Measuring the influence of winter conditions on largemouth bass behaviour using both biotelemetry and laboratory studies

Abstract

Studying the winter ecology of freshwater fishes has been a focus of much past and present research. Because of obvious constraints with studying fish in situ during the winter, few studies have made links between laboratory findings and observations made in the natural environment. Recently, new developments in biotelemetry have provided a way of assessing the winter ecology of fish in a natural setting. At present, however, there are few, if any, studies that attempt to make direct links between field and laboratory results. This research focuses on the reaction of largemouth bass (Micropterus salmoides) to winter conditions using both biotelemetry and laboratory components. In the first part of the study, biotelemetry-derived swimming activity is assessed across a range of temperatures (4.0-25°C). As well, swim tunnel-derived Ucrit swimming speeds and burst swimming ability across similar temperatures were evaluated. In both cases, swimming activity and speeds decreased as temperatures decreased. In biotelemetry-derived measurements, swimming activities increase late in winter, possibly suggesting acclimatization. In the second part of the study the effect of hypoxia on winter habitat selection was investigated. Biotelemetry-obtained locations of largemouth bass were compared to the distribution of dissolved oxygen throughout the lake at numerous times throughout the winter. In addition, experiments were conducted in a laboratory setting on winter juvenile fish to determine the behavioural and physiological impacts of hypoxia. The results of these experiments revealed a behavioural response in the lab and habitat avoidance in the field at an environmental oxygen level of approximately 2 mg/L of dissolved oxygen. The combination of biotelemetry with laboratory data has demonstrated that more informative results about the winter ecology of freshwater fishes can be derived. In the future, usefulness of this combined approach in assessing the impacts of climate change on fish populations will be invaluable.