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UK Biodiversity Indicators 2023. Indicator D1a: Fish size classes 2023


Updated 14 November 2023.

These documents support indicator D1a – Fish size classes. The documents include a datasheet. Technical documentation for the indicator is available at:

The indicator shows changes in the proportion, by weight, of large individuals equal to or over 50 cm in length in demersal (bottom-dwelling) fish populations in the North Sea. Changes in the size structure of fish populations and communities reflect changes in the state of the fish community. Fluctuations in values between years are expected given inter-annual fluctuations in the distribution and abundance of North Sea fish populations and sampling variation.

These resources may not be fully accessible for all users. If you need a copy of any of these resources in a different or more accessible format, please get in touch.

More information on UK Biodiversity Indicator D1a is available on the UKBI D1a webpage.

Resource type Publication

Topic category Environment

Reference date 2023·11·14

Department for Environment, Food and Rural Affairs, UK. 2023. UK Biodiversity Indicators 2023.

The UK Biodiversity Indicators were created to provide a measure for reporting on the UK’s progress towards meeting international biodiversity goals and targets and were first published in 2007.

Responsible organisation
Communications, JNCC distributor

Limitations on public access No limitations

Use constraints Copyright of data and/or information presented in these resources may not reside solely with the distributor (JNCC). For more information, please contact

Metadata date 2023·11·14

Metadata point of contact
Communications, JNCC

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