Ground-breaking study tracks sunfish

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Scientists from UK, Portugal and USA have managed to successfully track Ocean sunfish accurately using a fast-acquisition global positioning system, setting the scene for a new era in fish biotelemetry.

Led by David Sims, the team of scientists published the results of their research in a recent issue of the journal PLoS ONE.

The study is considered a breakthrough in fish biotelemetry because previous methods of tracking large pelagic fish involved methods that were considerably less accurate and sometimes slower in retrieving data.  

Using Fastloc GPS enabled the scientists to track fishes in near real-time and with greater positional accuracy.

Tracking devices
The team studied the movements of the Ocean sunfish, Mola mola, by attaching the tracking devices to three individuals caught in the Gulf of Cadiz.

Although two of the devices stopped transmitting data shortly afterwards, the third device remained active, transmitting a wealth of data for nearly three months.

The data indicated that the sunfish travelled towards warmer waters to the south as winter progressed. 

Although this migratory pattern identified here was expected based on current knowledge of sunfish biology, the research team also found a previously unknown behaviour from the GPS data.  

Stopovers
The sunfish was found to make apparent ‘stopovers’ in localised areas that were interspersed with faster movements on straighter course headings.  The scientists interpret the stopovers as encounters with preferred pelagic prey such as gelatinous zooplankton, the distribution of which is highly patchy.

According to the authors, “he results signal the potential of GPS-tagged pelagic fish that surface regularly to be detectors of resource ‘hotspots’ in the blue ocean and provides a new capability for understanding large pelagic fish behaviour and habitat use that is relevant to ocean management and species conservation.”

For more information, see the paper: Sims DW, N Queiroz, NE Humphries, FP Lima and GC Hays (2009) Long-term GPS tracking of ocean sunfish Mola mola offers a new direction in fish monitoring. PLoS ONE 4, e7351.