MLMA Master Plan 6. Ecosystem-based Objectives

The MLMA seeks to preserve the health of fish stocks and the ecosystems that support them (§7050(opens in new tab)). When the law was passed, the concept of EBFM was relatively new, but has since become a common foundation of fisheries law and policy at the state, national, and international level. This chapter focuses on three specific objectives described in the MLMA: 1) limiting bycatch to acceptable types and amounts (§7056(d)(opens in new tab)); 2) maintaining habitat health (§7056(b)(opens in new tab)); and 3) conserving ecosystem health and diversity (§7050(b)(1)(opens in new tab)).

Limiting bycatch to acceptable types and amounts

NOTE: This section draws largely from the work of the Bycatch Working Group (BWG), a group of stakeholders convened by the Commission in 2015. The BWG was created to help inform the MRC and Commission’s review of bycatch management, specifically through the Department’s effort to amend the Master Plan. The Department used as much of the consensus language from the review as possible in the development of the section on bycatch below.

Definition of bycatch

During most fishing activity, fishing gear may catch other fish and marine species in addition to the species that is being targeted. For example, commercial and recreational fishermen using hook-and-line(opens in new tab) often cannot tell which species of fish they will catch. There are many terms used to describe this: bycatch, discards(opens in new tab), non-target, incidental catch(opens in new tab), and so forth. Sometimes these terms are used interchangeably, but their implications differ subtly.

The Department has historically considered the species or species complex managed by an FMP to be the target of that fishery. The definition of bycatch includes target species that are discarded because they are of undesirable size, sex, or quality, or prohibited due to size, season, catch limit, or sex restrictions, as well as non-target species that are either undesirable or required by law to be discarded (§90.5 and §91(opens in new tab)). The MLMA mandates that unacceptable amounts or types of bycatch be addressed through conservation and management measures.

California halibut trawl tow with bycatch. (CDFW photo by Kristine Lesynak)
California halibut trawl tow with bycatch. (CDFW photo by Kristine Lesynak)

This section of the Master Plan focuses on what may constitute unacceptable bycatch and how this bycatch may be addressed. To assist this discussion, the following are definitions of categories of catch and the standards to which they should be managed.

  • A target species is defined as any species that is a primary target of the fishery and the principal focus of management efforts. Identification of target species is discussed in Step 2 below. These species are managed to the sustainability standard of the MLMA (see Chapter 5).
  • Incidental catch is defined as fish caught incidentally during the pursuit of the primary target species, but legal and desirable to be sold or kept for consumption. Some may define these species as secondary targets or retained bycatch. For purposes of FMP development these species should be accounted for and must be managed either as target species under the sustainability standards outlined in Chapter 5, or as bycatch under the bycatch standard described below. In making this determination, the Department will consult with stakeholders and may consider the criteria associated with identifying emerging fisheries as discussed in detail in Chapter 9. The Department should articulate the basis for its determinations in the relevant FMPs. Identification of incidental species is discussed in Step 2 below.
  • Bycatch, as defined by the MLMA, means “fish or other marine life that are taken in a fishery but are not the target of the fishery. Bycatch includes discards” (§90.5(opens in new tab)). The MLMA provides additional clarification that discard means fish that are taken in a fishery but not retained because they are of an undesirable species, size, sex, or quality, or because they are required by law not to be retained (§91(opens in new tab)). This includes the following:
    • Discretionary discards:
      • Fish that are legal but undesirable or unmarketable due to species, size, quality, condition, etc.
      • Legal fish that are less desirable than other fish by species or size (high grading), particularly when total take is limited in number or weight by species, species complex, or not retained due to limited storage capacity.
    • Regulatory discards(opens in new tab):
      • Fish that are required by law not to be retained.

As noted in Step 3 below, discarded catch may be returned to the sea alive, dead, or dying, and it is important to assess the mortality rate to evaluate impacts. While all discards are defined as bycatch (§90.5(opens in new tab)), the discard of live catch may not pose a risk to a bycatch species, and discarding can be an effective management strategy to protect some individuals (e.g., juveniles, sex-specific) in which survival is expected to be high.

Assessing and addressing bycatch impacts

To achieve the goal of minimizing unacceptable bycatch, the MLMA requires that the Department manage every sport and commercial marine fishery in a way that limits bycatch to acceptable types and amounts (§7056(d)(opens in new tab)).

