22 April 2010

Echeneis naucrates

Today, Wednesday, I carried out (successfully) my first two significant decompression dives. I was a little bit nervous, but I completed them without any trouble whatsoever. The dives themselves passed quite quickly without much of note, primarily because I was focused on the technical aspects of the dive. Until every step becomes automatic, it's difficult to be fully aware of the sights around you. This is no different than novice recreational divers, who will often swim right past amazing things because their attention is focused on what needs to be done next.

One thing, which is otherwise unusual in diving, that comes into play with extended decompression is boredom. You are often considerably far off the bottom, so you can't pass time by looking at little creatures. If visibility is poor you might see nothing at all. You just have to float in blue space (or worse, silty brown space) and wait for time to pass. I've actually heard there are dive computers that have video games on them specifically for long decompression stops. The longer of my two decompression stops today was 20 minutes - not so long that it was difficult to pass the time. But this was one of those lucky occasions that flew by because of a visitor. Almost immediately after arriving at our first stop, a large (2ft) Remora (Echeneis naucrates) came swimming around!

Photo from ID guide.
I was so disappointed that I didn't have my camera because I would have gotten incredible pictures!

Remoras are a type of suckerfish. You almost never see them swimming around on their own (as this one was). They're always attached to a larger host, usually sharks, rays, turtles, or whales. They're not parasites, though. They actually provide a service to the animals they hitch rides on by cleaning off parasites and algea. This one must have recently cleaned up it's host and moved on to find another. And it found, in us, great candidates!

They normally affix themselves to the underside of their hosts.

The top has a strange and (I found out today) very abrasive pad.

For the duration of the decompression, the Remora attempted to affix itself to our undersides, fins, tanks, and anything it could come into contact with! They're not dangerous but there's something a little uncomfortable about a large fish trying to hang onto you!

They are very strange looking. It's actually hard to tell which side is up and which side is down. But it seems the top of their heads has the ribbed pad and their mouths slope upwards. They've also got strange fins that fan out in an X pattern, making it hard to tell up from down. I guess for them it doesn't matter much. If they're just holding on to their hosts it doesn't matter if they're upside down holding on from beneath, or rightside up grabbing on above.

It was really enjoyable to watch it try to attach to Denis (my instructor) and the other two divers in the area. I let it get close and actually come in contact a few times, but I didn't want to let it really get a hold of me.

My computer is more conservative so it gave me about 6 minutes more decompression time than my instructor's computer gave him. When his decompression was finished he signaled (using diver sign language) that he was going to the surface, and that I should buddy-up with the Remora to finish my decompression. I laughed. Surely, he was kidding. But he went up! He knew I'd be find by myself (I was only 4 meters down at this point and could have theoretically cut the stop short). Anyhow, the Remora must have seen him give the "buddy-up" signal (see image below) because as soon as I was alone, it really went for me! It snuck up from behind and tried to grab onto my thigh. And then my fin. It made several attempts at my stomach and chest too. By this point I was actively shooing it away! I wasn't afraid, but I don't know how strongly they can hold on. I didn't want to end up with a 2 foot long fish permanently attached to my torso!

He gave this signal and then pointed at the fish.

Even at the surface it was still going for me. When I got out of the water it probably attached itself to the boat, but I couldn't be sure. It was a rather entertaining experience.

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