Shark Tagging: A Review Of Conventional Methods and Studies

The tagging of sharks using conventional tags has long been recognized as a valuable means for studying various aspects of their life history, migrations and movements, and population structure. Conventional tags are defined as those that can be identified visually without the use of special detection equipment. Tagging studies specifically targeting sharks began in the late 1920's, and today numerous cooperative shark tagging programs exist worldwide. Cooperative programs depend on the joint participation of scientists and public volunteers to accomplish research objectives. Benefits and problems of these programs are discussed using the tagging methodologies, protocols, and results of the National Marine Fisheries Service Cooperative Shark Tagging Program. An additional 63 shark tagging studies and programs of all types are reviewed. Information useful for behavioral, biological, and fishery management studies can be derived from data resulting from these studies, including species and size composition, sex ratios, spatial and temporal distribution, migrations, movement patterns, rates of travel, delineation of pupping grounds, distribution of maturity intervals, indices of relative abundance, and recognition of individuals. Specific tagging experiments can be designed to provide additional data on age and growth, homing and site fidelity, dispersal rate, residence time, movement rates, tag shedding, and population parameters (e.g. size, mortality, recruitment, exploitation, interaction rates, and stock identity). Sources of bias inherent in tagging and recapture data include mortality, variation in tagging effort and fishing pressure, non-recovery and non-reporting of tags, and tag shedding. Recent advances in tagging methodologies that complement and extend conventional tagging studies will further our knowledge on shark movements and migrations, particularly in the areas of resource utilization and management, space utilization, and population dynamics.