Chinese sturgeons are seasoned travelers, undertaking a round-trip journey of some 2,000 miles (3,500 kilometers) every year from the East China Sea to their spawning grounds in the Yangtze River.
But in recent years this ancient cycle has been blocked by the Gezhouba Dam, built in the 1980s. Since that time subsequent dams have placed new, possibly insurmountable, hurdles in the sturgeons' upstream path and thrown the future of the species into serious doubt.
Heavy shipping traffic, overfishing, and water pollution have also plagued Yangtze River waters and taken a heavy toll on these aquatic behemoths. Some scientists think fewer than a thousand individuals may remain.
Chinese sturgeons can grow to enormous proportions, with large specimens topping 16 feet (5 meters) and 1,000 pounds (450 kilograms). These prehistoric-looking giants have a sharklike form, with large pectoral fins, a rounded snout, and rows of pronounced ridges running the length of their spine and flanks.
Chinese officials have made efforts to safeguard the sturgeon, including curtailed fishing and the creation of a conservation area below the Gezhouba Dam to serve as an alternative spawning ground. They've also attempted to replenish the fish's dwindling numbers by breeding millions of fry in captivity and releasing them into their native rivers. So far such efforts have met with little success.
Sturgeons may face long odds, but the fish has survival in its genes. Sturgeons have lived in the Yangtze for perhaps 140 million years, and this relic of the dinosaur era is sometimes dubbed a "living fossil."
Some reports suggest the sturgeon may already be adapting to its changing environment. Studies suggest its diet is shifting from less abundant bottom dwellers, like clams, to more plentiful earthworms.