An Improved Method for Marking Crayfish

AbstractAn improved method of marking crayfish by refinement of punching holes in uropods and telson and clipping pleura was developed. The method, with at least 10 800 codes, provides an economical and practical approach to temporarily mark and individually identify crayfish, and is particularly useful for marking a large field sample. The method was tested by marking Pacifastacus leniusculus both in laboratory and river. The marks on the crayfish, ranging from 30 to 75 mm carapace length (CL), from the river lasted more than one year (or 2-3 moults). The table of 10 800 codes, in which most reliable codes are also indicated, is given to facilitate further application. The method is suitable for field studies on population size, density and dispersal or migration of animals as no significant effects on the survival of marked crayfish of >30 mm CL were found. However, care must be taken if the method is applied to estimate growth because a remarkable reduction (~20%) in the moult increment of CL after marking treatment was observed in crayfish, ranging from 33.4 to 46.6 mm CL, under laboratory conditions.