The generalized energy budget for fish (i.e., Energy Consumed = Metabolism + Waste + Growth) is as relevant today as when it was first proposed decades ago and serves as a foundational concept in fish biology. Yet, generating accurate measurements of components of the bioenergetics equation in wild fish is a major challenge. How often does a fish eat and what does it consume? How much energy is expended on locomotion? How do human-induced stressors influence energy acquisition and expenditure? Generating answers to these questions is important to fisheries management and to our understanding of adaptation and evolutionary processes. The advent of electronic tags (transmitters and data loggers) has provided biologists with improved opportunities to understand bioenergetics in wild fish. Here, we review the growing diversity of electronic tags with a focus on sensor-equipped devices that are commercially available (e.g., heart rate/electrocardiogram, electromyogram, acceleration, image capture). Next, we discuss each component of the bioenergetics model, recognizing that most research to date has focused on quantifying the activity component of metabolism, and identify ways in which the other, less studied components (e.g., consumption, specific dynamic action component of metabolism, somatic growth, reproductive investment, waste) could be estimated remotely. We conclude with a critical but forward-looking appraisal of the opportunities and challenges in using existing and emerging electronic sensor-tags for the study of fish energetics in the wild. Electronic tagging has become a central and widespread tool in fish ecology and fisheries management; the growing and increasingly affordable toolbox of sensor tags will ensure this trend continues, which will lead to major advances in our understanding of fish biology over the coming decades.

Remote bioenergetics measurements in wild fish: Opportunities and challenges ☆

The ability to produce estimates of the metabolic rate of free-ranging animals is fundamental to the study of their ecology. However, measuring the energy expenditure of animals in the field has proved difficult, especially for aquatic taxa. Accelerometry presents a means of translating metabolic rates measured in the laboratory to individuals studied in the field, pending appropriate laboratory calibrations. Such calibrations have only been performed on a few fish species to date, and only one where the effects of temperature were accounted for. Here, we present calibrations between activity, measured as overall dynamic body acceleration (ODBA), and metabolic rate, measured through respirometry, for nurse sharks (Ginglymostoma cirratum), lemon sharks (Negaprion brevirostris) and blacktip sharks (Carcharhinus limbatus). Calibrations were made at a range of volitional swimming speeds and experimental temperatures. Linear mixed models were used to determine a predictive equation for metabolic rate based on measured ODBA values, with the optimal model using ODBA in combination with activity state and temperature to predict metabolic rate in lemon and nurse sharks, and ODBA and temperature to predict metabolic rate in blacktip sharks. This study lays the groundwork for calculating the metabolic rate of these species in the wild using acceleration data.

Correlations of metabolic rate and body acceleration in three species of coastal sharks under contrasting temperature regimes

Swimming speeds and metabolic rates of semi-captive juvenile lemon sharks (Negaprion brevirostris, Poey) estimated with acceleration biologgers

We propose a novel signal processing method for a laser-interferometer-based displacement measurement system with significantly improved time resolution that enables us to measure transient state vibration with an instantaneous frequency of 100 MHz. In this method, a reference light is modulated by a sinusoidal waveform, and dynamic displacement is derived from the envelope curves of the interference signal. Using a phase modulator to emulate dynamic displacement with an instantaneous frequency of 100 MHz and a maximum peak-to-peak amplitude of over 100 nm, we confirmed that the proposed method can be used to measure fast dynamic displacement with 1 ns time resolution within 2.6 nm standard deviation.

https://iopscience.iop.org/article/10.7567/APEX.11.012501/pdf

Interference signal processing for dynamic displacement measurement with 1 ns time resolution

This paper presents an improved method for our recently proposed dynamic displacement measurement based on triangle phase modulation. The use of deep phase modulation eliminates the need for preliminary measurement of half-wave voltage V π for the phase modulator. We demonstrate displacement measurement with tens-of-nanometer scale taking place within a few micro seconds, where the temporal resolution is 33 ns. A long-term stability is also realized by employing a simple feedback control for the interferometer. The measurement precision is proved to be as high as that in the previously developed system that required careful preliminary measurement of V π .

http://iopscience.iop.org/article/10.1088/1361-6501/aa5d4b/pdf

Dynamic displacement measurement based on triangle phase modulation without preliminary measurement of half-wave voltage for phase modulator

