Nightswimming

U-M News is reporting that researchers at the University of Michigan may have found the key to how round gobies (Neogobius melanostomus) managed to spread so quickly through the Great Lakes. Round gobies are typically bottom-dwellers, which would make it difficult for them to get sucked into ballast water, since ships typically take on ballast near the top of the water column. Now a new study has discovered that when the gobies first hatch, the tiny larvae rise to the surface of the water at night, to find food and presumably evade predators, and then descend again in the morning. The new insight into round goby behavior also provides an insight into how ships become a vector for this invasive fish species.

Interested readers can find the abstract to the original research article here, but to see the full version you'll need a subscription to the Journal of Great Lakes Research. Thanks to John R. from Don Watcher for sending in a link to the story.