They forgot..
The information gathered by the 2.4g device should help scientists determine what stresses a fish out – climate change, human infrastructure projects, that kind of thing.
The most important stress is being treated as a fishy guinea-pig. It stresses out humans if they haven't given permission, so I don't see why a fish should be any less strressed. Its not as if they can sign a release document stating they absolve the scientists of any unforseen side effects from being attached to a pen-cap sized device.