DELTA SCIENCE: Lead Scientist Dr. Callaway updates the State Water Board on science efforts in the Delta

At the May 21st meeting of the State Water Board, Lead Scientist Dr. John Callaway updated Board members of ongoing science efforts in the Delta.  In his update, Dr. Callaway discussed the advisory panel report on biological goals, the results from the recent research solicitation, and a paper on salmon resiliency in the face of climate change.


State Water Board staff requested the Delta Science Program to put together an advisory panel to provide input on the developing of biological goals for the update to the Bay Delta Plan, asking them to look specifically issues related to salmonids, other native fish, and ecosystem processes.  The panel had six members and was led by former Delta Lead Scientist Cliff Dahm; on the panel were two scientists with a strong salmon focus, two with native fish, and two looking at ecosystem processes.  The panel started their work at the end of last year; they produced a draft report, held a public meeting, and received input from stakeholders; and the final report was completed in April.

Advisory panels give input on science behind the policy issues and what science should be considered in setting policy.  The panel did not give specific recommendations on exact goals, but instead were asked to focus on the approach to developing goals and the science behind the goals.

Recommendations on salmonids

The panel was specifically asked to look at a recent report on the Stanislaus River that used an approached called the viable salmon population approach and if that approach would be appropriate for use on other tributaries and the Delta to understand salmon population dynamics and to set goals.

The panel felt that it was a valuable approach,” Dr. Callaway said.  “They focused on salmon abundance and salmon productivity and they looked at using stock recruitment approaches, understanding the relationship of the adult population to the outgoing juvenile population and what is driving that relationship as a key way to understand dynamics within the population.”

The panel noted that rather than having a goal such as ‘doubling the population’, they suggested a focus on growing the population, or the abundance of population over time.  “They highlighted that if you have a population that is growing over time, you really need to look at this not only year to year but in five and ten year periods.  They highlighted the value of long-term monitoring data to understand this.”

The panel also highlighted the importance of understanding wild populations versus hatchery populations.  “The challenge currently is that there is not very good data in separating those,” he said.  “The goal is really around the wild populations and being able to manage them, so some of their recommendations were to look at ways we could get better data on wild runs versus hatchery runs, and also better data on individual tributaries.  Clipping the tags for all fish is their recommendation so that you could clearly distinguish between wild and hatchery fish.”

Recommendations for other fish

One of the panel’s recommendations was to consider all the fish in the ecosystem; given that some native species such as the Delta smelt have populations that are so small now that it’s hard to understand whether dynamics in the population are due to particular forcing factors or just random variations in the population.  So the panel recommends considering both native and non-native species; they also note the striped bass may be a surrogate as it has many of the same characteristics as some of our native fish.  The panel also noted that the growing populations of predatory fish are something to be concerned about, so the panel recommends looking at a broad range of species.

The panel again highlighted the importance of existing monitoring data.  “There is less data available for our native fish in terms of population dynamics, so we can’t do the kinds of population recruitment analysis for other individual native species, but we do have very good data on abundance and distribution from the work that the IEP and the others have been doing across the Delta,” Dr. Callaway said.   “There is not as much information up into the tributaries, so I think we do need to grow that data up into the tributaries.”

The panel recommended rather than looking at individual species, look at species groups.  The panel identified six different kinds of fish communities that could be useful that would give us an understanding of the range of the different needs across the fish communities within the estuary and the tributaries.

Ecosystem processes

The panel looked at the ecosystem structure, which are things such as vegetation, temperature, and the physical conditions as well as the chemical conditions of the ecosystem.  They also looked at ecosystem functions, such as productivity, plant growth, nutrient dynamics, turnover of nutrients, and food web support.  They noted that there is much less data available on ecosystem processes then for fish-focused efforts.

The panel stressed the need to look at productivity,” Dr. Callaway said.  “Primary productivity, whether that’s productivity in the channels of plankton or on the margins in terms of marshes and riparian areas, that plant growth, whether it’s algal, plant, or otherwise, is what’s driving the food web.  But in many cases, a challenge for our fish communities is the lack of available food resources, so we need to think about how do we get a better understanding of food productivity; then as we do more restoration, look to see are we really making large scale changes in overall productivity.”

