Abstract
Simple SummaryMeasuring metabolic rates in free-swimming fish would provide valuable insights about the energetic costs of different life activities this is challenging to implement in the field due to the difficulty of performing such measurements. Thus, the calibration of acoustic transmitters with the oxygen consumption rate (MO2) could be promising to counter the limitations observed in the field. In this study, calibrations were performed in rainbow trout (Oncorhynchus mykiss), and a subsample of fish was implanted with such a transmitter and then followed under aquaculture conditions. The use of acoustic transmitters calibrated with MO2 appeared to be a promising tool to estimate energetic costs in free-swimming rainbow trout, and for welfare assessment in the aquaculture industry.Metabolic rates are linked to the energetic costs of different activities of an animal’s life. However, measuring the metabolic rate in free-swimming fish remains challenging due to the lack of possibilities to perform these direct measurements in the field. Thus, the calibration of acoustic transmitters with the oxygen consumption rate (MO2) could be promising to counter these limitations. In this study, rainbow trout (Oncorhynchus mykiss Walbaum, 1792; n = 40) were challenged in a critical swimming test (Ucrit) to (1) obtain insights about the aerobic and anaerobic metabolism throughout electromyograms; and (2) calibrate acoustic transmitters’ signal with the MO2 to be later used as a proxy of energetic costs. After this calibration, the fish (n = 12) were implanted with the transmitter and were followed during ~50 days in an aquaculture facility, as a case study, to evaluate the potential of such calibration. Accelerometer data gathered from tags over a long time period were converted to estimate the MO2. The MO2 values indicated that all fish were reared under conditions that did not impact their health and welfare. In addition, a diurnal pattern with higher MO2 was observed for the majority of implanted trout. In conclusion, this study provides (1) biological information about the muscular activation pattern of both red and white muscle; and (2) useful tools to estimate the energetic costs in free-ranging rainbow trout. The use of acoustic transmitters calibrated with MO2, as a proxy of energy expenditure, could be promising for welfare assessment in the aquaculture industry.
Highlights
Fish use swimming for many activities and show a wide range of interspecific differences in the expression of their behaviors, which are linked to the ecology of species [1]
The metabolic rates (standard metabolic rate (SMR) and maximum metabolic rate (MMR)) are important indicators of fish metabolism, as well as the aerobic scope (AS)), allowing us to estimate the scope for aerobic performances [4,5]
Positive correlations were observed between Ucrit and body weight (BW) and to collect morphometric data (TL) (R2 = 0.55 and 0.66, respectively; p < 0.001 for both)
Summary
Fish use swimming for many activities (e.g., to escape from predators, catch prey, migrate, reproduce) and show a wide range of interspecific differences in the expression of their behaviors, which are linked to the ecology of species [1]. The oxygen consumption rate (MO2 ) during swimming activity is considered an indicator of energetic costs [2,3] In this sense, the metabolic rates (standard metabolic rate (SMR) and maximum metabolic rate (MMR)) are important indicators of fish metabolism, as well as the aerobic scope (AS)), allowing us to estimate the scope for aerobic performances [4,5]. Great interest has been oriented toward the development of indirect methods for assessing the energetic demand in free-ranging fish both in nature and aquaculture environments [11,12,13,14,15] From this perspective, the continuous development of telemetric technology has provided a useful contribution for remotely monitoring fish in their environment via physiological tags (e.g., accelerometer tags, electromyogram tag or heart rate sensor) [13,16,17]
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