Usage of Internal Heart Rate Bio-Loggers in Arctic Fish

• Main Author: Kuchenmüller, Luis L.
• Format: Thesis
• Language: unknown
• Published: 2021
• Subjects: Arctic; Boreogadus saida; Climate change; polar cod
• Online Access: https://epic.awi.de/id/eprint/57258/; https://epic.awi.de/id/eprint/57258/2/MSc_LKuchenmueller.pdf; https://hdl.handle.net/10013/epic.45618b26-8472-471c-a384-e03aade26da8

By anthropogenic cause, even the most optimistic climate models (i.e. SSP1–RCP2.6) predict the Arctic system to heat up by more than 4°C until the year 2100, relative to the present. For ectothermic fishes, energy demand is fundamentally determined by temperature. As energy is physiologically limiting, their means to cope with climate change are limited. Therefore, understanding the impact of environmental changes on bioenergetics is imperative for the management of marine ecosystems. In recent years, the species-specific relevance of heart rate (ƒH) as a proxy for energy expenditure has been highlighted by the scientific community. The advent of bio-logging sciences has enabled ƒH observation in free swimming individuals. For Arctic fishes, however, harsh environmental conditions have restricted the pursue of ƒH bio- logging so far. To bridge this knowledge gap, we partnered with Star-Oddi, who developed a novel, internal ƒH and temperature bio-logger, calibrated for temperatures down to –5°C. In the present study, this bio-logger was implanted in the cold-adapted Arctic specialist polar cod (Boreogadus saida) and the ƒH bio-logging methodology was progressed in simulation of the ecologically relevant temperature range (i.e. 0 to 8°C) and free-roaming exercise (i.e. critical swimming speed (Ucrit) tests). Bio-logger positioning with exterior-facing electrodes and increase in sampling frequency from 100 Hz to 125 Hz improved electrocardiogram (ECG) quality significantly (p < 0.0001 and p = 0.02, respectively), due to decreased electromyogram (EMG) noise penetration and more distinct mapping of processed ECG characteristics. Under these settings, in the range of 0 to 4°C, in relation to 1180 manually calculated ECG traces, 80 ± 1.5% of on-board processed ƒH measurements displayed highest quality (i.e. QI = 0) with a confidence of ∆ƒH = 0.45 ± 0.56 bpm. Furthermore, 53 ± 5.5% of measurements displayed highest quality homogenously across swimming velocities up to Ucrit. Hence, present ƒH bio-logging methodology ...