Sacramento River Fall-run Chinook Salmon – Applying an Integrated Ecosystem Assessment along the US West Coast

 

 

At a Glance

How does an Integrated Ecosystem Assessment (IEA) approach differ from previous NMFS efforts to conserve and manage Fall-run Chinook salmon?  

-       In the past, NOAA managed salmon stocks primarily based on biological factors, such as stock size.  Today, the IEA approach enables scientists to consider additional ecological and anthropogenic relationships, such as species interactions and effects of environmental conditions on salmon life history, along with public needs and interests, in one management framework.  The IEA has the potential to provide a more inclusive and integrated process finding solutions that maximizes the human and environmental benefits of salmon conservation. 

 

What are the environmental factors NMFS is considering?

-       Ocean conditions (e.g., sea surface temperature and upwelling)

-       Fresh water conditions (e.g., flow, temperature)

-       Forage (prey) species

-       Predators

-       Environmental variability and climate change

 

What are the anthropogenic factors NMFS is considering?

-       Freshwater use and management

-       Commercial and recreational fishing

-       Safe, reliable seafood (e.g., restaurants, grocery stores, fish markets and sustainable seafood efforts)

 

How does the IEA improve management?  The IEA will:

-       Promote stability of salmon stocks by reducing variability in salmon survival

-       Promote economic stability by reducing variability in commercial and recreational fisheries

-        Promote balance in trade-offs among salmon biology, fisheries, freshwater user groups and regional economics

 

Chinook salmon are anadromous and semelparous: beginning life as eggs buried in freshwater streams, they swim downriver and through estuaries as juveniles to spend years as adults at sea, before returning to their natal river to spawn and die.  Throughout their lives, Chinook salmon interact with a diverse array of human activities, including agriculture, hydropower, transportation, and fishing. An IEA approach to management, in which all user sectors are considered, is a progressive approach for the protection of the Sacramento River Chinook salmon. 

 

 

With the IEA, we will be better able to address specific questions for users such as: What is the ultimate impact of changing river flow rates on salmon populations and at what cost to users? Does changing flow rates equate to substantially more adult salmon? What is the impact of fishing during different seasons on protected salmon stocks? How do these options interact?
The benefit of using an IEA approach is to provide a process to holistically manage the stock by considering all user sectors and the needs of salmon throughout their life cycle.  Ultimately, our goal is to improve the conservation and management of this important species by providing a means for managers and the public to determine the best way to accommodate trade-offs for any given management strategy. The IEA supports the Pacific Fishery Management Council’s Salmon Fishery Management Plan, the California Department of Fish and Game’s efforts to improve freshwater practices, supports industry (such as hydroelectric companies and agriculture businesses) to better manage water use and helps the public to become better informed.

 

 

 

The IEA process for Sacramento River Chinook salmon is constructed around appropriate models to evaluate the factors affecting the salmon at every stage through their life-cycle.  Specifically, the sensitivity of salmon at different life stages to management decisions must be quantified and then evaluated in combined management strategies. These models and their evaluation are developed by scientists from the Southwest Fisheries Science Center.  For example, in freshwater, we know dam removal has an impact on salmon survival, but does dam removal lead to significant gains in return numbers, catch, and economic benefit?  To address this question, the SWFSC and its collaborators has implemented models to evaluate the biological and economic trade-offs of dam removal in northern California. While this work was done on the Klamath River in northern California, insights can be gained for other systems, such as the Sacramento River.  As Chinook
Chinook salmon (Oncorhynchus tshawytscha), are an iconic species of California’s rivers and the waters of the California Current and North Pacific Ocean, the source of the largest commercial and recreational salmon fisheries in California, a key ecosystem component and a Species of Concern under the Endangered Species Act.
salmon move downstream to estuarine waters, such as are found in the San Francisco Bay Delta, they are also impacted by the diversion of water resources and degradation of habitat. SWFSC researchers are developing models to evaluate the survival and condition of salmon related to habitat degradation of the estuarine ecosystem in which salmon exist. Strategies are also being evaluated to determine the benefit of altering current water management and hatchery practices. For salmon during the oceanic phase of their lifecycle, members of the IEA and SWFSC have developed models to describe the oceanographic and trophic relationships leading to increased or decreased survival in the ocean. With additional support from the National Aeronautics and Space Administration (NASA), these ocean results are currently being coupled to regional oceanographic modeling systems output to improve forecast for salmon fisheries. Finally, we have an on-going project funded by the Ocean Protection Council and California Sea Grant to combine the results of these models into a single framework to allow for a holistic evaluation of management strategies both in isolation and combined.

 

 

The following sections discuss how NOAA’s research on Sacramento River fall-run Chinook salmon supports the components of the IEA: engagement, status, risk, assessment, and management strategy evaluation.


