Validating Star-Oddi heart rate and acceleration data storage tags for use in Atlantic salmon (Salmo salar)

Abstract

AbstractBackgroundData storage tags (DSTs) record and store information about animals and their environment, and can provide important data relevant to fish culture, ecology and conservation. A DST has recently been developed that records heart rate (fH), electrocardiograms (ECGs), tri-axial acceleration and temperature. However, at the time of this study, no research using these tags had been performed on fish or determined the quality of the data collected. Thus, our research asked: do these DSTs provide reliable and meaningful data? To examine this question, Atlantic salmon (1.4 ± 0.7 kg) were implanted with DSTs, then swam at increasing speeds in a swim tunnel after 1 week of recovery. Further, in two separate experiments, salmon (2.4 ± 0.1 kg) were implanted with DSTs and held in a large tank with conspecifics for 1 week at 11 °C or 6 weeks at 8–12 °C.ResultsExternal acceleration (EA) and variation in EA (VAR) increased exponentially with swimming speed and tail beat frequency. The quality index (QI) assigned to ECG recordings (where QI0means very good quality, and QI1,QI2and QI3are of reduced quality) did not change significantly with increasing swimming speed (QI0 ~ 60–80%). However, we found that the accuracy of the tag algorithm in estimatingfHfrom ECGs was reduced when QI>0. Diurnal patterns offHand EA were evident from the time the salmon were placed in the tank. Heart rate appeared to stabilize by ~ 4 days post-surgery in the first experiment, but extended holding showed thatfHdeclined for 2–3 weeks. During extended holding, the tag had difficulty recording lowfHvalues < 30 bpm, and for this reason, in addition to the fact that the algorithm can miscalculatefH, it is highly recommended that ECGs be saved when possible for quality control and so thatfHvalues with QI>0can be manually calculated.ConclusionsWith these DSTs, parameters of acceleration can be used to monitor the activity of free-swimming salmon. Further, changes infHand heart rate variability (HRV) due to diurnal rhythms, and in response to temperature, activity and stressors, can be recorded.