Not only was the fish, caught by Chad Hester, massive, weighing at least 36 pounds, but it was also a rare piebald blue catfish. The species of fish can be identified by their distinctive white and black markings.

“Honestly never would have imagined catching one,” Hester told Newsweek. “Not only catching one but the size it was able to grow to. Amazing fish!”

Hester, who returned the catfish to the water, described his catch in a Facebook post on October 14, the day he and a friend landed it.

“Landed something special this morning. First Piebald I’ve ever caught and it was a dandy too. 36 lbs and released within minutes for another fisherman to enjoy in the future,” Heston wrote.

He told Fox 2 Now: “I freaked out. I was like holy cow.”

In the Facebook post, the fishing enthusiast also described the method he used to catch the fish, which involved using Asian carp as bait with an 8-ounce bank weight and a 9/0 team catfish double action hook.

“[The catfish] Swam off good and even gave us a show before he swam off. Absolutely gorgeous fish. I will never forget that moment,” Heston continued. “Always thought they were the unicorns of the river.”

In September, Scenic City Fishing Charters staffer Joe Jellison was captaining a boat when a tourist also caught a piebald blue catfish, this time in the Chickamauga Dam, Tennessee.

He told Field & Stream how rare the fish is: “They are quite rare—one-in-a-million chance of getting one. They are actually blue catfish with a genetic mutation. We typically catch blues and channels when drift fishing, so seeing the piebald catfish surface was quite the surprise.

“Many fishermen will fish their whole life and not catch a piebald catfish.”

Lower Mississippi River Conservation Committee (LMRCC) describes the piebald catfish as the rarest type of blue catfish. “One variety of blue catfish is the rarest: the piebald blue. ‘Piebald’ is a portmanteau of ‘magpie’ (a black and white bird) and ‘bald’ (for white patch or spot) and refers to a distinctive, but highly variable pattern of mottling in animals.

“Having the same size and shape as an ordinary blue catfish, piebald blues stand out because of their white skin marbled with prominent black and/or gray blotches. Catching one makes for a memorable experience.”

The LMRCC says that of almost 35,000 catfish caught by the U.S. Army Engineer Research and Development Center Fish Ecology Team in 17 years, only two piebald blues have been landed. Additionally, these catches were separated by a decade, occurring in 2002 and 2012.

Hester told Newsweek why he returned this rare “catch of a lifetime” catfish to its natural habitat. “I released it to help give it a chance to spread its genes and to give another fisherman the opportunity to catch it in the future when it becomes even bigger.”