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synaptic potential. . ., polarity inversions due to openings of the circuit, etc." However, some of the concepts established by the Biarritz researchers are difficult to understand and have been questioned by other researchers (Hume, 1984; Sharber, personal communication). In 1991 during an electrofishing-injury workshop in Bozeman, Montana, N.G. Sharber introduced another explanation for the responses of fish to an electric field. According to this theory, often referred to as the Bozeman paradigm, the observed responses of fish, including muscular seizures resulting in spinal and related injuries, are comparable to responses of humans and other animals subjected to electroconvulsive therapy and can be similarly explained as phases of epilepsy, specifically automatism, petit mal, and grand mal (Sharber and Black, 1999; Sharber et aI., 1994, 1995; Sharber, personal communication). How the underlying concepts of the Biarritz para- digm fit in the context of the Bozeman paradigm, and vice versa, has yet to be well explored. Because the phases of epilepsy are understood to be disorders of cerebral func- tion, Sharber et al. (I 994), and Sharber and Black (I999) suggested that the electric-field responses observed in fish are due to various levels of overstimulation of the central nervous system, either directly to the brain or short-circuited through the spinal cord. However, other researchers, including Haskell et al. (I 954), Vibert (I 963, 1967b), Lamarque (I 967a, 1990), Edwards and Higgins (I 973), and Wydoski (I980), concluded that the various responses elicited in fish by an electric field are the result of direct stimulation of not only the central nervous sys- tem, which controls voluntary reactions, but also the au- tonomic nervous system, which controls involuntary reactions, and muscles themselves. Haskell et al. (I 954) and Lamarque (I967a, 1990) demonstrated that tetany in DC and muscular bends of the body toward the anode upon circuit closure in DC, or repeatedly in PDC, can be induced by direct overstimulation of efferent nerves or nerve endings associated with muscles. In those experi- ments, either efferent nerves were severed from the spi- nal cord, or the spinal cord was destroyed or removed prior to electric-field exposure. Muscular bends of the body often resulted in what was or would have been movement (taxis) towards the anode. There is surely some truth to both paradigms, and perhaps a better understanding of the responses of fish to electric fields will require an integration of the two (possibly along with aspects of the power-transfer theory discussed below). The major intensity-dependent re- sponses of fish described by both paradigms (reactive detection, undirected or inhibited swimming and taxis, and narcosis and tetany) are illustrated in Fig. 11 and discussed later in more detail. The electro-physiological SNYDER 23 mechanisms involved in epilepsy and electroconvulsive therapy might or might not be much better understood than those for the responses of fish to electric fields. In either case, a collaboration of biologists, including ex- perts in neuro-physiology, should be fruitful for both dis- ciplines. Certainly, the observed results of the Biarritz experiments and others mentioned above are valid under the conditions in which they were performed, but a much more complete and defmitive understanding of the electro- physiological mechanisms involved is needed to better determine what electrical-field parameters and conditions will optimize desired electrofishing responses and mini- mize injury and other adverse effects. Theory of Power Transfer from Water to Fish Kolz and Reynolds (1989a) suggested that electro fishing should be viewed as a power-related phe- nomenon. More specifically, they hypothesized that the responses of fish to electric fields are directly related to the magnitude of power density (product of voltage gra- dient and current density) in the fish and that the in-fish power-density threshold for each response is constant (fixed) and independent of water conductivity. Accord- ing to their theory of power transfer (Kolz, 1989a), when water conductivity (cw) equals effective fish conductiv- ity (Cj), 100% of the power density in the water is trans- ferred to the fish (applied power density in the water, Dw, equals power density in the fish, Dr). But, as water con- ductivity either increases or decreases relative to the ef- fective conductivity of the fish (conductivity mismatch), power transfer to the fish is progressively less efficient. To establish or maintain a desired level of power density in the fish under conditions of conductivity mismatch (perhaps just above the threshold for a specific response), power density in the water must be progressively in- creased beyond that of the match condition in accord with the relation Dwl Dj = (I + qi I (4q), where q = cwl cf (the conductivity mismatch ratio; Kolz, 1989a). Subscript frepresents effective in-fish values which match corre- sponding in-water values, subscript w, at the minimum of the curve represented by this equation. When plotted on the log-log graph of power-density ratio versus water-conductivity ratio in Fig. 12, or the unique four-way log graph (Figs. 6 and 13) used by Kotz and Reynolds (1989b), the above relation yields what Kolz and Reynolds referred to as a normalized curve for pre- dicting the increase in applied power-density needed to maintain a constant level of power-density in a fish (the curve minimum) as water conductivity changes. Note that the curve is symmetrical with a rounded bottom, like an