Heart Rate and Activity Measurements as Welfare Indicators in Aquaculture
Loggers used: DST milli-HRT, DST milli-HRT-ACT, DST centi-HRT and DST centi-HRT-ACT
Several recent papers explore the use of Star-Oddi’s leadless heart rate and activity loggers in Atlantic Salmon (Salmo salar), an important and valuable fish for aquaculture.
The papers highlight various practical aspects of measuring heart rate and activity in fish, including anesthetics, surgical approach, and recovery, as well as discussing how heart rate and activity measurements can provide information on diurnal rhythms, routine behaviors, stress levels and subsequent recovery trajectories. This information can be used as a continuous welfare indicator during aquaculture practices.
Real sea-cage examples include Gamperl et al. that measured Atlantic Salmon (Salmo salar) Cage-Site Distribution, Behavior, and Physiology During a Newfoundland Heat Wave  with DST milli-HRT-ACT and Warren-Myers F et al. that measured Heart Rates Across Season and During Crowding Events  in Atlantic salmon for over 5 months.
Swimming performance unaffected by bio-loggers
Hvas et al. published a paper in the journal Fish Biology exploring Heart Rates of Atlantic Salmon during a critical swim speed test and subsequent recovery . Star-Oddi’s DST milli-HRT heart rate and temperature loggers were implanted in Atlantic salmon post smolt at 12ºC. The difference between tagged and untagged fish was not found to be statistically significant during a swim trial, suggesting that the bio-logger did not affect swimming performance.
Before the swim speed test, heart rate peaked at 65 bpm during the day and nearly 40 bpm during the night. During the test, heart rate was raised approximately exponentially with swimming speed until a plateau was reached at the final speed prior to fatigue with a maximum of 85.2 +-0.7 bpm.
Equivalent results demonstrated with a larger logger
Zrini et al. corroborated Hvas et al’s swim results in a paper titled Validating Star-Oddi heart rate and acceleration data storage tags for use in Atlantic salmon (Salmo salar) . Here, activity parameters were measured in addition to heart rate and temperature during a critical swim speed test using Star-Oddi’s DST centi-HRT ACT loggers.
In addition to the swim speed test, they presented various other results, including details on tagging, results on a 6 week study in a 2.4kg salmon, double tagging fish with temperature and depth tags in addition to the DST centi-HRT-ACT loggers, quality assessment of the recordings and heart rate variability (HRV) measurements based on stored ECG data.
A valuable welfare indication tool
A third paper on this topic, published by Hvas et al. in 2020, evaluated Heart rate bio-loggers as welfare indicators in Atlantic salmon (Salmo salar) aquaculture . Apart from details on the surgical approach and recovery, including an x-ray photo of the implant (DST milli-HRT) in a 1.2kg Atlantic salmon shown below, the authors conducted a 13 week trial studying the growth of the fish, as well as crowding stress trials at week 11, 12 and 13. Their results highlight the potential of bio-loggers as a welfare assessment tool in aquaculture.
Heart rate and activity as proxies for stress in fish
Finally, Svendsen and Före et al. published two papers from an experiment where they use Star-Oddi’s DST milli-HRT, DST centi-HRT and DST centi-HRT-ACT loggers to evaluate Heart rate and swimming activity as stress indicators for Atlantic salmon (Salmo salar)  and Heart rate and swimming activity as indicators of post surgical recovery time of Atlantic salmon (Salmo salar)  in 55cm salmon kept at 4.2°C.
In addition to details on surgical approach and recovery the study included bloodwork and a stress experiment with lowering water level and chasing of the fish. Their results indicated that heart rate and activity can be used as proxies for fish stress.
Gamperl AK, Zrini ZA, Sandrelli RM. Atlantic Salmon (Salmo salar) Cage-Site Distribution, Behavior, and Physiology During a Newfoundland Heat Wave. Frontiers in Physiology Vol. 12 (1269)
Warren-Myers F, Hvas M, Vågseth T, Dempster T and Oppedal F. Sentinels in Salmon Aquaculture: Heart Rates Across Seasons and During Crowding Events. Front. Physiol. (2021) 12:755659.
 Hvas M, Folkedal O, Oppedal F. Heart rates of Atlantic salmon (Salmo salar) during a critical swim speed test and subsequent recovery. Journal of Fish Biology, (2021), Vol. 98(1).
 Zrini Z, Gamperl K. Validating Star-Oddi heart rate and acceleration data storage tags for use in Atlantic salmon (Salmo salar). Animal Biotelemetry, (2021), vol 9.
 Hvas M, Folkedal O, Oppedal F. Heart rate bio-loggers as welfare indicators in Atlantic salmon (Salmo salar) aquaculture. Aquaculture Vol 529, 2020.
 Före M, Svendsen E, Ökland F, Gräns A, Alfredsen JA, Finstad B, Hedger RD, Uglem I. Heart rate and swimming activity as indicators of post-surgical recovery time of Atlantic salmon (Salmo salar). Animal Biotelemetry, (2021), Vol 9.
 Svendsen E, Före M, Ökland F, Gräns A, Hedger RD, Alfredsen JA, Uglem I, Rosten CM, Frank K, Erikson U, Finstad B. Heart rate and swimming activity as stress indicators for Atlantic salmon (Salmo salar). Aquaculture, (2021), Vol. 531.
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