Striped Bass: Population dynamics and ecology of an iconic alien species

Summary: 
Synthesize research and other biological information on striped bass (Morone saxatilis) in the San Francisco Estuary, as compared to populations on the Atlantic Coast and elsewhere. Write a monograph on their biology. Organize a workshop. Generate one or more quantitative life history models. Develop a network of biologists interested in striped bass.

The striped bass is a non-native fish very important to the San Francisco Estuary (Estuary) and watershed. Since their introduction around 1879, striped bass have been the apex predator in areas of the Estuary not infested with submerged aquatic vegetation. Striped bass supplanted three native species as top predator: extinct thicktail chub, the extirpated Sacramento perch, and Sacramento pikeminnow in the lower watershed. All three native species were (are) substrate spawners that likely suffered severe spawning failure from hydraulic gold-mining sediment, just as striped bass arrived.
Striped bass share many life-history adaptations with native fishes such as Sacramento sucker, Sacramento splittail, white and green sturgeon, Sacramento hitch, and Sacramento pikeminnow. These adaptations allow persistence in predictably variable environments: long lifespan, high egg production, large body size, and long-distance spawning migrations. Striped bass, being anadromous, require a functional riverine-estuarine ecosystem to flourish and thus reflect the health of the watershed. For example, young striped bass, like native longfin and Delta smelt, need high zooplankton abundance for food. They also need turbid water for protection from predators,  as well as high river flows to carry larvae to the turbid, food-rich areas of the Estuary at the interface of fresh and salt water. Similar to white sturgeon, adult striped bass appear cued to higher river flows to attract them upstream for spawning, with low-water years seeing fewer adult striped bass in the Sacramento River than wetter years.    
All this suggests that the striped bass should be monitored as a major species whose status at all life stages reflects the health of the Estuary, much as they were in the 1950s -1970s. The striped bass is the most abundant fish in the Estuary that requires a functioning estuary to complete its life history, from the rivers to the Golden Gate. It has the distinct advantages of still being common, of being found throughout the Estuary, and of having long-term surveys designed to monitor its populations. It is not, and never has been, a major predator on Delta smelt or native minnows (Nobriga and Feyrer 2007, Thomas 1967, Stevens 1966).  It is one of many piscivorous predators in the Estuary and appears to be a problem only where special conditions concentrate predators and prey (e.g., Clifton Court Forebay). Striped bass have considerable human value in the watershed, supporting recreational fisheries for both harvest and catch-and-release sport in the Sacramento River and tributaries, the entire San Francisco Estuary, and the coastal ocean.  
The long-term decline of striped bass seems to have many interacting causes that have changed through time, tracking the decline of most estuarine fishes in the upper Estuary including American shad, Delta smelt, and native resident fishes. However, the severe decline of juvenile striped bass in agency surveys of the mainstem is not reflected in Suisun Marsh, suggesting the marsh may be a refuge/nursery area.
The striped bass formerly has been the focus of many studies in the Estuary and currently is well-studied on the East Coast; new information on East Coast populations may inform understanding  drivers of the Estuary's population. The purpose of this agreement is to 1) review existing studies and data sets, 2) bring striped bass experts from other regions together to review and share information, 3) evaluate the importance of the Suisun Marsh for striped bass in the Estuary and in the Pelagic Organism Decline (POD), 4) publish a review of striped bass life history in the Estuary with a discussion of the usefulness of striped bass as an indicator of the Estuary's health, 5) develop a life-history model, and 6) determine what actions may be necessary to improve the management of striped bass in the Estuary.

Activity 1.

Compile a list of everyone who has been or is involved in studies related to striped bass, and consult with them to avoid duplication of effort and to find hidden data.  Identify key biologists on the East Coast, in Oregon, and in southern California (striped bass are abundant in State Water Project reservoirs such as Pyramid and Castaic, and those fish likely originated in the Delta) who could help the understanding of what is known about the non-Estuary populations and their role as a ‘sink’ striped bass a portion of the striped bass population.  Identify opportunities for cooperative studies.

Project Background                                                                              

Many researchers and environmental managers are working on striped bass projects in the eastern United States. Many of these efforts remain unknown or poorly understood by managers in California, although the studies could inform management of striped bass and other native fish in the Estuary. Compiling a list of striped bass researchers, and contacting the key biologists working on striped bass projects could be a cost-effective approach to help with understanding striped bass life history and management in the Estuary by learning from published and unpublished studies, as well as professional opinion.

Objectives

(1) Identify data or information that already exists that isn’t being used to manage striped bass in the Estuary.

