• re-identification
• metric learning
• recall
• neural network
• deep learning
• artificial intelligence
• triplet loss
• zebrafish

Fishes are widely used in scientific research due to some particular characteristics, like the strong similarity of their genome with the humans’ one or the very short life cycles; moreover, many of them provide simpler systems than other animals like mice and pigs for the study of complex processes. A typical task to be performed when studying different fish individuals during their life is re-identification, in which individuals of the same species under study must be recognized at different growth stages in order to understand the progress of the breeding, matching different weights and lengths obtained at different times. For this task, in some cases, it is enough to use GPS tags or microchips, but they’re not a feasible solution for tiny fishes like the Danio rerio (zebrafish), which is one of the most used animals in scientific research, in particular considering their juvenile stages. The purpose of this study is, therefore, to exploit a metric learning approach applied through a Triplet Loss Network to build software able to perform, starting from an input image, the re-identification task in order to ease the whole study process by providing the most similar identities to the researcher and decrease the selection pool for re-identification. With this approach, we were able to obtain a 96% recall@10 over a group of 30 identities and 44.57% over 180 identities taken from our own zebrafish dataset.