Gross mismatches between salmonid stocking and capture record data in a large Alpine lake basin in Northern Italy suggest a low stocking effectiveness for an endangered native trout

Abstract

Stocking of native and non-native fish species is a widespread practice commonly used to enhance inland recreational fisheries, appropriate when intense harvesting and the degradation or lack of suitable habitat decrease the abundance of the managed species below carrying capacity. In spite of its popularity, this practice is often poorly informed by scientific information. Salmonids are arguably the most popular and commercially valuable freshwater fishes being managed for recreational fisheries. Stocking of both native and non-native taxa has been practiced for almost two centuries in Europe, dramatically altering the structure and function of riverine and lacustrine ecosystems. In the Verbano-Cusio Ossola Province, northern Italy, within the Lake Maggiore catchment, we measured large numerical mismatches between stocking of cultured native (Salmo marmoratus) plus non-native trout taxa (S. trutta, S. ghigii, Oncorhynchus mykiss) and the number of fishes captured by local anglers. These observations highlight the need for future studies to estimate the stocking effectiveness of S. marmoratus, a critically endangered species of significant cultural and economic value.