Fish exposed to an Exxon Mobil Corp. oil spill into the Yellowstone River are safe to eat despite some crude found in their internal organs, Montana wildlife officials said Thursday.
No oil was found in fillets cut from 58 fish taken from the river for laboratory testing in mid-July, according to Montana Fish, Wildlife and Parks.
Small amounts of oil were detected in the livers and gonads of some of the fish.
Agency spokesman Robert Gibson says the contamination potentially could harm the health of the fish but not people who catch and eat them.
"We know there wasn't anything that would be dangerous for people," Gibson said. "But in fatty organs, where toxins have a tendency to accumulate, that's where we don't know if (oil) will accumulate over time."
Exxon Mobil's Silvertip pipeline broke and leaked an estimated 42,000 gallons of oil into the flooding river near Laurel on July 1.
Much of the oil was swept away; only about 400 gallons have been recovered. Pockets of oil have been found along the bank, on islands and on the riverbed along dozens of miles of the river.
The results of the fish sampling are in line with other tests that have found oil but not at levels considered dangerous to humans in soil from agricultural lands along the river. Tests of municipal and residential drinking water supplies have been negative.
For the fish sampling, three species were tested for oil: smallmouth bass, rainbow trout and long-nose suckers. They were caught along an approximately 30-mile stretch of river starting just upstream of Laurel and ending below a diversion dam in Huntley.
Fillets were removed from the fish and tested for hydrocarbons to determine if they were safe to eat. Digestive and reproductive organs also were tested.
A Montana State University fisheries professor said Thursday's results should be reassuring for anglers, but raised concerns about future reproduction among fish that had evidence of internal oil.
Fisheries scientist Alexander Zale's students have been doing research for the last three years on the stretch of Yellowstone hit by the spill. He said indications of problems might not surface until next year, when the fish are older. Zale hadn't seen the results of the state's testing but hoped to review them.
"If (oil) is in their organs and getting into their eggs and sperm, you never know how that might affect things," Zale said.
He said one change in the river that researchers have noticed is that there appear to be fewer fish this year in the Yellowstone's backwaters and side channels -- areas where much of the oil contamination was concentrated. But Zale said that could be a result of spring flooding and not necessarily oil.
A spokeswoman for Exxon Mobil referred questions about oil in fish to Montana Fish, Wildlife and Parks.