Cognitive abilities were studied in rainbow trout, the first continental fish production in Europe. Increasing public concern for the welfare of farmed-fish species highlighted the need for better knowledge of the cognitive status of fish. We trained and tested 15 rainbow trout with an operant conditioning device composed of self-feeders positioned in front of visual stimuli displayed on a screen. The device was coupled with a two-alternative forced-choice (2-AFC) paradigm to test whether rainbow trout can discriminate 2-D photographs of conspecifics (S+) from different visual stimuli (S-). The S- were applied in four stages, the last three stages representing increasing discrimination difficulty: (1) blue shapes; (2) black shape (star); (3) photograph of an object (among a pool of 60); (4) photograph of another fish species (among a pool of 60). Nine fish (out of 15) correctly managed to activate the conditioning device after 30–150 trials. The rainbow trout were able to discriminate images of conspecifics from an abstract shape (five individuals out of five) or objects (four out of five) but not from other fish species. Their ability to learn the category "fish shape" rather than distinguishing between conspecifics and heterospecifics is discussed. The successful visual discrimination task using this complex operant conditioning device is particularly remarkable and novel for this farmed-fish species, and could be exploited to develop cognitive enrichments in future farming systems. This device can also be added to the existing repertoire of testing devices suitable for investigating cognitive abilities in fish.

对虹鳟鱼的认知能力进行了研究，虹鳟鱼是欧洲第一个大陆鱼类生产。公众对养殖鱼类福利的关注日益增加，突出表明需要更好地了解鱼类的认知状态。我们训练和测试了 15 条虹鳟鱼，该装置由位于屏幕上显示的视觉刺激物前面的自喂食器组成。该设备与两种可选的强制选择 (2-AFC) 范例相结合，以测试虹鳟鱼是否可以从不同的视觉刺激 (S-) 中区分同种 (S+) 的二维照片。S-分四个阶段应用，最后三个阶段代表越来越难区分：（1）蓝色形状；（2）黑色形状（星形）；(3) 一个物体的照片（在 60 个池中）；(4) 另一种鱼类的照片（在 60 种鱼群中）。9 条鱼（共 15 条）在 30-150 次试验后正确激活了调节装置。虹鳟鱼能够区分抽象形状（五分之五）或物体（五分之四）的同种图像，但不能区分其他鱼类。讨论了他们学习“鱼形”类别而不是区分同种和异种的能力。使用这种复杂的操作性调节装置成功的视觉识别任务对于这种养殖鱼类特别显着和新颖，并且可以用于在未来的养殖系统中开发认知丰富。该设备还可以添加到适用于研究鱼类认知能力的现有测试设备库中。