Nick Mavar, a commercial salmon fisherman known for his tenacity and resourcefulness who was also a deckhand on the Discovery Channel’s extreme fishing reality show “Deadliest Catch,” died on Thursday at a hospital in King Salmon, Alaska. He was 59.

His death was confirmed by his wife, Julie (Hanson) Mavar. His nephew Jake Anderson said that Mr. Mavar had a heart attack on Thursday while on a ladder at a boatyard in Naknek, Alaska, where he ran his fishing operation, and fell onto a dry dock.

He was pronounced dead at a hospital, Mr. Anderson said.

The Bristol Bay Borough Police Department in Naknek confirmed that Mr. Mavar had died but declined on Friday evening to share additional details.

“Deadliest Catch,” which follows crab fishermen on their strenuous and sometimes brutal job off the Alaskan coast, is one of the top-rated programs on basic cable, drawing millions of viewers.

The show premiered in 2005, and Mr. Mavar appeared in 98 episodes, working on a fishing boat called the F/V Northwestern until 2021.

Mr. Mavar left the show while filming an expedition in 2020 after his appendix ruptured, revealing a cancerous tumor, Mr. Anderson said.