MLMA Master Plan Appendix H. Essential Fishery Information and Data Collection Strategies

Data collection is an essential component of fisheries management. Data collected through ongoing monitoring provides the scientific and technical information necessary to understand fishery operations, estimate the status of exploited stocks, evaluate fishery impacts on the ecosystem, and develop appropriate management regulations. It is this ongoing source of information that allows future management decisions to be adaptive, even when there is uncertainty during the design phase. A well-designed data collection and monitoring program is central to meeting management objectives.

The Master Plan is required to contain a description of the research, monitoring, and data collection efforts that the Department conducts (§7073(b)(3)). This appendix defines the various kinds of biological, ecological, and socioeconomic EFI and maps them onto the categories of data needed to make fishery management decisions. It then gives an overview of the types of data collection protocols that can be used to collect the various kinds of data required for fisheries management and describes the monitoring procedures in place in California. Finally, it describes some alternative sources of data that may be available when it is necessary to assess data-poor fisheries that lack historical information.

As with the other appendices, it is anticipated this overview will continue to be expanded and refined as part of Master Plan implementation so it can serve as an effective resource to managers and stakeholders.

Collecting biological information on an angel shark caught by CDFW staff while trawling for California halibut. (CDFW photo by Trung Nguyen)

Primary data needs for fisheries management

Fisheries management is primarily concerned with estimating the abundance of a fish stock and determining whether it is at a healthy level. Data is collected and analyzed to monitor fish stocks and estimate stock status. This is primarily done by fitting data to population models, also known as stock assessments, or by using other analytical techniques to estimate a metric of stock status (see Appendix I for more information).

Stock assessments usually require three primary categories of information: abundance, biological, and catch data. These three types of data and their collection methods are described in Table H1.

Table H1. Description of types of data used in fisheries management and their collection methods.
Data Definition Types of Data Collection Methods
Abundance Absolute or relative index of the number or weight of fish in the stock. Size and/or weight of fish collected or observed per sample unit. Statistically-designed, fishery-independent survey that samples fish at many locations throughout the stock’s range.
CPUE can be used as a proxy for abundance.
Biological Information on population dynamics processes. Fish size, age (via otoliths or scales), maturity, fecundity, natural mortality, and movement. May be collected during fishery-independent surveys or tag-recapture studies, or be obtained from observers and other fishery sampling programs.
Academic programs and cooperative research with the fishing industry are other important sources of biological data.
Catch The amount of fish removed from a stock by fishing, and the effort used to remove those fish. Number, weight, and species composition of removals (including discards). Dockside monitoring (also known as port sampling), logbooks, on-board observers, EM, and telephone surveys.
Effort data, including type and amount of gear used, time, day, and location of fishing.

Additional data needs for fisheries management

While Table H1 summarizes the core data needs for assessing the status of target stocks and developing HCRs, the population health of target stocks is just one component of fisheries. Fisheries are complex socioecological systems, and the MLMA specifies both socioeconomic and ecological goals and objectives for management of the state’s fisheries.

As discussed in Chapter 7, the MLMA’s socioeconomic objectives for fishery management include: 1) observing the long-term interests of people dependent on fishing for food, livelihood, or recreation (§7056(i)); 2) minimizing the adverse impacts of fishery management on small-scale fisheries, coastal communities, and local economies (§7056(j)); and 3) being proactive and responding quickly to changing environmental conditions, and market or other socioeconomic factors, and to the concerns of fishery participants (§7056(l)). In addition, the MLMA requires that FMPs include a summary of the economic and social factors related to the fishery (§7080(e)). If additional conservation and management measures are included in an FMP, a summary of the anticipated effects of those measures on relevant fish populations and habitats, fishery participants, and coastal communities and businesses that rely on the fishery (§7083(b)) is needed.

Additionally, as fisheries management agencies around the world move towards EBFM, there is increased focus on collecting data to monitor the impacts of fishing at the ecosystem level. The MLMA lists the following as an objective: “Support and promote scientific research on marine ecosystems and their components to develop better information on which to base marine living resource management decisions” (§7050(b)(5)). This objective suggests that the ongoing collection of ecological data is also important for managing California’s fisheries in a holistic manner.