(2) Identify biologists or managers able to help obtain new information about biology of striped bass, and identify partnerships with other organizations that would benefit DWR’s and CDFW’s management of striped bass in the Estuary.

(3) Evaluate different types of habitat restoration techniques and strategies that are being used elsewhere and determine their applicability to the Estuary.

Specific Tasks

Create a network of striped bass biologists that work together on various questions and collaborate on new projects.
Use existing information from other researchers and striped bass management strategies throughout the United States to inform management needs in the Estuary.
Develop comparison studies between California and Oregon striped bass, and between Chesapeake Bay and the Estuary.
Conduct a literature review of all information from the U.S. on striped bass life history including factors such as predation, disease, population dynamics, and anthropogenic population effects.
Included with the literature review will be a review of habitat restoration techniques and strategies being used throughout the United States and a discussion of whether these could be applied to the Estuary to benefit striped bass and native fish.

 

Activity 2.

Conduct a workshop on striped bass ecology and management, inviting all possible cooperators including East Coast scientists. Provide a summary of the workshop including presentation abstracts.

Project Background

There have been few, if any, workshops in the region dedicated to striped bass in the past 20 years. Other species of fish have been the main focus of large interagency and public workshops in California during this time period. A striped bass workshop would renew discussion between managers and biologists to help inform managers of the Estuary of new modeling, sampling techniques, and habitat management.            

Objectives

Facilitate the use of existing information for managing striped bass in the Estuary.
Develop opportunities for collaboration on various ongoing and upcoming striped bass projects.
Identify  new projects or studies that are needed for management to better understand striped bass behavior and ecology.
Identify new monitoring techniques that are being used in other states that may be more helpful than our current monitoring strategy.

Specific Tasks

Determine a venue for the workshop.
Identify speakers and researchers.
Obtain co-sponsors (e.g. Delta Stewardship Council,  IEP)
Advertise to public and other stakeholders.
Ensure the necessary amenities.

 

Activity 3.

Write and publish a review paper on striped bass life history in the Estuary that would include summarizing all data in existing monitoring programs, similar to Moyle et al. (2004) for splittail. The review is to include a discussion of the suitability of the striped bass as a sentinel species whose population reflects the health of the Estuary.  Can the Estuary be managed in part for striped bass and also support Delta smelt and other native species?

Project Background

A lot of information is available about striped bass from state agency and university fisheries surveys. Data from these surveys has been analyzed separately but has not been analyzed as a whole. Synthesis of the entire suite of monitoring data is needed to understand if the species in the Estuary and Delta can be managed to benefit striped bass and native fish.

Objectives

Determine if the Estuary can be managed for striped bass and also support native fish species such as Delta smelt, longfin smelt, salmonids, and sturgeon.
Evaluate the potential for striped bass to be a sentinel species whose population reflects the health of the Estuary.
Summarize major trends in striped bass populations in California.
Identify any correlates or drivers to population trends.
Determine if telemetry studies could improve management of striped bass in conjunction with native fish in the Estuary.
Identify information from existing behavioral laboratory studies that could be beneficial to the management of striped bass in the Estuary.
Identify behavioral studies that can be conducted in California that could help in management of the species.
Summarize and evaluate the major trends in the recreational and commercial striped bass fishery in the Estuary over the last 40 years.
Use the lessons learned in California and from other states to make recommendations to improve management of striped bass in the Estuary.

Specific Tasks

Conduct a literature review of existing monitoring programs in California.
Identify current California state, federal, and local striped bass managers.
Obtain information and datasets not readily available online.
Use existing scientific papers to help identify population trends.
Collaborate with IEP and other researchers that have conducted telemetry studies on striped bass movement in the Estuary and Delta.
Write and publish a summary peer-reviewed similar to Moyle, P.B., R. D. Baxter, T. Sommer, T. C. Foin, and S. A. Matern. 2004. Biology and population dynamics of Sacramento splittail (Pogonichthys macrolepidotus) in the San Francisco Estuary: a review. San Francisco Estuary and Watershed Science [online serial] 2(2):1-47.

 

Activity 4.

Conduct an analysis of juvenile data from all surveys to evaluate how much of the POD decline is the result of a shift of juvenile striped bass to shallower water including Suisun Marsh than is sampled by the agency programs. Evaluate the Suisun Marsh as a striped bass nursery and as seasonal refuge for adult striped bass.

Project Background

The steep decline in young-of-year striped bass production observed in the estuary's main axis has been accompanied by less severe trends in other life-history stages and in peripheral habitats. For example, age-1 and adult striped bass abundances from shallow water habitats have not dwindled as precipitously as mainstem young-of-year fish (Sommer et al. 2011). Young-of-year abundances in Suisun Marsh otter trawls, which sample mid-channel, have exhibited a mild long-term decline at most. Further, Suisun Marsh beach seines have shown no long-term trends in abundance, while annual adult indices in Suisun Marsh have generally increased since 2000. 

