Complementary use of density estimates and hunting statistics: different sides of the same story?

Abstract

The use of hunting statistics for population monitoring has often been criticized because such data are affected by several sources of error. Still, for many harvested populations, hunting statistics are the only available data source and cautious use of such data may be valuable for management. Here we assessed to what extent long-term monitoring of Svalbard rock ptarmigan spring densities and hunting statistics (bag size and proportion of juveniles in the hunting bag) reflect similar population fluctuations. We found a decreasing trend in both bag size and proportion of juveniles in the bag, but no trend in ptarmigan spring densities. However, annual fluctuations of ptarmigan spring density and bag size were correlated. Together, these time series indicate that both population abundance (bag size) and recruitment (proportion of juveniles in the bag) are decreasing, but the reproductive component fraction (density of territorial males) is not yet compromised. This biological interpretation remains, however, uncertain due to lack of hunting effort data. Monitoring programs using hunting statistics should therefore critically discuss and evaluate what the hunting statistics reflect and fine-tune the hunter data collection to obtain maximum biological relevance. Still, our results illustrate that the combination of population estimates and hunting statistics can provide more nuanced information about the population status than the density estimates alone.