White muscle lactate and pyruvate concentrations in rested flounder,Platichthys flesusand plaice,Pleuronectes platessaa: a re-evaluation of handling and sampling techniques

Rapid fixing of skeletal muscle by a ‘freeze-clamp’ technique results in up to a 3-fold lower lactate, a slightly higher pyruvate concentration and a 2- to 4-fold decrease in lactate/pyruvate ratio, to the lowest value yet recorded for fish muscle, when compared with the more usual method of direct immersion in liquid nitrogen. This is attributed to the faster cooling rate of freeze-clamped muscle minimizing ‘sampling anoxia’. Immobilizing fish either by anaesthetic or stunning produces no significant change in metabolite levels. It is concluded that it is relatively easy to handle quiescent flatfish, but light anaesthesia ensures no muscular activity.