Fig. 1. Number of movements per hour in chorionated (chorion intact) and dechorionated (chorion removed) rainbow trout embryos over a period of 25 h. Negative numbers indicate times before hatch, time 0 indicates the 5-h interval in which hatching occurred (defined as when the embryo body was free of the chorion), and positive numbers indicate times post-hatch. Values are means ± s.e.m. (N=4). *Significantly different from chorionated values (P<0.05).