Cooperative Fish and Wildlife Research Units Program: New York Cooperative Fish and Wildlife Research Unit
Education, Research and Technical Assistance for Managing Our Natural Resources

Close-kin mark-recapture is a powerful new method for the assessment of fish and wildlife populations. Unlike traditional mark-recapture techniques, the use of kinship as an identifying “mark” is robust to many forms of capture heterogeneity including variation in gear efficiency and tagging-based effects such as loss and differential mortality. In addition, close-kin methods can be applied to a wider range of sampling designs than traditional methods including single-occasion surveys, can provide retrospective historical abundance estimates, and can produce survival estimates from as few as two sampling occasions. We evaluated the ability of close-kin mark-recapture to provide estimates of abundance and adult survival, and then compared results to those from traditional mark-recapture. This analysis incorporated data from a three year study of lake resident brook trout (Salvelinus fontinalis) where individuals were both physically (Passive Integrated Transponder, PIT) tagged and genotyped for 44 de novo developed microsatellites with high throughput sequencing. Traditional mark-recapture estimates were derived using Pollock’s Robust Design, relying upon three primary “open” sampling occasions and four secondary “closed” occasions. We found that close-kin methods produced contemporary estimates of adult abundance and survival that were similar to those produced by traditional mark-recapture in both magnitude and precision. Furthermore, close-kin mark-recapture provided abundance estimates for multiple years prior to sampling and, when restricted to data from a single year, could still produce reliable abundance estimates for at least one and as many as three years. Retrospective abundance estimates corresponded with those from a separate historical two-sample mark-recapture dataset. This study provides support for the use of close-kin mark-recapture as a robust and sampling-efficient alternative to traditional mark-recapture methods of assessing population parameters.