Stimulus-specific development of learning ability during habitat shift in pre to post-recruitment stage jack mackerel

Abstract

Marine fishes often experience major habitat shifts during their life history, and previous studies have shown that the learning capability of fish change ontogenetically and in accordance with such habitat shifts. However, because all of these studies used a single type of conditioned stimuli (CS), they failed to detect qualitative changes in learning capability. Here we tested the hypothesis that preparedness for learning changes ontogenetically in jack mackerel Trachurus japonicus, which undergo a drastic change in habitat preference during their life history as they move from offshore pelagic waters to coastal and demersal rocky reefs. Groups of juveniles measuring 40 mm standard length (SL) (pelagic stage) and 60 mm SL (demersal stage) were conditioned to food rewards in response to three different CS; the presence of a surface structure, mid-water structure, and aeration. The results showed that small juveniles tended to become conditioned to the surface stimulus faster than they did to the mid-water stimulus. Conversely, large juveniles responded to the mid-water stimulus significantly more quickly than they did to the surface stimulus. These results suggest that stimulus-specific learning capability in T. japonicus changes ontogenetically, facilitating adaptation to their life-history strategy.

What to copy: the key factor of observational learning in striped jack (Pseudocaranx dentex) juveniles

“…Our previous study confirmed the ability for observational learning in jack mackerel (Trachurus japonicus) juveniles: fish that observed other individuals feeding at the aeration in an adjacent tank were conditioned to aeration as a stimulus to initiate feeding more quickly than fish that did not observe this conspecific behaviour (Takahashi et al 2012a). Here we tried to tease apart the process of observational learning and thus elucidate the essential mechanism of this social behaviour.…”

Can red sea bream Pagrus major learn about feeding and avoidance through the observation of conspecific behavior in video playback?

“…The size of fish may have induced the different results of observational learning between Experiment 1 and 2. Our previous studies showed that learning capability in fish changes ontogenetically and between conditioned stimuli [22,23]. We also found that the ontogenetic change of observational learning in T. japonicus coincides with that of social interaction [24].…”