MLMA Master Plan Appendix K. Management Measures to Regulate Fishing Activities

This appendix provides an overview and considerations associated with a range of management measures and approaches that are applied globally. Applicability of a specific management measure to California’s fisheries needs to be considered on a case-by-case basis. 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.


Managers have a suite of possible regulatory mechanisms, known as controls, available to them to ensure sustainability. These include restrictions on catch, effort, gear, season, size of fish, and fishing areas. The best choice will depend on a variety of factors, including the biology of the species, how the fishery is prosecuted, socioeconomic issues, and governance capacity.

When used properly, fishery controls not only provide conservation benefits, but also help to make the fishery more sustainable and economically stable. Controls can also allow depressed stocks to recover and may prevent collapse. Controls on effort that limit fishing capacity may be especially useful in fisheries that experience increases in fishing due to volatile prices for fish.

Fishery controls are usually classified as either input controls or output controls. If the control measure implemented directly constrains fishing effort, it is an input control, and if it constrains the catch, it is an output control (Morrison 2004). The controls summarized in this appendix provide an overview of the kinds of tools available in the fishery manager’s tool box as well as considerations associated with each.

CDFW wildlife officer on patrol. (CDFW photo)

Input controls

Input controls relate to who does the fishing, and when, where, and how they can fish. They include restrictions on the type and amount of fishing gear used, number and size of fishing vessels, amount of time fishing vessels can fish, and number of participants in the fishery. Each of these restrictions effectively limit the amount of fishing effort and are thus referred to as effort controls(opens in new tab).

Input controls assume that fishing effort is a useful proxy for the amount of fish stock captured each year. When fishing effort increases, all else being equal, managers expect the magnitude of fish caught to increase. As a result, managers may use input controls as a means of limiting catch and, by extension, fishing mortality. However, there is frequently uncertainty regarding the relationship between effort and catch. This section discusses the various types of input controls available to managers, as well as their respective strengths and weaknesses (see Table K1 for a summary).

Table K1. Summary of types of input controls and associated considerations. Note that multiple controls may be applied simultaneously.
Type Description Benefits Considerations and limitations
Effort limits Limits on number of vessels or participants. Highly applicable across a wide range of fisheries.

Requires less monitoring and is easier to enforce than catch limits.

Limiting entry may help prevent over capitalization.
Requires knowledge of relationship between effort and catch to set limits.

Usually requires multiple controls to curb “effort-creep”.

Limiting entry to fisheries may restrict access to fisheries and limit employment opportunities.
Gear restrictions Restrictions on the number, type, or size of fishing gear used. Widely applicable to any fishery that uses gear. Often paired with other controls.

May be used to:
● Limit fishing efficacy;
● Protect particular size/age classes from harvest;
● Prevent bycatch of other species; and
● Reduce the negative impacts of fishing gear on the habitat.
Restrictions may increase the cost of fishing for fishermen.

Restrictions may limit ability of fishermen to innovate new gear types.
Temporal restrictions Restrictions on the time when fishing can occur, including:
● Seasonal closures;
● Restrictions on time of day/days of the week when fishing is allowed; and
● Tending requirements for passive gear
Temporal closures can indirectly reduce fishing mortality by reducing the number of days that fishing is allowed each year.

Seasonal restrictions may be used to protect vulnerable life history stages (i.e., spawning aggregations, reproductive stages).

Tending requirements reduce lost gear, bycatch mortality, and ghost fishing in passive gear fisheries.
May not reduce fishing mortality if efficiency or amount of fishing gear is very high.

May encourage fishing during hazardous sea conditions.

May encourage change in type/amount of gear used in response to closure; may encourage illegal fishing.
Spatial restrictions Restrictions on where fishing can take place. May be rotational, in response to triggers, or permanent. Easily understood by user groups.

Easy to enforce in nearshore environments.
May increase crowding and cause a race to fish in remaining open areas.

Not appropriate for managing highly-mobile species.

