Journal Article Environmental stimuli improve learning capability in striped knifejaw juveniles: the stage-specific effect of environmental enrichment and the comparison between wild and hatchery-reared fish

Makino, Hirona  ,  Masuda, Reiji  ,  Tanaka, Masaru

81 ( 6 )  , pp.1035 - 1042 , 2015-11 , Springer Japan
First online: 02 September 2015
Hatchery-reared fish often show different behavioral traits from their wild counterparts, possibly due to the lack of environmental stimuli. Here, we aimed to reveal the stage-specific effect of environmental stimuli on the development of learning capability in striped knifejaw Oplegnathus fasciatus. The fish were raised for 15 days (50–65 days post-hatch) or 30 days (50–80 or 90–120 days post-hatch) in either conventional rearing tanks (control) or in a structurally enriched tank containing bricks, artificial sea grass, and plastic pipes (enriched environment), and were examined for learning capability using Y-maze reward conditioning. The learning capability of wild juveniles was also examined, and their scores were compared with those of hatchery-reared fish (which we previously reported). Only fish in the 50–80 days post-hatch enriched-rearing group showed significantly better scores than those in the control group, and wild fish performed better than hatchery-reared ones. The present results indicate that, although the learning capability of hatchery-reared fish is inferior to that of wild fish, exposure to a highly structured environment at an appropriate stage promotes the development of learning capability. Such environmental enrichment can potentially improve the viability of hatchery-reared fish when they are released into the wild.

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