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Ecology and salmon related articles

NOAA Builds Its Own
Crystal Ball for Fish Predictions

by Bill Rudolph
NW Fishletter, January 17, 2013

By tracking biological and climatic variables in the Pacific, scientists from NOAA Fisheries and Oregon State University say they have been able to accurately predict spring Chinook returns to the Columbia River for the past couple of years.

A new paper, published in the peer-reviewed PLOS ONE [Public Library of Science], called Multivariate Models of Adult Pacific Salmon Returns, analyzes results from tracking 31 different variables over an 11-year period to come up with a prediction for 2012 upriver spring Chinook returns. The NOAA researchers estimate was 179,000 fish, close to the observed return at Bonneville of 186,000 fish plus an estimated lower river harvest of 16,000 fish, which added up to 202,000 fish--a prediction that was off by only 12 percent. When fewer variables were included in the model, estimates of the 2012 return jumped to a range between 300,000 and 600,000.

The 2011 prediction, based on data through 2010, matched the observed return of over 221,000 fish nearly perfectly; it was off by only 6 fish, according to the authors of the paper.

They said none of the indicators stood out as the best predictor for future returns, but a few were significant, especially those that gaged potential salmon prey and salmon growth, along with large-scale indicators of sea surface temperatures.

But other indicators at local and regional levels didn't seem to nearly as important. Only one local indicator--sea surface temperature from November to March made the top 10, according to the paper.

"Interestingly," said the authors, "this particular indicator represented the temperature during the winter prior to ocean entry, suggesting that the relationship between winter ocean temperature and salmon survival is indirect, and perhaps operates mechanistically by mediating ocean productivity or prey resources the following spring." They said this idea was supported by the lower rank in importance of SST from May through September.

The paper said jack abundance prior to the year of adult return ranked only 11th to 18th out of the 31 indicators. "Indeed," they said, "many of the indicators that had been found significant in other modeling efforts showed little contribution in this analysis. Jack abundance is the major element in the predictive modeling by Columbia Basin harvest managers in the U.S. v. Oregon process.

And indicators that represented the Columbia River environment ranked even lower. River temperatures ranked between 22nd and 24th in importance, while flows came in near the bottom. Curiously, upwelling indices also did not seem to play much of a role.

The researchers also reported their June smolt surveys correlated better with adult returns than those conducted in May. That, along with previous research that suggested smolt size at marine entry was not related to adult returns, but fish size a month later, was related, "suggest that feeding, growth, and concomitant mortality between May and June are important drivers for setting salmon year-class strength."

But the paper noted that top-down drivers of spring Chinook survival like predators such as hake, can still play important roles in the size of adult returns, especially for those Columbia river fish that migrate north soon after they enter the ocean.

The authors said their modeling approach "promises to be important to salmon management in the Pacific Northwest," because their large suite of indicators can capture the complexities of the ocean environment in ways other models that rely on only one or two indicators cannot. But they said future data collection of some indicators can be expensive, while others not so much. But if future collection relies on fewer indicators, they cautioned that prediction error in forecasts could easily double.

With management agencies setting quotas for the multi-million dollar Columbia River fisheries, and still trying to get ESA-listed stocks past the nets and hooks, the authors said the cost of inaccurate forecasts is significant, but by optimizing information to estimate future returns, "managers can more efficiently apportion catch and plan for future scenarios, resulting in more equitable fisheries and a better chance of recovering these threatened and endangered species."

BPA funds part of the data collection involved in this work and has previously said it is not part of the Basin's core F&W funding, but independent scientists have found the work to be important. Supporters of the ocean research now have to justify funding and try to work with freshwater managers.

Last March, NOAA Fisheries' assistant regional administrator Bruce Suzumoto told the Northwest Power and Conservation Council that the ocean research was especially important because it provided a context for "what we do in fresh water. Bad ocean conditions can mask our freshwater activities and lead to some misinterpretation of the successes of the actions, and what types of actions we should be taking." He said the physical and biological ocean indicators developed by NOAA were helping harvest managers make fish predictions, and were playing a role in the development of early indicators that could warn managers of potential problems for some of the fish populations coming back to the basin.

As more data from the research is collected, Suzumoto said it would be incorporated into the agency's lifecycle modeling effort, which is likely to form the basis of the analytical structure of future BiOps. It could also be used to change fish transport operations or hatchery release schedules to match ocean conditions. He noted this is already being done in Alaska's Prince William Sound, where hatchery releases are scheduled to coincide with plankton blooms.

At that same meeting, Bill Maslen who heads up BPA's fish and wildlife division, said the researchers had been doing "pioneering work that has been a fruitful effort." but he noted that some of the questions asked during the review were not appropriate. "They are management and policy questions which are informed by that research," he said. "I think we need their help in determining how that research can be applied in a meaningful way. It's not their question to answer in entirety."

To a certain degree, those linkages between ocean and freshwater are still hypothetical. Maslen said. That doesn't mean they're not real, but either "we haven't focused enough to strengthen them given the high variability that we see," or there may be linkages, "but the managers and policy folks haven't made the choice to actually utilize that information," he said.

Maslen said more focus was needed on causal mechanisms, linkage to freshwater activities, and how that information could be used. He said it was great work but questioned whether it was the responsibility of the Action Agencies to fund all of it.

More than $25 million has been spent on ocean research over the past decade. Fiscal year 2011 costs for the NOAA research, which included multiple contracts, added up to $2.1 million; the Canada-U.S. Shelf study cost $456,000; and the acoustic tracking study came in at $2.14 million. Shutdown costs for the acoustic tracking research were pegged at $656,000 for FY 2012.

Bill Rudolph
NOAA Builds Its Own Crystal Ball for Fish Predictions
NW Fishletter, January 17, 2013

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