Stress in largemouth bass

Authors: Thompson, L
Journal: North American Journal of Fisheries Management 28:1059–1068
Year: 2008
Where: Carleton University, Ottawa, Canada

Largemouth bass were hooked using rod and line used by anglers. The fish were put into a tank on a boat, where blood samples were taken. Fish were exposed to air, ranging from 1 second to 15 minutes, mimicking exposure to air by anglers. The fish were then observed for 30 minutes and another blood sample was taken. A radio tracking device was attached to the fish before they were released.

Canadian researchers found that whenever largemouth bass were removed from the water, the fish’s breathing rate increased, indicating stress. Also, the level of the enzyme Alanine Aminotransferase (ATS) increased, indicating permanent tissue damage. When the bass were out of the water for long periods, they showed abnormal behaviour, and rather than leaving the release site normally, they tended to linger there.

The scientists were particularly concerned about largemouth bass which have young to look after. An attack on them by anglers means that they are not present, or not fit enough, to fan their eggs to bring in oxygen and keep away silt, or to protect them against predators.

SUB-LETHAL DISTURBANCES

"A number of sublethal differences (e.g. physiological disturbances and behavioral impairments) were evident in the longer-air-exposure treatment group."

"In all instances, air exposure had a significant affect on the opercular rate of the largemouth bass."

"... opercular rate is a good behavioral metric because of its sensitivity to stress."

SIGN OF PERMANENT TISSUE DAMAGE

"The baseline concentration of AST (an enzyme) for male largemouth bass was elevated significantly during the cool water treatment period."

"Because AST is an intracellular enzyme that is predominately located in the heart and liver, its appearance in plasma is a common and reliable indicator of permanent tissue damage in vertebrates."

THE LONGER OUT OF WATER,
THE GREATER THE ABNORMAL BEHAVIOUR

"The fish exposed to air for longer durations tended to exhibit behavioral impairments and remained close to the release site longer than those exposed for short periods."

YOUNG FISH SUFFER

"Nesting males are extremely vulnerable to capture because they provide parental care for their brood by defending their nests against brood predators and fan their eggs to provide oxygen and keep them free of silt."
Fish Pain