Scientists Seek Cause in Texas Dolphin Deaths

Dolphins have been turning up dead or dying on the Texas coast this year at twice the normal rate, and no one knows why.

More than 220 bottlenose dolphins have been found dead since January, mostly within a 50-mile stretch of the southeastern coast in Calhoun and Aransas counties, just north of Corpus Christi.

In a normal year, 50 to 100 dolphins turn up dead along Texas’ 360-mile-long coast from February through April.

“Our people in our lab were thinking, ‘Something’s different here,’ ” said Tom Wagner, a fisheries biologist with the state Parks and Wildlife Department.

One theory is that this year’s record-setting rains have flooded the bays with runoff pollutants, such as toxic heavy metals or fertilizers. Fertilizer can stimulate the development of naturally occurring toxins.

Dolphins give birth in the late winter and early spring, but no connection has been established between the deaths and calving; dolphins of all ages have been turning up dead.

The National Marine Fisheries Service has collected tissue samples, examined the carcasses, sampled water and watched for new strandings.

The materials have been sent to labs around the country. The results probably won’t be available until late summer, said Gerald Scott, a fisheries biologist.

But Scott said, “Based on our prior analyses and prior investigations, it’s unlikely that any one thing will pop out as the ultimate cause of death of these animals.”

For example, a die-off in 1987 and 1988 that killed about 750 dolphins on the East Coast was attributed in part to a biological toxin, said Nina Young, marine mammal coordinator for the Center for Marine Conservation in Washington. But a conclusive cause was never found.

And in 1990, about 300 dolphin deaths were recorded from Texas to Florida, many of them attributed to the cold weather.

“What’s eluded us (in the past) is a sort of smoking gun,” Young said. “We can’t attribute any of these mortalities to any one specific cause.”