Annotated image dataset for automated fish counting in a passage channel (Astyanax lacustris)

Annotated image dataset for fish detection and counting by computer vision (single class, YOLO format). Built from eight videos of Astyanax lacustris (yellowtail tetra, "lambari") passing through a monitored PVC channel during a commercial-handling counting simulation (campaign canaleta_pvc_260717, 17 July 2026, at the partner farm Lambari Itumbiara, Itumbiara-GO, Brazil). It contains 776 images, 5,649 bounding boxes and 191 negative (fish-free) images (24.6%), split by source video into train (519), val (104) and test_normal (153). It includes a manifest with per-file SHA-256, data.yaml and build reports. It corresponds to the dataset of the training run reported in the associated master's dissertation (run t_20260724T140336_d13f3a). Observational recording of the producer's routine commercial handling; no experimental procedure was imposed on the animals.