Humans have explored less than five percent of the ocean, and even routine catches can yield startling mysteries. A fat, pink, “alien-looking” fish caught by a tourist fishing boat in 2016 led a race to identify the animal.
Jaime Rendon, captain of the Dr. Pescado, was alarmed when he caught the fish, which he described to the Pisces Sportfishing Fleet as having “raspy skin, three rows of tiny teeth, and three gill slits on each side of the head”. But what confused him the most were the strange, dark eyes.
Rendon was concerned that the fish belonged to an endangered species, so he released it alive. But as his pictures did the rounds of the internet, people chimed in with their guesses about its species. Eventually, when the photos were sent to marine biologists, they were able to determine that it was probably a swellshark (Cephaloscyllium ventriosum).
Despite its name, the swellshark is a species of catfish commonly found in the Eastern Pacific.
This one was difficult to identify because it was far pinker and fatter than a swellshark usually is. But marine biologists were able to come up with tentative explanations for both facts.
The fish’s pinkish-white color is probably a result of albinism or leucism (a condition where only part of the pigment is lost).
Since both conditions make it harder for animals to survive in the wild, it’s an exciting discovery!
Both in captivity and in the wild, a threatened swellfish will bite its tailfin, making its body into a ‘U’ shape. Then, it sucks in a mouthful of water, inflating itself up to twice its uninflated size.
It’s thought to do this because its rounded shape and increased size make it more difficult for predators to bite it. The mystery swellfish must have been stressed by the boat’s attempts to catch it, swelling up as a defense mechanism. Released back into the water, it would have deflated quickly.
Rendon was right to release his catch; although the swellfish isn’t officially endangered, its low egg production means its numbers regenerate slowly.
The swellfish isn’t a new discovery, and it’s definitely not the first sign of an alien invasion. But it’s another reminder about the gorgeous diversity of life in our oceans – and our responsibility to look after it.