Indicator 14.4.1 Proportion of fish stocks within biologically sustainable levels

Not available for this indicator

The indicator comprises two broad measures – the percentage of fish stocks in seas around the UK that are i) harvested sustainably (the first four series), and ii) at full reproductive capacity (the last three series).

Measures are based on a group of 20 species in 57 stocks for which there are reliable estimates that allow the sustainability of the stocks to be evaluated. The indicator stocks include a range of local and widely distributed species of major importance to the UK fishing industry. 14% of the stocks within the dataset are interpreted to be straddling stocks (see Definitions field). Therefore, these data do not fully follow UN specifications for this indicator.

Series on ‘exploitation level’ (first four series) give the percentage of stocks relative to the level capable of producing Maximum Sustainable Yield (MSY). Regarding sustainability, the aim is to increase the proportion of stocks fished at or below the fishing mortality target FMSY, and reduce to zero the number of stocks of unknown status relative to FMSY.

Series on ‘biologically sustainable status’ (last three series) show trends in the spawning stock biomass of stocks of UK interest with respect to safe biological limits. Safe biological limits are where the biomass is above the level capable of producing Maximum Sustainable Yield (MSY Btrigger). Regarding sustainability, the aim is to increase the proportion of stocks with spawning stock biomass (SSB) at or above MSY Btrigger and reduce to zero the number of stocks that have unknown status relative to MSY reference points.

Please see the definitions field for definitions of each series. These may differ to those used by FAO.

United Kingdom

Percentage (%)

Blim - A lower limit threshold for spawning stock biomass below which there is a high risk of reduced reproductive capacity.

MSY - Maximum Sustainable Yield.

FMSY - Rate of fishing mortality to achieve MSY in the long term. The instantaneous mortality rate of a fish stock caught and removed due to fishing that will result (usually after a long period of time) in a population size that enables a fish stock to deliver the maximum sustainable yield.

MSY Btrigger - A threshold for spawner biomass (body-weight of all mature fish) of a fish stock at which that stock can deliver the maximum sustainable yield.

Proportion of fish stocks that are not fully exploited - Proportion of fish stocks that are not overexploited with respect to FMSY. The percentage of stocks fished at or below the level capable of producing Maximum Sustainable Yield (FMSY).

Proportion of fish stocks that are fully exploited - The percentage of stocks fished at a level that falls within the acceptable mortality range. This is likely to be a conservative estimate as it only includes stocks in the upper half of the FMSY range. These are acceptably fished in the internationally agreed management plans but above the reference point used previously for Good Environmental Status.

Proportion of fish stocks that are overexploited - The percentage of stocks fished above the level capable of producing Maximum Sustainable Yield (FMSY).

Proportion of fish stocks within biologically sustainable levels - The percentage of stocks with spawning stock biomass at or above the level capable of producing Maximum Sustainable Yield (MSY Btrigger).

Proportion of fish stocks not within biologically sustainable levels - The percentage of stocks with spawning stock biomass below the level capable of producing Maximum Sustainable Yield (MSY Btrigger).

Straddling stocks - Straddling stocks are found to move across boundaries between EEZ waters or between EEZ and high seas (e.g. tuna stocks), and that are caught by multiple countries.

Not available for this indicator

Proportion of fish stocks that are not within biologically sustainable levels = Percentage less than MSY Btrigger but greater than Blim + Percentage below MSYBtrigger and below Blim (where available)

The indicator follows improved methodology published in 2021 and is not directly comparable with data shown here previously. The method changed to bring it in line with the proposed Multi-Annual Plans. All stock data are derived from ICES Advice. See Lynam et al, Cefas (2021) International (ICES) and national (UK) fish stock and shellfish stock data from 2020 assessment year. Cefas, UK. V1.

Please see UK Biodiversity Indicators 2021 - B2. Sustainable fisheries for analysis, and further information on the fish stocks included in the measure. Technical details can also be found in the UKBI 2021 B2 - Technical Background Document B2 (xlsx).

This indicator is being used as an approximation of the UN SDG Indicator. Where possible, we will work to identify or develop UK data to meet the global indicator specification. This indicator has been identified in collaboration with topic experts.