May require an understanding of spatial distribution of fishing and habitat.

Effort limits

Effort limits restrict the amount of effort that can be used in a fishery, and can come in many variations, such as limits on the number or capacity of vessels, number of participants, trip length, etc. These are primarily designed to reduce or cap the efficiency of the fleet by limiting how much can be caught in a given time period.

The number of permits and vessel size are common metrics for assessing or limiting fleet capacity. Fisheries where the number of participants is capped are referred to as limited entry or restricted access fisheries. The Commission has adopted a policy that guides the development and implementation of commercial restricted access programs. The development of these programs is often controversial, resource intensive, and can lead to litigation. They are nevertheless an invaluable tool for management.

If a restricted access program is already in place and it is determined that the existing fleet is too large to meet biological or socioeconomic goals, additional management actions may be needed to reduce fleet capacity. One option is to create permit transfer restrictions such as requiring new entrants to acquire two permits to enter the fishery or making some permits non-transferable. However, it may take many years to achieve the desired fleet size with this approach. Reducing fleet size on a faster time scale, which may be necessary in fisheries that are near collapse may require a permit buyback program, which often removes the least efficient and/or least active vessels in a fishery.

Effort limits usually require fewer management resources than catch limits, making them an attractive option for many fisheries. However, they provide managers with limited ability to achieve a specific catch level or harvest rate. And even with effort limits in place, effort often tends to gradually increase. This means that overfishing can occur even with effort limits in place. Effort restrictions that limit the number of participants can also reduce access to the fishery and employment opportunities.

Gear restrictions

Gear restrictions place limits on how the fishing gear is configured as well as prohibit certain types of gear in a fishery (e.g., prohibition on use of bottom trawls to take Spot Prawns). This could include mesh size requirements on trawl or gill nets, size of vessels, number of traps, length of nets, etc. Gear restrictions can be used in three different ways: 1) reduce the capacity or efficiency of each individual fisher, in order to reduce the amount each person can catch in a given time period; 2) modify the selectivity of the fishery so that particular sizes or species of fish are vulnerable to the gear, while others are immune; and 3) minimize or reduce habitat destruction and bycatch. Gear modifications are the primary way in which fisheries managers control for ecosystem impacts.

Spatial restrictions

Spatial restrictions, which limit or dictate the area in which fishing activities can occur, are another form of input control. They provide areas of refuge from harvest, which can reduce fishing mortality. These might be used to reduce the spatial footprint of the fishery, protect particular habitat, or remove fishing from areas where fish aggregate to spawn. Spatial restrictions can be either permanent, such as with MPAs, semi-permanent such as with Rockfish Conservation Areas (RCAs), or be part of a rotational management scheme designed to spread fishing activities over a wider area. Closures can also be invoked in response to stock-related targets and limits.

Spatial restrictions are easily understood by user groups and are relatively easy to enforce in nearshore settings. However, spatial restrictions may increase crowding and competition in open areas. In addition, they require a relatively high level of understanding about habitat types, as well as how those habitats relate to the health of the fish population. While fish in the closed areas are protected from fishing, fishing mortality may be very high in open areas, with negative consequences for the stock. Additionally, spatial management is not suitable for high-mobility species because they are likely to range beyond the extent of the spatial closure and thus become vulnerable to fishing activities.

Temporal restrictions

Temporal restrictions limit the period in which fishing activities are allowed to take place. This can be done by specifying the time of day or days of the week when fishing activities can take place. Temporal restrictions can also take the form of a seasonal limit. Seasonal limits can be used to limit fishing mortality provided there is some understanding of how fishing effort over time corresponds with harvest level. Seasonal limits are also used to protect species during important life stages. Examples include closures to protect spawning aggregations or to remove fishing effort during the reproductive season. Seasonal closures can also be used to restrict catch of non-target species. This type of management approach can limit fishing mortality and make monitoring or enforcement easier for the managing agency. It has also been used in fisheries targeting spawning aggregations to allow some spawning to take place in the absence of fishing pressure.

