On 4 March 2020, the Department for International Trade of the United Kingdom published initiation notice No. 0002 concerning the transition anti-subsidy investigation on imports of certain rainbow trout from Turkey. Notably, the investigation concerns the existing EU trade defence duty introduced by Commission Implementing Regulation (EU) 2015/309 of 26 February 2015, see related state act. The products subject to investigation are classified under HS code subheading 0301.91.90.11, 0302.11.80.11, 0303.14.90.11, 0304.42.90.10, 0304.82.90.10, and 0305.43.00.11. This investigation was initiated by the Department for International Trade without an application from the domestic industry.

The United Kingdom is at present only conducting reviews of existing EU trade defence interventions as part of the Trade Remedies (Dumping and Subsidisation) (EU Exit) Regulations 2019 (as amended). The conclusion of any transition anti-subsidy investigation will first be implemented following the United Kingdom's withdrawal of the European Union following the transition period. During the transition period, all EU trade defence interventions are imposed by the UK. 

On 30 November 2021, the Department for International Trade of the United Kingdom decided to maintain the definitive duty imposed on imports of certain rainbow trout from Turkey. The rate of the duty ranges from 1.5% to 9.5% depending on the company. The duty is set to expire on 31 January 2026.