Technique de marquage en masse de civelles (Anguilla anguilla L.) par balnéation rapide dans le fluorochrome. Application au marquage à la tétracycline de 500 Kg de civelles

Abstract

Immersion of elvers (Anguilla anguilla L.) in an hyperosmotic solution (5% sodium chloride) for about 3 and a half minutes, and then immersing them in another solution containing 1% of tetracycline chlorhydrate (CHTC) or 2% of calcein (DCAF) during 3 and a half minutes exposure, resulted in a fast uptake of these two vital fluorochroms into the fish and a labelling of calcified organs (vertebrae and otoliths). Similar results were also obtained by placing the fish in a solution containing both 5% of sodium chloride and 1% CHTC or 2% DCAF for 3 and a half minutes. This osmotic shock is proposed as a practical technic for vital mass labelling of larvae or fry since the simultaneous osmotic shock and balneation is a significant improvement of the method by reducing considerably the time of contact between fishes and labelling solution. We propose an application of this technic for labelling 500 kg of elvers with tetracycline. The experiment needed one and a half day for five persons to carry out the operation. The results are of very good quality, since we obtain 100% of labelled specimens, 70% of which are highly labelled. Then it is possible to label an important quantity of fishes in a reduced time. The problem of in situ recognition of the labelled animals is discussed.