Fish o' the Day - ocean sunfish

May I introduce to you the world's heaviest bony fish. The ocean sunfish, Mola mola, is also one of the strangest-looking of our finny friends. It looks for all the world like somebody caught a monstrous fish and discarded the head -which promptly swam off. Adult molas routinely reach about six feet in length and tip the scales at about a ton. That's a lot of mass in a relatively short length, but that's explained by the fact that the fish is essentially a solid block of tissue. The molas are members of the same order as the pufferfish and porcupinefish, the Tetraodontiformes. There are even some suggestions that they produce toxins similar to those for which the puffers are known.

Ocean sunfish are cosmopolitan in tropical and temperate oceans. Although there is a perception that they spend all their time basking at the surface, they're actually more likely to be found in deeper waters. Some researchers believe that, when they are seen basking, they're accumulating heat energy for their dives into deeper water. Sunfish feed primarily on jellyfish and other cnidarians, and must consume large quantities to support their bulk.

The ocean sunfish has a couple of other superlatives among the fish. They have the smallest number of vertebra of any bony fish, and their spinal cord of even a large individual is only inches long. Also, the female Mola produces the largest number of eggs of any known vertebrate, in the neighborhood of 300 million. Those eggs hatch out and develop into a tiny, spined fry.

Sunfish seem to be doing OK, although there is a tremendous by-catch associated with swordfish fisheries. They're not generally considered edible, although some Asian cultures (of course) consider them a delicacy.

Here's a nice dive video of a Mola with a group of false moorish idols engaged in what appears to be cleaning activity.