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CORVALLIS - A flawed method of research has contributed to a dramatic decline in fish populations across much of North America, researchers from Colorado State University and Oregon State University have charged in an international scientific journal.

"Although our failure as a society to conserve stream fishes is tied to complex economic, cultural, and philosophical issues, we contend that there is also a fundamental problem plaguing the scientific basis for much stream fish conservation biology and management," write the scientists in an article in the June issue of Bioscience.

The problem is that for decades fisheries ecologists have studied short fragments of rivers and streams over two- to four-year periods, drawing conclusions "only weakly linked" to the large-scale, long-term challenges that land managers often address.

The article's authors - Kurt Fausch of Colorado State University and Christian Torgersen, Colden Baxter and Hiram Li of Oregon State University - note that rivers and streams are "by their very nature long ribbons of aquatic habitat," moving and changing over long periods of time. A more effective method of studying the processes that interact to influence fish populations would be to develop a continuous view of an entire "riverscape, unfolding through time," say the authors.

The stakes are high, they assert.

"One symptom of our incomplete understanding," say the authors, "is the alarming rate of decline over the last 50 years of fishes that inhabit rivers and streams of North America."

"The public is aware that salmon are disappearing from the Pacific Northwest, with about a quarter of the 214 stocks of anadromous (ocean-going) salmon and trout imperiled a decade ago. Even little-known small fishes native to Great Plains and southwestern desert streams have suffered drastic declines."

Ensuring that "a modicum of stream fish biodiversity is sustained for future generations," the four scientists say, will require different ways of thinking, sampling riverscapes and planning landscapes.