Uses of each technology
- Dual mode
When it’s used:
Acoustic biotelemetry is generally used to monitor those creatures living or moving in deep water or salt water habitats. Lotek offers acoustic systems to track a wide variety of marine inhabitants, such as salmon, trout, plaice, cod, crabs, sea turtles, and many others.
Acoustic Telemetry Systems:
|Transmitter||L-AMT Series||MAP Series||R Series||MM Series|
|Autonomous Receiver||WHS4250||WHS3000 Series||WHS2000||All MAP and R Code Receivers|
|Cabled Receiver||LHP Series Hydrophones|
|MAP600 Series Receivers|
|Software||WHS4250 Host||MAPHost||WHS2000 Host||MAP/R Code Software|
|Smallest Transmitter Weight (In Air)||0.3g||0.9g||5.5g||5.5g|
|High Speed Mobile Tracking||X||X|
|Temperature, Pressure and Motion Sensors||X||X|
|Signal Collision Immunity||Medium||High||Low||High|
|Sample Rate for Transmissions||High||High||Low||High|
|Transmitter, Receiver, and Software Available||X||X||X||X|
Unique Identity Codes
(The Long & Short of Acoustic Telemetry)
Listen to a JSATS tag:
Listen to a MAP tag:
Listen to an RCODE tag:
How it works:
Seawater covers more than 70% of the Earth’s surface, and is home to many of its creatures. But salt water presents unique challenges to those wishing to track marine wildlife. Radio waves are highly absorbed by salt water, making them a poor choice for sending messages through the ocean.
Sound waves, on the other hand, are not similarly impeded by seawater. What’s more, sound can travel more than 4 times faster in water than in air, allowing near real-time listening over long distances with the right tools. For these reasons, acoustic signals are the preferred communication tool for researchers who wish to track fish and wildlife in marine habitats in real time.
As with radio, acoustic telemetry requires transmitters to send signals and receivers to hear them. In between those two, one additional piece of equipment is used in acoustic telemetry. A hydrophone is a type of underwater microphone that receives acoustic signals, which are then either stored or converted into radio signals for rapid transmission through the air to the receiver on the shore.
Lotek has expanded the boundaries of acoustic telemetry as well. Our powerful MAP System employs CDMA coding (similar to that found in cell phones) to allow the simultaneous detection of countless unique individuals on a single acoustic frequency. Equally innovative is the MAP System’s ability to discern its tags reliably even in the acoustically noisy ocean environment.
Why so many acoustic telemetry systems?
Three different types of acoustic telemetry systems for fisheries monitoring have evolved over the years from specific research questions, data requirements and environmental constraints.
So what’s the long and short of acoustic telemetry?
Each system evolved to address a specific application space. Outside the respective application space, each system will be less effective than the system designed for that particular application space. No one system performs optimally in all application spaces.
Tracking coastal migration patterns, characterized by relatively low noise and low traffic requires low cost receiving systems that use very little energy. Attributes of low cost and low power make deployment of acoustic “gates” or “curtains” practical because a single gate could consist of upwards of 100 receivers, each requiring ships and crew for deployment and retrieval for data download or battery replacement. Under these conditions, a simple, single frequency analog receiving system is optimum. Individual transmitter identities are generated through a unique sequence of pulses in time. The total number of unique IDs is a function of the number of pulses that make up the ID and the number of available/allowable time delays between pulses. For example, one R64K codeset ID is made up of a unique sequence of eight pulses with the entire set consisting of over 64,000 unique IDs. In order to mitigate the impact of signal reflection or reverberation, the eight pulses are spread out in time requiring over two seconds for transmission of a single ID.
Tracking in rivers or estuaries characterized by high velocity, high noise or high traffic requires a more robust receiving system and corresponding encoding method, resulting in relatively higher power requirement and cost than a simple analog system. Simultaneous detection and tracking of multiple tagged individuals at high rates, perhaps outfitted with depth, temperature or motion sensors under high noise conditions requires a more sophisticated digital receiving system similar to those used to manage cell phone traffic. Digital systems can pack a huge amount of data within a very short pulse, but require more power to detect and decode that information in real time. A three pulse MAP code is transmitted in less than ¼ second and allows for over 80,000 unique IDs.
In order to track the smallest fish and minimize the impact of tagging on survival, a system was developed to produce the smallest possible tag. JSATS Juvenile Salmon Acoustic Telemetry System was developed to track thousands of salmon smolts in the Columbia River for the U.S. Army Corps. of Engineers. In an environment also characterized by high velocity, high noise and high traffic, the JSATS system uses a single 31-bit digital pulse emitted in less than 1 millisecond and provides over 65,000 unique IDs.
How it works:
Radio is an excellent type of signal to use when tracking animals, in part because radio waves can transmit information rapidly and for long distances in air. Radio signals can also be made to transmit effectively in fresh water, but not through salt water.
To track an animal with radio, you need to equip it with a device, called a transmitter, that can send you a signal. In addition, you yourself need to be equipped with a device, called a receiver, that can detect that signal. Both devices have antennas attached to them to aid them in their tasks.
