Swimming activity and energetic expenditure of captive rainbow troutOncorhynchus mykiss(Walbaum) estimated by electromyogram telemetry

Abstract

Rainbow trout Oncorhynchus mykiss (Walbaum) are usually cultured at high densities to maximize production, but little is known about the physiological and behavioural consequences of high-density ®sh culture. The purpose of this study was to develop quantitative correlates of activity for ®sh held under conditions of increasing density. Fifteen hatchery-reared rainbow trout (mean fork length = 432.3 6 9.2 mm) were implanted with activity (electromyogram; EMGi) transmitters and randomly assigned to each of three replicate tanks. Original tank densities (15 kg m ±3 ) were then increased to 30 and ®nally to 60 kg m ±3 at weekly intervals by adding additional ®sh. Remote telemetry signals indicated that activity increased with increasing stocking density. Fish were relatively inactive during the middle of the day, with diel activity patterns not differing among treatments. Fish were more active during periods of darkness, with activity increasing with increasing stocking density. Relationships between swimming speed, EMGi activity and oxygen consumption were developed using a respirometer and used to estimate oxygen consumption of the ®sh in the density treatments. Average oxygen consumption estimates increased with increasing density treatments as follows: low density = 75.6 mg kg ±1 h ±1 ; medium density = 90.0 mg kg ±1 h ±1 ; and high density = 102.6 mg kg ±1 h ±1 . Telemetry permits quanti®-cation of the effects of increasing density on ®sh activity. Physiological telemetry devices may provide a useful tool for remotely monitoring animal welfare correlates under controlled conditions for ®sh exposed to different husbandry conditions and may prove a valuable tool for the aquaculture industry.

Fin condition and growth among rainbow trout reared at different sizes, densities and feeding frequencies in high-temperature re-circulated water

“…Instead, the difference in feed conversion ratio is possibly explained by higher metabolic rates at high densities. Cooke et al (2000) reported that rainbow trout oxygen consumption was 12% higher at 60 kg m -3 than at 30 kg m -3 , and Bé gout Anras and Lagardè re (2004) observed more swimming activity when rainbow trout were crowded (136 kg m -3 ) than when they were kept at lower densities. The lower feed utilisation at the high density in our experiment 2 may consequently be due to higher metabolic demands at 124 kg m -3 than at 45 kg m -3 , although aggression seemed more prominent at the low density, as indicated by the poorer condition of the dorsal fins.…”

Environmental impacts of coastal fish farming: carbon and nitrogen budgets for trout farming in Kaldbaksfjør7%%FONT_ERR%%ur (Faroe Islands)

“…Assuming an average swimming speed of 0.5 to 1.0 bl s -1 (Juell 1995, Cooke et al 2000, the total inorganic carbon release in the 77 d was from 33 to 44 t (Fig. 10).…”

Behavioural indicators of welfare in farmed fish

“…rainbow trout (Cooke et al 2000) and Atlantic halibut (Kristiansen et al 2004). Similarly, EMG profiles showed that sea bass reared at higher stocking density used on average 25% more energy than at lower stocking density (Scolamacchia 2009).…”

“…Several different tests have historically been used to quantitatively evaluate the swimming activity of fish (Beamish 1978). The ones most widely applied to assess the physiological condition of fish are critical swimming speed, U crit (Wolter and Arlinghaus 2004), recovery tests Jain et al 1998;Wagner et al 2004) and muscular activity measured via electromyogram (EMG) (Cooke et al 2000;McFarlane et al 2004;Chandroo et al 2005;Lembo et al 2008) or remotely measured by physiological telemetry sensors. EMGs give a quantitative estimate of both swimming speed and metabolic costs of activity during swimming (mostly due to oxygen consumption).…”