(The following is a response to the June 20 commentary in Western Farm Press on the recent National Marine Fisheries Service's biological opinion about the fate of several fish species and the operations of the state and federal water exporting delivery systems.)

NOAA's National Marine Fisheries Service recently completed a biological opinion that determined the state and federal systems exporting water from California's Central Valley would likely jeopardize a number of threatened or endangered species with extinction, and put habitats critical for their conservation at risk.

We also suggested reasonable and prudent ways state and federal agencies could ensure the survival of winter and spring-run Chinook salmon, Central Valley steelhead, the southern population of North American green sturgeon and Southern Resident killer whales, which rely on Chinook salmon runs for food. These would be the minimum necessary actions to allow for continued operation of the federal and state water projects in coexistence with the threatened and endangered salmon, sturgeon, steelhead, and killer whales. The biological opinion also provides an incidental take exemption for the lawful take of these protected species so the water projects can operate in a manner consistent with the federal Endangered Species Act.

We at NOAA firmly believe that what is at stake here is not just the survival of a number of different species, but the health of an entire ecosystem. The current state of salmon, sturgeon, and killer whales is yet another sign of an ecosystem under stress.

From the beginning, our biologists, scientists and managers clearly understood that we wanted to minimize the social and economic costs to farmers, residents and communities that have historically depended on the Delta for their water supplies.

Drought is a natural phenomenon in California; yet in these drought years, farmers and other water users can experience significant hardship. We were keenly aware of this hardship, and our biologists and hydrologists took great care to craft actions that would not exacerbate impacts of drought, while still allowing for the survival of the species.

When we were asked by the federal Bureau of Reclamation to provide this opinion, we knew our results would be highly controversial no matter what our research suggested.

Water is a highly contentious topic in California, for both the economy and the environment. So we incorporated not only our own agency's scientific input, but that of two independent science organizations to ensure our findings were solidly grounded in the best available science.

For more than four years, we studied the water operations in the Central Valley and the needs of the species at risk of extinction. We also realized that the Central Valley Project infrastructure is old and in need of serious repair if it was to work with the needs of salmon and other endangered and threatened species. It was difficult and demanding work, and certainly one of the most complicated scientific analyses ever conducted by our agency.

In some cases, we and our partners found answers to serious problems. For instance, warm water temperatures below Shasta Dam were killing salmon nests downstream and seriously degrading the environment for the rearing of salmon fry. Working with the Bureau of Reclamation, we modified when cold water will be released from the dam, thereby lowering water temperature and protecting the eggs and fry. This remedy requires only better coordination of when flows should be released.

In other cases, like the San Joaquin River, we found that more than 90 percent of the steelhead die as they try to make their way back to the ocean because there is simply not enough water and velocity in the river. And although these animals are notoriously tough — they have adapted over thousands of years to California's droughts — they simply cannot survive without more water flow during their peak migration periods in April and May.

Protecting these threatened or endangered species will cost an estimated 5 percent to 7 percent of the available annual water exported by the federal and state pumps — or about 330,000 acre feet per year.

The total combined water exported is approximately 6 million acre feet per year. Compared to the total, 330,000 acre feet (or 5.5 percent) is a relatively small amount. Moreover, this water during April and May is intended to create positive flows in Old and Middle rivers to ensure that juvenile steelhead successfully migrate through the lower San Joaquin River during their peek migration period.

Again, the stakes for the entire ecosystem and the fishery economy are very high. Economic disaster declarations have been declared two years in a row for commercial and recreational fishermen who rely on fall run Chinook salmon produced from the Central Valley water system. And while these fish are not currently in danger of extinction, we know the actions of this plan will also help in protecting their long-term viability as an economic engine for California's economy. Just like farming, a healthy economy grows from a healthy environment.

While the difficult actions we suggest in the opinion came from a dispassionate, science-based approach, the science itself is clear. And while many actions can be readily accomplished, others will require new investments and changes to water operations.

We need to take the necessary actions to ensure the survival of these species for their sake, for the economy, and the sake of the entire ecosystem.