To track more than one subject at the same time, you need a way to give each one a unique signal that you can identify. In conventional biotelemetry, radio signals are made unique by varying either their frequency or their “beeping” rates. Both strategies have their limitations. One of Lotek’s great innovations in biotelemetry has been the introduction of the digitally encoded radio tag, which transmits a unique numerical code that differentiates it from all other tags, even those transmitting on the exact same frequency. This allows a researcher to track hundreds of subjects on any one frequency, which has greatly improved scientists’ abilities to increase the sample sizes of their studies.
Another significant advance has been our miniaturization of radio tags. We now offer digitally encoded radio tags that are tiny and light enough to be used on fish as small as 10 centimeters (3.9 inches) long. Quite an improvement over the early days of biotelemetry, when the transmitters themselves were almost that long!
When it’s used:
Radio biotelemetry can be used in water, on land or in the sky. A huge range of animals can be tracked with this technology: Lotek has radio tags and collars that can be placed on fish, birds, mammals and amphibians of almost any size, from tiny salmon smolts to full-grown elephants.
How it works:
Smaller creatures like fish can also be equipped with devices that record and store tracking information for retrieval at a later date. Known as archival or data storage tags, these instruments are placed in or on fish and act like tiny computers, constantly sensing and recording the environmental conditions that they travel through. Incredibly, the tags can take new readings as frequently as every 4 seconds if desired. Despite their small size, Lotek archival tags have batteries and memories with enough capacity to collect data for several years. They are also constructed to ensure reliable operation at depths of up to 2000 meters and temperatures as low as -5° C.
Archival tags measure water temperature, water pressure and light levels. From these, researchers can reconstruct an impressively detailed daily history of a fish’s travels. The pressure reading reveals its precise water depth, and the light measurements contain enough information to allow calculation of the fish’s latitude and longitude, using an elegant process known as light-based geolocation. The unsurpassed light sensitivity of Lotek archival tags ensures that users can gather the most accurate geolocation estimates possible.
As with some types of GPS work, archival tag research relies on equipment retrieval for its success. Some tags have labels that offer rewards to whoever catches the fish, and it’s not unusual for these rewards to be claimed from surprisingly faraway locations. Lotek has also introduced a second retrieval option: archival tags with “pop off” mechanisms. Like remote-release GPS collars, these tags can be programmed to detach from their subjects at specific times. Once detached, they float to the surface of the water and emit signals to facilitate recovery.
When it’s used:
Archival tags offer an excellent alternative for monitoring aquatic, avian and terrestrial species when radio or acoustic telemetry is not possible or practical. Lotek tags have been used on such diverse species as tuna, salmon, cod, plaice, sharks, sablefish, lake trout, turtles, penguins, albatross and platypuses.
How it works:
In radio and acoustic systems, signals travel from a transmitter to a nearby receiver. By contrast, animals equipped with GPS, Argos and Iridium collars do most of their communicating with satellites in outer space. The collars take advantage of services afforded by two multiple-satellite systems, the “Global Positioning System” (GPS) and the “Advanced Research and Global Observation Satellite” (Argos). Each system operates in a unique way: GPS satellites transmit positional data to receivers on the ground, while Argos satellites receive positional and other data from transmitters on the ground, and relay that information back to ground stations situated elsewhere. We manufacture collars that can utilize either system to full advantage.
For example, our GPS collars can take positional snapshots at numerous pre-defined intervals all day long. The first of their kind, these collars also boast impressive data storage capabilities, keeping a record of the animal’s migratory history until the collar and/or its information is retrieved. Never before have biologists been able to obtain such a rich and accurate mapping of an animal’s movements, to within an error of less than five meters.
Another exciting innovation has been the addition of remote-release capabilities to our collars. Biologists can now activate a mechanism that automatically detaches the data-rich collar from the animal. This eliminates the need to recapture the creature at the end of the study, reducing both the expense to the researcher and potential trauma to the animal. Once detached, the collar changes its radio beacon signal to help the researcher find it.
When it’s used:
GPS, Argos and Iridium systems are used to track animals such as coyotes, wolves, caribou, sheep, cattle, mountain lions, bears, moose, deer and cougars, as well as sea turtles, marine mammals and birds. Recently, Lotek has also added GPS locator capabilities to other products, such as our SRX 600 receivers.
How it works:
Dual mode transmitters are designed by Lotek to allow a single transmitter to be detected, decoded and logged by more than one receiving technology, thereby leveraging infrastructure from multiple vendors and allowing for collaboration amongst scientists. For example, our combined acoustic/radio tags are capable of transmitting signals in both radio and/or acoustic mode, allowing researchers to monitor species that move between marine and freshwater environments without having to double-tag them.
When it’s used:
Dual mode systems are used whenever more than one technology is required in a study. Examples of our combined technology systems include:
- transmitters that are designed for use with both MAP and SRX radio receivers
- transmitters that emit both acoustic and radio signals
- transmitters that alternate between MAP acoustic and SRX acoustic transmission
- transmitters that alternate between MAP acoustic and "R-code" acoustic transmission