An Encounter with a Sunfish

Warm waters are bringing Mola mola further north.

I enjoy a nice nap after diving. Boats can lull you into this delightfully relaxed place – and naps on boats are awesome – but when somebody yells for you to get your mask, the feeling may be the opposite of relaxation, but it’s better than awesome.

The Mola mola or ocean sunfish is the world’s heaviest bony fish (teleost), regularly growing to 2,000 pounds and three metres from fin to fin. They are a pelagic species thought to travel long distances and dive to several hundred metres, spending extended amounts of time at depths greater than 200 metres. After these deep dives they can be spotted basking at the surface to warm up.

This guy was flapping around near a kelp bed at the entrance to Maey Channel near Calvert Island.  Going from sleeping to jumping in with a 10-foot tall Mola mola was almost enough to give me a heart attack; while these fish look completely maladapted to living, he was shockingly agile. He was splashing around at the surface and didn’t seem agitated with me swimming alongside him. He let me close enough to see the sores on his back and the tiny copepods hanging on to him. As he continued splashing about on the surface the only thing he didn’t seem too crazy about was having me dive underneath him.  With a couple wiggles of his enlarged dorsal/anal rudders he flew forward to splash around on his own.

This sunfish was surrounded by several fishing boats out for salmon, with large schools of salmon, herring, and sand lance seen in the area. This is a dangerous place for a Mola mola to be hanging out, as there a lot of boat traffic, in addition to predators that Mola mola share with salmon. Sea lions, sharks, and orcas have been known to eat ocean sunfish, and with salmon making their way inland we have been seeing increased numbers of Steller sea lions and orcas coming in near the kelp beds.

All of this danger found in kelp forests begs the question: why bother? It turns out kelp beds are like Mola mola carwashes. Sunfish are suspected to hang out near kelp forests with hopes of getting cleaned of their many parasites by fish and birds. Their leathery skin quickly becomes covered in these parasitic copepods, worms, and all kinds of other nasty hangers-on, leading to large sores if they aren’t cleaned. Gross.

Mola mola can travel up to 27 kilometres per day looking for tasty jellyfish snacks like by-the-wind sailors, lion’s mane jellies, and moon jellies, all of which are found off the central coast of B.C. Some studies have found stomach contents from huge variations in depth, showing that they’ll feed at the surface, in deep water, near the seafloor, and even in shallow eelgrass beds.

More Mola mola have been spotted in BC recently due to the warm “blob” of water in the northeast Pacific. But with kelp returning to the central coast thanks to a growing otter population, hopefully Mola mola sightings in this part of the world will remain more common.