Lack of food called health threat for fish

Friday, Jan. 12, 2001 | 11:20 a.m.

For the first time a scientific study has linked the lack of food sources in the Las Vegas Bay -- not toxic chemicals -- to a major health threat for game fish.

However, scientists working for the Southern Nevada Water Authority said they will continue studying the effects from chemicals, toxic pesticides and drugs found in Las Vegas Valley runoff flowing into Lake Mead, the area's major source of drinking water.

"The study is interesting, because it is the first time fish starvation has been proved," said Kim Zikmund, the Las Vegas Wash coordinator for the Southern Nevada Water Authority.

The water authority is conducting its own studies on changes in hormones and enzymes in the fish that live in the bay, she said.

In a final report delivered Thursday, biologist Jim Pollard of UNLV's Harry Reid Environmental Research Center said a two-year study of 660 fish in the bay and Lake Mead failed to show effects from toxic chemicals, but did indicate large-mouth bass and stripers starved in autumn when chad, a smaller fish, was scarce.

Pollard initiated the fish study after the U.S. Geological Survey reported in 1997 that pesticides, insecticides, heavy metals and other substances flowing from the Las Vegas Wash through the bay to Lake Mead were causing male carp to produce female egg yolk protein. Normal male fish show no evidence of protein.

With $50,000 of UNLV research funds, Pollard began collecting four species of fish, including large-mouth bass, blue gill, channel catfish and striped bass.

At first Pollard thought the smaller fish indicated that some pollution source was affecting the fish, because they were not growing to full size.

But as the study continued through 1999, fish experts found that chad, the primary source of food for the bass, were low during the 1998 fall season. The size of the bass improved in spring 1999 when enough chad appeared.

"There's no evidence there's a contaminant problem in the bay," Pollard said, but added that he cannot rule out subtle effects in the fish from fossil fuels, chemicals or prescription and over-the-counter drugs.