Scientific diver collecting data in a kelp forest (CDFW photo)

Essential Fisheries Information

The MLMA states that FMPs are to summarize the best scientific and other relevant information available, and to collect necessary additional information if this does not significantly delay FMP preparation (§7072(b)).

Table H2 demonstrates how the major EFI categories are related to the major types of data required to make fishery management decisions and provides examples of each. In addition, the various EFI categories are explained in detail below.

Table H2. Summary of the type of information that may be applicable for each essential fisheries information category, and how they meet the basic data requirements necessary for fisheries management.
Data needs for fishery decisions EFI categories Examples
Abundance Estimates of abundance Absolute or relative abundance of fishable population, standardized CPUE index.
Biological Age and growth characteristics Size at age, length frequency, maximum length, maximum age.
Distribution of stocks Habitat preferences by life history stage, range, genetics, depth preferences.
Movement patterns Seasonal migration, ontogenetic movements, changing environmental conditions, home range.
Reproductive characteristics Fecundity, size/age at maturity, sex ratio, spawning periodicity and areas, size/age of sex change.
Catch Total mortality Landings, dead loss, discard mortality rate, discards (species and amount), research take, natural mortality, target species catch in other fisheries.
Effort Gear type and specifications, fishing location, number of trips, fleet capacity, effort/trip, boat size/capacity. Note: CPUE can be used as an index of abundance.
Socioeconomic Economic Price/lb., market dynamics revenues, business costs, cost of management.
Social Gear type and specifications, fishing location, number of trips, fleet capacity, effort/trip, boat size/capacity.
Ecological Ecological interactions Endangered, threatened, or protected species interactions, predator/prey, trophic role, other species encountered, habitat interaction, amount and type of bait.

Target stock Essential Fisheries Information

Age and growth

Age and growth studies typically measure how long a species lives, the age at which it reproduces, and how fast individuals grow. This information is very important to determine a population’s ability to replenish itself, the rate at which it might be harvested, and the age at which individuals will reach a harvestable size. Changes in the age structure and growth rate of a population also serve as indicators of that population’s health. Fish age often cannot be determined externally, so individuals must be harvested for age information.

Stock distribution

A stock is a population unit that is selected for management purposes. It may be defined based on its ecology, genetics, harvesting location, and/or geographic separation. Discrete stocks of a given species may have very different growth rates, reproductive schedules and capacity, and even ecological relationships. Stock distribution refers to where a stock is found and is important in addressing jurisdictional issues.

Indices of abundance

By its very nature and size, the ocean prevents highly accurate animal population counts. Managers and scientists rely instead on estimates and indices of abundance. An index of abundance is an indirect measure of the size of a population and is often obtained by counting a portion of the population using the same methodology each year, or by comparing counts between areas using similar techniques. This information is used by managers to calculate estimates of the total population size and determine appropriate harvest levels.

Movement patterns

Information on distribution patterns and the movement of fish can provide resource managers with important insights about a stock’s vulnerability to harvest. Certain species may aggregate in specific areas for spawning, travel in predictable patterns, or move to certain locations that make them especially vulnerable. Insights into the movement patterns of fish are vital to the development of management strategies based on regional catch quotas or MPAs.


Recruitment refers to a measure of the number of fish that survive to a particular life stage and is often used to predict future population size. Some examples include: the number of offspring that reach the juvenile stage (i.e., larval recruitment), the number of individuals that survive (recruit) to the next year (e.g., age two recruits), the number of fish that reach sexual maturity (i.e., recruit to the spawning population), or in the case of a fishery, the number of fish that recruit to the catchable component of the population. Young-of-the-year (i.e., individuals less than one year old) are frequently counted for many fish species and used as an index of larval recruitment success.

Many highly-valued species depend on successful recruitment events for replenishment. Recruitment success can be highly variable because it depends on the proper combination of many factors. As a result, the sustainable harvest of the fishery may depend on only a few strong cohorts (i.e., born the same year) to provide harvestable stocks until the next successful recruitment event. Resource managers must consider this variable recruitment success when setting harvest levels by allowing sufficient portions of stocks to escape harvest and provide spawning biomass for future recruitment successes.


