Fish Kills
Monday, November 5, 2001
Copyright © 2001 Gary Valle'. All Rights Reserved.

Near the beginning of September, 2001, I was sitting on the bank of the Lower Kern River, downstream of the Borel Powerhouse, watching dead fish float by.

A friend was supposed to meet me, and while waiting, I pondered the River. A beaver had gnawed on a nearby Cottonwood and a few small dead fish were floating in an eddy and were trapped in the rocks along the shore. A number of dead fish were also in the river. I wondered, how many?

I counted approximately 15-20 dead fish on the surface passing by every 10 seconds. So, that's 120 fish a minute, or about 7200 an hour. Assuming not all fish were on the surface, a very rough estimate was 10,000 dead fish an hour were going by that point.

This was a dramatic number, and difficult to believe, but as I walked upstream I saw more and more fish littering the shoreline, and at the head of a small island, there were literally mounds of small fish. Maybe the estimate was not exaggerated. What kind of fish were these and what killed them?

Fish kills can occur for many reasons, but the most common is low levels of dissolved oxygen in shallow reservoirs, lakes and ponds. (Both natural and man-made.) Water in the Lower Kern is released from Lake Isabella, a reservoir completed in 1953 for flood control and irrigation. Following three years of below average snowpacks, the lake was at about 20% of its capacity.

I had heard that a fish kill had occurred recently at Lake Isabella. Were these fish simply washing down from the reservoir?

I found the answers to many of my questions in the Bakersfield Californian article, Fish, bird die-offs don't worry officials, by Jill Hoffmann.

According to the article, these fish are Threadfin Shad and they were killed when they entered the Borel Canal and were flushed through the Borel Powerhouse.

A Dept. of Fish and Game biologist said, "the shad die-off is not expected to affect the overall population at the lake."