FAIRBANKS — A Yukon River fish processing plant at Kaltag that was named one of the “greenest fisheries” in the world is closing its doors this summer.

The operator of the plant blamed a fishing time limit imposed by the Alaska Department of Fish and Game, a limit he believes is unnecessary because his business does not target the depleted king salmon run. However, a manager said the department had to impose the limit to protect king salmon and treat fishermen along the river equitably.

Doug Karlberg, owner of Yukon River Gold, said the department’s limit left him with too little time to make money. He leases the plant from the city of Kaltag.

“In order for that plant to survive, it needs about 35 days of processing time,” he said.

Yukon kings begin swimming up the river before the summer chums, but the two runs usually overlap for a few weeks. Regulators only allowed the fishwheels that supply the Yukon River Gold plant to begin operating once the kings had passed the Kaltag area. That gave the plant about 20 days to work on the remaining portion of the chum run, and it wasn’t enough to pay the bills, Karlberg said.

“We don’t have any more money to lose,” he said.

“I was forced to close it down,” Karlberg said. “And now we have a record chum run in the Yukon River and the people are having to sit there with no jobs.”

The seasonal plant employs about 70 workers from villages in the area. Many are high school students. The plant operated for four years.

Karlberg buys only chum salmon from local fishwheels. Those wheels are monitored so any other types of fish, including king salmon, are immediately thrown back in the Yukon River — alive and unharmed, Karlberg said. The low bycatch prompted Fisheries International magazine, in its January edition, to name the Kaltag plant one of the best fisheries in the world.

For two years, Fish and Game stationed observers in Kaltag to watch the fishwheel and processing operation. Last year, Karlberg said, the observers saw there was no king bycatch.

The department’s area manager, Steve Hayes, said that’s not quite the case. “There has been some bycatch taken,” he said.

Hayes said he can’t tell Yukon River subsistence fishermen that “every king counts, and they can’t catch them” if he doesn’t tell the same thing to commercial fishermen that supply Yukon Gold.

Severe restrictions have been imposed on subsistence king salmon fishing along the Yukon River this year, Hayes said.

During four of the past five years, he said, the Yukon River did not meet the king salmon escapement goals established by a treaty with Canada. Hayes said about half the Yukon’s king salmon spawn in Canada’s waters.

“We’ve had to be very conservative trying to protect these kings,” he said. “Unfortunately, because of that, we’ve had to let a surplus of chum up the river.”

Hayes said Fish and Game met with Karlberg this spring and said his operation could open in the last week of June, a week earlier than last year but still well after the summer chums began passing Kaltag.

“As far as commercial fishing for chum, I think it could have been a very viable thing this summer,” Hayes said.

Karlberg said the plant has year-round bills to pay. It is now closed for the summer and will be reviewed this fall by Fish and Game and the local economic development corporation.

“We will leave the door open for federal and state managers to change their policies over the summer,” Karlberg wrote in a press release. “If they change these policies, enabling economic viability of this plant, we will be delighted to reopen the plant in 2012.”