Reproduction encompasses information such as the number of eggs a female produces, the average age an individual becomes sexually mature, and whether a female bears live young or broadcasts eggs into the water. This type of information helps managers determine the ability of a population to replenish itself, and at what level it might be harvested. This knowledge allows them to set appropriate open seasons, areas, size limits, escape mechanisms for traps, and net mesh-size restrictions based on spawning considerations.

Total mortality

Natural and fishing mortality rates comprise the sum of all individuals removed from a population over a fixed period of time, often over one year. Fishing mortality is the rate at which animals are removed from the population by fishing and can be calculated from landings information if the population size can be estimated. Natural mortality refers to all other forms of removal of fish from the population, such as predation, old age, or disease. This information is used to predict how many animals remain to reproduce and replenish the population. Mortality figures are used by managers to calculate the number or weight (i.e., biomass) which may be safely harvested from a population or stock on a sustainable basis.

Ecological Essential Fisheries Information

Ecological interactions

Studies of ecological interactions assess the relationship of the species with other animal and plant species and the physical environment. For example, the harvest of an organism has an effect on both its predators and prey. In addition, fishing activity may have unintended effects on fish habitat or other species inhabiting the area. Ecosystem-based studies consider how oceanographic parameters, habitat, trophic (e.g., food, energy) dynamics, community structure, competition, or fishing mortality affect the health and abundance of organisms.

Oceanographic features include many biological (e.g., primary production, nutrient levels) and physical (e.g., current, temperature, salinity patterns) variables that can provide valuable insights into the abundance, distribution, and condition of a particular species or stock. Their predictive value makes long-term trends in oceanographic data, coupled with other biological information parameters, especially important in fisheries management.

Certain biological and physical variables may prove to be valuable indicators of climate change.


Habitat investigations are useful to fisheries managers because they can identify the importance of specific physical parameters to the species of interest and associated biological assemblages.

Socioeconomic Essential Fisheries Information

It is important that fisheries managers have a clear understanding of the current economic condition of the community and fishery under regulation, and of the likely socioeconomic consequences of regulatory changes to the fishery. This includes direct impacts to resource users, such as reduction in landings revenue due to lower catch quotas and shorter fishing seasons, as well as indirect or “downstream” economic impacts to local employment or associated industries.


Habitat investigations are useful to fisheries managers because they can identify the importance of specific physical parameters to the species of interest and associated biological assemblages. Demographic information typically consists of data relating to a population and groups that comprise it. Examples of demographic data include age, gender, ethnicity, race, education level, income level, residence location and type, and household size. In a fisheries context, the population includes fishery participants (i.e., commercial, recreational and subsistence fishermen, and fish buyers), those who provide goods and services in support of their activities, other members of the communities where they are based or operate, and consumers of seafood. Demographic data and analyses may be used to: characterize individuals, communities and other aggregates of people, including sociocultural groups, fisheries, and associated communities; identify historic variability and change in populations and groups; and measure change or impacts resulting from management action or other factors. Demographic changes, in turn, can signal changes in motivations, values, and practices.


Practices are the ways people do things and include where, when, and how they participate in fisheries and fishery-related activities. More specifically, practices include how vessels, equipment, and gear are configured and used, whether and how certain species are targeted, caught, and handled, and how the catch is distributed. Practices also include patterns of use in time and space of fishery resources, marine areas, coastal harbors, and infrastructure. These necessarily include analyses of characteristics such as: vessel length, hull material, fish holding capacity, engine type and horsepower; type of navigation, fish-finding, and gear-handling equipment; gear types, configurations, and number of units; and number of crew and their roles. The characteristics of the shore side operations may vary in many ways, including whether operations for receiving fish are mobile or fixed, the size and function of these operations, and the handling, processing, and distribution operations. Understanding fishery-related practices is key to identifying sources and solutions for ecological and socioeconomic concerns.


