Abstract
The state of the fish movement changes during the duration and it is shown that fish move to the low velocity zone or swim upstream. The acceleration and the velocity are the factors that effect on the swimming behaviors. The porpose of this study is to make clear that effects of the negative acceleration and the velocity during deceleration on the swimming behaviours of Nipponocypris Temminckii (Kawamutsu). The peak velocity was fixed, the negative acceleration and the latter velocity were changed. The swimming behaviors in open channel were recorded with a digital video camera. As a result, the threshold value of the negative acceleration that Nipponocypris Temminckii decides the migration direction is approximate -0.5(1/s2). Nipponocypris Temminckii migrated upstream when the negative acceleration was smaller than -0.5(1/s2). On the other hand, Nipponocypris Temminckii migrated downstream when the negative acceleration was greater than -0.5(1/s2). In addition, it is suggested that the deceleration trigger upstream migration. In contrast, there is little effects of the latter velocity on swimming behavior.