Consistent with this objective, each FMP must include all the following:

  • Information on the amount and type of bycatch (§7085(a)(opens in new tab)).
  • An analysis of the amount and type of bycatch based on the following criteria (§7085(b)(opens in new tab)):
    • Legality of the bycatch under any relevant law;
    • Degree of threat to the sustainability of the bycatch species;
    • Impacts on fisheries that target the bycatch species; and
    • Ecosystem impacts.
  • In the case of unacceptable amounts or types of bycatch, FMPs must include conservation and management measures with the first priority to minimize bycatch and the second priority to minimize mortality of discards that cannot be avoided (§7085(c)(opens in new tab)).

Section 7085(opens in new tab) can be used as the basis for a four-step process to identify bycatch and consider its impacts, as follows:

Step 1. Collection of information on the amount and type of catch.

To determine how to minimize unacceptable bycatch, managers should first gather information on all the species caught in a fishery. Some fisheries require state or federal observers or Electronic Monitoring (EM) to record catch data, and some recreational fisheries participate in state observer programs. However, most recreational fisheries and many commercial fisheries operate without such monitoring. If observer data are not available, dockside sampling, logbooks and landing receipts, Federal Stock Assessment and Fishery Evaluation reports, recreational report cards, creel surveys, directed fishing surveys, or communications with participants can be used to identify the full suite of species caught and the amounts of bycatch.

If information is unavailable or insufficient to understand what is caught in a fishery, the Department can prioritize the collection of these data and clearly state this as a research need in ESRs and FMPs.

Step 2. Distinguishing target, incidental, and bycatch species.

Once information about the type and amount of catch is identified, it is necessary to determine which species are the target of the fishery, which are incidental catch species, and which are bycatch species. In some situations, target or incidental catch species of the wrong size, sex, or condition may be discarded and become bycatch per the MLMA’s definition. Differentiating target species from incidental catch and bycatch species is not always obvious (e.g., recreational “catch and release” species). Targets can change over time and vary among participants. Nevertheless, the development of FMPs present opportunities to engage with stakeholders and consider criteria for categorizing catch.

These criteria may include the following:

  • The intended target(s) of participants as evidenced by landings data.
  • The marketability of landed commercial species or the desirability of recreational species.
  • Historical use patterns of the fishery.
  • Whether the species is being managed as a target species under another FMP, or under other state or federal law or regulation.

While the MLMA creates a distinction between target species and bycatch, impacts to any species caught must be understood and addressed appropriately regardless of the categorization. In the case of target species, impacts need to be managed so that sustainability is maintained. In the case of bycatch, impacts need to be managed so that they are acceptable as discussed below. Incidental catch species need to be managed to either target or bycatch standards according to the needs of the fishery as determined by the Department. While the statutory language surrounding these two standards is different, their goals are similar and as a practical matter, achieving them may often involve the same strategies and management measures.

Step 3. Determining “acceptable” types and amounts of bycatch (§7085(b)).

The MLMA assesses the acceptability of the amount and type of bycatch using four criteria: 1) legality of the take of bycatch species; 2) degree of threat to the sustainability of the bycatch species; 3) impacts on fisheries that target the bycatch species; and 4) ecosystem impacts (§7085(b)). These criteria have not been further defined in regulation, and it may not be possible to identify a uniform definition of “acceptable” that is appropriate across California’s diverse suite of fisheries. However, structured, MLMA-specific inquiries may provide a practical means of conducting fishery-specific analysis of impacts and identifying means for minimizing unacceptable types of bycatch. If after considering all four criteria the Department determines the amount and type of bycatch to be unacceptable, then further management action is required. The questions provided below for each of the four criteria (§7085(b)(1-4)) can be used to consistently assess what is “acceptable” bycatch within a particular fishery. Responses to these questions are not proposed to be used in a formulaic or prescriptive way, but rather are intended to provide a structured basis for managers to consider the issue and articulate the findings.

(1) Legality of take of bycatch species

This criterion includes any species that might be illegal to take or retain under any relevant state, federal, or international law.