Motivations are the reasons why people do the things they do. Although it is often assumed that individual behavior is fully rational and driven by reason, with economic motivations, growing evidence indicates that individuals are motivated by a complex mix of social, cultural, and economic values. An understanding of fishery participants’ motivations for fishing and related activities can be used to develop management options that create appropriate and effective incentives for compliance, and to evaluate those options in terms of their acceptability, compliance, and socioeconomic outcomes.


Institutions are the formal (e.g., regulations) or informal (e.g., shared understandings of where and how gear is set, the distance between operations) norms, rules, and strategies that govern peoples’ behavior. Formal institutions include those specific to a given fishery, and those that pertain to other state- and federally-managed fisheries, broader marine space use, coastal land use, environmental protection, food production, public heath, and other relevant topics. Understanding the formal and informal institutions that affect fishery participants and associated communities is useful for evaluating the potential efficacy and outcomes of fishery management actions, and for guarding against unintended consequences (e.g., effort shifts from one species to another, or to potentially sensitive or vulnerable areas).


Relationships include the social and economic connections among people that are ongoing and meaningful to those people. In fisheries, such relationships include those among fishermen, buyers, and providers of supporting goods and services, within and among fishing families and communities, and between fishery participants and fisheries managers. Relationships can also be among organizations and communities, through which information and social and economic resources flow. They reflect interdependencies among those connected for a range of tangibles (e.g., income, goods, services, practical support) and intangibles (e.g., information, shared identity, sense of belonging). Information about these relationships is useful for understanding how the fisheries-human system functions, and for assessing social and economic impacts of change.


Fisheries-relevant capital includes the natural, human, physical, and financial resources needed and used by fishery participants and communities to sustain their activities and generate associated benefits (e.g., livelihood, recreation, sustenance). Natural capital consists of the ecological system, including living resources and habitat. Human capital includes people, and the skills and knowledge they possess individually and collectively. Physical capital includes vessels, equipment, gear, ports and other landing sites and facilities, and seafood processing facilities. Financial capital includes the monetary resources used to purchase or provide physical capital and goods and services to enable human activities. Understanding the types of capital needed, available, and used by fishery participants, fisheries, and communities is useful for better understanding fisher-related behavior, social and economic impacts, and opportunities and challenges to effective adaptation to environmental and regulatory change.


Employment relevant to fisheries and their management includes part- and full- time, seasonal, and year-round jobs in fishing and seafood production and those jobs associated with the provision of supporting infrastructure and goods and services, including related research and management activities. Changes in fishing opportunities and activities can have direct, indirect, and induced effects on employment among fishery participants, goods and service providers, and others in the associated communities and economies. Jobs gained or lost in one part of the human system affect those in other parts of the system. Employment information is useful for evaluating the impacts of management change on fishery participants, communities, and economies.


Revenues consist of payments received by fishery participants and businesses for fish landed, handled, processed, and sold. Revenue also includes payments received for fishery-related goods and services, ranging from charter fishing trips to vessel, gear, equipment, gear sales, boat rentals, fuel, bait, and ice. Revenues may originate and circulate primarily within a community, although they typically come from and/or circulate outside a given community. Information about fishery-related revenues is useful for assessing the impacts of changing resource availability and management on fishery participants, fisheries, fishing communities, and the overall economy. Moreover, changes in revenues, such as the ex-vessel price for commercially-caught species can signal a change in fishing practices.

Data collection strategies for fisheries management

The EFI outlined above provides a comprehensive list designed to guide fisheries managers in improving their understanding of a stock. While ideally managers would have all categories of EFI for all stocks, the Department is working with limited resources and currently information is lacking for many fisheries in California. In prioritizing data collection efforts to support the acquisition of EFI, it is necessary to think about how the data collected will inform management. One strategy is to consider all the components of the management strategy (i.e., data collection protocol, data analysis/assessment HCRs, and management measures) simultaneously because the available data will dictate which assessment methods and HCRs are feasible. Managers will need to assess the potential costs and benefits associated with implementing additional data collection activities. To aid in that process, this section gives a broad overview of the various monitoring options available to fisheries managers, their relative costs, and the type of data they produce.

