Conventional tags

The simplest, most inexpensive tags placed on marine animals are uniquely identifiable plastic tags, which are attached externally using a customised stainless steel needle. Fish release and recapture details provide information on animal dispersal and distribution. Fish condition, sex, size and weight are also sometimes recorded, and contribute to estimates of growth rates and changes in condition. The rate at which conventional tags are returned can be used to estimate both natural and fishing mortality rates, which are important inputs into fishery stock assessments. Thousands of conventional tags have been deployed on juvenile southern bluefin tuna off southern Australia to provide vital information for assessments of the population. Conventional tagging is 'fishery dependent' because it only collects information on fish in the area of, and captured by, the fishery.