February 8, 2003
From: Brian Penney
Sorry I've been quiet so long. Busy defending my thesis, etc.
I have a few anecdotal reports on slugs moving. In the Northeastern Pacific, Melibe leonina is famous for its sudden appearances and disappearances, often moving en masse into seagrass beds. I've heard that they float in and out with the tide, but I haven't seen it myself.
Cadlina luteomarginata in Barkley Sound, British Columbia, seems to consistently appear in certain places over the course of the year. In winter, I find great numbers at a protected site near the marine station. (on average, say >100 individuals along a 30m stretch of shallow subtidal). All of them are small, less than 4cm. These disappear in the spring, and during the summer I find larger individuals at more exposed sites. This suggests to me that this species may settle in "nursery areas" and then move to sites with more food resources. However, I have never actually tracked their movement, so this is only a guess.
It's an interesting topic.