California Recreational Fisheries Survey sampler collecting information from anglers at Trinidad dock. (CDFW photo)
Urchins in net. (Jim Cork/Shutterstock photo)

Fishery-dependent data

The MLMA dictates that the Department is the primary agency responsible for the acquisition of EFI and that the collection of the necessary data is best collected through the ongoing cooperation and collaboration of participants in fisheries (§7060(a-c)). For this reason, fishery-dependent monitoring is often the primary mechanism for monitoring fish stocks. Fishery-dependent data are collected directly from the commercial and recreational fisheries. Data are usually collected via dockside monitors, at-sea observers, self-reporting through logbooks, EM and reporting systems, telephone surveys, Vessel Monitoring Systems (VMS), or cooperative research initiatives, and can provide information on fishing effort, landings, CPUE, discards, species composition, and biological information.

Fishery-dependent data are generally more economical to collect and typically consist of a relatively large sample size. Because of this, fishery-dependent sampling protocols usually form a core component of any management strategy. Table H3 summarizes the types of data that can be collected with commonly used fishery-dependent monitoring protocols, as well as the relative cost of each. Table H4 summarizes the Department’s current monitoring activities. These tables can be used to help select the type of monitoring program needed to implement a particular stock assessment technique and HCR when developing a new management strategy. Additionally, they can be used to assess an existing monitoring protocol to determine whether the existing protocol is providing all possible data.

There are known biases associated with data obtained via fishery-dependent monitoring. These biases must be identified before fishery-dependent data can be incorporated into stocks assessments. For example, the most common and easily collected fishery-dependent data is catch and effort information from commercial or recreational fishers, usually summarized in the form of CPUE, or catch rate. CPUE is often used as an index of abundance in stock assessments when fishery-independent abundance data are absent because it can be assumed that the catch is proportional to the product of fishing effort and density of the fish. If catch and effort can be measured, then density and abundance can be estimated. However, CPUE can change for many reasons, including changes to the gear over time (e.g., through increasing efficiency or regulations designed to decrease efficiency), spatial distribution of fishing, or time of day or year when fishing occurs. Changes in any of these variables may lead to a change in the CPUE in the absence of a change in the underlying abundance of the stock, which can sometimes limit the applicability of CPUE as an index of abundance. The impact of these additional factors can be accounted for through a statistical process called catch-effort standardization. For this reason, it is important to fully document any historical management or market changes that may have influenced these factors, and FMPs provide managers with an opportunity to do this in a comprehensive manner. Additionally, a comprehensive management program that employs both fishery-dependent and fishery-independent studies in a complementary fashion can be used to help identify these biases and provide a more complete picture of the stock status.

