ESTIMATION OF FISH ACTIVITY COSTS USING UNDERWATER VIDEO CAMERAS

Swimming speed and activity costs of dace (Phoxinus eos x P. neogaeus) were estimated in the held using underwater video cameras. Activity c osts were estimated by converting swimming speeds and the number of mo vements into swimming costs. Average swimming speed ranged from 6.7 to 12.2 cm . s(-1) across 2 h periods and varied significantly among dat es and time of day. The time spent swimming by dace ranged from 616 to 17 640 s 2 h(-1). Activity costs per 2 h period ranged from 2.1 to 40 .2 J 2 h(-1) and were strongly correlated to the time spent swimming. Daily activity cost estimated using the cameras averaged 128.9 J day(- 1) and was equivalent to 1.7 times the standard metabolic rate. Activi ty cost predicted using a bioenergetic model in conjunction with indep endent estimates of consumption and growth rates averaged 138.8 J day( -1). This study indicated that swimming characteristics and activity c osts of dace varied significantly both within and among days. These an alyses also indicated that equally valid activity costs for fish in th e field can be estimated using video cameras and the difference betwee n consumption and growth rates. (C) 1996 The Fisheries Society of the British Isles