Evaluation and use of a portable field kit for measuring whole-blood lactate in sharks

Measurement of lactate is becoming a common procedure in assessing the physiological effects of capture stress in sharks, although the necessity to measure the concentrations in the laboratory limits the ability for field assessments. Portable lactate analysers offer an alternative, but await validation against laboratory assays for sharks. The present study assessed the reliability of a portable Lactate Pro analyser for measuring whole-blood lactate in the school shark, Galeorhinus galeus, in the field. Laboratory determination of whole-blood and plasma lactate obtained by spectrophotometry was highly correlated with field determinations. Because shark lactate concentration can exceed the upper detection limit of the portable analysers, which were designed for mammalian use, a method for dealing with values greater than the maximum detection limit was evaluated. Whole-blood diluted by 50% with acidified saline solution, tap water and distilled water gave measured values of 55, 56 and 52%, respectively, of the original values, allowing accurate estimation of concentrations exceeding the upper detection limit of the analyser. These findings indicated that the Lactate Pro can be used to rapidly and reliably measure lactate for sharks in the field