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<br />humans and other animals subjected to electroconvulsive
<br />therapy (Sharber et ai., 1994, 1995; Sharber and Black,
<br />1999). As discussed later under "Responses of Fish to
<br />Electric Fields," he correlates these epileptic phases-
<br />automatism, petit mal, and grand mal-with the more familiar
<br />and well-published descriptions and explanations of
<br />electrofishing responses, particularly those he refers to
<br />as the "Biarritz paradigm" espoused by Blancheteau et ai.
<br />(1961); Lamarque (1963, 1967a, 1990);Vibert(1963, 1967b);
<br />and Blancheteau (1967) following their intensive
<br />investigations at the Biarritz Hydrobiological Station in
<br />France.
<br />Another new theory views electrofishing as a power-
<br />related phlmomenon (Kolz and Reynolds, 1989a; Kolz
<br />et ai., 1998). Designated as A Power Transfer Theory for
<br />Electrofishing by Kolz (1989a), it explores the relation-
<br />ship betwe:en electrical power in water and in fish as a
<br />function of the ratio of conductivity of water to the effec-
<br />tive conductivity of fish. This theory, like the Bozeman
<br />paradigm, is discussed later in more detail under "Re-
<br />sponses ofFish to Electric Fields."
<br />Interal~tions of fish, water, and electricity are a very
<br />dynamic, complex, and poorly understood mix of physics,
<br />physiology, and behavior. Perhaps because there are so
<br />many variables, Reynold's (1995) quote ofW.G. Hartley
<br />seems particularly apropos for the field of electro fishing:
<br />"There an: no experts, only those who have not been
<br />found out." This suggestion is not intended to discredit
<br />or belittle the extremely valuable contributions and
<br />knowledg~: of many researchers who have spent much of
<br />their I ives studying the effects of electric fields on fish or
<br />using and developing electrofishing techniques but rather
<br />to indicate that, despite their efforts, we still have much
<br />to learn and many discrepancies to resolve. Noting that
<br />most recent research focuses on descriptive comparisons
<br />of electrofishing techniques and their injurious effects,
<br />Paul and Miskimmin (1997) recommended that future
<br />research include more carefully designed experiments to
<br />test clearly defined hypotheses. Reynolds (1995)
<br />suggested that researchers network worldwide "to unite
<br />the techniques of electric fishing and its theoretical
<br />foundation." Although that theoretical foundation is still
<br />far from complete, there is need for a coordinated program
<br />of future electrofishing research. Such a program should
<br />optimize resources at all levels, ensure comparability of
<br />data, and test validity of results through independent
<br />replication of experiments.
<br />
<br />Results - Electric Fields in Water
<br />
<br />Electrofishing (sometimes referred to as electric or
<br />electrical fishing, electroshocking, or simply shocking),
<br />
<br />SNYDER 9
<br />
<br />as well as the use of electrical barriers, screens, and some
<br />forms of anesthesia, depends on the generation of a suf-
<br />ficiently strong electric field around or between electrodes
<br />in water to elicit the desired responses by targeted fishes.
<br />The size, shape, and nature ofthat field, as defined by the
<br />distribution of and changes in its electrical intensity, are
<br />determined largely by container or basin configuration
<br />and dimensions; conductivity of the water and bounding
<br />or surrounded media and substrates; position, size, and
<br />shape of the electrodes; and the peak electrical potential
<br />(voltage differential), type of current, and waveform gen-
<br />erated between those electrodes. These factors were dis-
<br />cussed extensively by Cuinat (1967); Novotny and Priegel
<br />(1971,1974); Sternin et ai. (1972, 1976); Halsband and
<br />Halsband (1975, 1984); Smith (1989); Novotny (1990);
<br />Meyer and Miller (1995); Reynolds (1996); and Kolz et al.
<br />(1998).
<br />
<br />Water Conductivity
<br />
<br />Water conductivity, water's capacity to conduct an
<br />electric current, is the most critical environmental factor
<br />in establishing an electrofishing field. The conduction of
<br />electricity (electrical energy) in water is an ionic phenom-
<br />enon. Conveyance of negative charges via electrons from
<br />negative to positive electrodes (cathode to anode) to
<br />complete an electrical circuit depends on electrolytic re-
<br />actions at the electrodes and an almost instantaneous
<br />chain of ionic movements and interactions (exchange of
<br />electrons) in the water between and around the electrodes.
<br />Accordingly, conductivity varies directly with the nature
<br />and concentration of ions (charged atoms and molecules,
<br />mostly from dissolved solids and dissociated water). In
<br />nearly pure water, which has a very low conductivity,
<br />ionization of water itself furnishes a substantial portion
<br />of the conducting ions. When electrofishing in very low-
<br />conductivity streams with inadequate power supplies,
<br />salt is usually added to water upstream of the sampling
<br />area to artificially increase its conductivity (Lennon and
<br />Parker, 1958; Zalewski and Cowx, 1990).
<br />Conductivity is the reciprocal of resistivity (ohms-
<br />cm), a term preferred by some authors, especially for very
<br />low-conductivity (high-resistivity) waters. Conductivity
<br />is usually measured with a conductivity meter as mhos or
<br />siemens (S) per cm (usually J.lmhos!cm or J.lS/cm; J.l = micro
<br />or 10-6). (Mho is ohm spelled backward to indicate the
<br />inverse relation between these units.) Following the
<br />International System of Units, the unit name siemens is
<br />used in the remainder ofthis report.
<br />Conductivity in natural waters ranges from as low as
<br />5 J.lS/cm in pure mountain streams (Gatz et ai., 1986;
<br />Zalewski and Cowx, 1990) to 53,000 J.lS/cm in sea water
<br />(Omega Engineering Inc., 1990). The upper limit for potable
<br />
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