Table H3. Common fishery-dependent sources and the type of data they can produce.
Monitoring approach Landing receipts/sales dockets Logbooks Creel surveys/dockside monitoring Onboard observers Interviews with fishery participants Market/processor sampling
Description Records the species, weight landed, and price paid by processors receiving fish. May also record sex or size composition (categorical) if prices differ. Information the Department requires all licensed fishermen to report. Vulnerable to self-reporting errors. Sampling protocol used to intercept fishermen when they are fishing from shore or landing their catch. Viable option for large-scale, industrial fleets. Can provide fine-scale information on all aspects of the fishery. A high proportion of observer coverage may be required. Useful for gathering historical information when data is lacking. Often provides qualitative rather than quantitative information. Sampling catch at the processor/market site. Useful when fishing activities are spatially disparate, but there are a small number of processors/ marketing sites.
Data collected
Historical information Yes
Socioeconomic/ operational information Yes Yes Yes
Gear Type/amount used Yes Yes Yes
Effort Yes Yes Yes Yes Yes
Fishing location Yes Yes Yes Yes
Catch per vessel Yes Yes Yes Yes Approximate
Total catch for fleet Yes Yes Yes
CPUE Yes Yes
Species composition Yes Yes Yes Yes
Bycatch/discards Possibly Yes
Size composition (detailed) Possibly Yes Yes Yes
Size composition Possibly Yes Yes Yes Yes
Sex composition Possibly Yes Yes
Reproduction/maturity Possibly Yes
Age composition Yes
Relative cost to implement Low Low Moderate High Moderate Low to moderate
Table H4. Summary of Department’s current data collection activities.
Tool Sector Collection frequency Description
License applications Both Annual Online registration (vessels and individuals) with fee collection using third-party software, managed by the Department.
Logbooks Commercial Per trip Paper except for CPFV logs, which run on dedicated tablets.
Landing receipts Commercial Per landing Paper, except for eight dealers registered with eTix system. Full transition to eTix in 2019.
Report cards Recreational Per season Paper, but anglers can enter data online via the Automated License Data System web portal.
On-board observers Commercial Set percentage of fleet covered per season Usually only for federal fisheries through NOAA federal observer program. Data not easily available to the Department.
Port/dock samplers Both Set percentage of fleet/docks covered per season Coverage varies by fishery and by season; core component of California Recreational Fishery Survey.
Catch monitors Commercial Per landing Independent staff who oversee landings; may or may not also be certified to collect biological samples.
Vessel Monitoring Systems Commercial Constant data stream while vessel is fishing Required for some federal fisheries, data collected by NMFS, but not readily available to Department science/management staff.
Electronic monitoring/ video cameras Commercial Constant data stream while vessel is fishing Only for a limited number of federal trawl fishery participants. Summarized data treated as federal observer data and may be unavailable to Department staff or available only in aggregate.

Landing receipts

The Department’s first major attempt to gather EFI began in 1916 with the use of landing receipts, or “fish tickets,” as they are commonly known. Commercial buyers are required to complete landing receipts when the catch is off-loaded onshore to track the amount of fish landed by weight or number, along with the fee due on those landings. These forms contain information on the species, general location fished, weight of the catch, and price paid for the catch. Many fish species are often grouped into multispecies market categories based on similar market value rather than separated into species-specific categories. This can present a problem when attempting to use this information in analyses. Although limited in scope and accuracy, information on landing receipts are often the only information available for a particular fishery.


Logbooks were developed to augment information obtained from landing receipts and require that fishermen record information such as catch, location fished, and time spent fishing for each time their fishing gear is deployed. The log is then sent to the Department. Logbooks seek to access the professional knowledge and observations of fishermen to improve fishery management. The utility of the information that they provide is dependent on its accuracy, timeliness, and return rate. Logbooks have the potential to be a very valuable source of fishery-dependent information, especially considering the relatively low cost to administer the program statewide. The Department is in the process of shifting from paper to electronic logbooks, and this transition provides an opportunity to revise the data that is collected, as well as overcome the lags associated with return and data entry that have been obstacles to the use of the data in the past. A 2017 review in support of the Department’s transition to electronic logbooks suggested that logbooks be redesigned to collect the information in Table H5 to increase their utility.

Table H5. Suggested data to be collected using the logbook format.
EFI category Data element Example data fields
Effort Activity and capacity Boat size/capacity
Date and time of trip start/end (number of trips)
Number of hooks
Number of traps set
Number of anglers on a charter boat
Gear type and specifications
Time of gear in water
Time spent targeting a species
Fishing location (fishing block)
Latitude/longitude, automated as much as possible
Total mortality Landed and discarded catch Number of individuals
Economic Price Price per pound landed condition
Ecological interactions Bycatch and discards Predation of hooked or discarded fish, by species

Creel surveys

Creel surveys entail interviews of sport fishermen at boat-launching ramps or at points where they are fishing from land (e.g., beaches, piers, and rocky coastline). Samplers typically gather information on the number of each species caught, number of each species kept, size and sex of kept fish, number of fish returned to the water, type of gear used, number of fishermen in the party, and total hours fished. Certain creel surveys may also collect socioeconomic data such as distance traveled from home or port, length of stay in the area, and expenditures. The accuracy and precision of these surveys depend largely on a good working relationship between Department staff and the fishermen being surveyed. Information collected on catch composition, CPUE, size limits, and fishing mortality are used to determine how the recreational sector of a fishery affects a resource.