The poor concordance between adult and young-of-year abundances in the Estuary's main channels suggests contributions of young-of-year fish from other sources. The simple annual abundance indices and trends in both the Suisun Marsh beach seines and otter trawls indicate that Suisun Marsh juveniles may contribute disproportionately to the adult striped bass population, likely due to the high abundance of zooplankton and macroinvertebrate food (Williamson et al. 2015, Montgomery et al. 2015) and the relative lack of invasive clams (Baumsteiger et al. 2017). Because Suisun Marsh is slated for numerous tidal restoration projects for native fishes and, by proxy, striped bass, understanding Suisun Marsh's role in estuary-wide striped bass production and thus management is imperative.

Objectives       

Examine the proportion of the adult striped bass population that rears in Suisun Marsh as young of year, and how that scales with area of aquatic habitat.
Evaluate what proportion of spawning striped bass in the Sacramento River is comprised of adult striped bass that fed in Suisun Marsh.
Compare intra-annual survival of young-of-year striped bass in Suisun Marsh and in the estuary's mainstem channels.
Compare the gut fullness in Suisun Marsh striped bass to striped bass in the Estuary's mainstem channels.

Specific Tasks

Analyze and publish existing information from the Suisun Marsh Fish Survey and the UC Davis Moyle Lab on dietary analysis of striped bass found in Suisun Marsh.
Obtain information and datasets not readily available online.
Use existing scientific papers to help identify population trends.

 

Activity 5.

Develop a striped bass population model for the Estuary, starting with a general conceptual model. Part of this should be a limiting-factors analysis to examine what life stage is most limiting to striped bass populations. It should also address data uncertainties, such as what effect big females have on the population when they decide to leave the Estuary during warm-ocean periods.

Project Background

Striped bass life history models have been developed using East Coast populations. There are currently many unknown factors that may be contributing to striped bass life history in the Estuary. Some of these unknown factors include sub-adult and adult behavior and biology in Suisun Marsh and in the Pacific Ocean. Further study of these life-history aspects and creating a life-history model will benefit future management of striped bass and other native fish in the Estuary.

Objectives

Evaluate what life stage (s) is most limiting.
Determine where females travel when they leave the Estuary during warm ocean periods.
Examine what happens to striped bass when they are living in the ocean.
Examine what happens to striped bass during their sub-adult life stage.
Determine if striped bass in the Estuary are moving  to other regions

Specific Tasks

Use information gathered from the literature-review efforts to develop a general conceptual model.
Analyze the limiting factors from existing data and research about striped bass in the Estuary.
Develop a life-history model.
Identify opportunities to coordinate an inter-state study to see if they are migrating between states.
Write and publish a peer-reviewed population/life-history model paper.

 

Summary of Deliverables.

Deliverable 1. Sources:  Compile a list of key biologists and managers working with striped bass in California and the United States leading to a network. From these sources and others compile a bibliography of key studies on striped bass, especially those since 2000. The bibliography will include published and gray literature.

 

Deliverable 2. Workshop: Conduct a workshop on striped bass ecology and management that will produce names and contact information for presenters and participants.  Produce a 5-10 page summary report of new information and lessons learned from the workshop.

 

Deliverable 3. Report:  Draft project report on striped bass ecology and population trends that summarizes objectives, methodology, results, and conclusions.

 

Deliverable 4. Life History Paper: Produce a draft review paper to be submitted to a peer-reviewed scientific journal on striped bass life history in the Estuary that would include summarizing data from relevant monitoring programs, similar to Moyle et al. (2004) for splittail. This will include an analysis of juvenile data from all surveys to evaluate causes of the POD decline, including changes in sampling effectiveness. Evaluate the role of Suisun Marsh as a striped bass nursery and as seasonal refuge for adult striped bass. Include a timeframe for publication submission and journals targeted.

 

Deliverable 5. Suisun Diets Paper: Produce a second draft paper to be submitted to a peer-reviewed scientific journal using data from the Suisun Marsh Fish Survey and from the UC Davis Moyle Lab on dietary analysis of striped bass found in Suisun Marsh. Include a timeframe for publication submission and journals targeted.

 

Deliverable 6. Population Model Paper: Produce a third draft paper to be submitted to a peer reviewed scientific journal developing a striped bass population or life cycle model for the Estuary, starting with a general conceptual model.  Include a timeframe for publication submission and journals targeted.

 

 

Collaborators: