Traditional tagging programs for tunas have several issues due to the practicality of implementing them that can impact their reliability, particularly if they are not well designed. These include tagging related mortality, tag loss, reporting rates, and tag mixing. A well-designed tagging study should minimize these issues and estimate their effect so they can be taken into consideration when the data is analyzed.
Close-Kin Mark-recapture (CKMR) is an alternative that eliminates or reduces the issues with traditional tagging data. This approach uses relationships between individuals (e.g., parent offspring, half sibling, etc.) to “tag” and “recapture” fish. CKMR does not require a fish to be released alive so tagging related mortality does not occur. Recaptures are through genetic samples so reporting rate is 100% and there is no tag loss. It also allows more sampling opportunities since the fish do not have to be released alive. Finally, the mixing rate might be higher because mixing occurs from when an individual is spawned until it is caught and therefore includes egg and larval dispersal and possibly juvenile and adult movement. Although, any effect of family relationship on the probability of capture may affect the results.
CKMR is a new approach in fisheries stock assessment and there is limited experience using the method. Most of the applications are individual case studies or ad hoc modifications of existing general models. There is yet to be a general stock assessment model that has a comprehensive CKMR integrated into the software.