc. In spite of-extensive research on this problem (Bodrova and Krayukhin, 1958,
<br />1959, 1960, 1961; Nusenbaum and Faleyeva, 1961; Danyulite, 1961, 1966, 1974;
<br />Nusenbaum, 1958,"1963; Pupyshev, 1967; Shentyakov, 1959, 1963, 19649 1968, 1970,
<br />etc.), many biophysical aspects of the effect of an electric current on fish have
<br />as yet been insufficiently studied.
<br />Peculiarities of the influence of some factors on the threshold of the reac-
<br />tion of fish in electric fields with an alternating current are discussed in the
<br />'article. The corresponding theoretical premises are confirmed by experimental
<br />data on the behavior of fish from the Volga-Caspian basin, the bream, Abrawis
<br />brtrma, and the pike-perch Luei,operea Zucioperea, in electric fields. The effec-
<br />tiveness of the action of electric fields on fish is usually assessed by the in-
<br />tensity of the electric field Eo the current density of the water S., by the
<br />nominal G, and the actual Ud tension of the fish body and current strength Ip,
<br />passing through the fish body, etc. The advantages and shortcomings of the indi-
<br />vidual criteria are known and in general the area of their application is deter-
<br />mined (Mayzelis, 1965; Sternin et al., 1972; Mel'nikov, 1973, etc.). In principle
<br />each of the assessment criteria presently applied can be used allowing for the
<br />specifics of the problem to be solved. However, for the accumulation and sum-
<br />marizing of data and the establishment of corresponding patterns it is expedient
<br />to adopt the single criterion which is theoretically and practically most justified.'
<br />As an analysis of the work submitted shows, the actual tension Ud in the body
<br />of the fish may serve as such a criterion.` It corresponds to a considerable de-
<br />gree to the mechanism of action of an electric field on fish and its determina-
<br />tion presents no difficulties.
<br />144 ISSNO032-9452/81/0001-0144$7.50/0
<br />0 1982 Scripta Publishing Co.
<br />The nominal tension of the fish body U1 which can easily be found experimen-
<br />tally is the criterion closest to the Ud. The difference between Ud and Ul is
<br />determined variously in the general electric conductance of the water JB and the
<br />fish body lp and consequently by the distortion of the electric field by the body
<br />of fish. It is proposed to assess the degree of distortion by the distortion
<br />factor Kz (Sternin et al., 1972):
<br />Kz- ED 1 (1)
<br />Eo - 1 +Ke(T0TN - 1) "
<br />where Eo, En are respectively in'the field intensity in the body of the fish and
<br />in the water, V/m; Ke is the coefficient of the shape of the body; YP is
<br />YOTN ya
<br />the relative electric conductance.
<br />The use of equation (1) was restricted by the absence of data on the value Ke.
<br />Our investigations have allowed an approximate empirical dependence to be estab-
<br />lished, connecting Ke with the biometric indices of the fish body:
<br />(( x
<br />Ke=\791 (2)
<br />P
<br />where h is the maximum body depth'otf the fish, m; Ip is the body length without
<br />the (',?&udal fin, m.
<br />By means of equation (2), according to the data of Gyul'bamov (1958), Shevtsov
<br />(1975) and Shatoba (1977)'on the biometric indicators of fish, we calculated and
<br />presented in the Table the values of K, for the main commercial fishes.
<br />The value of the distortion factor can be obtained by calculation from experi-
<br />mental data, since'
<br />KE = U,
<br />(3)
<br />Estimated Values of Coefficients of Body Shape
<br />Species Be Species... I Se
<br />1
<br />Argentina silus (Aseaaius) 0,0196 Theragra ehalcogramma 0,0582
<br />Osmerus eperlanus eperlanus 0,0289 (Pall.)
<br />(L-)
<br />Salmo eratta L - - -
<br />0,0484 - Galdropsarus mediterraneus 0,0484
<br />(L.)
<br />Mallotus ofllosus vtllosus 0,0064 Afolva molva (L.) 0,0164
<br />(Mull). " 11 1
<br />la ea harengus -.membras L.
<br />0,0400 Eleginus navaga (Pall.) 0,0324
<br />Melanogrammus aegle/anus 0
<br />0576
<br />C. harengus harengus L. 0,0400 ,
<br />(L)
<br />- - C. pallast pallast Val.
<br />Sprattus spraitus (L.) - - 010400
<br />- 0,0361 Afiz amestrttus poutassou 0,1600
<br />(Risso) _
<br />I
<br />Anarhichas minor O1. 0,7840 Pollachius virgins (L.) 0
<br />0576
<br />Sebastes viuiparas Kr. -- 0,0789 ,
<br />Gadus morhua morhua L. 0
<br />0361
<br />- S. mentella Travin - - 0,0784 ,
<br />G. morhua callarlas L 0
<br />0441
<br />Notolhenta roast marmorata 0,0440 ,
<br />Macrourus ber/ax Gunn. - 0
<br />0289
<br />Fisher - - - ,
<br />M. rupestris Lacbp. 0
<br />0196
<br />N. squamifrons C,inth.
<br />Scomb
<br />s
<br />b
<br />L 0,0484 ,
<br />Abtennes anastomella (Val.) 0,0169
<br />S
<br />er
<br />eom
<br />rus
<br />. 0,0256 phyraena argentea (Gir,) 0,0169
<br />Trachurus trachurus (L.) 0,0324 Platessa platessa (L.) 0,180!
<br />Beryz decadactylus Cuv. 0,0676 Pleuronecies Zlesus L. 0
<br />1601
<br />Odontogadus merlangus 0,0576 ,
<br />Bippoglossus hippoglossas (L.) 0,1160
<br />euzinus (Nord.) Reinhardtius hippoglossotdes 0
<br />0900
<br />Merlucaus merlucaus (L.) . 0,0256 ,
<br />(Wall.)
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