A limited moose-hunting season set for next fall won't contribute to the disturbing decline in Minnesota's moose population, state wildlife officials said Tuesday.

About 50 moose are expected to be killed in the bulls-only hunting season that will open Sept. 29.

"There's no biological reason to not have a limited hunt,'' said Dennis Simon, Department of Natural Resources wildlife section chief. "Moose hunting is part of our hunting heritage. We need to manage moose for their intrinsic value and iconic presence, but also to maintain that hunting tradition we have.''

The state's moose population, now estimated at 4,200, has dropped by half in the past five years, and some say if the trend continues the animal could disappear here in 20 years.

But DNR researchers say hunting isn't the cause of the decline and doesn't significantly affect the population.

"Bulls-only hunting mortality is not a significant factor in the moose population decline,'' said Erik Thorson, acting DNR big game program leader.

That's because, like deer, one male moose can breed with multiple female moose, so as long as most cows are being bred, the overall moose population can be sustained or grow. Currently, the bull-cow ratio is high enough to ensure that virtually all cows are being bred, so the loss of some bulls to hunting shouldn't significantly affect the population, Thorson said.

Researchers have been studying the moose population for years, using radio-collared moose, and believe the decline is related to disease and parasites, including liver flukes, winter ticks and brainworm. Closing the hunting season won't stem the long-term decline, they say.

The loss of 50 moose to hunters reduces the chances of a person seeing a moose in northeastern Minnesota, said Rolf Peterson, a wildlife researcher and member of a moose advisory committee. "Fifty moose harvested is 50 fewer moose,'' he said.

"Even though hunting is not causing the decline, it makes sense to reduce hunting pressure in an orderly manner if the population continues to decline,'' he said.

The state's moose-management plan says hunting should stop if:

•The bull-to-cow rate drops below 67 bulls per 100 cows for three consecutive years. While that rate fell to 0.64 bulls per cow in 2011, it rose this year to 1.08, the highest since 2006.

•Overall hunter success drops below 30 percent for three consecutive years. Hunter success was 58 percent last year.

•The harvest success rate for any individual hunting zone averages less than 20 percent for three consecutive years. That happened in two zones, which will be closed this fall.

Last fall, the DNR cut the number of moose-hunting permits to 105, down from 213 in 2010. And this fall, it will cut the number to 87.

Since 1991, the moose hunt has been a once-in-a-lifetime hunt, meaning hunters who receive permits through a random drawing system are ineligible to reapply. Applications are available from April 2 to May 4. The season will open Sept. 29 and end Oct. 14.

Last year, 92 hunters killed 53 moose. In setting the new quota, DNR officials said they considered the harvest by the Bois Forte, Fond du Lac and Grand Portage bands, which also conduct moose-hunting seasons. Those bands killed 31 moose last year.

Meanwhile, some residents suggest the state's wolf population is to blame for the moose decline, but officials say their research indicates that isn't the case.

"Wolves were a relatively minor mortality factor for adult moose -- about 10 percent of mortality,'' said Simon. "There's no evidence wolves are limiting moose populations.''

And Peterson said an expected wolf-hunting season next fall also won't affect the moose herd.

Doug Smith • 612-673-7667