Secondary productivity is the organisms that are eating all of that, whether it’s the zooplankton or the organisms in the mud,” he continued.  “They are providing the food resources for the fish and the birds and the other high level animals within the system.”

The panel also mentions looking at the water column and what’s happening with the plankton, he said, noting we have much better information on that and much less information on productivity in the marshes, and in that component.


Chair Esquivel asked if there were other examples of similar work around development of biological goals for various watersheds.  Dr. Callaway noted that other systems are making similar efforts; the report highlights work being done in Florida, Australia, Missouri, and Louisiana.  “I think the challenge here is the mix of dynamics,” he said.  “It’s water quality, it’s water flow, restoration – all of those issues make for understanding the driving forces is more challenging.”

Board Member Dorene D’Adamo noted that in the report where they outline the distinction between areas where quite a lot of information already exists, for example in the estuary, as opposed to the tributaries.  “Could you make an overly simplified comment on this regarding the lack of information?  Do we just need more funding in order to obtain the information, or is there something about the areas in the watershed in which we don’t have as robust information as say in the estuary where it’s more challenging to gather that information?”

Dr. Callaway acknowledged that lack of funding contributes to the problem, but the bigger issue is scale.  As the focus expands beyond the Delta, moving the monitoring up into those other areas with the intensity that is in some of the existing areas is just a huge challenge.  “I think what we really need to do is if we’re going to set these goals now, what are the priorities in terms of monitoring?  We can’t collect everything.  Setting the goals and having clear objectives is most critical for anything, but then linking the monitoring to those goals so we’re making sure we’re collecting the right kind of information so that we can understand the signal and understand the change that we’re hoping to see as we start to make management improvements.”

Dorene D’Adamo said that she was present when the panel discussed the recommendation, ‘focus on maintaining growing populations, rather than a simple goal of doubling.’  “I found it fascinating because I’ve always viewed the doubling goals as more of a policy goal as opposed to something that is attainable based on science,” she said.  “I don’t know that I would be able to distinguish that fine line between policy as opposed to science, so could you provide us any comment that would help us as we read through the report regarding growing populations rather than the simple goal of doubling?

There isn’t the science to support the idea that doubling the population is really the goal we should be achieving and that if we get to that, we’re done, and if we don’t get to it, we failed,” Dr. Callaway said.  “But we want to keep the populations moving in the right direction.  I think what they were pushing towards was in terms of the science, there isn’t clear evidence that that is better than tripling the population or increasing population by 50%, so I think an aspirational goal of doubling the population is really probably valuable, but in terms of whether we’re making progress, making sure that we’re moving in the right direction is what we should be doing and hopefully we make progress towards that doubling goal or better.”


In September of 2018, the Delta Stewardship Council, the Department of Fish and Wildlife, and the Bureau of Reclamation put out a call for proposals for research.  They received 62 proposals with the total request of $43 million.  Dr. Callaway noted that it is significantly more than has come in for the standalone proposals so it by working together and leveraging outreach, they could bring in a much broader group of proposals and be more selective in terms of identifying the top funding opportunities.

The Stewardship Council funded 15 proposals for a total of nearly $10 million, using all the funds in the budget for this year as well as a portion of money from next year’s budget; the Department of Fish and Wildlife funded 11 proposals for $7 million.  About a third of the proposals were funded, so they were able to be pretty selective.

They had outside reviews of the proposals and two separate review panels, so they received significant input as to the science merit and rigor as well as the management actions.  Then they coordinated with the Department of Fish and Wildlife and with the Bureau of Reclamation in the final funding decisions.

For the projects the Council funded, they focused on the Science Action Agenda to identify the priority science areas that aren’t being addressed by individual agencies.  There are five categories: human dimensions or social science issues; monitoring, data management, and modeling; science synthesis or using existing data to synthesize and improve our understanding; efforts around habitat restoration; and efforts around species of interest like the salmon and Delta smelt and other endangered species and the stressors that are affecting those populations.

