"We believe that some contaminants are accumulating behind the dams by settling out in the sediment as the water slows," Feist said, adding that at this point this is a hypothesis.
"Fish residing in the reservoir behind the oldest dam had the highest contaminant loads," Feist added, "and exhibited reduced growth and reproductive fitness when compared to fish sampled in other locations. These data suggest that some contaminants may be accumulating behind dams over time."
North America's largest freshwater fish, white sturgeon can grow to 20 feet in length, weigh more than 1,500 pounds and live for more than a century. The fish have always been an important food source for Oregon's Native Americans, and now as salmon runs diminish, white sturgeon fillets and steaks are increasingly sold in fish markets.
But because of their potentially high contaminant levels, Schreck cautions consumers to not eat the fish at every meal.
During the last 25 years, white sturgeon have experienced a sharp drop in population in the upper reaches of the Columbia River. In 1990, the Committee on the Status of Endangered Wildlife in Canada designated the white sturgeon as "vulnerable," only to reclassify it as "critically imperiled" in 1994.
Today, the fish, which are caught commercially and for sport on the lower Columbia, are listed as endangered in Canada. Fishing for white sturgeon is regulated by the state, with size limits precluding anglers from taking juvenile fish or large, older fish.