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7.4 Proportion of fish stocks within safe biological limits

Modified on 2012/11/05 11:39 by MDG Wiki Handbook Categorized as Goal 7


Goal 7. Ensure environmental sustainability Target 7.A: Integrate the principles of sustainable development into country policies and programmes and reverse the loss of environmental resources Target 7.B: Reduce biodiversity loss, achieving, by 2010, a significant reduction in the rate of loss


The proportion of fish stocks within safe biological limits is defined as the proportion of fish stocks or species that are exploited within the level of maximum sustainable biological productivity.

This indicator is expressed as a percentage.

The Food and Agriculture Organization of the United Nations (FAO) has divided the world oceans into 21 statistical areas, and stock assessment is carried out based on these statistical areas. In total, 584 fish stocks and species have been monitored since 1974, with stock assessment information on 441 stock or species. The stock assessment classifies fish stocks into 3 categories: non-fully exploited, fully exploited, and overexploited. The stocks within safe biological limits are those classified as non-fully exploited and fully exploited.

The maximum sustainable biological productivity is the largest yield (or catch) that can be taken from a fish stock over an indefinite period, commonly called the Maximum Sustainable Yield (MSY). The aim of this threshold yield is to achieve the maximum productivity of fish resources while maintaining biodiversity and proper functioning of the relevant ecosystems for present and future generations.

When fishing drives down the biomass of a fish stock below the level at which an MSY can be produced, the stock is said to be overexploited. In contrast, the stock is non-fully exploited if its biomass is above the level corresponding to MSY. When population size is maintained at or close to the level that produces MSY, the species is said to be fully exploited, allowing the population to continue to be productive indefinitely. Sustainable fishery management aims to control fishing pressure so that the stock is maintained at the most productive level.

The biomass of a fish stock is the quantity, usually by weight, of a stock at a given time. Whether a fish stock or species is overexploited is judged based on the estimate of current stock biomass relative to its virgin stock level. This information can only be obtained through stock assessment, although some alternative methods may be used when no adequate data are available.

Method of computation
This indicator is calculated as the number of fish species with a stock assessment of non-fully exploited or fully exploited divided by the total number of fish species with a stock assessment and multiplied by 100.


This indicator provides a means of monitoring progress and changes in the exploitation and management of global fishery resources as a direct measure of sustainability. It is an important reference for policy formulation and decision making related to sustainable management of fishery resources at the regional and global levels by international institutions.

The United Nations Conference on the Law of the Sea, the United Nations Fish Stocks Agreement, the Plan of Implementation of the 2002 World Summit on Sustainable Development, the strategic goal of the Conference of the Parties to the Convention on Biological Diversity (CBD) in 2010, among others, all refer to the MSY-based reference points and targets. Many countries, including Australia, New Zealand and the United States, and the European Union set their management targets based on MSY.

The indicator is currently estimated at regional and global levels, which are less useful for fisheries management at national level because the incorporation of fish stocks having different stock status at the FAO statistical areas may lose information at stock level. National policy and management strategy require information and indicators specific to the fish stocks and fishing areas relevant to each country.


All United Nations member countries are asked to report their annual landings by fish species or species group to FAO. The Handbook of Fishery Statistical Standards provides comprehensive definitions of concepts and details of standard classifications applied by the international agencies. The Handbook does not attempt to include details of national systems, many of which were developed for specific national purposes and thus differ from systems used internationally. Nevertheless, authorities considering introducing or revising national statistical systems are encouraged to ensure that the system developed incorporates a high degree of compatibility with the international standards described in the Handbook.

To ensure data quality, each collection is documented to highlight definitions and to specify the structure, sources, coverage, processes, intended use, etc.

Formal stock assessment requires time series of both catch and effort data, together with other biological parameters. Catch means biomass of a fish species that was caught or landed. Fishing effort is a measure of fishing intensity, usually measured as the number of fishing vessels multiplied by time spent fishing. Although FAO collects statistics on the numbers of fishermen and fishing vessels in different categories, no fishing effort data have been collected.

The FAO database covers only official statistics provided by member countries. Regional scientific committees and management bodies are other important sources of fisheries data. However, their significance in data collection varies from commission to commission. For example, a number of tuna commissions have their own data collection system.


At the international level, the indicator can be calculated separately for each FAO statistical area as well as being presented globally. In addition, for specific fish species or groups it is useful to show the degree of exploitation, as an aid to determining policy on which species need particular attention.


Data quality varies from country to country. In some countries, there is no specific system or network for collecting statistical data on fish catches and other fishery data. Fishery landings data are often reported by national governments in aggregated form rather than by fish species. Many fish stocks do not have adequate data to support formal stock assessment. In such cases FAO evaluates their stock status using simple ad hoc methods that are less data-demanding, but this introduces greater uncertainty. Fishing has a major influence on the abundance of fish populations. However, it is widely recognised that other factors, such as environmental changes, coastal development, climatic change, predator-prey interaction and habitat modification also play an important role.


Women play an important role in fisheries activities, particularly in developing countries. They are the dominant actors in fish production, processing and marketing, and many are involved in small-scale aquaculture operations. Many of the poorest families in rural communities are headed by women. Safeguarding their continued access to fish will not only ensure the food security but also the economic welfare of their families and households. Although gender issues in fisheries were often side-lined, gender mainstreaming in this area has recently been improving


The Food and Agriculture Organization of the United Nations (FAO) is the agency in charge of publishing and monitoring global data for this indicator. International and regional data are included in the bi-annual FAO publication “State of World Fisheries and Aquaculture (SOFIA)”. The FAO’s fisheries statistical database includes data from 1950 and is updated every year (www.fao.org/fishery/statistics/en).

No international comparability issues have been identified, as FAO is the sole agency that has such comprehensive fishery statistics data. Quality control is applied while compiling the data and training is offered to member countries to increase professional skills. However, the reliability of the data reported by member countries cannot be checked.




FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS (2003). Coordinating Working Party on Fishery Statistics: Handbook of Fishery Statistical Standards. Rome. Available from www.fao.org/fishery/cwp/search/en

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS (2005). Review of the State of World Marine Fishery Resources (FAO Fisheries Technical Paper No. 457). Rome. Available from www.fao.org/fi/oldsite/eims_search/1_dett.asp?calling=simple_s_result&lang=en&pub_id=172962.

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS (2011). The State of World Fisheries and Aquaculture 2010. Rome. Available from http://www.fao.org/docrep/013/i1820e/i1820e00.htm.

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS (biannual). Review of the state of world marine fishery resources (FAO Fisheries and aquaculture Technical Paper 569). Rome. Available from http://www.fao.org/fishery/publications/technical-papers/en

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