ENGAGEMENT

Scoping, the first step of the IEA process, is a means of identifying the interests, concerns and goals in managing complex natural and anthropogenic systems by consultation with user groups.  The on-going nature of the Sacramento River fall-run Chinook salmon management and monitoring precluded formal scoping; however, diverse user and management groups have been, and are actively, engaged in the IEA process with NOAA scientists. Examples of these groups include researchers, fisheries and freshwater managers at state and national agencies, hatchery managers, commercial and recreational fishers, and hydropower companies. A short list of interests, concerns and guidance from these groups, include:     

  • Engagement with the Pacific Fisheries Management Council identified maintaining salmon stock at high enough levels to both provide sufficient catch and sufficient number of fish returning to sustain the stock
  • Engagement with the hydropower companies and state freshwater management agencies identified interest in finding ways to open rivers for spawning salmon while maintaining sufficient gains from dams to support freshwater needs for hydropower, flood control, homes, businesses and agriculture. 
  • Engagement with hatchery managers identified the need to understand how current hatchery practices may weaken the natural population through competition and interbreeding and to improve hatchery protocols.

 

INDICATOR SELECTION

Within the IEA framework, “indicators” provide an efficient means of assessing the status of biological factors as well as environmental and anthropogenic pressures on natural systems, relative to pre-agreed upon benchmarks. In the Sacramento River fall-run Chinook salmon IEA, scientists assess indicators of the status of salmon and on ecological, physical and anthropogenic features of the environment that have a significant impact on salmon.  Examples of these indicators include:

 

Salmon - The Sacramento Index, a salmon index of adult abundance used by managers, informs us about salmon abundance, production, and variability of the stock. NOAA scientists measure condition of the stock by examining trends in hatchery contribution, age structure, and size at age. We use these measures to represent indicators of salmon health.

 

 

The status of each of the biological, environmental and anthropogenic indicators…are estimated by NOAA, in collaboration with other state and federal agencies and the Pacific Fisheries Management Council.
Environment - Freshwater and ocean conditions affect salmon and need near real-time evaluation to quantify the pressures affecting salmon at any given time (including indicators of forage health and predator abundance). Therefore, in freshwater NOAA scientists monitor and model flow and temperature which can affect survival at the earliest stages and in the ocean we monitor and model wind, upwelling, and temperature characteristics which relate directly to production of the system and early survival in the ocean, growth, and later maturation of the salmon. As well, freshwater and marine predators are monitored concurrently with the distribution and abundance of salmon prey species. Ultimately, we have an ecosystem view of the salmon through their lives including the environmental pressures, prey resources and the potential impact of predators.

 

 

Humans - NOAA scientists also monitor anthropogenic pressures that can affect salmon. We track variability in freshwater flow regulated by dams, water withdraws, hatchery practices, and commercial and recreational fishing.

 

STATUS

Within the IEA framework, “status” refers to process of assessing the level of each of the previously-determined indicators so that they can later be compared to baseline or threshold conditions (see below for “Assessment”).  Within the Sacramento River fall-run Chinook Salmon IEA, the status of each of the biological, environmental and anthropogenic indicators listed above are estimated by NOAA, in collaboration with other state and federal agencies and the Pacific Fisheries Management Council.  Many different methodologies are utilized.  For salmon, studies on the abundance, productivity and variability for different salmon stocks along the coast are conducted on a regular basis by either the SWFSC or the Pacific Fisheries Management Council.  For environmental indicators, NOAA and its collaborators use ship-board observations, satellites, and oceanographic models to evaluate the current status of the environment and the potential stress or benefit brought with it.  For human activities, NOAA scientists utilize a variety of measures, such as the US Geological Survey’s gauges of stream flow, levels of recreational and commercial fishing based on port sampling, and research cruises to assess the relative abundance of hatchery fish in the ocean.   

 

RISK

Figure 2. Shasta Dam on the Sacramento (photo provided by Cindy Thomson)

NOAA scientists working within the IEA framework evaluate risk for the Sacramento River fall-run and a number of other Sacramento River stocks, including protected runs, within the river system. Our estimation of risk for Sacramento River stocks takes into account environmental factors, forage (prey) base, predator factors and human impacts such as fishing and human water use for homes, businesses and agriculture that potentially affect the viability of the salmon stocks.  We have quantified the status of indicators, as previously discussed, for the salmon and each of the identified pressures. The real-time risk, then, is determined by evaluating how close the current abundance of salmon is to a minimum number needed for stock stability (status) coupled with the status of current pressures affecting salmon. In this analysis we also consider the relative impact of each of the stressors allowing for a holistic and balanced estimation of risk.

 

 

The real-time risk, then, is determined by evaluating how close the current abundance of salmon is to a minimum number needed for stock stability (status) coupled with the status of current pressures affecting salmon.
A specific example can clarify how risk is determined. Assessment reports track trends in salmon stock abundance and are used to determine the relative risk of fishing on achieving escapement goals. Beyond the fisheries aspects, we evaluate risk by overlaying flow and temperature characteristics in freshwater to evaluate potential concerns of early habitat degradation. We collect data on river emigration numbers to provide information about the status of the salmon stock before entering the ocean and before ocean mortality.  We also track water level, river temperature and estimates of water withdraws from the river (for human uses) to assess river conditions and their impact on salmon viability. In the ocean, we have numerous trawl surveys that inform us about the prey and environmental conditions that salmon will be exposed to as they leave the freshwater system. These ocean surveys have proven very effective at measuring salmon productivity (abundance and variability in abundance). Finally, we evaluate risk by overlaying these various stressors on the status of the salmon - and environmental conditions – to get as accurate assessment of risk as possible. Many of these studies have been completed and we use them to quantify the actual impact of each of the stressors named above on the Sacramento River stocks individually and in combination.

