It’s the first time that I’m writing about an animal of which I have no photo yet. I haven’t had the chance to dive near a Sunfish, but they fascinate me and I wanted to read more.
My luck was this paper: The biology and ecology of the ocean sunfish Mola mola: A review of current knowledge and future research perspectives by E.pope et. Al
The first, not surprising, fact is that we haven’t gathered a lot knowledge about all the most famous marine animals. There’s yet a lot to discover about Molas, whale sharks, mantas etc. There are two more Mola species, M. alexandrini and M. tecta, which are smaller than our species.
Want an example for how little we know? It seems there isn’t a single study about the diet of Sunfish. They have been seen eating jellyfish, but there’s reason to believe that jellyfish make only a small portion of their diet. They might eat fish, crustaceans and molluscs as well. It would seem like a wonder if a fish could grow that tall with only jelly on the plate. The largest mentioned specimen was 332cm long! A specimen of 270cm weighed 2.3t, so the bigger one must have been near 2.8t! Since Molas are deepdivers, they go 500m deep, we have no idea what they’re doing at the bottom of the ocean.
The common name varies with the regions, and that’s always confusing! Many European countries call them Moon fish, and some Skandinavien countries say Lumpfish. In German and Polish it is also the Head-only fish. That’s all pretty far away from the real meaning of Mola, what means millstone. Again common names are not very reliable when it comes to identification. It’s a blessing when the scientific name is as easy as Mola. We should use that.
To me the name Sun fish totally made sense when I first saw a photo of a larvae. The look like a drawing of a sun! A Mola mola female produces some 300 million eggs, which is probably the highest number of eggs in all vertebrates! Maybe you want to look out for a tiny sun while waiting for a giant millstone next time?
Maybe due to their shear size, one should think these fish are sluggish. A bit naive when you think about it. How, or why would such giants in the ocean be incapable of steering their direction? It has been found that they travel as fast as other large marine animals, like blue sharks. The direction they took during observation was independent from currents, so that we can say Sunfish swim as fast and directed as other fish. They just don’t look like it.
Sunfish migrate to the surface to warm up, that’s why the name is popular. That might be only part of the story though. They could as well present their selves to birds and other fish, to get parasites removed. I haven’t found recordings of Molas using cleaning stations as other fishes do.
I would like to add another thought I haven’t found in papers: The sunlight might also play a role in removal of parasites. I guess parasites from the deep sea have issues with UV light and would leave the Mola alone while tanning. The same effect can be seen with ants: when ants discovered food in your bag, put it in the sun, and all ants run.
Molas can not only be found in more places than you might think. Unbelievably 40k Molas are caught, mostly as bycatch, each year. In the Mediterranean Sea, the USA, Japan and Taiwan. The last two countries also have a market for Molas as food. It is not exactly known how many Molas Japan catches. Mola mola occurs aroundtheglobe, and are threatened by fishing big times.
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