Biotelemetry

In recent years, researchers have become increasingly reliant on remote devices to address a wide range of science and management questions, in a variety of species, including; marine mammals, turtles, teleost fishes, chondrichthyans, crustaceans and cephalopods. Tools such as biotelemetry (radio and acoustic telemetry) and biologging (archival logger) devices offer a sophisticated means of evaluating the behaviour, spatial ecology, energetics, and physiology of free-living animals in their natural environment. 

Ultrasonic Acoustic Telemetry
Photo Credit: CJ Crooks
 
Acoustic telemetry tools have been used in the study of marine animal behavior for over 60 years. It was in the 1960s, however, when electronic devices capable of emitting or transponding sound energy first came to be used to track individual sharks. Ultrasonic frequencies are used (34 to 84 KHz) to ensure the size of the ‘package’ carried by the tracked fish is small having a minimal impact on their behavior. In practical terms, coded sound pulses at a known frequency emitted from a transmitter attached to a fish are detected using a directional or omni-directional hydrophone. These signals are then processed through either a submersible static receiver or portable / manual receiver. Animals can therefore be actively tracked via vessel or passively monitored through deployment of receivers in specific locations. For sharks the use of these electronic devices has revolutionised our understanding of how marine predators move in relation to ocean processes across a range of ecological scales.
 
At the sharklab
 
Both passive and active acoustic tracking have been used extensively to examine fine and coarse scale movement patterns across various spatio-temporal ranges. For example Dr. John Morrissey, Dr. Fred Sundstroem and Dr. Bryan Franks examined space and habitat utilisation of juvenile lemon sharks (Past Research - Spatial Ecology). During his PhD, previous Sharklab director Dr. Tristan Guttridge also used static receivers in combination with wild observations and proximity receivers to investigate refuge use and aggregation formation (Past Research - Social Behaviour). More recently we have also been using a large array of static receivers to monitor aggregation formation and migratory behavior of large coastal sharks in Florida, for example bull, lemon and hammerhead sharks. Currently we have a variety of projects in Bimini using these devices including studies investigating:
  1. Within and between variation in receiver detection capabilities under different environmental conditions. Collaboration with Sonotronics.
  2. Personality traits of wild juvenile lemon sharks. Home range size estimates and excursions out of these areas used as proxy for exploratory behavior.  
  3. Feeding ecology. In combination with accelerometry loggers we hope to determine feeding events their frequency and possible location in relation to prey communities. (Current Research - A Day in the Life & Daily Energy Budget).
In terrestrial studies scientists have recently begun to use novel proximity data loggers that measure the frequency and duration of contacts between individuals. These have allowed researchers to derive estimates of contact rates between individuals and to examine relationships of these with population density, habitat and the transmission of disease. For sharks that are cryptic and elusive such technology would be particularly useful for examining social and or predator-prey interactions.
 
At the sharklab
 
During his PhD research, in collaboration with Sonotronics, our previous Sharklab director Dr. Tristan Guttridge used this terrestrial concept and designed a prototype acoustic proximity receiver. The receivers are small enough to be carried by juvenile sharks (>80cm), are able to detect other animals with acoustic transmitters at high resolution (0-4m), have adjustable detection ranges, memory and variable battery power. At the moment Dr. Guttridge is also collaborating with Dr. Culum Brown, Dr. Joanna Wiszniewski and PhD student Nathan Bass at Macquarie University. This exciting project will further develop these receivers and will investigate Port Jackson shark aggregations and migratory behavior. In combination with novel social network analysis they plan to determine whether sharks have preferred partners that they rest or migrate with and whether they associate with other individuals of the same sex or size?
 
