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SCHRECK ET AL.: ELECTROSHOCK: PHYSIOLOGICAL RESPONSES BY TROUT 77 I'electrocardiogramme a augmente de fa4on marquee. Les diagrammes raectrophoretiques de 13 isoenzymes provenant du foie, des muscles blancs et du plasma ont demontre qu'il n'y avait aucune difference en[re les poissons pris a !'aide d'un carrelet et ceux qui ont ete captures par courant electrique. 11 semble probable que les reactions des poisons aux electrochocs soient attribuables aux effets combines de traumatismes, aux facteurs associes a une depense accrue d'oxygene et aux suites du syndrome de ('adaptation gencrale au stress. Une periode prolongee de plus de 6 h dolt s'ecouler avant que le poison ne revienne a son etat initial. Received August 8, 1975 Accepted October 3, 1975 lte~u le 8 aout 1975 Accepte le 3 octobre 1975 ELECTROSHOCKING devices are widely used to col- lect fish, but there is great variability in effective- ness of shocking as a collecting technique (Collins et al, 1954; Webster et al. 1955; Larimore 1961; Boccardy and Cooper 1963; Edwards and Higgins 1973) . Although used as a capture method for the estimation of fish populations (Libosvarsky 1966), electrofishing may affect subsequent cap- ture of fish (Libosvarsky 1967; Cross and Stott 1975). We investigated the physiological consequences of electroshock-induced paralysis in rainbow trout (Salmo gairdneri) as part of an investigation into the efTicacy of electroshocking for population esti- mation. The assumption tested was that once a fish is able to swim after being shocked, it rapidly returns to normal physiological condition. Few studies have addressed this subject in detail, al- though reports have been published on the general effects of shocking on physiology (Hauck 1949; Haskell et al. 1954; Camargue 1967; Halsband 1967; Chester Jones et al. 1969) and growth (Halsband 1967; Ellis 1973; Kynard and Lons- dale 1975) of fishes. Bouck and Ball (1966) con- cluded that capture by electrofishing presented a more "uniform" stress than angling or seining. We were also interested in evaluating the use of electrofishing gear to capture fish for physiologi- cal analysis from waters under the influence of some perturbation such as a pollutant or pesticide. That is, does capture by electroshock produce significant stress on an individual to reduce or negate its value as a sample for determining the stress placed upon it from its environment? Such usefulness of electroshocking in the collection of fish for physiological studies in the laboratory was demonstrated for glucose (Chavin and Young 1970), free fatty acids (Minick and Chavin 1972), and cortisol (Singley and Chavin 1975). Materials and Methods GENERAL PHYSIOLOGY Forty-eight 15-mo-old hatchery-reared rainbow trout (average weight, 169 -~ 5.4 g sE) acclimated for 3 days were shocked in an outdoor, cement race- way (28.2 m X 2.4 m X 0.43 m) at the Wytheville National Fish Hatchery, Wylheville, Va. on 3 May 1974. A portable Georator49 generator delivering 230 V and 2.3 A DC was employed. The two electrodes spanned the width of the raceway and were passed once from the lower to the upper end of the raceway (at 1145 h), over a period of approximately 1 min. -This method simulated electrofishing in a stream. The ambient water had the following characteristics: tem- perature 12.8 C, hardness (CaCO,) 120 mg/liter, pH 7.9, and conductivity 227.0 µmho. Twelve fish were collected before they had re- covered from the paralysis (0 time), killed by a quick blow to the head, rapidly weighed, and exsanguinated into a heparinized test tube after severance of [he caudal penduncle. Blood was also collected in micro- hematocrit tubes for determination of packed cell volume (hematocrit) and blood cell constituents. Both gonads were weighed for determination of gonadosomatic indices. The remaining shocked fish appeared to "recover" in 5-] 0 min. Twelve fish from this group were rapidly captured by netting and sampled as previously described at intervals of 1-, 3-, and 6-h post shocking. We netted and sampled 12 fish from a neighboring raceway at times 0 and 6 h to provide standards for comparison. Electrodes were passed through the control raceway but were not energized. Plasma was obtained by centrifugation and stored at -15 C. Blood smears were made and stained with Wright's stain. Numbers of lymphocytes, heterophils, and thrombocytes were determined and expressed as a percentage of the total leucocyte count. Glucose con- centrations were determined by the Glucostat method (Worthington Biochemical Corp.) from 0.1 ml plasma. Lactic acid was measured by the Lactate test - UV method (Boehringer Mannheim Corp.). Pooled (1:1) samples from two fish, totalling 0.5 ml plasma were used. Plasma protein concentrations were measured with an American Optical Goldberg refrac- tometer. Calcium and magnesium concentrations were determined from 0.02 ml plasma by use of a Perkin- Elmer 403 atomic absorption spectrophotometer. Androgens were quantified in 0.05 ml plasma by com- petitive protein binding assay as proposed for testos- terone by Murphy (1968 ), modified for 17p-hydroxy- steroids by Rosenfield (1971), as outlined by Schrenek et al. (1972a) . We assayed corticoids in 0.05 ml plasma as proposed by Murphy (1964, 1967 ), using the "total" concentration of corticosteroids ap- proach by Donaldson and Dye (1975) .