On last week's edition of NPR's Science Friday, they talked about a must-see video of a sperm whale stealing a sablefish off of a fishing line near Alaska. After watching it myself, I can confirm that you should check it out.
Fisherman have been upset about stolen fish for quite some time. The problem isn't just that the whales are stealing the fish- it's that many of them aren't leaving evidence. This affects the estimate of the sablefish "fishable population," which in turn affects fishing quotas. If the fishermen could estimate how many fish were being stolen, these numbers could be included into the totals.
The video reveals not only how the whales are committing the crime, but also how fisherman might overcome the problem. Whales emit sonar pulses to hunt for food. These pulses bounce off of their prey and back to the whales, helping them gauge size and distance. In the video, these pulses can be heard quickening as the whale reaches the line. Then, instead of ripping off the fish, the whale bites down on the line and shakes the fish loose. He keeps emitting the pulses until the fish is released, but doesn't make any more noise until he has freed his own teeth from the line.
Researchers now think that they might be able to count how often fish are being stolen by tracking patterns of these sonar pulses. However, they're quick to point out that this video only catches one whale in the act, so much more investigation is needed.
Here's the video from Science Friday, and here's an article from National Geographic with a little more info. I encourage you to at least check out the video- just seeing the whale emerge from the corner of the screen, mouth open and teeth pointy, like a creepy shadow puppet, is surreal.