Evaluation and use of a portable field kit for measuring blood lactate as a stress indicator in sharks.

AWRUCH C. A.; SIMPFENDORFER, C.; PANKHURST, N. W

Congreso; Sharks International Conference; 2010

James Cook University

Understanding the stress physiology of sharks that are caught and released is recognised as an important criterion for assessment and effective management of sustainable fisheries. Measurement of blood and plasma lactate is becoming a common procedure in assessing the physiological effects of capture and handling stress in sharks, but the necessity to measure levels in the laboratory limits the ability for rapid field assessments. Portable lactate meters offer an attractive alternative, but few studies have evaluated their capability for analysis of shark blood. This study examined the responses of Squalus acanthias and Rhizoprionodon taylori to capture stress by angling, to assess the accuracy and reliability of a portable Lactate ProTM analyser for measuring lactate. For both species, blood lactate concentrations determined using the portable analyser were highly correlated with increasing length of the stress period. Laboratory determination of plasma lactate values obtained by spectrophotometry showed a high degree of correlation with field determinations.  Since shark lactate levels can rise above those experienced by humans (for whom the meters are designed) it was also necessary to validate a method for dealing with values above the maximum detection limit. Whole blood diluted by 50% using acidified saline solution and chilled freshwater gave measured values of 58% and 49% of original values, respectively, allowing accurate estimations above the upper detection limit of the meter. These findings indicate that portable lactate meters are a useful tool to quickly and accurately evaluate blood lactate levels as a response to stressors in sharks in the field.