We intentionally wanted to look at a broad range of issues and so we were able to fund across a wide range,” said Dr. Callaway. “You’ll notice that human dimensions or social science is definitely the smallest piece of the pie; that’s a function that we didn’t really get a lot of proposals in that area, and so we’re really trying to cultivate more interest in social sciences.

The proposals cover a wide range of issues, such as the effects of contaminant issues on salmon populations and smelt populations, productivity issues and the transfer of that productivity into the food web; subsidence reversal; carbon dynamics and climate change issues; and risks to levees.  In addition, there were other proposals that were funded by the Department of Fish and Wildlife.

Michael George asks about the fate of the projects that weren’t funded.  Dr. Callaway said the Council wouldn’t have funds next year, but the Department of Fish and Wildlife will have another call for Prop 1 proposal soon and applicants are encouraged to resubmit.  They are also preparing letters with information from the panelists so they will get some feedback and improve their proposals next time around.

I want to emphasize that we don’t want to do this as a one-time thing; we want to have some consistent funding for research so that the university researchers and the agencies that received funding will know there is that opportunity and they will be able to start growing their research students and staff so they can be better prepared the next time these opportunities come around,” said Dr. Callaway.

RESEARCH PAPER: Managing for Salmon Resilience in California’s Variable and Changing Climate

Lastly, Dr. Callaway talked about a paper that came out last year, Managing for Salmon Resilience in California’s Variable and Changing Climate, noting that this paper was a result of a workshop that occurred in 2015.  This report has been updated and includes information not included in the workshop.  The effort was led by Bruce Herbold, retired from the US EPA, and includes a number of other authors.  The paper highlights that there are many impacts to the salmon populations which have led to a reduction in the genetic diversity of the population, which in turn, has reduced their ability to be resilient to stressors like climate change.

The paper makes the point that by restoring habitat diversity, it’s more likely to result in a diverse population, and one way to do that is by restoring habitat diversity, that’s more likely to result in a diverse population.

A mix of habitat opportunities are going to create opportunities for different individuals within the populations, create different traits, and lead to more population diversity and more overall resilience,” Dr. Callaway said.  “The paper focuses on habitat but similar things could be thought about in terms of flow dynamics, if we have a mix of characteristics on the flow, that also is going to lead to a diverse population.”

The paper noted that over time, wild populations have been declining while hatchery populations have increased, which has led to the overall fitness or condition of the natural or wild population declining over time.  With California’s naturally variable climate being amplified by the effects of climate change, this has led to a reduction in the natural population and less opportunity for the natural population to recover and respond.

The report identified four areas that could improve resiliency, all focusing on habitat issues:

  1. Improve upstream access by providing access to areas above dams that were historically available to the salmon populations
  2. Reduce stresses by restoring areas within the lower part of the watershed to address food availability, water temperature, and water quality
  3. Restore life-history diversity by having juveniles that are moving out at different times rather than a single pulse, and thinking how to benefit them through all the different life from the upper watershed all the way down through the estuary and out into the ocean and across the whole continuum of their life history back to adulthood and reproduction.
  4. Improve artificial propagation by addressing hatchery issues and working with hatcheries so that they can continue to provide benefits in terms of growing the hatchery population but don’t have negative effects on the wild populations.


The Delta Science Plan has been updated.  Final plan will be out soon.  Some of the key components are  that it really focuses on awareness of climate change issues, incorporates social science as well as natural science issues, encourages better communication between scientists and decision makers; improving science governance, and developing a topic-specific science plans.

DPIIC Science Initiative: The Delta Plan Interagency Implementation Committee (DPIIC) recently endorsed the effort to encourage forward-looking science, or rather than doing the science just for today’s problems, thinking about what should we be doing to address upcoming problems, not only climate change, but also new invasive species, land use changes, and other impacts.  The DPIIC has set up four working groups to look at issues around current funding and ensuring that funds are being used efficiently in providing information of value.   The working groups will be putting together implementation plans for presentation at the November meeting of the DPIIC.

Delta Independent Science Board reviews: The Delta Independent Science Board is a group of ten outside scientists who give input and advice to the Stewardship Council and provide independent reviews of relevant science issues and efforts in the Delta.  They are currently working on a review of the Interagency Ecological Program and a review of the Delta Regional Monitoring Program.


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