The 2024 Bluefin Tuna Catch and Release Recreational Fishery (CRRF) marked a historic milestone for sustainable fishing in English waters, particularly in Devon and Cornwall, where Atlantic bluefin tuna have made a remarkable comeback. At Atlantic Bluefin Tuna UK, we’re committed to providing anglers with the most accurate and transparent information about this fishery. This page outlines the methodology behind the Marine Management Organisation’s (MMO) Official Statistics for the 2024 CRRF season, offering insight into how the data was collected, processed, and reported. Whether you’re an angler planning a 2025 trip or a conservationist interested in the fishery’s impact, understanding this methodology will deepen your appreciation for the CRRF’s role in sustainable fishing.

1. Background

In 2024, the UK launched the English Catch and Release Recreational Fishery (CRRF) for Atlantic bluefin tuna (BFT), allowing permitted vessels to catch and release BFT using rod-and-line methods in English waters. The fishery, which ran from August 3 to December 31, 2024, was a significant step forward after a three-year scientific research program by the Centre for Environment, Fisheries and Aquaculture Science (Cefas). The MMO managed the fishery, issuing permits to 93 vessels (81 of which were active), with numbers proportionate to the quota available for incidental BFT mortalities.

Under the Sea Fisheries (International Commission for the Conservation of Atlantic Tunas) (Amendment) (No. 2) Regulations 2024, the CRRF is strictly catch-and-release, and vessel owners and skippers are legally required to report all trips to the MMO within 24 hours of return, whether or not BFT were caught. Permit holders must submit detailed data on their trips and catches, which the MMO uses to monitor and manage the fishery. This data is also submitted to the International Council for the Conservation of Atlantic Tunas (ICCAT) to meet the UK’s international reporting obligations.

The 2024 official statistics, released by the MMO on March 19, 2025, provide a comprehensive overview of the season’s activity in Devon and Cornwall, including:

  • Vessel numbers and activity (e.g., 1,014 trips by 81 active vessels).

  • Fishing outcomes (e.g., 3,359 BFT caught, 83% trip success rate).

  • Gear usage, catch per unit effort, and BFT details (e.g., average length of 167.7 cm, estimated weight of 95.5 kg).

  • Release status (98.7% released in good to excellent condition) and quota uptake.

2. Data Source

The MMO collected data through a mandatory trip report questionnaire, which vessel owners or skippers submitted within 24 hours of returning from a trip. These self-submitted reports were entered via the Qualtrics platform and included:

  • Vessel and owner details.

  • Locations (ICES Statistical Rectangles).

  • Gear used (e.g., daisy chains, spreader bars).

  • Bycatch information.

  • BFT-specific data: total number caught per trip, straight fork length (SFL) in inches, fight time (minutes), recovery time (in 5-minute groups, e.g., 0-5 minutes), and release status.

Permit holders were required to submit reports for all trips, even those without BFT captures, ensuring a complete dataset for analysis.

2.1 Processing
The MMO processed the data using an integrated development environment, merging permit holder submissions with MMO vessel licensing information to categorize vessels as private or charter. This merge used a unique identifier combining vessel name and permit number. Data cleaning addressed user input errors (e.g., incorrect vessel names or permit numbers) by filtering against a list of correct IDs and manually correcting erroneous entries.

To estimate BFT weights, the MMO converted straight fork lengths (SFL) from inches to centimeters, then applied the following formula to calculate round weight (RWT):

  • RWT (kg) = alpha x (SFL(cm)^beta), where alpha = 3.51 x 10^-5 and beta = 2.8758.

This formula, sourced from Rodriguez-Marin et al. (2016), is specific to Eastern Atlantic BFT stocks and aligns with the methodology used in the 2021-2023 English Catch and Release Tagging (CHART) program. Lengths entered as ≤3 inches or in meters were adjusted accordingly during conversion.

3. Disclosure Control

To protect personal data under the Data Protection Act 2018, the MMO implemented strict disclosure controls:

  • All vessel and owner details were removed from the dataset.

  • Location data (ICES Statistical Rectangles) was excluded to prevent identification of vessels in areas with few registered boats, such as specific regions in Devon and Cornwall.

  • Dates of activities were aggregated into weekly periods to avoid revealing specific trip days. The 2024 season (August 3 to December 31) spanned 21 weeks and 4 days, with week 22 consisting of only 4 days.

These measures ensure that the published statistics protect the privacy of permit holders while providing valuable insights into the fishery’s performance.

4. Revisions Policy

The MMO follows a revisions policy to ensure users have access to the most accurate data. Revisions to the 2024 CRRF statistics may occur due to:

  • Additional Data: Late submissions from permit holders, despite strict reporting requirements.

  • Data Corrections: Updates to database entries after verifying outliers (e.g., BFT sizes or activity locations) with permit holders.

  • Processing Errors: Corrections to data processing mistakes identified post-publication.

Revised figures are published annually, and users are encouraged to refer to the latest MMO statistics. Previous editions are available on the MMO website for those interested in examining the impact of revisions. The MMO adheres to the Department for Environment, Food and Rural Affairs’ (Defra) policy on revisions and errors, which can be found on the Defra website.

5. Coherence with Other Sources

The 2024 CRRF statistics are comparable to other catch-and-release fisheries for BFT in the UK and adjacent waters, such as:

  • The English CHART program reports (2021-2023), which laid the groundwork for the CRRF.

  • ICCAT summaries (2021-2023), which provide broader context on BFT populations in the Atlantic.

Unlike the MMO’s commercial fishery statistics, this dataset focuses solely on recreational catch-and-release activities and does not include landings data. This distinction ensures clarity for users comparing recreational and commercial BFT fisheries in the UK.

6. Glossary of Terms

  • Catch per Unit Effort (CPUE): The number of BFT hookups divided by the number of trips, indicating fishing efficiency.

  • Charter Vessel: A vessel in the CRRF that takes paying anglers on trips targeting BFT.

  • Daisy Chain: A rod-and-line fishing gear towing a string of lures on a single line, with the final lure containing a hook.

  • Fight Time: The duration from when a BFT takes the hook (hookup) to when it’s brought alongside the vessel.

  • Hookup: When a BFT takes the hook and is effectively caught by the angler.

  • ICES Statistical Rectangles: A gridded system by the International Council for the Exploration of the Sea, dividing the northeast Atlantic into 1-degree longitude by 0.5-degree latitude rectangles for location reporting.

  • Private Vessel: A vessel in the CRRF used for private trips, not taking paying anglers.

  • Recovery Time: The time allowed for a BFT to recover before release, grouped into categories (e.g., 0-5 minutes, 5-10 minutes).

  • Release Status: The condition of the BFT at the point of release (e.g., good, excellent).

  • Spreader Bars: A rod-and-line fishing gear towing multiple lures perpendicular to the line, with one lure containing a hook.

  • Straight Fork Length (SFL): The straight-line distance from the tip of the BFT’s upper jaw to the fork of its tail.

  • Success Rate: The percentage of trips where at least one BFT hookup occurred.

Learn More About the CRRF

The 2024 CRRF season was a resounding success in Devon and Cornwall, with 3,359 BFT caught and a 98.7% healthy release rate. Dive deeper into the season’s results on our [2024 CRRF Statistics] blog post, or explore the [Atlantic Bluefin Tuna UK Season] page for details on past and upcoming seasons. Ready to experience the thrill of catch-and-release fishing in 2025? Book a trip with one of our trusted skippers in Devon and Cornwall on our [Fishing Guides] page.