UNALASKA -- State and federal officials are advising pregnant women and young children to limit the amount of northern pike they eat from the Kuskokwim and lower Yukon rivers because the fish contain a toxic form of mercury.

The guidelines result from a study done in 2005 and 2006, when biologists sampled 163 pike from 11 sites in the Yukon Delta National Wildlife Refuge.

At high levels, methylmercury can hinder brain development in fetuses, babies and children. The Alaska Division of Public Health and the U.S. Fish and Wildlife Service said the levels of methylmercury are not particularly dangerous, but they've established guidelines for pregnant woman and children younger than 12.

People outside the at-risk groups can eat as much pike as they want.

The state has studied hair samples from more than 80 Alaska women, and none had dangerous levels of mercury, said Lori Verbrugge, the state's environmental public health program manager.

"These (guidelines) are just to give people an idea of what they can do without worrying at all," Verbrugge told The Dutch Harbor Fisherman newspaper.

Under the guidelines, published on the state's Web site, the agencies recommend:

• For Yukon pike of any size, or for Kuskokwim pike greater than 2 feet, eating no more than eight meals a month if fresh, or one meal a month if dried.

• For Kuskokwim pike shorter than 2 feet, eating no more than 16 meals a month if fresh, or four meals a month if dried.

Pike plays a large role in western Alaska subsistence diets, and many people catch it under the ice with hooks or nets each spring as the fish migrate. Mercury enters rivers from a variety of sources, such as mining runoff, forest fires and volcanoes.