Investigation Upon the Cardiorespiratory Physiology of the Brook Trout, \u3cem\u3eSalvelinus fontinalis\u3c/em\u3e, and Carp \u3cem\u3eCyprinus carpio\u3c/em\u3e

Few biological problems have exci ted greater public concern in recent years than those associated with the pollution of inland waters by toxic and eutrophying agents. Once initiated, the successional changes which follow inevitably lead to loss of aesthetic qualities and, normally, the replacement of a desirable biota with a less useful species complex. In the northern and mid-western states, where sport and commercial fisheries constitute an economic asset of some considerable value, much effort has been directed toward the establishment of realistic criteria for water quality, mechanisms for the abatement of aquatic pollution, and the reestablishment of suitable species in reclaimed bodies of water. With regard to the first of these the classical approach has been that of evaluating mortality levels following acute exposure to pollutant action (Finucane, 1969; Walker, et al,, 1964; Berger, et al., 1969). It is increasingly appreciated, however, that a realistic assessment of water quality requires detailed information upon the more subtle effects of long-term exposure to sublethal conditions. Attempts to evaluate this aspect of the overall problem have generally centered upon determinations of growth rates (Hayes, 1945; Kinne, et al., 1962; Wood, 1932) and similar organismic activities under field and laboratory conditions (Orr, 1955; Moore, 1958; Loeb, 1964). More recently efforts have, however, been made to delineate more thoroughly the physiological capabilities and limitations of critical species , such as desirable game fish in-terms of systemic functions and their interactions (Beamish, et al., 1964; McFarland, 1959; Hughes, 1962, Hickman, 1965) . Much the same progression has been followed in efforts to reclaim and reconstitute polluted lakes, streams and. rivers. In general, given that the pollutant sources have been controlled, reclamation involves removal of undesirable species and their replacement with others of economic value. This process normally requires poisoning procedures, (Berger, et al., 1969; Walker, et al., 1964), and these have frequently been employed in the absence of any detailed knowledge of the physiological effects of the agents used, species differences in susceptibility or response, and similar factors. Here too, a knowledge of physiological response is critically required. The present study was undertaken with three primary aims. The first of these lay in the development of a flexible system for the evaluation of centrally-important physiological variables in routinely active, unanesthetized animals under well-controlled conditions. Emphasis was placed upon the interactions of the cardiovascular and respiratory systems in the satisfaction of oxygen demand. Evaluation of basic cardiorespiratory parameters requires anesthetization of specimens prior to the emplacement of a variety of electrodes and sampling catheters. Several recent studies on cardiac function (Beamish, 1964; Randall, et al., 1965; Marvin and Heath, 1968; Garey, 1970), respiration (Hart, 1943; Beamish, 1964; Stevens and Randall, 1967), carbohydrate metabolism (Chavin and Young, 1970) and hematology and ionic balance (Houston, et al,, 1969) clearly indicate that marked deviations in physiological status are the usual aftermath of interventions of this type . Consequently, an understanding of the physiological sequelae of anesthesia and surgery becomes prerequisite to valid utilization of manipulative techniques. The second goal of the study was, therefore, the description of the sequence of changes in cardiovascular respiratory function following anesthesia and surgery, and the definition of the time interval required for restoration of normal function, that is, stability and reproducibility of the parameter measures. Finally, a preliminary investigation of the physiological action of one commonly-used toxicant, Antimycin A, was undertaken. This antibiotic has been shown to possess two of the basic characteristics of a good toxicant namely, efficiency at very low concentrations, and subsequent rapid degradation (Derse and Strong, 1963). Ahmad, et al., (1950) found Antimycin A to be a potent inhibitor of succinoxidase; later it was demonstrated that it specifically blocks the passage of electrons at a site between cytochrome b and cytochrome c (Potter and Reif, 1952). Antimycin A has been shown to decrease oxygen uptake in kidney, liver and brain both in vitro and in vivo in rainbow trout and channel catfish. (Schoettger, 1970) However, the tissue or organ sites of action in fishes are not established. Therefore, the third goal of this study was to investigate the cardiorespiratory responses to Antimycin A in two species which are known to differ in sensitivity toward this toxicant (Walker, et al., 1964). Two species have been used in the investigation. Of these the brook trout, Salvelinus fontinalis, is characterized by relatively high levels of oxygen demand, marked respiratory dependence, little capacity for anaerobiosis and marked stenothermality (Beamish, 1964; Randall, et al., 1965; Stevens and Randall, 1967). By contrast, the carp, Cyprinus carpio, is metabolically less active, displays little respiratory dependence, may, under certain circumstances, function as a facultative anaerobe, and is among the most eurythermal of freshwater fishes (Hart , 1943; Hughes and Shelton, 1962; Beamish, 1964; Serfaty, 1965). The former species was selected as reasonably typical of a desirable species highly sensitive to pollutant action, while the latter may be regarded as a species type likely to become seriously competitive with desirable forms under conditions of chemical and thermal pollution and accelerated eutrophication