Species Spotlight – Ocean Sunfish

The ocean Sunfish is a fascinating creature who has captured the imagination of everyone who meets them with their unique appearance. Sunfish are known to be the heaviest bony fish in the sea and can exceed 1,000 kilograms in weight. Enormous in size, the Sunfish moves in a way that is both awkward but graceful, truly one of the most fascinating and unique creatures on our planet.

During our Bremer Bay Orca and Perth Canyon Blue Whale seasons we spend much of our time close to the deep sea canyons which Sunfish love to call home. The nickname Sunfish refers to their habit of resting at the waters surface, sunning themselves in a behaviour believed to help regulate their core body temperature. Sunfish prefer water temperatures above 10°C and as they feed at depths between 200-600 meters in very cold water at times, basking in the sun for periods of time can help to warm up after these hunting dives in the depths of deep sea canyons.

  • Distribution is worldwide in temperate to tropical offshore waters
  • Lifespan is unknown but may be a very long time with some bony fish living up to 100 years
  • Record for most eggs hatched with 300 million little ones being born into the big blue
  • Preferred diet is squid, crustaceans, sponges, sea grass and jellyfish
  • Can weigh up to 1,000 kilograms and be over 3 meters in size
  • Swims in a sculling like motion and cruising speed is 3km per hour

They also have a fascinating jaw structure, the mouth of a Sunfish is fused and ideal for feeding on jellyfish and sponges. This means their facial expression is permanently fixed and looks similar to a mix of parrot beak and duck face pout! We often sight Sunfish calmly sculling across the surface of the ocean on calm days, only stopping to slurp up delicious jellyfish they find on their journeys. Eventually they will return back down to the depths to spend approximately 70% of their time feeding in the 200-600 meter range where they remain unseen and continue their mysterious lives.

Sunfish numbers worldwide are not well known but believed to be vulnerable, Australian Sunfish sightings are not overly rare and can often be observed during offshore whale watch experiences or fishing trips. The main concern for this species is becoming caught in fishing gear or as bycatch, especially when targeting the same prey as commercial fishing. Predation is not overly common, although Sea Lions have been known to target them. Orca have been observed in the waters off Bremer Bay playing with Sunfish, but not consuming them as it does not appear they are part of the Orca’s diet. Incredible footage can be scene below of a juvenile Sunfish fiercely defending itself from the playful antics of young Orca, he survived and swam away a little flustered but wiser.