Thinking outside of the box: Monitoring heart rate and body temperature in rainbow trout, Oncorhynchus mykiss, using a bio-logging system

Abstract

Abstract Conducting true ecophysiological studies on fish has been difficult due to there being few methods for monitoring vital responses in natural environments. Techniques such as bio-telemetry and bio- logging show great promises in ecophysiological research, bringing researchers and animals out of the lab and one step closer to monitoring a fish’s physiology in its natural habitat. One potential with this approach is the possibility to conduct research on several fish at once during a long time period something that is not possible using the traditional hard wired monitoring techniques. This method also opens up possibilities for using larger tanks and even mesocosm settings when studying fish. In this study we test the capability for STAR-ODDI’s DST milli-HRT bio-logging system to monitor heart rate and body temperature in rainbow trout, Oncorhynchus mykiss. With this system, we were interested in investigating laboratory induced stressors while using heart rate as an indicator for distress. Our results show that grouping fish together is a surprisingly powerful stressor as it elicits a significantly stronger heart rate response than netting and chasing the fish. We also found that the fish were quite susceptible to confinement stress, where fish housed in a small tank traditionally used for hard wired studies (with very limited space for the fish to swim around in), had a significantly higher heart rate compared to fish housed in a larger tank. We also found that using a traditional chasing protocol to stress the fish, the scope of the heart rate (maximum – minimum heart rate) is underestimated by nearly 30% compared to using forced social interaction. These results give new insights in the stressful effects of laboratory environments on research fish and shows that the new STAR-ODDI system can be used successfully for these types of studies.