Robert W. McCauley

Temperature Tolerances of North American Freshwater Fishes Exposed to Dynamic Changes in Temperature

Traditionally lower and upper temperature tolerances of fishes have been quantified in the laboratory via three different experimental approaches: the Fry or incipient lethal temperature (ILT), critical thermal (CTM) and chronic lethal (CLM) methodologies. Although these three experimental laboratory approaches generate endpoints which are quantitatively expressed as a temperature, are determined experimentally with random samples of fish acclimated to specific temperatures, and involve both time and temperature as major test variables, they do not quantify the same response. All three approaches generate valuable, albeit different, information concerning the temperature tolerance of a species. In this review we have summarized published research concerning the tolerance of North American freshwater fishes to dynamic changes in temperature, i.e., tolerance is tested by methods that gradually change temperatures until biological stress is observed. We found more than 450 individual temperature tolerances listed in 80 publications which present original dynamic temperature tolerance data for 116 species, 7 subspecies and 7 hybrids from 19 families of North American freshwater fishes. This total represents about 1/3 of the families and 1/6 of the known North American freshwater species. Temperature tolerance data were partitioned by experimental approach, i.e., critical thermal method (CTM) and chronic lethal method (CLM), and direction of temperature change. Although both CTM and CLM expose fish to dynamic changes in water temperature, these two methods differ in temperature change rates and test endpoints, and hence measure different aspects of thermal stress. A majority of the 80 studies employed CTM to assess temperature tolerance, in particular determination of CTmaxima. One or more CTmaxima has been reported for 108 fishes. Twenty-two fishes have reported highest CTmaxima of 40°C or higher. Several species in the family Cyprinodontidae have generated some of the highest CTmaxima reported for any ectothermic vertebrate. For a variety of reasons, data concerning tolerance of low temperatures are less plentiful. Low temperature tolerance quantified as either CTminima or CLminima were found for a total of 37 fishes. Acclimation temperature exerts a major effect on the temperature tolerance of most North American fish species and it is usually strongly linearly related to both CTmaxima and CTminima. Although we uncovered dynamic temperature tolerance data for 130 fishes, only a single dynamic, temperature tolerance polygon has been published, that for the sheepshead minnow, Cyprinodon variegatus.

Whole-Animal Physiological Processes for the Assessment of Stress in Fishes

General stress in fish often can be indirectly revealed by standardized laboratory tests in which stressed and healthy individuals are compared. In this paper, various techniques by which selected physiological processes of whole animals are used to detect stress are reviewed and evaluated. Reviewed tests fall into three categories. In the first, the resistance is measured in fish challenged by clearly definable stressors such as temperature, oxygen, and salinity. These methods have the advantage of economy of time, effort, and equipment. In the second category, highly integrative physiological activities such as growth and swimming are quantified. Here more complicated equipment and testing procedures are required. Methods of measuring swimming capacity range from the simple bench top “fish wheel” to elaborate swimming performance tunnels in which the oxygen consumption of the fish is simultaneously measured. The third category comprises methods of monitoring experimental subjects exposed to water-borne pollutants. The cough reflex test, for instance, estimates stress from relationships between chemical concentration and cough frequency. A more sophisticated, state-of-the-art approach is multiparameter monitoring which may lead to an understanding of the nature of the morbidity of stressed fish. Here continuous records are made of many body functions simultaneously. Although no single method appears to be the most sensitive for all stressors, there is a best method for each stressor, depending upon its effects. Investigators have the task of choosing among an array of methods, a technique which is both suitable to the fish species, their laboratory facility, and the potential stressor.

Reconciling the two methods of measuring upper lethal temperatures in fishes

SynopsisThe models developed here provide a precise quantitative description of the course of the thermal destruction experienced by fish during a slow heating experiment. However, a broader view of this work is that each of the abrupt transfer and slow heating techniques determines experimentally a functional relationship; the interdependence of these functional relationships is the actual focus of this study. In particular, it is shown that data from either type of experiment can be used to predict the observations from an experiment of the other type under certain assumptions.

Influence of Acclimation Temperature on Preferred Temperature in the Rainbow Trout Salmo gairdneri

Abstract The relation of preferred temperature to acclimation temperature of 29 rainbow trout 15 months old was examined during summer. Fish were acclimated to 5, 10, 15, 20, and 25 C, respectively, and tested individually in an electrically controlled shuttlebox device. Body temperatures monitored by a radiothermometer ingested by the fish closely approximated occupied temperatures to within 0.2 C. No significant differences were found in preferred temperature over the acclimation range studied. The calculated final preferendum was 11.3 C. Fish regulated environmental and body temperature with the same precision as they selected temperature in a spatial gradient.

Effect of Air Temperature on Growth of Largemouth Bass in North America

Abstract We examined the relationship between air temperature and growth for geographically disparate populations of largemouth bass Micropterus salmoides by use of published data in conjunction with climatological records. The thermal component of climate best correlated with growth was accumulated day-degrees over 10°C. This measure ofclimate was suggested by a simple model in which growth rate is proportionate to temperature in excess of 10°C. Correlations (0.79–0.84) between total mean lengths each year (years 3–8) and accumulated day-degrees were significant, and indicated that more than half the variability in growth may be attributed to environmental temperature. Theoretical growth curves reconstructed from these regression lines agreed well with those observed for natural populations.

Rates of Gain and Loss of Heat Tolerance in Channel Catfish

Abstract Thermal acclimation dynamics of channel catfish Ictalurus punctatus were quantified by using time-series critical thermal maximum (CTMax) estimates. Data consisted of CTMax determinations from 57 groups of 10 fish each. Respective CTMax values ranged from 30.9°C to 42.1°C for acclimation temperatures between 10°C and 35°C and increased 0.45°C for each 1°C increase in acclimation temperature. Rates of heat tolerance gain for fish transferred from low to high temperatures were not constant but decreased geometrically with respect to time until end-acclimation levels were reached. Fish transferred from high to low temperatures showed similar geometric patterns of tolerance loss; however, progressive decrease in CTMax was relatively slow and was interrupted after 24 h by a consistent 72-h acclimatory stasis. Differential patterns of heat tolerance gain and loss suggest that both processes place a premium on heat tolerance conservation. Acclimation times were influenced directly by absolute difference...

Thermal Tolerance of the Alewife

Abstract The alewife Alosa pseudoharengus often dies in large numbers in the Great Lakes during the spring. The reasons for this mass mortality are still unclear although one of the causes is believed to be thermal death when alewives encounter warm inshore temperatures. Published reports on upper lethal temperature indicate that the ultimate upper lethal temperature of adult alewives is near 25 C. In contrast, young of the year appear to have an ultimate upper incipient lethal temperature slightly above 30 C. Published values of thermal tolerance of the adults may be low because of the difficulty of obtaining healthy specimens for experimentation. We found that when adult alewives were well adapted to laboratory conditions they could survive temperatures several degrees higher than predicted. The ultimate upper lethal temperature was estimated to be in the range 31–34 C.