 

 

 

Figure 3. The Sacramento and San Joaquin River systems cover a great deal of California’s Central Valley and feed into an incredibly complex delta system. Chinook salmon have historically occupied the majority of this system as spawning adults, fry and emigrating juveniles.  A number of anthropogenic stressors have reduced the capacity of the system to provide salmon secure habitat and exodus including: dams, water diversions, habitat alternation and urbanization. 

Figure 3. The Sacramento and San Joaquin River systems cover a great deal of California’s Central Valley and feed into an incredibly complex delta system. Chinook salmon have historically occupied the majority of this system as spawning adults, fry and emigrating juveniles.  A number of anthropogenic stressors have reduced the capacity of the system to provide salmon secure habitat and exodus including: dams, water diversions, habitat alternation and urbanization.  

ASSESSMENT

By using the life cycle models and incorporating human activities at each stage, the management strategy evaluation…will allow for better informed management choices
Within the IEA framework, “assessment” is the means by which NOAA scientists compare the status and trends of indicators relative to baseline or threshold conditions. In the context of the Sacramento River fall-run Chinook salmon IEA, assessment reports for salmon are used to evaluate the current state of the stock relative to a benchmark abundance threshold for escapement, the number of fish returning to the spawning ground (thus “escaping” the fishery). Within the IEA framework, NOAA scientists examine trends in stock abundance together with trends in stressors to better understand the system and to provide better information for managers. Using the stock trends and interactions between stressors and the stock NOAA scientists can also forecast the potential trends of the stocks in the future. As an example, the relationship between the upwelling and prey abundance when salmon are juveniles and later abundance of adult salmon has been observed and modeled by SWFSC scientists. In this case, the abundance of adult salmon in the ocean, a value on which management is based, can be forecasted with relatively good accuracy based on prey abundance in the ocean the previous years; this will allow for an assessment of salmon abundance years in advance.  Recent salmon returns are consistent with these models and initial estimates for 2013 and 2014 are being examined. Information on adult abundance can also help managers to protect an adequate number of spawners needed for sufficient juvenile production. In another example, the relationship between stream conditions and the viability of juvenile salmon has been observed and modeled by NOAA in collaboration with NASA and academic partners.  Researcher from the SWFSC along with collaborators has developed stream and river temperature models that can be used to assess the habitat affecting juvenile salmon in the freshwater environment as they migrate toward the ocean. These models are being used by the Sacramento River Temperature Task Group, a group of federal and state agencies deciding how much and at what temperature water should be released.   

 

 

 

Figure 4. Spatial patterns of offshore transport, krill, and juvenile Chinook salmon in coastal central California during May-June.  Abundance of krill is the long-term mean number of individuals collected per net haul (black dots) 1990-2010. Abundance of salmon is total number of individuals collected during 1990-2010.  The transport values 2000-2010 were estimated from the QuickSCAT satellite.

 

Figure 4. Spatial patterns of offshore transport, krill, and juvenile Chinook salmon in coastal central California during May-June.  Abundance of krill is the long-term mean number of individuals collected per net haul (black dots) 1990-2010. Abundance of salmon is total number of individuals collected during 1990-2010.  The transport values 2000-2010 were estimated from the QuickSCAT satellite.

MANAGEMENT STRATEGY EVALUATION

With a fully developed IEA, salmon and users are considered simultaneously in the analysis, allowing for appropriately allocated management choices. One of our first steps in accomplishing this goal of holistic management is to understand how variability at each of the salmon life stages ultimately relates to the overall productivity of the stock.  We are in the process of building such a model, a salmon “life history” model, which will take into account the impact of managerial actions at different salmon life stages.  This is a significant improvement from the past in which managers based their decisions largely on the biology of fish the last year of their life.  These old models estimated the variability in abundance of the population but did not allow for discrimination among impacts that take place at different life stages, and thus did not allow managers to mitigate specific impacts effectively.  The current modeling project is funded by the California Ocean Protection Council and California Sea Grant.

 

By using the life cycle models and incorporating human activities at each stage, the management strategy evaluation, key element of the IEA process, will allow for better informed management choices based on quantified trade-offs among various management options.  With the IEA, we will be better able to address specific questions for users such as: What is the ultimate impact of changing river flow rates on salmon populations and at what cost to users? Does changing flow rates equate to substantially more adult salmon? What is the impact of fishing during different seasons on protected salmon stocks? How do these options interact?  The management strategy evaluation process provides a means for managers and the public to determine the best way to accommodate trade-offs for any given management strategy.  Ultimately, the IEA provides a process for synthesizing existing information into a format that will help managers make better informed decisions on the conservation and management of salmon in our ever-changing, multi-faceted environment.