The IUCN (International Union for the Conservation of Nature) is an international organisation that works to conserve nature and the natural environment. The IUCN is based in Switzerland and has around 1,000 full-time staff, around 1,200 member organisations, made up of both governmental and non-governmental bodies. Additionally, thousands of experts and scientists work for the organisation on a voluntary basis. These experts provide the scientific advice and information for the IUCN to make their conclusions about the conservation status of species around the world. The IUCN also takes action by creating hundreds of conservation projects across the world and also aims to have an influence on worldwide environmental policies, conventions and laws. The IUCN website states that the organisation is “the global authority on the status of the natural world and the measures needed to safeguard it.” Since 2019 the Director General of the IUCN has been the Swiss biologist Bruno Oberle.

The IUCN has a worldwide reach and is used by many organisations, groups and governments to organise which species are most at risk of becoming endangered or extinct. The redlist of threatened species across the world which is produced by the IUCN is also a reference point for many conservation organisations. There is also a redlist that monitors the status of ecosystems around the world.

Fish and marine species are extensively covered by the IUCN and this website (as well as many others) uses the ICUN guidelines to identify which fish species are in danger of becoming endangered through overfishing or habitat destruction.

The System Used

The ICUN carries out extremely detailed assessments of the global range of a species – full details of this process can be found here – and then assigns a category to the species to denote its conservation status. These categories range from Least Concern (which means that the species is not under threat and may be abundant) to Extinct. A wide range of factors is used to decide where to place a specific species on the scale – speed of decline, population distribution, the state and size of habitat and the sustainability of harvesting methods are all taken into account. Species are classified on a global basis but regional assessments are also carried out.

There are seven categories on the scale, plus an additional two categories:

Extinct (EX) – used when there is no reasonable doubt that the last individual of a species has died.
Extinct in the Wild (EW) – used when the only remaining members of a species exist in captivity.
Critically Endangered (CR) – species at extremely high risk of becoming extinct in the wild.
Endangered (EN) – species at extremely high risk of becoming extinct in the wild.
Vulnerable (VU) – Species at a high risk of becoming endangered.
Near Threatened (NT)  – Likely to become endangered in the near future.
Least Concern (LC) – Species at the lowest risk. Species included in this category may be abundant and widespread.

Data Deficient (DD) – Not enough information to come to a conclusion about where to place the species on this scale.
Not Evaluated (NE) – The IUCN has not yet been able to evaluate this species.

British Sea Fish and Criticisms

This website lists the IUCN status of the fish UK anglers target to provide an indication of the conservation status of each species. However, some caution is needed as a number of the IUCN assessments have been carried out many years ago and are therefore out of date (this is something the IUCN is clear and upfront about). For example, cod are classed as species of Least Concern in Europe based on an assessment carried out in 2013. Since then an Ices (International Council for the Exploration of the Seas) report in 2019 found that European cod were at “critical levels” and the species lost its Marine Stewardship Council sustainable status in 2019. This will not be reflected in the IUCN rating of Least Concern (globally cod are rated Vulnerable but this is based on an assessment carried out in the mid-1990s). Bass are another example of this. The IUCN’s last assessment of bass stocks in Europe was carried out in 2015 and categorised the species as one of Least Concern, albeit with a declining population trend. Since 2016 overfishing has seen bass numbers plummet and there have been limits and restrictions being placed on recreational and commercial fishing in order to try and allow bass stocks to recover. Again, this is something the IUCN rating currently fails to register (but bass are classed as Near Threatened in the Mediterranean, based on a 2007 assessment).

As assessments are so detailed and take up so much time and resources they often become out of date and do not reflect recent changes in the numbers of a species. Despite these criticisms, the IUCN system does provide an extremely useful overview of the conservation status of different species and offers a detailed analysis of the threats facing vulnerable and endangered species. For these reasons, the IUCN remains the global standard of assessing the conservation status of species around the world.