CHARACTERISTICS OF ELECTROFISHING EQUIPME NT

The basic characteristics of five types of electrofishing equipment (I battery powered and 4 with petrol engines) commonly used in the Czech Republic were studied. Different engine capacities, pulsation (Hz), t ypes of anode and reaction of fish to electric field were tested. It i s possible to see from the results (Fig. 2) that the most commonly ava ilable electrofishing equipment (200 - 250 V, 2 - 4 A) is fully suitab le for the task required and that it is not necessary to increase powe r levels. Greater weight, price and safety of the other equipment inve stigated did not neccesarily produce any greater efficiency. The batte ry equipment studied showed that it was convenient for small water cou rses or small fish only. The standard type of anode used (aluminium sq uare, area 7.1 dm2) was generally found to be adequate, though for sma ll fry, an anode with the smaller surface area (copper ring, area 1.6 dm2) providing higher voltage gradients in a smaller electric field (F igs. 3 and 4) was found to be an improvement. The recommendation by R i h a (1975) and B o h l i n et al. (1989) that the electrode: cathode areas be of the ratio 1 : 3 - 4 was confirmed by this study. The mean minimum voltage gradients needed for narcosis, electrotaxis and excit ement for the studied fishes (Gobio gobio, Alburnus alburnus, Leuciscu s cephalus and Carassius auratus) was found to be 0.78, 0.22 and 0.08 V/cm, respectively (Tab. II). The gradients found were similar to thos e described by C u i n a t (1989) and L a m a r q u e (1967), who obta ined the results in the range of 0.30 - 1.30, 0.10 - 0.87 and 0.05 - 0 .12 V/cm, respectively.