Fingerprinting pike: The use of image recognition to identify individual pikes

摘要

It is difficult to determine the individual behaviour, growth, and survival of large predatory freshwater fish without stressing or even killing them. In this study, we tested the ability of an image recognition program to identify individual recaptured pike (Esox lucius) based on skin pattern. We and local anglers caught 209 pike individuals, including 45 recaptures, over the course of 1.5 years. The software correctly identified the image of all recaptured fish as already present in the database. Based on recaptures, we predicted a population of 560 pike in the lake and showed a much more comprehensive size structure than seen using standardized gillnet sampling which only yielded four pike. Angling and photographic identification involving reporting by citizen-scientists provided valuable temporal data in a non-invasive manner compared to traditional sampling. This methodology is based on freeware software and removes the need for any tagging equipment. It can potentially be used on other freshwater fish species and larger populations if the skin pattern is distinctive. However, it relies on the willingness of anglers to report their catches.