Technically the same species, the two fish types will be treated differently

By MATEUSZ PERKOWSKI

Capital Press

Steelhead deserve Endangered Species Act protection despite their ability to interbreed with rainbow trout, according to a federal appeals court.

The two types of fish are technically the same species, Oncorhynchus mykiss, but steelhead migrate to the ocean while rainbow trout stay in rivers and streams.

Six irrigation districts in California -- Modesto, Turlock, Merced, Oakdale, South San Joaquin and Stockton East -- filed suit against the federal government in 2006, claiming the threatened species designation resulted in reduced water deliveries and increased regulations.

According to the irrigation districts, the federal government violated the Endangered Species Act by treating steelhead differently from rainbow trout, which don't face extinction.

The National Marine Fisheries Service, which made the listing decision, countered that the steelhead can be protected as a "distinct population segment" of the species because it has a different life cycle than the rainbow trout.

Offspring from steelhead can stay in fresh water and boost rainbow trout populations, but research has shown that it's rare for rainbow trout offspring to adopt the migratory life cycle -- thus hindering their ability to regenerate steelhead populations, the agency said.

A federal judge in California sided with NMFS in 2008, ruling that "in a case riddled with complex and uncertain scientific information, deference is owed to the agency's expert knowledge of the subject matter."

The irrigation districts appealed to the 9th U.S. Circuit Court of Appeals, claiming the judge did not correctly interpret the Endangered Species Act and that NMFS adopted its policy without sufficient rationale.

On Aug. 20, a three-judge appellate panel acknowledged the "practical difficulties" presented by the listing, noting that "plaintiffs may have to protect both the steelhead and the rainbow trout, even though only the steelhead is threatened."

However, NMFS was entitled to categorize steelhead as a "distinct population segment" of the species and its policy was supported by adequate evidence, the appellate court said.

"We agree with the district court that under the ESA, interbreeding is not alone determinative of whether organisms must be classified alike where, as here, they develop and behave differently," the ruling said.