California shellfish farmers

California shellfish farmers: Perceptions of changing ocean conditions and strategies for adaptive capacity

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The shellfish aquaculture industry along the U.S. West Coast is particularly vulnerable to ocean acidification (OA), given the negative effects of low pH on shellfish survival and growth. We present the results of interviews conducted with West Coast shellfish farm owners and managers in order to investigate perceptions of OA and environmental change and identify specific strategies for adaptation.

Coastal communities and resource users experience a wide range of environmental and livelihood stressors, including intense resource competition, urbanization, and environmental degradation that affect the resources upon which they rely. Climate change exacerbates these stressors and creates new pressures on coastal environments and the people whose livelihoods depend on them.

The majority of academic work on climate change impacts has investigated biophysical assessments and responses to these environmental stressors. While scholars have begun to explore the social, economic, and policy aspects of adaptation to these biophysical changes, much of this work remains primarily theoretical.

“One such system for which climate adaptation will be critical in coming years is marine aquaculture, especially shellfish aquaculture (defined here as culture of bivalves and mollusks).”

Relatively little is known about how aquaculture operators, and the extended communities reliant on aquaculture operations, perceive and respond to ocean acidification (OA) and other environmental stressors, or about specific actions they have taken or needs they have to prepare for or mitigate environmental stressors.

As such, shellfish aquaculture serves as an opportunity to conduct integrative research on social-ecological systems that improves the understanding of adaptive capacity in the face of current and future climate impacts.

“In the state of California, new attention has gone toward aquaculture, with investment in aquaculture-related research and the development of a state-wide aquaculture plan.”

However, this region is uniquely exposed to climate change-induced stress via OA and other environmental stressors, which can be of particular concern for shellfish aquaculture. The research presented focus on shellfish aquaculture in three focal regions of the state of California: Humboldt, Point Reyes, and the Central Coast.


It was conducted semi-structured interviews with the owners and/or primary managers of aquaculture operations in the three focal regions (Figure 1), with three to four interviews conducted per region.

California shellfish farmers

Interviews were designed to address the outlined research questions, using guides from past fisheries work in the region as an underlying framework.

The guide was pre-tested with shellfish aquaculture experts to ensure the questions were clear and relevant. Interviews were coded for themes using the software Atlas.ti, with analyses performed in R (Atlas.ti, 2021; R Core Team, 2018). Based on the interviews, it was generated a first set of codes to analyze interviewees’ perceptions of environmental change.

Interview transcriptions were reviewed to generate a comprehensive list of environmental factors that interviewees observed to be changing or believed were impacting their operations. This initial list was then reviewed and refined to develop an environmental factor codebook of 17 unique types of change observations.

After generating this list of strategies from interviews, it was reviewed the list for themes and refined the list to develop an adaptive strategy codebook.


California’s regional aquaculture landscape

Interviews were requested with representatives from 13 shellfish operations across all of these regions combined, out of the 19 total operations in the state. It was received 11 responses, resulting in a sample size that represents over half the operations in the state (Table 1).

California shellfish farmers

Oysters were the most common species cultured by those interviewed, and were the primary species grown by 8 out of the 11 farms.

Perceptions of environmental change and impacts

Across all interviews, marine disease and pathogens were frequently mentioned as environmental impacts (Figure 2).

California shellfish farmers

This was often mentioned in general terms, for example, “There was a huge virus or something all up and down the West Coast of America. It took out so many oysters, some farms lost 90 percent of their oyster crop, and when you’re waiting a year for something to be able to harvest it, that’s a huge loss”.

However, in other cases, specific diseases or pathogens were mentioned, which included Norovirus, Paralytic Shellfish Poisoning (PSP), Vibrio, E. coli, and Herpesvirus.

Rainfall and algal blooms were also mentioned in numerous interviews, often due to the association these factors have with marine disease and pathogens. Water temperature was also frequently noted, and in some cases, growers reported that water temperatures were becoming warmer.

Carbonate chemistry factors were also mentioned by many growers, but unlike all other environmental factors depicted in Figure 2, growers were specifically prompted for whether they thought they had experienced OA-derived changes or impacts, making it challenging to evaluate grower perceptions of the relative significance of OA compared to other factors mentioned.

Adaptive capacity strategies

Given the myriad of stressors and impacts growers experience, interviewees identified a variety of potential associated adaptive strategies to ensure their operations survive change from both OA and broader environmental, social, economic, or regulatory challenges.

The specific strategies discussed by growers can be described by three overarching categories:

1) adapting regulatory policies and networking with external partners,

2) flexible strategies for farm management, and

3) drawing on scientific research and expertise.

1.Policy and networking

The most frequently discussed strategies fell within the policy and networking category, with permitting / regulatory changes and network development / reliance being the most commonly discussed adaptive strategies (Figure 3).

California shellfish farmers

When permitting and regulations were discussed, this typically came in the form of commentary that difficult, expensive, and time-consuming permitting processes inhibited overall ability to adapt or remain resilient to change, a challenge that has been described previously regarding aquaculture in both California and the United States more broadly.

2.Farm management.

