In 1983, Amos Barkai, a graduate student at the University of Cape Town, was investigating the effects of bird guano runoff at the beach when he noticed something that took his research in a new direction. The waters around Malgas Island were teeming with lobsters, so much that you had to move lobsters to see anything else. Meanwhile, around Marcus island, just 4 kilometers away, there were no lobsters at all. To determine why, Barkai arranged to move a thousand lobsters from Malgas to Marcus to see if they would survive and thrive.
On the day of the experiment, Barkai was alone in the water, as he was working with a topside crew that didn’t dive (something that would make university dive safety officers extremely uncomfortable nowadays. Of course, this was the ’80s, and things were different). First, the boat stopped at Malgas, and Barkai collected the lobsters for the transfer. A short 4 kilometer boat ride later, and both he and the lobsters entered the waters by Marcus. And that meant he was the only one to witness what happened next.
“Visibility was great that day, and virtually the entire sea bottom started to move,” he said.
That movement was countless whelks. They started to climb onto the newcomers, sticking to their legs. “I didn’t know then, but they’d started to suck them alive, basically. It was like a horror movie,” Barkai said. “It actually was a bit frightening to watch.” The lobsters simply didn’t know how to respond. They were outnumbered and overwhelmed.
“To my horror, in about 30, 40 minutes, all the lobsters were killed.”
The whelks had literally sucked all the meat out of the lobster shells. Barkai felt bad for the lobsters, and figured he must have conducted the experiment wrong. Then he immediately set about figuring out why the lobster prey had become the lobster predator in a nearby environment. Read what they found that made the two areas different, and what it means for sea management, at Discover magazine. -via Metafilter