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www.sea-technology.com September 2014 / st 33 Freshwater Challenges From the outset, using satellite tracking technol- ogy in a freshwater envi- ronment seemed foolish. Traditionally PSATs had poor geolocation esti- mates (on the order of 100 nautical miles) and poor sensor performance (accu- racy of 20 meters, plus or minus). These were a few of the challenges facing the SeaTag product line. We set out to make a tag that had better methods of geolocation and could be magnitudes more accu- rate, with the goal to transition the technology into fresh- water. Older tagging technologies relied solely on light levels to acquire a latitude and longitude estimate and then would look at the sea surface temperature of the water to help off- set large errors. This technology simply would not work in the freshwater environment due to the sometimes brackish waters (i.e., low light levels) and the variable water surface temperatures. In addition, the release mechanism (i.e., how a tag releases itself from a fsh) required the conductivity of saltwater to function. Simply put, old tags would not func- tion in the freshwater environment. SeaTag turned the freshwater community on its end with new release methods that work in fresh or saltwater, and have better geolocation and greater accuracy (about 10 times) than older technologies. SeaTag devices are equipped with three-axis magnetometers and large, wraparound light sensors. The larger light sensors give the tag a better chance at acquiring light at greater depths, while the magnetometer serves as a method of geolocation independent of light for latitude. These methods proved to greatly enhance geoloca- tion estimates, with average errors on the order of 30 nauti- cal miles (compared to 100 nautical miles or more). While U nderstanding fsh mi- gration and behavior is nothing new; however, the tools that enable us to achieve this are. If you want- ed to learn where fsh went a hundred years ago, it was necessary to count the fsh individually as they passed certain markers or in catch on a vessel. Of course, methods im- proved as companies devel- oped conventional plastic ID tags, acoustic pinger tags, coded wire tags, electronic archival tags and then satel- lite transmitting tags. A majority of these earlier technologies were developed for freshwater use (coded wire tags, conventional tags and acoustic pinger tags), creating a large data gap in the tools for the oceanic environment. This bred the development of the electronic archival tags and subsequently the satellite transmitting tags, which have enlightened our understand- ing of sharks, tuna, sea turtles and all other marine mega- fauna. However, these technologies never translated back to freshwater. Until recently, there was little to no technology overlap. If you wanted to study movement behavior in a large fresh- water body of water, your toolbox was limited. However, in the last fve years Desert Star Systems (Ma- rina, California) has been developing methods to move oceanic technology into large bodies of inland waters. The beneft of satellite tag technology is that the data can be streamed back to the researcher via satellites. Therefore, data recovery is autonomous, whereas archival tags must be physically recovered. Desert Star has designed and manufactured a line of electronic animal tags called SeaTag. What makes these pop-up satellite tags (PSATs) unique is their ability to func- tion in both freshwater and saltwater. Tracking Marine Life In Freshwater Environments New Tags Overcome Challenges of Freshwater Research By Thomas Gray Michigan Department of Natural Resources personnel attach a SeaTag-MOD to a lake trout.