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  • Christopher Stephens, MSc

What is a Sunfish? Which Sunfish?

Updated: May 18

Ocean Sunfish? Freshwater Sunfish? A Gigantic Mix-up


Pumpkinseed Sunfish at Diver Lake, BC, Canada

A few years ago, I photographed a young Ocean sunfish Mola mola 30 miles off the west coast of Vancouver Island in British Columbia, Canada. I have encountered many interesting fish in my field research over the years but the Ocean sunfish was definitely the weirdest of the lot.

Ocean sunfish, Pacific Ocean off Vancouver Island

The Ocean sunfish ponderously patrols ocean waters all across the temperate and tropical zones, acquiring apt names in different languages as it goes.

A Polish name for the creature is samogłów or "head alone", while in Chinese it is termed fān chē yú or "toppled wheel fish". This toppled position allows the fish to sun itself, a behavior that gave the creature its English name "sunfish".


Ocean sunfish are related to puffer fish as members of the order Tetraodontiformes. Reaching up to 5,100 lbs, the Ocean sunfish is the heaviest bony fish in the world. It may grow over 10 feet long and measure nearly 14 feet from dorsal fin top to anal fin bottom. More commonly, weights of up to 2,200 pounds and adult sizes around 6 feet in length with a fin span of 8 feet are reached. In line with the Polish name, the Ocean Sunfish holds the world record for having the shortest spinal column relative to body size and least vertebrae of any fish. The dorsal and anal fins evolved as matching flippers to propel the Schwimmender kopf or "swimming head" as it is called in German.


Now what about those tiny, colorful little fish that look like a pet cichlid you see at lakes, ponds and stream edges? Introduced to Western North America and Europe from their natural range in Eastern North America, Pumpkinseed sunfish Lepomus gibbosus measure up to 11 inches long with bright colors, a rounded shape and a strictly freshwater habitat. They are entirely unrelated to the enormous Ocean sunfish. Members of the order Perciformes (perch-like) fish, Pumpkinseeds are related to perch, bass, walleye, groupers and gunnels.


Sometimes used as a food fish and other times sold as an aquarium pet for freshwater fish tanks, the Pumpkinseed sunfish are a popular food source for many species of aquatic birds like Hooded mergansers, Belted kingfishers, Great blue herons, Great egrets, Double-crested cormorants and Pied-billed grebes. The author's photo was taken at Diver Lake in North Nanaimo, British Columbia, Canada after waiting 20 minutes for the sunfish to pose while guarding a stretch of marshy shoreline.


All in all, if you swim with an Ocean sunfish, you will be the smaller of the two, while even a large Pumpkinseed would fit on a dinner plate. Neither fish are generally dangerous, though the author was once nipped on the nose by a curious Pumpkinseed and there is a case of an Ocean sunfish leaping onto a human in a boat. To support Ocean sunfish conservation, avoid littering and help clean up plastic on beaches. Bags can be mistaken for jellyfish and ingested, causing starvation and internal blockages.

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