As with other controls, temporal restrictions have potential drawbacks. If a fishery is constrained to a specific time frame, fishers may be incentivized to deploy more gear and/or make more trips in an attempt to catch as much as possible before the fishery closes. This can lead to negative impacts from excess fishing gear on habitat and bycatch. In addition, increases in the amount or efficacy of fishing gear could undermine the ability of temporal closures to restrict fishing mortality.

Poached abalone seized by CDFW. (CC photo by KQEDQuest)
Enforcement of recreational fishing regulations. (CDFW photo)

Output controls

Output controls dictate what is allowed to be harvested. These include catch limits, which are restrictions placed upon the weight or number of fish that may be caught in a given period of time. Output controls also include limits on the species, size, and sex of fish that may be landed. Output controls provide a more direct mechanism to control harvest than input controls. However, output controls may require higher levels of data collection and enforcement to apply them effectively. This section discusses considerations associated with each (see Table K2 for a summary).

Catch limits

Catch limits are the most direct way to control harvest and achieve a desired harvest rate. They also provide a direct way to build a precautionary buffer into a management strategy when there is uncertainty about the dynamics of the stock. The most common form of catch limit is a TAC, which is an annual aggregate limit for all sectors (recreational and commercial), set at a level expected to maintain resource sustainability. TAC-based management will generally have higher data collection and analysis needs to identify an appropriate catch limit. This is because catch limits are usually set based on the current stock size and productivity of the stock, which in turn is usually determined through population modeling and quantitative stock assessment (see Appendix I). Additionally, to be effective, TACs also require in-season monitoring to ensure catch limits are not exceeded. This can be achieved either by monitoring the catch in real-time using self-reporting of landings (via fishers or processors), onboard observers, or dockside monitoring. As TACs generally have higher data collection, analytical, and enforcement needs than other types of controls, they may be most appropriate for higher-value fisheries with more centralized landing sites.

When a TAC is reached the fishery is closed. Because this creates uncertainty around how long the season will be open, a TAC can create a “race to fish”. This can have a number of unintended consequences. It can fuel excess capacity in terms of larger boats, more gear, etc. TACs also provide an incentive for under-reporting of catches, as well as high-grading, where fishermen discard in favor of higher value catch. These discards may result in fishing mortality that is not accounted for in the landed catch data. In some fisheries TACs are monitored by having a series of short open periods and then counting the landed catch during the closures. These are known as “derby fisheries” and can encourage fishing when conditions are dangerous. Derby fisheries can have adverse effects on fishery profits by flooding the market and driving down the price, or by reducing the quality of the landed product due to time constraints. Allocating portions of the TAC to individuals (such as in the federally-managed Pacific groundfish trawl fishery) can help address these issues, but the costs of ensuring individual accountability through observers or EM can be high.

Trip limits are another form of catch limit, in which the total catch per trip is capped. Often this type of control is paired with a limit on the total number of trips to achieve a desired total catch level. Trip limits can be an effective means of controlling or reducing effort; however, they also require sufficient monitoring and enforcement to be effective. Similar to TACs, trip limits can encourage discards as fishermen high-grade in order to maximize the value of their catch.

Bag limits

A bag limit is a form of recreational catch limit that restricts the number of fish, invertebrates, or plants that may be landed in a day. Bag limits do not limit the total aggregate catch in the fishery unless there is some type of limit on participation as well (such as that realized through the requirement of a report card), but they may be an effective mechanism to limit harvest in small-scale fisheries. They are primarily designed to limit recreational catch to what could be reasonable utilized by an individual or family. They are usually combined with an overall possession limit to be most effective. Bag limits have the advantage of being simple for user groups to understand and relatively easy to enforce. However, bag limits do provide an incentive for high-grading, and thus may result in discard mortality.

