Ontogenetic changes in the spatial learning capability of jack mackerel Trachurus japonicus

Ontogenetic changes in learning capability were studied in jack mackerel Trachurus japonicus juveniles ranging from 20 to 95 mm standard length (L_S) collected from either pelagic or coastal habitats. Simple spatial and reversal learning tasks were used to estimate learning capability. There was no size dependence in the scores of simple reward conditioning using a Y-maze, whereas the scores of reversal learning tasks showed a clear sigmoidal curve of increase with an inflexion point at 51.7 mm L_S. The increase in this learning capability coincided with the size at which juveniles recruit from offshore pelagic to coastal rocky habitats.