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.

Mr. Mavar was also injured while shooting an episode in 2011, when a large hook came loose during an intense storm and struck him in the face, breaking his nose.

In the fishing community, Mr. Mavar was known for overcoming adversities, including the cancer and an earlier heart attack, said Mr. Anderson, who appeared on “Deadliest Catch” while crabbing in Bristol Bay with Mr. Mavar and other members of his family.

Nickola Mavar Jr. was born on Oct. 21, 1964, in San Pedro, Calif., to Nickola Mavar Sr. and Maureen (Whelan) Mavar.

He grew up in a fishing family, and his father was a fisherman who emigrated from Croatia in 1959. While a mechanical engineering student in California, the elder Mr. Mavar at first fished part time until becoming a commercial fisherman, according to an interview with an oral history program at the University of Alaska Fairbanks.

When the younger Mr. Mavar got his own start in fishing in the early 1990s, the costs to obtain a permit and run a fishery meant he could not afford a fully functioning boat, Mr. Anderson said.

Mr. Mavar, lacking dish soap and sponges, often washed dishes with Windex, slept in trash bags to keep dry in a flooded boat, and reeled up the net by hand because of broken hydraulics, Mr. Anderson said.

“You could give the guy a tin pail, and he could make it catch fish,” he said. “You could give him a bicycle, and he could make it float.”

One of Mr. Mavar’s boats, named Miss Colleen after his sister, was purchased from his father when he retired, Mr. Anderson said. Soon, he ran a fishery in Alaska, then later took a job working for Mr. Hansen on the Northwestern, which brought him to the show.

“The passing of Nick Mavar spread through the fishing community like wildfire,” Mr. Hansen wrote on social media, adding that Mr. Mavar had worked on his family boat for more than 25 years and was a good friend.

After leaving the Northwestern, Mr. Mavar captained his own salmon boat in Bristol Bay and golfed frequently with Ms. Mavar, whom he married in 2021, Mr. Anderson said.

In addition to Ms. Mavar and his father, Mr. Mavar is survived by two children from a previous marriage, Myles and Emme Mavar; a stepdaughter, Jensen Weynands; two brothers, Brian and John; and a sister, Colleen.

Throughout nearly two decades on television, Mr. Anderson said, Mr. Mavar did not care much about the fame that came from being on the show.

“He was a fisherman through and through,” Mr. Anderson said, “and the camera was something that was just there.”

Emmett Lindner contributed reporting.