Detecting changes in distribution and abundance using harvest data in two sympatric bear species in Southeast Alaska

Monitoring wildlife populations in remote landscapes is challenging due to the difficulties of conducting field surveys. However, harvest data, which are routinely collected by management agencies, offer valuable insights into population trends. Brown bear Ursus arctos and American black bear U. americanus are commonly harvested game species with specific management objectives, regulations, and regimented reporting requirements in southeast Alaska (SEAK). In recent decades, changes in the distribution and abundance of these species have been reported along the coast of SEAK. We synthesized brown and black bear spatio‐temporal mortality data from 1995 to 2022 to assess changes in the abundance and distribution of each species. Using a two‐stage state‐space Bayesian model with age‐at‐harvest data, we estimated abundance over time for both species on the central and northern mainland coast of SEAK. We also analyzed hunter effort and success data and examined the spatial clustering of harvest locations. On the central mainland coast of SEAK, we found an increase in brown bear hunter success in sync with a decrease in hunter effort, an increasing trend in the harvest and a stable estimate of the population. In the area, we found that black bear hunter success rates were generally stable, efficiency increased as hunters spent fewer days to harvest a bear, and we estimated a declining trend in the black bear population. Spatial statistical analysis revealed that brown bear harvest locations clustered around black bear harvest sites, supporting a shift in harvest patterns of the former species toward the southeast where the changing distribution patterns were reported. These findings suggest that hunters along SEAK's central mainland coast are encountering brown bears more frequently and support the observations of increasing brown bear abundance relative to black bear availability. This study highlights the value of integrating spatio‐temporal mortality data to detect changes in sympatric species distributions.