That Fish Blog – Aquarium Advice and Information

Melissa here. When you think of fish that are swimming around in the ocean, most people think of clownfish and damsels swimming around through the tentacles of anemones with corals and live-rock creating the backdrop of that picture perfect image. Ever wonder what is out beyond the reef? There are many awesome creatures that lurk around in the middle of nowhere, far away from the beautiful reef. One of these awesome fish is the Ocean Sunfish, or Mola Mola. Ocean sunfish are the largest known bony fish, weighing in on average 2,000 lbs for an adult. One of the largest Ocean sunfish ever recorded weighed nearly 5,000 lbs!

Ocean sunfish are usually seen near the surface in open water, swimming upright or on their side soaking up the rays or the sun like a large solar panel. Don’t let their position side fool you into thinking they are sick. It is theorized that they “sun” themselves to warm up from a deep dive. It is known that they also spend a great deal of time below 200 meters. That is quite a ways down.

Ocean sunfish are among the strangest looking fish. The posterior half of their body appears to be cut short. They do not have a caudal fin, instead they have clavus which is an extension of their dorsal and anal fin rays. The fish is laterally compressed, looking like a large oval with a paddle shaped fin on the top and bottom. Their skin is like gritty sandpaper covered in a mucus layer that can be as thick as 5 cm. They are also loaded with internal and external parasites (there is a link at the end if you would like to see the list of parasites that cover the ocean sunfish). Juveniles resemble puffers with their large pectoral fins, a tail fin and body spines that are uncharacteristic of adult sunfish.
Their diet consists mainly of jellyfish, squid, crustaceans, small fish, and lots of zooplankton. As its diet suggests, the Ocean sunfish feed across the ocean depths, from the surface to deeper waters, and in some areas, even the ocean floor. You can only imagine how much food these fish must eat on a daily basis to sustain themselves! They are very difficult to keep for long periods of time in captivity, even in the largest system, so Ocean sunfish are not seen in many public aquariums, but there are a few that have taken on the challenge of keeping them on display. The Kaiyukan Aquarium in Osaka, Japan and The Oceanario in Lisbon, Portugal both have Ocean sunfish on display. In the United States, The Monterey Bay Aquarium is the only one to house a mola mola. The longest known ocean sunfish in captivity made it 10 years. In the wild, they can live 100 years or so. Their growth rate is still undetermined, but a young Mola Mola at the Monteray Bay Aquarium went from a slim 57 lbs to 879 lbs in a mere 15 months. It also sprouted to a height of nearly 1.8m. Fattened up on a diet of squid, fish and prawns, this fish had to be airlifted out by helicopter and released into the bay after outgrowing its tank.
It is generally accepted that ocean sunfish larvae will become millions of times bigger during their life cycle. As you can see, this is definitely not a fish you would find at That Fish Place, but you might come across it while scuba diving, so keep your eye out. Ocean Sunfish are found in both temperate and tropical waters. A lot that remains unknown about the secret lives of ocean sunfish!
Here are some great websites about ocean sunfish: http://oceansunfish.org/ has a fun map showing sightings of ocean sunfish
http://www.earthwindow.com/mola.html has awesome pictures of ocean sunfish.
http://www.oceansunfish.org/lifehistory.html this site has a list of parasites that have been found on ocean sunfish.

Image referenced from Wikipedia.