FAIRBANKS - The Alaska Department of Fish and Game is gutting moose hunting seasons on the North Slope this fall because of a "drastic" drop in the moose population.

The department announced on Monday that practically all moose hunting north of the Brooks Range will be closed because the moose population had dropped by 50 to 75 percent in the last few years.

"We found a surprising and drastic reduction in moose numbers earlier this month," area biologist Geoff Carroll at the ADFG office in Barrow said in a press release issued late Monday afternoon. "We need to cut back on moose harvest while we see how the population responds."

The department is closing all moose hunting for nonresidents and the only resident hunt that will be open is an Aug. 1 to Sept. 14 season in game management unit 26A, which will be two weeks shorter than normal. Three drawing permit hunts that were scheduled to be held in the two units will also be canceled, as will a winter, either-sex hunt in unit 26A. 

Poor nutrition as a result of last year's late spring and poor conditions last summer are probably to blame for the decline in the population, biologists say. Very few 10-month-old calves were seen during spring surveys in April, indicating that most of last year's calf crop died off during the winter. Predation by wolves on weakened moose may have also contributed to the decline, biologists said.

"Moose on the North Slope are on the northern edge of their range and I don't think it takes too much of a change to affect them," eastern North Slope area biologist Beth Lenart at ADFG in Fairbanks said. "The growing season is so short that any alteration can make a difference."

According to moose surveys conducted by biologists last month, the number of moose in unit 26A on the western North Slope has declined by 50 percent since 2011 while the moose population in unit 26A on the eastern North Slope dropped by almost 75 percent since last year.

Biologists counted only 208 moose in unit 26A this spring, down from a count of 609 in 2011. In unit 26B, meanwhile, biologists counted 109 moose his year compared to 400 last year.

Similar results were also seen in unit 26C, which extends east of unit 26B to the Canadian border, but there is no moose hunting season in unit 26C.

Biologists have documented severe declines in the North Slope moose population before, most recently in the mid-1990s, according to Caroll and Lenart.

In unit 26A, which stretches from the Dalton Highway to the west coast, the moose population got up to approximately 1,550 moose in the early 1990s with a harvest of about 60 moose a year but the population plummeted more than 75 percent between 1992-97, at which point hunting seasons were severely restricted, Carroll said.

The unit 26A population reached a low of 326 moose in 1997 before climbing back to 1,180 in 2008 and hunts were reinstated. The population declined again in 2009 and has remained low since, with an average harvest of under 15 moose a year.

Similar population fluctuations were seen in unit 26B, which extends east of the Dalton Highway to the Canning River, but on a smaller scale, Lenart said.

The harvest and hunting pressure in both units is relatively low, primarily because of access. Last year, a total of nine moose were reported killed in unit 26A, five by hunters with drawing permits and four in the general hunt, while just two moose were killed in unit 26B, both by hunters with drawing permits.

Unit 26A is a controlled-use area that prohibits the use of airplanes for moose hunting unless the hunter has a drawing permit. Hunters without permits must walk at least five miles off the Dalton Highway — motorized vehicles aren't allowed in the Dalton Highway Corridor — before they can shoot a moose. As a result, most of the hunting pressure comes from hunters with drawing permits or locals who live in the unit.

In Unit 26B, meanwhile, there is a drawing permit hunt during the first two weeks in September but the general hunt is held during the first two weeks in April. Either way, hunters must walk at least five miles through the Dalton Highway Corridor or fly in before they can shoot a moose. Since 2006, only one moose has been killed in the general season, Lenart said.

There were a total of 22 permits issued for the three drawing permits on the North Slope this year, 10 for two hunts in unit 26A and 12 for a hunt in unit 26B. Hunters who were drawn for permits will receive letters explaining the closure, ADFG said.

ADFG will monitor the moose numbers in both areas and reinstate hunting seasons when the population allows, Lenart said.

Contact staff writer Tim Mowry at 459-7587. Follow him on Twitter: @FDNMoutdoors.