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.
Can we do CKMR outside the model and use the results as inputs into the assessment model?
Do we have to program CKMR in the initial model or can we add it easily afterwards?
What other features of an integrated assessment model do we need to consider that we might not otherwise (e.g., aging error)?
Will CKMR greatly increase computational times and are there efficient methods to implement CKMR (particularly in RTMB) including parrel computing??
How does CKMR interact with fine scale spatial temporal dynamics assessment model?
What are the current software and applications that integrate CKMR into assessment models and are there any substantial advantages identified?
What are the experiences with coding CKMR within integrated models?
Are tuna populations too large for CKMR?
Is CKMR cost effective for tuna?
Are there any fatal issues with CKMR for tunas that might come up that we have not really considered?
Will there be enough applications to make it worthwhile putting it in the general tuna stock assessment model, and should we put it in the first version, or perhaps wait until a later version?
Will FIMS adequately implement CKMR in the medium term or do we need to create a RTMB model?
Fisch, N. 2025. Expected improvements in precision when integrating opportunistic close-kin mark-recapture data into fisheries stock assessments. Fisheries Research, 281:107222. https://www.sciencedirect.com/science/article/abs/pii/S0165783624002868?via%3Dihub
Punt, A.E., Thomson, R., Little, L.R., Bessell-Browne, P., Burch, P., Bravington, M. 2024. Including close-kin mark-recapture data in statistical catch-at-age stock assessments and management strategies. Fisheries Research, 276: 107057. https://www.sciencedirect.com/science/article/abs/pii/S0165783624001218
Webber D, Parma A, Ianelli J, Hillary R, Eveson P (2025). sbt: Southern bluefin tuna stock assessment model. R package version 3.0.0, https://github.com/quantifish/sbt