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How Does Hypoxia Affect Tropical Freshwater Fish?

Nicole Flint

James Cook University, TOWNSVILLE, AUSTRALIA

THEME: ASFB (Poster)

This contribution deals with a problem ubiquitous to freshwater and estuarine environments world-wide. Low dissolved oxygen in rivers and creeks can have major ecological effects, from fish kills to less obvious but more insidious sublethal effects. Very little information is currently available on the sublethal effects of hypoxia on freshwater fish from tropical regions. Some sublethal effects of hypoxia on fish in temperate areas include changes in behaviour, altered metabolism and physiology, deterioration of major organs, reduction in reproductive output, lowered endurance and swimming capacity, and reduced growth. All these effects have major implications not only for individual fish and populations, but also for ecosystems. Predator and prey relationships may be altered under hypoxic conditions, and such parameters as habitat selection and avoidance are also affected. This contribution addresses the need for research into the sublethal effects of hypoxia on freshwater fish from tropical regions, and results of preliminary investigations are presented. Results include data from field- collected fish as well as from aquarium experiments, and are related to actual conditions experienced by fish in tropical waterways.