According to New Atlas, it is especially important to monitor tiny, vulnerable individuals if you want to examine how fish are affected by hydroelectric dams. That's why American scientists have developed what is said to be the smallest fish tracking tag in the world.
The inexpensive device, created by a team at the Pacific Northwest National Laboratory (PNNL) in the United States, is specifically designed to track the larvae of threatened American eels, octopus and large-scaled salmon. It is aptly named the eel/lamprey acoustic label, or ELAT.
The cylindrical tool, which measures only 12 mm in length and 2 mm wide, is smaller than the 15 x 3.38 mm label previously developed by PNNL. It weighs 0.08 grams in air and only half as much in water. Like previous devices, it is injected into captured and released fish, and as the animals swim in local waterways, they emit a sound pulse every five seconds.
In the case of the ELAT tag, these pulses are "as long as a football field" when they cross the water, where they are received by a data record underwater receiver that has been installed near potential obstacles such as dams. Its unique lithium-fluoride battery was reportedly developed by PNNL and has twice the energy of a typical AAA battery — which allows the tag to transmit its pulses for 30 days.
In laboratory tests, it was found that the label did not affect the swimming ability of juveniles. As a result, salmon juveniles shorter than 3.7 inches (94 mm) were previously not appropriate, but now with THE ELAT label, this figure can be reduced to 2.3 inches (58 mm). What's more, in field trials, almost 100 percent of the labeled fish were subsequently detected in different types of river environments, including dam effluents.
Daniel Deng, a mechanical engineer at PNNL who led the project, said: "This label offers the possibility of tracking the movement of various species and life stages that we could not have studied before. ”
The study was described in a paper recently published in the journal Cell Reporting Physical Sciences.