Wednesday, October 1, 2008

Dead Eels

Dead eels have been washing up in Bonaire. Divers are reporting seeing dead eels that otherwise looked quite healthy. Certain species seem to be more susceptible than others. Nobody knows what's killing the eels, but there was a similar epidemic of eel deaths about 13 years ago. That outbreak was due to a bacterial infection that affected the nervous system and lateral line (that's a line that runs along the side of a fish and provides the fish with sensory information regarding pressure changes in the water -- e.g., something moving toward it). The marine park was trying to get an eel shipped to a lab in Puerto Rico for them to look into it, but the process of getting all of the permits is going to take too long, so Ramon (the marine park manager) is going to fly a person in to look at the eels here. Hopefully there will be a clear solution to the epidemic or the epidemic will be short lived. (Pictures: Top left- spotted moray; Top right and video below -- sharptail eel; bottom R&L -- goldentail moray)

Below is a video of a sharptail eel foraging (it may take a minute to load). Unlike many eels, you'll see this species out foraging during the day. Pay attention to a few details in the video below. First, notice how being "eel-shaped" can be useful in this foraging mode. Second, in the beginning of the video you'll see a dark fish hogging the view, it's a damselfish (I'll talk more about them another time. Many damselfish, like this species, could be considered feisty, territorial farmers.) Third, watch the fish that starts following the eel around; it's a small grouper called a Graysby. Why do you think that it's following the eel around? I'll give you my ideas below.

I think that this Graysby is either using the eel as cover (I frequently see predators on the reef use that kind of behavior) or, perhaps more likely, it is waiting to see if the eel scares something out of a hole that it can rush in and eat (another common behavior on the reef).

No comments: