Modelling the bycatch of Anguilla marmorata using a generalized depletion model with an example from the Taiwanese glass eel fisheries for Anguilla japonica

•We quantify the impact of glass eel fisheries on Anguilla marmorata using a generalized depletion model with transit stock structure.•The fisheries had similar impacts on targeted A. japonica and the bycatch A. marmorata in exploitation rate and relative escapement.•Similarities in early life history characteristics could indicate possible ecological origins for the bycatch of A. marmorata.