  1. Is the species covered under the Endangered Species Act (ESA), Marine Mammal Protection Act (MMPA), Migratory Bird Treaty Act (MBTA), Billfish Conservation Act (BCA), Magnuson-Stevens Fishery Conservation and Management Act (MSA), Fish and Game Code, Title 14 of the California Code of Regulations, Title 50 of the Code of Federal Regulations, or another FMP?
  2. Are there prohibitions against the take of the bycatch species using a specific gear type employed in prosecuting the fishery?
  3. Is the species a target species that requires discard of individuals based on size limits, seasons, or gear type restrictions?
  4. Is the discard mortality rate known?
  5. Are special permits required to retain or interact with the species (such as incidental take permits), does the fishery currently have such permits, and do the levels of bycatch comply with them?
  6. Does the species have an incidental catch allowance, ACL, or other restrictions on the amount, size, or sex of catch allowed, and does the catch comply with them?

Recommended actions:

  1. If legality is not assessed, this should be conducted.
  2. If legality has been assessed and the take is found to be illegal, it may be considered unacceptable and Department action or consultation with responsible state or federal agencies may be necessary.
  3. If legally-sanctioned rates of mortality exist, the Department should evaluate if the rate of injury and mortality is being exceeded, potentially through consultations with other responsible state and federal agencies.
    1. If the rate is within legally-sanctioned injury or mortality rates, then bycatch is likely acceptable in relation to this criterion.
    2. If the rate exceeds legally-sanctioned injury or mortality rates, the bycatch may be unacceptable and management action may be necessary.

(2) Degree of threat to the sustainability of the bycatch species

This criterion considers the impact of the relative level of bycatch within the fishery on the biological health of a particular bycatch species for which the bycatch is considered to be significant: that is, if the type or amount of bycatch compromises the ability of the population of the bycatch species to maintain a sustainable level. If the particular bycatch species is the target of another managed fishery, it may be possible to refer to a state or federal stock assessment or management plan to understand how the current level of additional catch is likely to impact that species. If there is little information about the status of the stock, the Department should identify a pathway and timeline for determining the fishery’s impacts. An initial step could be to conduct a PSA, which may provide insight on the degree of threat to the sustainability of the bycatch species. Understanding the impacts to species that are identified as relatively vulnerable through a PSA could be identified as a research need. A level of take that compromises the sustainability of the population would be unacceptable under the standards of the MLMA.


  1. Has a peer-reviewed risk assessment of the vulnerability of the particular bycatch species to overfishing been conducted (e.g., PSA)?
  2. Does a population status estimate or stock assessment exist for this species, and is there confidence in the underlying data such that a reasonable determination can be made if the stock is considered healthy, overfished, or depleted?
  3. Are there any existing state and/or federal management measures, and are they effective in ensuring sustainability?
  4. Is the bycatch the product of recreational catch-and-release practices?
  5. What is the estimated discard mortality rate given the characteristics of the fishery and gear type?
  6. Do any post-release studies exist to verify the estimated mortality rate
  7. What is the probability of mortality exceeding levels that have been scientifically determined to be necessary for the continued viability of the species?

Recommended actions:

  1. If the level of risk to a state-managed species for which bycatch is significant has not been assessed, the Department should identify this as a research need in the ESR or FMP of the target species.
  2. If a risk assessment has been conducted:
    1. If risk is low, bycatch of the species is likely acceptable for this criterion.
    2. If risk is high, bycatch of the species may be unacceptable and the Department should consider additional management measures.

(3) Impacts on fisheries that target the bycatch species

This criterion considers whether the current level of bycatch within the fishery negatively impacts the management of another fishery or the fishermen that target the fishery resource. This is particularly an issue for fisheries which may only land the primary target species (e.g., Spot Prawn). Factors to consider may include increasing competition between fleets that target certain species by capturing species managed under federal rebuilding plans or by increasing mortality of juveniles targeted by another fishery.


  1. Does a directed fishery exist for the bycatch species?
  2. Has the bycatch and associated discard mortality been accounted for?
  3. Is bycatch affecting the directed fishery management strategy (i.e., restrictions on size, sex, or season)?
  4. Are the impacts of bycatch considered and made explicit in an ESR or FMP?
  5. Is the species constrained under a federal rebuilding plan and will bycatch compete with fleets that target the species?
  6. Is there a management allowance for percent of catch or a prohibition on retention?
  7. If there is a directed fishery for the species, have there been:
    • Reductions in opportunities or income for participants in fisheries that target the bycatch species?
    • Reductions in fishery quotas or opportunities (e.g., time and area closures) based on bycatch issues?
    • Early closures of a fishery based on higher-than-expected bycatch?
    • Changes in fishing, processing, disposal, and marketing costs due to bycatch?
    • Changes in the social or cultural value of fishing activities due to bycatch?
    • Negative socioeconomic impacts from bycatch on fisheries and/or fishing communities which target or need incidental catch of this species?
    • Negative impacts to juveniles of a species targeted by another fishery?