Dockside/market sampling

Dockside or fish market sampling is used to collect commercial landings data after the catch has been off-loaded and, in the case of multiple-species landings, separated into market categories. These data provide important information on total weight, species composition, size, sex, age, and maturity of the species being landed. It is important to note, however, that this type of sampling provides imprecise estimates of fishing effort, and little to no information on bycatch or discards. Fishery landing statistics collected from this sampling allow fishing mortality rates to be calculated (excluding any discard mortality).

On-board sampling

Scientific observers accompany commercial and sport fishermen on fishing trips to collect biological and socioeconomic data at sea. Observers collect information on the location fished, total catches (not just landed), and the species, size, sex, and maturity of fish caught. In some fisheries they also collect (or have collected in the past) data on bycatch, discards, and interactions with birds and marine mammals. This information also can be used to verify logbook and creel survey data. On-board sampling also has the potential to address socioeconomic gaps in EFI. On-board observers collect EFI that cannot be obtained by other means (e.g., bycatch, precise fishing locations of each unit of fishing effort).

CDFW staff sampling Pacific herring. (CDFW photo by Tom Greiner)
CDFW staff sampling Pismo clams. (CDFW photo)

Fishery-independent data

Fishery-independent data come from sources other than directly from the fishery. They are collected from surveys designed and conducted by scientists to gather information on fish stock abundance and biology. These surveys are specifically designed to follow consistent methods using the same gear for the duration of the survey in order to develop unbiased and independent indices of abundance. Since the data are not influenced by specific management measures (e.g., size and bag limits(opens in new tab), season closures, mesh sizes) or socioeconomic factors, they present an unbiased accounting of stock health. These surveys often collect biological data and abundance information and may be able to sample components of the fish stock that are not accessible using commercial gears (e.g., juvenile fish). They can also collect information on fish habitat characteristics and environmental factors.

Fishery-independent survey methods vary widely, and may include standardized trawl surveys, dive surveys, hook-and-line surveys, etc. The choice of survey mode is driven principally by the species being monitored, availability of suitable vessels and personnel, and the ability to maintain continuity of survey time series. The Department may contract with commercial fishing vessels to conduct sampling provided it occurs separately from fishing activities.

Fishery-independent research collects standardized information often on all life stages and not just what is marketable or utilized by the fishery. Greater technology and more sophisticated equipment are often required compared to typical fishery-dependent data collection. While fishery-independent data usually have fewer biases, they are relatively more expensive to collect, may have smaller sample sizes and smaller spatial scales, and may not be collected every year. Historical data collection protocols, and any changes in protocols that have occurred over time, should be fully documented in an FMP or elsewhere.

Fishing surveys

Rather than rely on a commercial or recreational fishery to provide the Department with samples, biologists often collect their own samples using a variety of gear. Since fisheries often use gear that selects certain sizes or a sex of fish or invertebrates, catches usually do not represent the entire population. By using gear that catches a representative sample of the entire population (e.g., trawls for some fisheries) the Department avoids such limitations of fishery-dependent samples.


Tagging animals provides EFI such as their movement, age, growth, and population size. Fish or invertebrates are captured alive, the size and catch location are recorded, and they animals are tagged externally (typically), and released. If they are recaptured at a later date, information can be obtained on their age, growth, and distance traveled since being released. Tagging studies are most frequently conducted with the advice and participation of fishermen, who are most likely to recapture tagged animals and return the tag and/or animal to the Department. Information on distribution patterns and movement of fish is valuable to resource managers because it allows insight into the areas and times that stocks are most vulnerable to harvest or environmental effects.

Egg abundance surveys

Surveys to estimate the abundance of eggs spawned by a particular species of fish or invertebrate are also used to estimate the size of a population, especially the reproductive portion of a population. This method also provides information on the amount and locations of reproduction, and spawning habitat preferences.

