International Bottom Trawl Survey Working Group (I​​BTSWG; outputs from 2024 meeting)

The International Bottom Trawl Survey Working Group (IBTSWG) coordinates long-term, fishery-independent bottom trawl surveys in the Northeast Atlantic and North Sea, providing data for stock assessments and analyses of the distributions and relative abundance of fish. IBTSWG also promotes the standardization of fishing gears and methods. The surveys are important platforms for additional data collection (e.g. fish larvae, stomach contents, fish tagging, and fish parasites). This report summarizes national contributions in 2023–2024 and plans for the 2024–2025 surveys.

In the North Sea, the surveys are performed in Q1 and Q3. The 2024-Q1 North Sea IBTS was impacted by storms and an enforced vessel change. Other factors (e.g. offshore infrastructure and static fishing gear) increasingly impact on access to some fishing areas and increases steaming times. Some surveys had to fish at stations relatively close to each other in order to ensure sampling in all rectangles.

The 2022-Q3 North Sea IBTS was broadly completed. The number of valid hauls and average tow duration were comparable to previous years. The abundances of 0-group cod and haddock were lower than the previous year.

The Northeast Atlantic surveys are conducted in Q1, Q3-4, with 14 national surveys operating over the continental from northern Scotland to the Gulf of Cádiz. Most surveys were completed successfully. The Portuguese survey was impacted by mechanical issues, and the Northern Irish survey was unable to operate in Irish waters. Further otter-trawl coverage of the western English Channel was completed by France, with these survey data now in DATRAS.

Further adjustments to the proposed new survey trawl were agreed, with intersessional work undertaken over 2024. The gears plans in the current report are likely to be subject to further, minor modifications, and should be finalised in the coming year.

The increase in the numbers of offshore infrastructure projects (e.g. windfarms) and number and extent of protected areas is impacting on the sites that can be sampled effectively by trawl surveys operating in many areas.

IBTSWG also met online with various data users, including relevant stock assessment groups, to present summaries of relevant surveys.

Correction (12 March 2025): Updated the list of authors.