Seven-foot living ’dinosaur’ lurks in Oregon

What’s seven feet long, 250 million years old, and currently lurking in the depths of Oregon’s Rogue River? It’s the green sturgeon, the craggy, shark-like fish that has quietly eked out a living since the time of the dinosaurs. But according to a new study published by researchers from the Bronx-Zoo based Wildlife Conservation Society and other groups, this living fossil is extremely vulnerable to both overfishing and habitat alteration such as water diversion for irrigation and pollution. The study appears in the current issue of the Journal of Applied Ichthyology.

Using radio-tracking techniques, the authors of the study found that once green sturgeon enter freshwater rivers to spawn they spend long periods of time in extremely small home ranges — sometimes just a 50-by-50 yard pool — shared by numbers of individuals. This, coupled with the fact that the fish breeds in just three North American rivers, including the Rogue in Oregon, and the Klamath and Sacramento in California, makes it particularly sensitive to human impacts.

“This study shows that green sturgeon can easily become the victims of human exploitation and habitat loss,” said Wildlife Conservation Society biologist Dan Erickson, the lead author of the study. “Precautionary management measures, such as the current sport-fishing regulations in the Rogue, may be justified to protect populations throughout its limited range.”

In the Rogue River, anglers can only keep sturgeon under 152 centimeters (just under five feet). Most found in the Rogue exceed this length.

One of 25 species of sturgeon found worldwide, the authors of the study say that the green is the least understood species due primarily to its limited breeding range. Once at sea, however, the fish can be found anywhere from Mexico to the Aleutian Islands.

The research team equipped some 19 green sturgeon with radio telemetry tags – no small feat for a fish that can weigh over 200 pounds. To capture sturgeon, the team set out gill nets and hauled the fish into shallow water, where they were measured, tagged and released.