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Real Down Time

Biologists cut a chunk out of the real-time, in-the-water, monitoring program of endangered fish distribution in the Delta early this year because it wasn't helping them tell water managers when it was safe to pump.

The cutback involved "Kodiak trawling" for salmon smolts in which two boats stretch a 15-foot-wide, 6-foot-deep net between them and trawl numerous interior Delta stations 10 times a day, five days a week between April and June. According to Cal Fish & Game's Kevan Urquhart, a recent review of five years of trawling data found no relationship between the number and kinds of smolts caught in their nets and those turning up at the pump's fish salvage facilities. "We were basically asked to use a little tiny net to find a depleted and patchy fish population in hundreds of miles of Delta waterways, and to then predict what would happen to the fish at two facilities that divert up to 55% of the Estuary's water," he says. In four out of the five years, total annual trawl catch was eight or less winter-run salmon.

While real-time monitoring using different methods has done well for predicting when Delta smelt are within danger range of the pumps, "no such effective mechanism has yet been found for salmonids," he adds. The reason may be that smelt are resident fish present all over the Delta day after day, unlike the more transient salmon. For this same reason, real-time monitoring of salmon at key entry and exit points to the Delta has been more effective than the interior Delta Kodiak trawls.

"Some people thought we needed to be able to pick out exactly which island the salmon happened to be around everyday," says U.S. EPA's Bruce Herbold. "But this kind of daily data from right in the center of the Delta turns out to be less realistic and useful, in terms of giving pump managers enough lead time to help the fish, than the data on when salmon come in and out of the system."

In the meantime, the Kodiak trawl data is being re-reviewed by interagency experts to see if something was missed. Some say other gear types should be considered; others say trawlings need to be stepped up to a mind-boggling 25-100 times a day. Whatever the outcome, such finetuning remains critical to the ongoing task of directing any water CALFED buys or banks to help fish when and where they need it most.

Contact: Kevan Urquhart (209)948-7800

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