We propose a simple and precise measurement method for high-frequency dynamic displacement It uses a fiber optic interferometer with a LiNbO3 phase modulator in the reference path The phase of the reference light is modulated with high-frequency triangle wave By monitoring the interference signal waveform, the change in the phase difference of the fiber interferometer and the displacement are measured without either complex calculation or complicated feedback system The proof-of-concept experiments show that displacement waveforms with relatively large amplitudes of several tens of nanometers are measured without distortion even when the vibration frequency is 1 MHz

https://iopscience.iop.org/article/10.1088/0957-0233/25/2/025202/pdf

Measurement of high-frequency dynamic displacement using light phase-modulated with triangle waveform

Understanding the energy expenditure of top predators is important because a collapse in them could trigger trophic cascades through ecosystems One such top predator, Japanese sea bass Lateolabrax japonicus, helps to balance the structure of the coastal marine ecosystem through predation In this study, accelerometry was applied to the Japanese sea bass to estimate its energy expenditure under natural conditions We attached accelerometers to five wild fish and measured metabolic rates such as the oxygen consumption rate (
 $${\dot{\text{V}}\text{O}}_{ 2}$$
 , mg O2 kg−1 min−1) using a swim tunnel Body beat frequency (BBF) was measured using the accelerometer The BBF was correlated with the tail beat frequency (TBF) by analyzing video recordings $${\dot{\text{V}}\text{O}}_{ 2}$$
 was related to swimming speed (U), TBF, and BBF We estimated the standard (459 kJ kg−1 day−1) and active (1240 kJ kg−1 day−1) metabolic rates when fish were not swimming and when they were swimming at the optimum swimming speed, respectively The energy required to compensate for the above metabolic rates are between 833 and 2756 kJ kg−1 day−1 using an assimilation efficiency of 07 and assuming that the growth rate is zero These costs were comparable to consuming one or two prey fish per day (eg, Japanese sardine: mean total length 155 ± SD 6 mm)

Estimation of metabolic rate from activity measured by recorders deployed on Japanese sea bass Lateolabrax japonicus

We demonstrate dynamic displacement measurement with phase-modulated light. Auto calibration using deep phase modulation makes the measurement independent of driving conditions of the modulator. Displacement of several tens nm for more-than-1-MHz vibration is successfully measured.

Dynamic Displacement Measurement System with Auto Calibration Using Deeply-Phase Modulated Light

We conducted calibration tests and field deployments of a newly developed micro CTD data logger on Japanese sea bass Lateolabrax japonicus to measure fine-scale movement and reconstruct micro-salinity profiles of estuarine habitat. In June, July and November 2013 and 2014, Japanese sea bass were caught in the Ohno (33° 12’ N, 131° 36’ E) and Oita (33° 16’ N, 131° 41’ E) Rivers in Oita Prefecture, Japan. In seawater tanks, the measurement drift for salinity was negligible over a 2 wk period (n = 8). Moreover, in the estuary, the values of standard seawater measured at preand post-deployment of sensors on fish were consistent to the first decimal place; therefore, sensor drift was negligible (n = 4, duration: 53−129 h). In situ measurements of depth, temperature, and salinity (conductivity) successfully revealed the microenvironment, and showed that Japanese sea bass often ascended from deep seawater to shallow freshwater at night. In all fish, over 99% of these excursions were completed within 10 min. The maximum duration of these excursions was about 6 h. This might be an effective strategy for temporal utilization of hypo-osmotic environments for foraging without physiological and energetic costs. This is the first report to clearly validate the accuracy of salinity measurement without sensor drift in free-ranging fish. The device and methods presented here can be applied to other euryhaline fish.

/pdf/micro-ctd-data-logger-reveals-short-term-excursions-of-1dyae7t55k.pdf

Micro CTD data logger reveals short-term excursions of Japanese sea bass from seawater to freshwater

We propose a measurement system for high-speed vibration displacement using an interferometer with triangle-wave phase modulation. Displacement less than ±45 nm by 1-MHz vibration is proved measurable within a standard deviation of 1.5 nm.

Naoyuki Miyata

Papers

Measurement of high-frequency dynamic displacement using light phase-modulated with triangle waveform

Estimation of metabolic rate from activity measured by recorders deployed on Japanese sea bass Lateolabrax japonicus

Dynamic Displacement Measurement System with Auto Calibration Using Deeply-Phase Modulated Light

Micro CTD data logger reveals short-term excursions of Japanese sea bass from seawater to freshwater

Precise measurement of high-speed vibration displacement using triangle-wave phase modulation