Using Capture-Recapture Models to Estimate Angler Abundance in Southern Lake Michigan

Recreational fishing is socially, economically and environmentally important to southern Lake Michigan. State fisheries agencies in Illinois and Indiana conduct routine angler surveys to estimate effort and catch. Despite the popularity of angling, current survey methods and fishing licenses fail to estimate the number of anglers each year. Capture-recapture methods have been extensively used in population ecology to estimate animal abundance. Previous attempts to use capture-recapture methods in recreational fisheries have been preliminary and likely violate the assumptions of the models used. Therefore, the objective of our study was to collect unique identification information from anglers and use capture-recapture models to estimate the abundance of anglers. Data were collected through creel surveys of boat and shore anglers from May to October 2015. We implemented a Jolly-Seber model using Program MARK to estimate angler abundance as 3,926 and 4,169 in the Indiana and Illinois portion of Lake Michigan, respectively. Future work will incorporate seasonality in angling effort and possible migration to refine the precision of our estimates. Our results establish the utility of open capture-recapture models for angling populations.  Accurate estimates of angler abundance in recreational fisheries may help understand declining angling participation and identify opportunities to enhance these fisheries.