Evaluation of visual implant elastomer and alphanumeric internal tags as amethod to identify juveniles of the freshwater crayfish, Cherax destructor

In the last few years there has been an increasing interest in using tradit ional animal breeding techniques to improve important traits such as growth rate in freshwater crayfish. However, a major impediment to such programs is an inability to reliably identify individuals or family groups for long periods because of the non-retention of external tags through ecdysis. Visu al implant elastomer (VIE) and visual alphanumeric (VIalpha) internal tags have proven useful in identifying finfish and amphibians. We evaluated the suitability of these two internal tags as a method to identify yabby (Chera x destructor) juveniles. Both tags proved useful in identifying juveniles b etween 0.1 and 4.6 g, with the VLE having the higher retention rate of the two tags (up to 92%, as opposed to 79% for the VIalpha tag). Mortality, as a direct consequence of tagging juveniles with the VLE and VIalpha tags was 13% and 11%, respectively. The ability to reliably identify C. destructor juveniles will increase the efficiency of selective breeding programs for t his species by allowing individuals and family groups to be pooled in growt h experiments, thereby decreasing the impact of confounding environmental e ffects. (C) 2001 Elsevier Science B.V. All rights reserved.