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CEMG2 Series EMG Transmitters

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  • Overview
  • Features
  • Explanation
  • Specifications
  • Applications

Based upon its predecessor (the EMG electromyogram transmitter), the coded electromyogram (CEMG2) transmitter represents one of the components of a field-proven system which enables researchers to record physiological data from free-swimming fish.

Designed to be mounted either externally or internally, CEMG2 transmitters measure muscle activity using probes inserted into the musculature of the fish. The CEMG2 Series provides you with a powerful quantitative estimate of the energetic costs associated with physical activity.

EMG tags allow researchers to:

  • investigate the metabolic costs associated with such activities as tail-beat frequency
  • calibrate to oxygen consumption through a series of measurements taken during periods of controlled activity
  • calculate and compare the energetic costs of various activities

Lotek has introduced a "field-proven" biotelemetry system designed to obtain, transmit and record the electromyograms (EMGs) produced in muscle activity of free-swimming fish as quantitative indicators of overall fish activity both in the laboratory and the field. EMGs are sampled, digitized, encoded and transmitted as ID plus Sensor Data; the intensity of muscule activity is represented by a relative value between 0 and 50. Transmitted EMG data is detected, decoded and stored by a radio receiver (SRX-DL3, SRX 400A W32, SRX 600 or SRX 800).

Active swimming at different speeds is only one element in determining the intensity of fish muscule activity and its underlying energy costs. Starts from rest and changes in speed, direction or position, all of which require acceleration or deceleration of fish mass, can be much more energy demanding than steady-state swimming. These sometimes scarcely noticeable changes of pace and direction that many fish make constantly, can be highly significant in the total movement energetics of daily activity regimes.

The CEMG2 biotelemetry system developed at Lotek can detect, transmit and store EMG data for post analysis of such movements. Electromyograms (EMGs) are records of bioelectric potentials that are strongly correlated with the strength and duration of muscle contractions. Indeed, EMG values averaged over time can be used directly as quantitative indicators of the intensity of fish activity. EMG values can be "calibrated" in terms of fish oxygen consumptions measured over periods of spontaneous activity or over the same times in swims of selected speeds and durations. This in turn allows investigators to obtain quantitative estimates of the metabolic costs of activity by wild fish under field conditions.

The System
The system is designed for extended duration studies of the swimming activity, behavior patterns and/or estimates of the energetics of activity in free-swimming fish both in the laboratory and in the field. All components of the system are compact, portable and rugged to facilitate use in the field. Removal of the system from the field is not necessary for retrieval of data. Data may be stored and averaged as required for particular applications and later transferred via RS-232 communication port to a laptop or remote computer via telephone, cellular or satellite link.

The system consists of:

  • One or more CEMG2 transmitters
  • An SRX radio receiver/datalogger (SRX-DL3, SRX_400A W32, SRX 600, SRX 800)
  • Antennas appropriate to the experiment/location
  • File management and communication support software

The implantable transmitter(s) (see specifications) contains an instrumentation amplifier for low voltage, high impedance EMG signals from the Teflon coated, stainless-steel electrodes embedded in the muscle. Signals are processed through an integrator, digitized and a coded radio sequence is transmitted representing unique identity and data (relative number between 0 and 50) Increasing muscle activity (EMG production) results in a corresponding increase in relative indicator. Operating life can be over one year based upon battery size and burst rate. Up to 212 unique IDs can be placed upon a single frequency. Consult with your Lotek representative to determine the optimum number of transmitters per frequency and burst rate. In general, a 2 second burst rate is recommended.

  Physical Specifications Calculated Life (days)*
Model Number Size
(dia x l)
2.0 sec
5.0 sec
CEMG2-R11-18 11 x 54 10 4.9 51 63
CEMG2-R11-25 11 x 62 12 5.7 74 89
CEMG2-R11-35 11 x 72 15 6.7 104 125
CEMG2-R16-25 16 x 62 25 13 178 215
CEMG2-R16-33 16 x 70 29 15 245 296
CEMG2-R16-50 16 x 87 33 16 356 430

Transmitter operational life varies based in part, upon environmental conditions to which they are subjected. For this reason, typical values for operational life may be specified, with guaranteed operational life defined as 80% of the typical value. All transmitters are guaranteed to meet stated specifications upon shipment. Any Lotek transmitter found to be defective, with respect to material, workmanship or guaranteed operational life, effective from date of shipment, will be repaired or replaced.

Radio telemetry has been used to obtain relative or qualitative estimates of fish activity, for the most part, through the use of mercury switches. The CEMG2 transmitter, in conjunction with the SRX receiver/dataloggers and peripherals, offers an incomparable means of quantitatively addressing activity and energy budget issues both in the lab and in the field, without the need for mercury switches.

Applications include:

  • assessing velocity barriers such as those presented in natural points of difficult passage, or man made barriers including culverts, bridges, dams, etc.
  • assessing the effect of temperature or chemical plumes
  • designing bypass structures by examining in-situ energy expenditures of fish in response to flow rate changes and structural design changes in ladders, weirs, etc.; and
  • effectively monitoring and assessing entrainment in-situ through use of the CEMG2/SRX system on a continuous basis.

Further information regarding surgical procedures, placement of transmitter, operations in the laboratory and the field can be found in:

EMG References

Weatherley, A.H., Rogers, S.C., Pincock, D.G. & Patch, D.G. (1982). Oxygen consumption of active rainbow trout, Salmo gairdneri Richardson, derived from electromyograms obtained by radiotelemetry. J. Fish Biol. 20, 479-489.

Kaseloo, P.A., Weatherley, A.H., Lotimer, J.S. & Farina, M.D. (1991). A biotelemetry system for transmission of electromyograms in fish as indicators of physical activity. J. Fish Biol.

McKinley, R.S. (1991). Measurements of activity and oxygen consumption for adult lake sturgeon in the wild with radio transmitted EMG signals. Ontario Hydro Research Division. Report CB91-1-K

Thorstad, E.B., Okland, F., FInstad B. & McKinley, R.S. (1998). Development and use of EMG telemetry transmitters recording fish muscle activity. Proceedings of the Nordic Conference on Fish Passage.

Okland, F., Thorstad, E.B., Finstad, B. & McKinley, R.S. (1998). EMG radio transmitters - a new method to record activity, swimming speed and migratory costs in upstream migrating salmonids in situ. Proceedings of the Nordic Conference on Fish Passage.