Underwater (in situ) surveys

The ability to deploy divers or equipment underwater to make direct observations of animals and habitats is important. This method allows a variety of EFI to be collected that cannot be collected using other methods, including information on detailed habitat preferences, ecological interactions, movement patterns, and non-lethal size/abundance information. Scuba-based projects are equipment-intensive and require a relatively large staff or partnership to ensure the requisite sampling effort.

Submarines and remotely operated vehicles are also capable of direct, in situ observation of the environment and living resources. Unlike divers however, their operation is not as severely constrained by depth, ocean conditions, or operating time. In addition, these units can carry a wide array of sensory equipment.

Hydroacoustic surveys

Hydroacoustic technology is familiar to most fishermen because it is the same technology used by depth finders and sonar to locate schooling fish or the ocean bottom. This method can be used to measure the size, distribution, and movement of fish schools, and to map and characterize the associated bottom or habitat type. It is most useful for species that exhibit schooling behavior.

Genetic investigations

Recently, scientists have refined genetic assessment techniques to sample populations to differentiate discrete fish or invertebrate stocks. Separate stocks of a given species may have very different life histories and this type of EFI may be used by resource managers in regional management strategies.

Grunion run at the beach by the Cabrillo Marine Aquarium in San Pedro. (CDFW photo by Diane Alps)

Alternative data sources for use in data-poor management

The management of many fisheries is hampered by a lack of data, specifically time series of the kinds of data described above. Data-poor fisheries are characterized by uncertainty in the status and dynamics of the stock or species, uncertainty in the nature of fishing (e.g., in terms of fleet dynamics and targeting practices), or having only basic or no formal stock assessments. Many of California’s fish stocks can be characterized as “data-limited” under this definition.

However, the MLMA requires that the fishery management systems in place protect the sustainability of the stock, regardless of the level of information available. When data are insufficient for a conventional stock assessment, alternative methods can be used to inform management decisions. Frequently, and as discussed in Appendix I, stock assessment methods rely on time series of catch, CPUE, or abundance to estimate how fishing has impacted a stock over time. Without information on historical conditions, it becomes difficult to estimate the current stock status relative to sustainable targets. However, several simple length-based assessment methods have been developed to provide insight into stock status from size composition data. Measurements of length composition of an exploited stock are inexpensive and simple to collect via port sampling, and representative samples of the catch can often be obtained within a single fishing season.

The addition of no-take MPAs to California’s seascape also provides an opportunity to improve the monitoring of California’s data-poor fish stocks. MPAs present an opportunity for the assessment of data-poor fisheries by acting as a reference area, allowing for the comparison of fished vs. unfished conditions in much the same way as comparisons against historical data. MPA-based stock assessment methods have relied on comparisons of catch rates, survey data, and size compositions inside and outside of MPAs. The Spiny Lobster FMP identifies reserve monitoring as a primary source of data used to estimate growth rates, longevity, natural mortality, fishing mortality, and stock size structure.

Market-based sources provide an additional opportunity to gather the data necessary to assess fish stocks. Size and species composition data may be available from processors and other buyers, who often keep records of the approximate size of fish purchased. These data may be binned into categories and can provide some sense of how fishing is impacting the stock, often over many years. Market-based data can also provide information on how stock composition and trophic level has changed over time, which provides a means of estimating the level of fishing pressure.

In fisheries that are essentially data-free, it is possible to gather qualitative information on the fishery from participants. By gathering information on the history of the fishery, the gear types used, species caught, fishing locations, and how things have changed over time, it is possible to characterize the likely risk that fishing poses to the stock. This is especially true when this method is paired with the “Robin Hood” approach (Punt et al. 2011), which borrows biological parameters estimated from related fish stocks in data-rich systems to understand the biological vulnerability based on the species life history. Additionally, a number of “rule of thumb” reference points have been developed based on life history characteristics and borrowing this information may allow these reference points to be applied to stocks for which no local data exist.


Punt, A. E., D. C. Smith, and A. D. M. Smith. 2011. Among-stock comparisons for improving stock assessments of data-poor stocks: the “Robin Hood” approach(opens in new tab). ICES Journal of Marine Science 68(5):972-981.

Photo at top of page: CDFW diver collecting data on urchin population. (CDFW photo by C. Catton)