Recommended actions:

  1. If socioeconomic impacts of bycatch have not been considered, this should be identified as a research need and integrated into future updates of ESRs or subsequent FMPs.
  2. If any impacts under Inquiry 7 above are identified, the Department should consult with fishery participants and others regarding these potential impacts. Depending on the presence and severity of impacts, the Department may find bycatch to be unacceptable, and management measures may be necessary.

(4) Ecosystem impacts

This criterion explores whether the current level of bycatch within the fishery impedes the ability of the bycatch species to fulfill its functional role within the ecosystem. This is difficult to assess for most species, but tools such as ERA may help provide useful guidance and qualitative information, even in data-poor circumstances.


  1. What is the ecosystem role of the bycatch species?
  2. Does scientific evidence show the amount of bycatch mortality significantly increases the risk that a bycatch species will be unable to serve its ecosystem role?

Recommended actions:

  1. If this information is not available, its collection should be identified as a research need in ESRs and FMPs. Managers should consider collaborations with external marine ecologists and other researchers to collect this information.
  2. If species ecosystem function is unlikely to be impeded, then bycatch is likely acceptable under this criterion.
  3. If species ecosystem function is likely to be impeded, then bycatch may be unacceptable per this criterion and management measures may be necessary.

Step 4. Addressing unacceptable bycatch (§7085(c)).

If the current type or amount of bycatch is deemed to be unacceptable based on the four criteria above, conservation and management measures are required that minimize the bycatch, and in cases where discards are unavoidable, the mortality of the discards (§7085(c)).


  1. Are measures in place to minimize the impact of the fishery on bycatch species and ensure the fishery does not overfish or hinder the recovery of bycatch species?
  2. Are bycatch management measures likely to decrease unintended, non-retainable, and/or dead catch of non-target species?
  3. Are bycatch management measures being implemented successfully?
  4. Have bycatch management measures been shown to be effective at reducing bycatch and/or bycatch mortality in similar fisheries?
  5. What is the economic impact of implementing management measures to reduce bycatch and bycatch mortality to those participating in the fishery in which the bycatch occurs?

There are a number of frequently used strategies for reducing bycatch and discard mortality. These measures and considerations associated with their use are detailed in Appendix M. They include minimum mesh size requirements, escape ports, descending devices, closed areas, depth restrictions, acoustic pingers, Light Emitting Device (LED) lights, and incidental take caps to name a few. However, understanding and implementing the most effective means of reducing bycatch while maintaining economic viability typically requires input from all stakeholders and close collaboration with the fishing industry.

Diagram of a typical rigid-grate Bycatch Reduction Device (BRD) used in the ocean shrimp trawl fishery
Diagram of a typical rigid-grate (double-ring) Bycatch Reduction Device (BRD) used in the ocean shrimp trawl fishery. The diagram depicts shrimp traveling through the BRD, and larger fish species deflected by the BRD and guided through the escape exit opening. (Source: CDFW; diagram and inset picture modified from Robert W. Hannah, ODFW)

Maintaining habitat health

The MLMA emphasizes the importance of habitat protection as a means of preserving healthy and productive marine resources (§7056(b)(opens in new tab)). While there are factors external to fishery management that may negatively impact habitat (e.g., storms, climate change, habitat loss due to development, pollution, etc.), protecting habitat from potential fishery impacts is essential to help maintain healthy fisheries, ecosystems, and communities in California. Healthy habitats provide space for the various life history functions of species that are necessary to create sustainable marine populations, including spawning, growth, feeding, and reproduction. Marine habitats are often utilized in different ways by an array of species, so impacts from fishing activities may have cascading effects on the ability of other species of ecological or economic significance to sustain themselves. To achieve the goal of protecting habitats the MLMA requires the Department to:

  • Manage every sport and commercial marine fishery with the objective that the health of the fishery habitat is maintained, restored, and where appropriate, enhanced (§7056(b)(opens in new tab)).
  • Include information about the habitat and known threats to the habitat in FMPs (§7080(c)(opens in new tab)).
  • Include measures in FMPs that, to the extent practicable, minimize adverse effects on habitat caused by fishing (§7084(a)(opens in new tab)).

