Separating wild versus stocking components in fish recruitment without identification data: a hierarchical modelling approach

Salmonid juvenile stocking programs are often poorly monitored due to the lack of identification between stocked and wild fish. In this study, a hierarchical Bayesian model is developed to take advantage of spatio-temporal variations of stocking and wild recruitment for estimating these two components despite the absence of identification data. It is first tested by means of simulated data, and then applied to the 37 years abundance data set of the Atlantic salmon population of the Allier catchment (France). Despite the absence of identification data, juvenile densities could be estimated and split into wild and stocked components. We found that the stocked juveniles contributed significantly to the total juvenile production, while the wild reproduction continued to provide an important contribution. This approach is encouraging and promising from a management advice perspective. It is flexible enough to accommodate for case study specificities and shows that long term monitoring of abundances can be useful to assess the impact of stocking programs even in the absence of direct means of identifying stocked vs wild fish.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author