Blood lactate levels as a biomarker for angling-induced stress in tigerfish Hydrocynus vittatus from the Okavango Delta, Botswana

Although critical in catch-and-release angling, no data are available on angling-induced stress in African gamefish. Blood lactate levels were used as a biomarker for angling-induced metabolic stress in tigerfish caught by angling in the Okavango Delta, Botswana. Blood was drawn and analysed for blood lactate from 66 anaesthetised fish. The landing time, handling time, body mass and total length were recorded prior to reviving and keeping the fish in aerated water for recovery before release. A strong positive relationship (r(2) = 0.607) was found between landing time and body mass, as well as significant elevations in blood lactate concentrations following rod-and-line angling, regardless of angling time. These data suggest that longer angling time significantly increases physiological stress, which may have an impact on breading success and mortality in tigerfish.