Filefish Surge Trickery

One of the great results of scuba diving a lot in one area is that I came to know the fauna of this area (the south of Negros Island in the Philippines, around Dumaguete) quite well, and that hence anything unusual, either an unusual species or an unusual behavior, sticks out to my mind. And that’s not only my mind, but the mind of my dive buddy Matt who was with me last week as well.

What we observed is a juvenile filefish which was staying in place in a spot with some quite significant surge. How did the tiny fish do it?

It held onto the vegetation with its mouth. When we arrived it was holding on to a piece of seaweed, and then it switched to holding onto a dead leaf of a coastal tree which had washed into the ocean. It didn’t directly hold onto the leaf, but to a layer of filamentous algae covering it.

Curiously I had photographed this behavior before, featuring a related species of filefish, in Sydney, Australia, many 1000 km away from the dive site I was at last week. Also, this filefish held on to a tunicate, not to a piece of vegetation:

Even a Paper on It

There is even a scientific paper on the behavior, featuring a different filefish, Amanses scopes, in the Red Sea:

Eyal, G., Eyal-Shaham, L., & Loya, Y. (2011). “Teeth-anchorage”: sleeping behavior of a Red Sea filefish on a branching coral. Coral Reefs, 30(3), 707-707.

The holding-on-to-the-benthic-fauna&flora behavior seems to be a filefish universal. Is there a name for this behavior? Anchoring?

Why are the filefishes doing this? I believe they roaming in feeding territories. A lot of reef fishes don’t venture very far as adults. They might have found a place with food and/or hiding places fitting their needs, and don’t want to venture far, into unknown, potentially less ideal parts of the coast. Any displacement by a strong surge or current might be quite disadvantageous for a small fish. Staying in place, and holding onto the substrate, is hence an adaptive strategy.

Footage

This is footage of the behavior. You can see that the fish changes the piece of vegetation it holds on to. You can also get an idea how strong the surge that night was.

I hope you enjoyed this episode of fish behavior,

Best Fishes,

Klaus