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Maximum flows not achieving maximum benefits for Stanislaus salmon

Fishery technician with FishBio work on a screw trap on the Stanislaus River near Oakdale. FishBio has been counting salmon on the Stanislaus for 25 years.
Fishery technician with FishBio work on a screw trap on the Stanislaus River near Oakdale. FishBio has been counting salmon on the Stanislaus for 25 years. Modesto Bee file

The study released this week by FishBio on the impact of fall pulse flows on salmon in the Stanislaus River should be mandatory reading for the men and women at the state water board. It uses scientific data gathered over 11 years to burst the myth that “more water equals more fish.”

As our districts have been saying for decades, the right amount of water, released at the right time, combined with other environmental improvements and fishery strategies, can truly accomplish the goal we all share – to increase the number of salmon that are hatched and return to spawn in the river.

Today, we have maximum flows without maximum benefit.

Various state and federal agencies continue to enforce a myopic and wasteful policy that encourages the irresponsible release of millions of gallons of water each fall in a desperate and unscientifically supported effort to attract spawning salmon. Worse, the state water board wants to double down on a failed strategy and impose additional flow mandates in the spring.

Water is one of many important components to help salmon, as the FishBio report again shows. It is based on data collected over 11 years – before and during the drought. The study looked at several environmental factors and their influences on salmon migration (dissolved oxygen, water temperature, food availability) and several management actions (fall pulse flows and installation of a rock barrier).

A few key findings should open some eyes:

The optimum fall pulse flow is 700 cubic feet per second. Above that, data show no additional benefit to fish. Yet, the fall flows often are more than double that at 1,500 cfs or higher. Over a typical seven- to 10-day fall pulse flow, that’s as much as 16,000 acre-feet of water that can’t be stored and used later by fish and farmers, or delivered by SSJID to its customers.

FishBio’s research clearly shows salmon are not attracted from the ocean or Delta by pulse flows – as the state often contends. Instead, they are already in the lower part of the river and are simply stimulated to move upriver to spawn. We know because we see how many fish immediately swim through FishBio’s weir near Riverbank.

At the weir, each fish is forced through a narrow channel, where photographs and imaging devices are used to identify it. Those data show that though the past two years have seen an impressive number of spawning salmon (14,356 in 2016 and 12,621 in 2015), very few are native to the river. They were hatchery fish that have been trucked in and released as juveniles on the west end of the Delta.

The installation of a rock barrier at the head of the Old River west of Stockton improved salmon migration. Basically, it’s a rock wall that keeps salmon from making a wrong turn while increasing the dissolved oxygen in the river – which is also good for fish.

There is no better sight than standing on the Knights Ferry Bridge in the fall and looking down to see salmon preparing to spawn. A healthy river with naturally sustaining salmon and trout populations is good for everyone. It was part of the legacy our forefathers left to us and that we intend to pass on to future generations.

Our districts have proudly funded FishBio’s work on the Stanislaus for a quarter-century. It is an important investment we are happy to make.

We strongly urge state and federal agencies to review the latest data, ask the appropriate questions and make decisions about adaptive management of salmon and other fish on the facts, not assumptions or guesstimates.

For instance, the state refused to cancel one fall pulse flow during the drought so FishBio could run a “control” and see how fish reacted. Instead, when the river would have been naturally low anyway, more water was released from New Melones. That’s shameful.

The study shows that pulse flows should be varied to mimic natural stream patterns for different times of the year and for different amounts of rain under wet or dry conditions.

You can’t manage what you don’t know. Continued investments in science and technology are critical to furthering our knowledge of the river. With our water supply increasingly limited, having a clear understanding of how much water is needed for fish, and when, is key to sustainably managing the Stanislaus River basin.

Bob Holmes is chairman of the South San Joaquin Irrigation District board of directors. Steve Webb is chairman of the Oakdale Irrigation District board of directors. For more information, visit SavetheStan.org.

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