The following describes steps for assessing and addressing impacts to habitat:

Step 1. Describe the habitat utilized by the target species at each life stage.

ESRs and FMPs should summarize the readily available information regarding the habitats of the target stock (§7080(c)). While ocean waters and their associated salinities, temperature, and nutrients are an important part of marine habitats, most marine habitat management focuses on benthic habitats, including habitat-forming plants and invertebrates. Benthic habitats are usually classified by three general types of substrate: hard, mixed, and soft. In addition to substrate types, habitats are frequently classified by depth, which influences the amount of light available to the species that live there. Benthic marine communities are often grouped by depth categories such as coastal, continental shelf, continental slope, and abyssal.

ESRs and FMPs should focus on habitats that are particularly sensitive. These include estuaries, sea grass beds, intertidal areas, rocky reef habitats, and kelp forests, which have been found to support a high diversity of species at critical life stages. In addition, these areas are often home to structural or biogenic organisms, which are those species that create habitats for other species. These include some plants, such as Giant Kelp and sea grass, as well as animals such as corals, gorgonians, and sponges.

Marine species may use multiple habitat types during different life stages or for different activities. It is important for managers to describe the habitats utilized for all activities that are crucial to survival and reproduction. If there are some life stages or activities where a species’ habitat association is unknown, collecting this information should be identified as an area for future study. ESRs and FMPs should also identify where additional understanding of habitat characteristics, functions, and fluctuations would improve management. See Appendix N for more information on habitat types and their characteristics and sensitivities.

Inquiries and recommended actions:

  1. What are the habitat needs of the target stock? How do these needs change throughout its life cycle?  
    1. For each life stage and major activity, identify the habitats utilized.
    2. If multiple habitats are used, it may be useful to rank the habitats in order of importance to the target stock.
  2. What is the spatial distribution of the habitats utilized by the target stock?  
    1. If possible, use existing habitat maps and what is known about the distribution of the stock to determine the spatial distribution of the habitats utilized.
  3. Are there particular life stages or activities where the habitat needs of the target stock are unknown or are only partially known?  
    1. Identify life stages and/or major activities where the habitats utilized are unknown as uncertain and requiring additional research.

There are a number of frequently used strategies for reducing bycatch and discard mortality. These measures and considerations associated with their use are detailed in Appendix M. They include minimum mesh size requirements, escape ports, descending devices, closed areas, depth restrictions, acoustic pingers, Light Emitting Device (LED) lights, and incidental take caps to name a few. However, understanding and implementing the most effective means of reducing bycatch while maintaining economic viability typically requires input from all stakeholders and close collaboration with the fishing industry.

Step 2. Describe the threats to the habitats utilized.

After describing the habitats utilized by the target species, the threats from both fishing and non-fishing activities to these habitats should be described using available information. For the vast majority of fish habitats, empirical measurements of habitat health over time are unavailable. However, some fishing gears are known to have greater impact than others, and some habitats are more vulnerable to disturbance. Most habitat damage from fishing gears occurs when the fishing gear comes in contact with the seafloor and with biogenic habitats in particular. For this reason, habitat threats from fishing gear are often assessed by considering the gear type, habitat type, and interaction between the two. Appendix M contains additional details regarding these interactions. The presence of MPAs or other spatial restrictions may help reduce a fishery’s impacts on habitat and should be explicitly considered when assessing impacts. Abandoned or lost fishing gear can also have negative impacts on habitats. These potential impacts should also be considered and addressed in ESRs and FMPs.

Threats based on non-fishing activities may include climate change, storms, pollution, coastal development, etc. While these threats are for the most part beyond the Department and Commission’s authority to regulate, they are required to be characterized (§7080(c)). Other state and federal agencies that do have authority over some of these impacts may be required by statute, regulation, or policy to consult with the Department. Having as complete an understanding as possible of habitat threats will help the Department effectively engage in these consultations and minimize impacts where possible.

