A key to unravelling how much damage the BP oil spill caused to sea life four years ago may be found in a tiny fish treadmill at the University of Miami Rosenstiel School of Marine and Atmospheric Science. This month a team of scientists at the school published a study concluding that mahi, a pelagic fish that occupies a big chunk of the commercial market, struggled to swim when exposed to crude oil from the Deepwater Horizon, even for just a brief time. Ed Mager, Post Doctoral Associate at the UM Rosenstiel School discusses the findings. Video by Emily Michot/Miami Herald Staff