This is the first time fish have demonstrated this ability.
In the study, archerfish were presented with two images of human faces and trained to choose one of them using their jets. The fish were then presented with the learned face and a series of new faces and were able to correctly choose the face they had initially learned to recognise. They were able to do this task even when more obvious features, such as head shape and colour, were removed from the images.
The fish were highly accurate when selecting the correct face, reaching an average peak performance of 81 per cent in the first experiment (picking the previously learned face from 44 new faces) and 86 per cent in second experiment (in which facial features such as brightness and colour were standardised).
In other news, an international study led by the Higher Council for Scientific Research (CSIC) in Spain has identified a genetic mechanism that allows for producing larger fish in aquaculture without increasing their levels of body fat or changing their lipid profile.
The results should help further research of the factors that control the growth and feed efficiency of cultured fish and so will open new avenues towards sustainability of animal production systems.
"By blocking the hormone system in zebrafish, neural systems that regulate satiety are modified, so that these animals could eat more. When fed with the same amount of food as the unmodified fish, its weight increases by up to 60 per cent and its length by 15 per cent, showing greater feed efficiency," explained CSIC researcher José Miguel Cerda, the Institute Aquaculture Torre de la Sal.