Inquiries and recommended actions:

  1. What gear types does the fishery utilize? What is the spatial extent and intensity of the use of each gear type?
    1. Map the approximate spatial extent of the fishery in terms of location, depth, and preferred fishing habitats.
    2. Map the approximate intensity of fishing gear applied in terms of gear per unit area.
  2. Which habitats utilized by the target stock are most vulnerable to fishing gear?
    1. Characterize the risk each gear type poses. If no local information on habitat impact is available, a resource such as the table in Appendix N may be used to understand the likely impacts of the major gear types.
    2. Rank the habitats utilized by the target stock in terms of their vulnerability to the gear.
  3. Taking MPAs into account, what is the spatial overlap between the footprint of the fishing gear and these vulnerable habitats?
    1. Areas with overlap between high impact gear (or high intensity of moderate impact gear) and vulnerable habitats may need habitat mitigation activities.
  4. What other (non-fishery) habitat threats exist?
    1. Identify and consider anthropogenic threats.

Step 3. Minimize or mitigate adverse effects fishing activity may have on habitat.

There are a number of strategies available to managers to protect habitats, and many of these have already been employed to protect California’s most vulnerable marine habitats. The most common strategies include MPAs, and restrictions on the type of gear employed, or how and where a gear type can be used. In some fisheries, fishermen have also developed gear modifications that may lessen the impact of bottom gear on habitat.

Guidance for addressing habitat includes:

  • Identify and describe the habitat needs of the target species at all life stages.
  • Identify which of the habitats utilized are most vulnerable to threats from fishing gear and non-fishing activities.
  • Note areas where there is little to no information available.
  • Identify the fishing gear used, spatial extent and intensity of gear, and how gear usage overlaps with vulnerable habitats.
  • Work with stakeholders to determine mitigation or protection measures that may be necessary to lessen the impacts of fishing activity in sensitive habitat areas.
  • Monitor and evaluate the effectiveness of habitat protection measures.
Species found on soft sediment substrate include rose-sand anemones, giant red sea cucumbers, various flatfish, and brittle stars. (CDFW/MARE photo)
Conceptual drawing of bottom trawling impacts on seafloor habitats. The net and metal plates drag along the seafloor. (USGS image by Ferdinand Oberle)

Conserving ecosystem health and diversity

The MLMA highlights the connection between healthy fisheries and healthy ecosystems and underscores the importance of considering the impact of a fishery on the ecosystem. To preserve the function of an ecosystem, impacts from non-fishery factors such as climate and environmental change should be considered. This reflects a broader recognition worldwide of the need for holistic approaches to fisheries management. However, ecosystems are complex and in constant flux, and the specifics of how they function are not well understood. Making management decisions in this context can be challenging, even in data-rich environments.

Fluctuations in environmental or ecological conditions can have significant impacts on the abundance of target species. The development of ecosystem indicators can be a valuable tool to help ensure that management measures can track and respond to such changing conditions. The discussion of HCRs in Chapter 5 and Appendix J addresses the development and use of ecosystem indicators.

The section below focuses on the impacts of fishing on the ecosystem and provides guidance on ecosystem information to integrate into ESRs and FMPs and how EBFM approaches can be applied using available information and tools.

An ecosystem-based approach to managing fisheries

EBFM requires that ecosystem impacts be considered broadly and consistently in fisheries management. It is a departure from traditional single-species management, in which management decisions consider each species in isolation and do not account for ecosystem dynamics, such as interactions with other species, effects of environmental changes or pollution, and impacts of other stresses on habitat and water quality. While there is widespread recognition of the importance of taking a holistic approach to fisheries management, implementing such an approach has proven difficult. As with other aspects of fisheries management, a lack of data and information can limit understanding of biological and human dynamics, but need not prevent taking action based on general principles and use of available data and knowledge. It is possible to apply the principles of EBFM when making management decisions even in the absence of the data underpinning complex models of entire ecosystems.

Gorgonians are delicate soft corals that grow on the seafloor, providing important habitat for fish and other marine life. (CDFW/MARE photo)
Kelp bass in a kelp forest. (Greg Amptman/Shutterstock photo)

Identification of species that play key roles in the ecosystem

One of the goals of the MLMA is to preserve the ecosystem functions that are essential for sustaining commercial and recreational fishery species over the short- and long-term (§7050(opens in new tab)). While the literature on ecosystem function continues to evolve, one practical approach to preserving these functions has been to identify the species that play key roles within the ecosystem and their trophic levels, and to ensure that these species are managed sustainably. Conserving the species that play these key roles provides a way to protect the ecosystem functions and services these species play, both directly and indirectly.