Size, sex, and species restrictions

Size limits are another output control that can be used to regulate what is landed in a fishery. Minimum size limits prohibit the take of fish until they reach a certain size, which can ensure that all fish have the opportunity to reproduce at least once before they become vulnerable to the fishery. Minimum size limits are simple to employ, easily understood by users, and highly effective at protecting breeding capacity of the stock. However, they require an understanding of the relationships between size/age and reproductive maturity to ensure that the size limit is appropriate. Maximum size limits can be used to protect the age structure of the stock by removing fishing pressure on older fish, which are more likely to be large mega-spawners. When minimum and maximum size limits are used in concert it is known as a slot limit.

Sex restrictions are prohibitions on taking fish or invertebrates of a particular sex, usually females. These types of controls are similar to size restrictions in that they are designed to protect the breeding capacity of the stock. Prohibitions on landing a particular species is another kind of output control used to manage bycatch. These are usually implemented to reduce the catch of non-target species, especially those that are ecologically sensitive. Regulations of this type may result in regulatory discards, in which restricted species are returned to the water, sometimes dead or injured, leading to fishing mortality not accounted for in catch reporting.

Table K2. Summary of types of output controls and associated considerations. Note that multiple controls may be applied simultaneously.
Type Description Benefits Considerations and limitations
Total Allowable Catch Restricts the total catch that can be taken by all sectors in aggregate during a particular time period (e.g., ACLs) With proper data and enforcement, an effective means of achieving a desired harvest level.

Appropriate for higher-value fisheries with centralized landing sites.
May create an incentive for discarding/high-grading as fishers attempt to maximize catch.

May create a “race-to–fish” scenario. Allocating to individuals can help, but has costs.

Requires higher levels of monitoring and enforcement than other controls.

Difficult in multi-species fisheries due to variable resilience/stock status.
Trip limits Limits on the amount of catch that can be landed on a single trip or within a specified time period With proper accounting and enforcement, an effective means of achieving a desired harvest level.

When combined with a TAC, can be an effective means of increasing the season length by protracting the time required to reach catch limit. This can reduce market gluts and improve price.
Requires higher levels of monitoring and enforcement than other controls.

May create an incentive for discarding/high-grading as fishers attempt to maximize catch.

Can make fishery less economically efficient.
Bag limit A limit on the daily amount a fisher can take. Used to restrict catch in recreational fisheries. May lead to high-grading and discard mortality as fishers attempt to maximize their catch.
Size restrictions Minimum size limit Increases the number of times a fish will reproduce before they are caught.

Easily understood by participants.

Easy to enforce.
Requires maturity at age/size information to be applied effectively.

May result in unaccounted for injury/mortality as undersized individuals are handled and released.

May result in unaccounted for injury/mortality as undersized individuals are handled and released.

Not appropriate for fisheries where barotrauma or other conditions result in high discard mortality.
Maximum size limit May provide some protection for the natural age structure of the stock.

Protects larger spawning females (mega-spawners).
Not an effective means of protecting breeding capacity on its own.

Not appropriate for fisheries where barotrauma or other conditions result in high discard mortality.
Slot limit (upper and lower size limit) Provides size refuge for both juvenile and large mega-spawners. Not appropriate for slow-growing species.

May lead to unaccounted for injury/mortality as fishers discard restricted fish.

Not appropriate for fisheries where barotrauma or other conditions result in high discard mortality.
Sex selective fishery A restriction on the harvest of one sex (usually on females) Prohibition on the take of external egg-bearing females (crustaceans) is another sex-selective provision that could be considered. May lead to unaccounted for injury/mortality as fishers discard restricted fish.

Not appropriate for fisheries where barotrauma or other conditions result in high discard mortality.
Species restrictions A restriction on what species can be landed Used to reduce bycatch of threatened or vulnerable species. May lead to unaccounted for injury/mortality as fishers discard restricted fish.

Photo at top of page: CDFW wardens checking a fisherman's catch of spiny lobster. (CDFW photo)