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Accelerometers
Photo Credit: CJ Crooks
 
A relatively novel technique to determine the locomotory activity of organisms uses accelerometers. These sensors have only recently become available from manufacturers (CEFAS) and are starting to become widely used in fishes. A typical fish swimming with caudal propulsion will exhibit repetitive contractions of the axial muscle, which sends bending waves down the body of the fish creating the characteristic tailbeat. Any segment of the tail therefore experiences cyclic changes in lateral position and associated changes in velocity as it moves from side to side, which is represented in the trace of the lateral acceleration as repetitive peaks with wave characteristics that vary with activity level and behavior (Current Research - A Day in the Life & Daily Energy Budget). It is from these cyclic tailbeat data (rather than forward body acceleration) that locomotory activity can be quantified with a number of approaches including frequency, amplitude, and various measures of overall acceleration. The tags are capable of logging 90 data points per second in each of the three planes of movement (heave, surge and sway), as well as, recording pressure and temperature every second.  
 
Accelerometers have proven an extremely effective tool in the study of animal behaviour, especially in the marine environment. They have been used in the study of swimming kinematics and spawning behaviour in fish, foraging ecology in seals and penguins as well as activity patterns and mating in sharks.
 
At the Sharklab
 
Our first attempt at using these loggers was in 2006 when Adrian Gleiss attached one to a sub-adult lemon shark in captivity. This initial pilot study led to a publication and Adrian starting a PhD at Swansea University with Prof. Rory Wilson. In 2012 scientists from Mote Marine Lab and BBFS were successful in obtaining an NSF grant using accelerometer loggers to estimate the field metabolic rate of sharks. Two of our research projects use acceleration output data to translate into actual shark body movements from which we can understand the energetic and behaviour of tagged individuals.
 
Pop-Up Satellite-Linked Archival Tag (PSAT)
These tags are electronic devices that are attached to a study animal and return environmental, biological and positional data to the researcher via satellite. The PAT archives depth, temperature, and light-level data whilst being attached to the animal. At a user-specified date and time, the PSAT actively corrodes the pin to which the tether is attached, thus releasing the PSAT from the animal. The PSAT then floats to the surface and transmits summarized information via the Argos Satellite System. Argos also uses the transmitted messages to provide the position of the tag at the time of release. PSATs are used to chronicle or ‘archive’ the habitat preferences, horizontal and vertical movements, fishery interaction, and post-release mortality rates of a variety of pelagic animals. Such detailed information can be used to contribute to the conservation of sharks, by informing stakeholders (e.g. fisheries managers) of our findings. Past studies using PSATS have revealed important biological and behavioural characteristics for a range of animals, as well as highlighting critical habitats and corridors of use.
 
At the sharklab
 
In the last few years we have used PSATs to monitor the migratory patterns of adult lemon sharks at our study site in Florida. Unfortunately lemon sharks seem to shed these tags fairly quickly through rubbing them off on the substrate. However despite this we have been able to record movements of adults from Florida to the Grand Bahama, Bahamas (~100km) and to Altamana Sound, Georgia (~700km). In the future we plan to use these tags to examine the movement patterns, habitat preference, survivability and post-release behavior of the endangered great hammerhead shark – a collaborative project with Dr. Dean Grubbs (Florida State University) and Dr. Demian Chapman (Stony Brook University) (Current Research - Conservation of Great Hammerheads).
 
SPOT tags are one of the most advanced technologies used in marine research today. Like PSAT tags they are able to transmit logged data to a satellite and are primarily designed for use on animals that swim at the surface, where a regular signal can be sent. However, unlike PSAT tags, data sent from tags to satellite is then sent on instantly via email to the researcher. The advantage of this is that animals can be tracked more precisely. SPOT tags have been used in research with dolphins, seals, turtles and sharks.
 
At the Sharklab
In 2012 the sharklab set deep water lines (Research Techniques - Capture Methods) off west Bimini catching five tiger sharks. The BBFS team worked with Dr Michael Domeier, attaching SPOT tags to three adult tiger sharks (all > 3m otal length). The movements of these sharks are still now being monitored and data continually received – updated daily on application Expedition White shark. This year we aim to continue our success with this project, tagging juvenile tiger sharks that frequent the Great Bahamas Bank. For tiger sharks this life history stage has received little attention and recent increases in juvenile tiger sharks captured on our longlines (Past Research - Historical Bimini Population Dynamics) has led us to believe that Bimini’s waters are a nursery area for them.  
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