Types of key species and their ecosystem roles include the following:

  • Keystone species are those that have been shown or are expected to have community-level effects that are disproportionate to their biomass.
  • Foundational, structural, or biogenic species are habitat-forming species (e.g., oyster beds, sponges, corals).
  • Basal prey species include small pelagic(opens in new tab) forage species such as krill, Pink Shrimp, Pacific Herring, squid, anchovies, and sardines. The high natural variability in the dynamics of these species can have large impacts on their predators and prey.
  • Top (or apex) predators are predators for which the removal of a small number of the species could have large or disparate ecosystem effects.

Changes to the structure of these species’ populations, which may include changes to the abundance, size structure, genetic structure, or distribution, should be monitored, and management measures should strive to maintain appropriate population structures for species in these roles to the extent possible. For example, the Commission has adopted a policy specifically for the management of forage fish(opens in new tab), which play a major role in the California Current Ecosystem (CCE)(opens in new tab) (Commission 2012). Forage fish are small pelagic organisms, such as Northern Anchovy, Pacific Sardine, Market Squid, and Pacific Herring that provide an important food source for larger marine organisms. They fill the critical ecosystem role of transferring energy from planktonic plant and animal life to larger fishes, marine mammals, and seabirds. Environmental conditions and climate regimes can have major effects on forage fish distribution and abundance.

Forage fish serve an important ecosystem role as food for seabirds, marine mammals, and larger fish. (Kojihirano/Shutterstock photo)

Consider management strategies with multiple control measures

Recent studies have found that an integrated management strategy, which is defined as one that involves a combination of management measures (such as size limits, gear restrictions(opens in new tab), spatial restrictions, effort restrictions, and quotas) to control fishing, is more likely to achieve EBFM objectives than those strategies that rely on a single restriction (Fulton et al. 2014). This is because while a single management measure may maximize catch in a single-species management context, different management controls may provide protection to different aspects of ecosystem function. For example, size limits or restrictions on mesh sizes might help to preserve more natural size and age structures in a population, so that the target species can continue to fulfill its ecological role (i.e., as predator or prey for other species in the ecosystem). Gear and spatial restrictions may reduce habitat and bycatch impacts. Seasonal restrictions may not only allow the target species to spawn, but also reduce bycatch of the species that feed on spawn during that time period. In this way, strategically employing a wider range of management measures may have benefits to the ecosystem as a whole.

Conduct Ecological Risk Assessments to understand which ecological links are most critical

The inherent variability, complexity, and uncertainty in ecological systems makes a complete understanding of ecosystem dynamics impossible. Nevertheless, the MLMA requires that management be based on the best available scientific information (§7050(b)(6)(opens in new tab)). Some experts have suggested that even a qualitative understanding of these relationships, such as an understanding of “who eats whom”, can be used to make decisions that account for ecosystem interactions (Patrick and Link 2015). In addition, there are analytical tools available, such as the ERA (described in Chapter 2), that can help identify which processes are most likely to impact ecological function, even when only qualitative or semi-quantitative information is available. Understanding the main drivers and major uncertainties of a system is important. This allows precautionary approaches to be applied only where needed, and can help to identify areas for future research.

Inquiries and recommended actions:

  1. Has the ecological role of the target species been identified? Does the target species play a key ecosystem role as defined above?
    1. Describe what is known about the trophic level, predators, and prey of the target stock throughout its life cycle.
    2. If the ecological role of the target species has not been identified, consider prioritizing the collection of this information as a research need in ESRs and FMPs.
  2. Is the target species a basal prey species?
    1. If so, additional consideration may be necessary to comply with the Commission’s Policy on Forage Species (Commission 2012(opens in new tab)).
  3. Has an ERA been conducted for the target species?
    1. If so, identify any major ecological threats, and consider applying management measures to mitigate those threats.
    2. If not, consider conducting an ERA for the fishery.
  4. Have the major areas of uncertainty in ecosystem dynamics been identified?
    1. If not, seek to identify the areas of uncertainty.
    2. If not, consider additional precaution to reflect the level of uncertainty.
  5. Are multiple control measures in place that may help to achieve EBFM objectives?
    1. If not, consider what, if any, additional measures may be needed to create an integrated management strategy as defined above.
  6. Has there been an assessment of how the target stock is likely to be impacted by changing environmental or ecological conditions?
    1. If not, consider the collection of EFI that can inform the development of environmental or ecological indicators.
    2. As indicators are developed, integrate into MSE analyses and HCRs as appropriate.

Photo at top of page: Schooling fish. (NOAA photo by Adam Obaza)