Growers mentioned a number of practical strategies surrounding the operations and management of shellfish farms that can facilitate adaptive capacity. Often, this came in the form of strategies allowing increased flexibility in the species or life stage cultured, or in the methods or location of the culture.

Culturing numerous or additional species and life-stages provided a type of insurance – akin to the ‘portfolio effect’ applied in both ecological and economic fields. In this way, growers’ businesses could maintain income and operations if one species or life-stage fared more poorly than the other due to mortality events, market shifts, or other factors.

Some growers identified this as a strategy that was likely to become more necessary in the future, to diversify their products and ensure a stable income under variable ocean conditions. Growers also expressed desire to alter or expand culture methods, equipment, or location to generate greater flexibility in operations.


The need to better understand drivers of shellfish health and mortality was mentioned in all but one of the interviews (Figure 3). Mortality events can be severe, and periodically lead to loss of the majority of shellfish in some lease areas or hatcheries.


Facilitating adaptive strategies

Interviews with growers revealed numerous environmental and other stressors affecting California’s shellfish industry and identified multiple strategies available to facilitate the industry’s ability to adapt to these stressors.

Adaptive strategies were often directly linked, in that reduction of one stressor could allow growers to allocate resources towards implementation of a strategy targeting other stressors. In particular, growers’ ability to implement a given adaptive strategy could often be facilitated by a modified permitting process.

California shellfish farmers

Indeed, the most frequently cited approach for adaptation was modified or expedited permitting and regulatory processes, as obtaining permits and complying with regulations are necessary precursors to making changes in most farm management practices, and permitting challenges acted as a barrier to slow or prohibit the implementation of such strategies.

For example, strategies such as the cultivation of additional species or the adjustment of gear or gear placement were challenged by the ability to get permits to implement these approaches, particularly on the time frames needed to keep pace with environmental change.

Similarly, adaptive strategies relating to networking and scientific partnerships require a significant investment of growers’ time, much of which is currently devoted to navigating complex or opaque permitting and regulatory processes.

Implications for adaptive capacity

Although this study was specific to the U.S. West Coast shellfish aquaculture industry, its relevance and linkages to the broader field of adaptive capacity are readily evident. The described strategies, while tailored to this specific community, can be more broadly categorized into domains of adaptive capacity observed across communities and geographies.

In one synthesis on the subject, Cinner et al. (2018) identifies five common domains of adaptive capacity: Assets, Flexibility, Social Organization, Learning, and Agency. By cross-examining these five domains and the grower-identified strategies, it is seen they can be operationalized across all 18 of the strategies (Table 3).

For instance, within the ‘flexibility’ domain, many of the described farm management strategies rely on a need for flexibility – such as the desire to alter the species or gear used for culture (‘species’ and ‘method/gear type’) or the ability to move equipment around their lease area (‘spatial flexibility’).

Similarly, growers identified numerous ‘assets’ needed to implement these strategies, for instance, access to the necessary equipment (‘methods/gear’) or facility types, such as a hatchery and a grow-out space (‘multiple life cycle stages’).

The ‘social organization’ domain is evident in the growers’ reliance on and desire to improve their networks to gain information and share data. Strategies falling within the ‘learning’ domain are clear in the identified scientific gaps, such as the desire for more information on the drivers of shellfish mortality or on OA conditions.


California shellfish farmers directly observe and experience numerous environmental changes, some of which are more easily observed or measured.

While most growers expressed concern for changing ocean conditions, it was often challenging for growers to make direct links between outcomes to their operations and changes that could not be easily observed or measured.

In particular, linking impacts or outcomes to OA posed challenges in their ability to implement direct
responses. Rather, OA was perceived more as an unknown and potential stress multiplier, and growers instead identified (and in many cases are implementing) a number of strategies that could help them adapt to changes resulting from environmental, economic, or political stressors.

Some strategies directly targeted OA (e.g., improving pH monitoring or developing OA-resistant broodstock), but the broad range of strategies supported adaptation to multiple diverse stressors to facilitate increased farm resilience.

“Facilitating adaptive capacity requires a coordinated approach that recognizes the interconnected nature of stressors and associated strategies, whereby reducing one type of stressor may allow growers to proactively allocate resources towards implementation of adaptive strategies relating to other stressors in order to improve overall resilience.”

By evaluating aquaculture operator-identified adaptive strategies and key challenges to their implementation, this work makes evident the need for improved policies, coordination, and scientific advances within the shellfish aquaculture industry and associated agencies.

This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “CALIFORNIA SHELLFISH FARMERS: PERCEPTIONS OF CHANGING OCEAN CONDITIONS AND STRATEGIES FOR ADAPTIVE CAPACITY” developed by: MELISSA WARD -San Diego State University; ANA K. SPALDING, Oregon State University, School of Public Policy, Coiba Research Station; ARIELLE LEVINE – San Diego State University; ERIKA ALLEN WOLTERS- Oregon State University.
The original version, including tables and figures, was published on MARCH, 2022, through OCEAN AND COASTAL MANAGEMENT.
The full version can be accesed online through this link:

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