Introducing MAKTAG, internal tagging of Atlantic Mackerel (Scomber scombrus) in the North Sea.

Introducing MAKTAG, internal tagging of Atlantic Mackerel (Scomber scombrus) in the North Sea.

Atlantic Mackerel is one of the largest fish stocks in the North Atlantic and is regarded as a commercially important and valuable species for the UK, and other Coastal States (Norway, EU, Faroes, Iceland and Russia). Mackerel are distinctive, with striped dorsal markings, reflecting patterns of sunlight through water, their appearance is memorable and familiar to many of us. Mackerel’s natural range extends from the Bay of Biscay to northern feeding grounds, beyond Iceland/Norway. While some surveys explore different mackerel life stages from eggs to adults, understanding movement requires tagging wild fish and releasing them back into the marine environment. In 2023, we started tagging Mackerel in the North Sea to better understand mackerel movement across the North Atlantic alongside international programmes.  

How do we tag Atlantic Mackerel?  

We tag a fish in good condition with an inert Radio Frequency ID (RFID) tag, then release the tagged fish back into the ocean. This tagging process was approved by the Animal Welfare and Ethical Review Body (AWERB) at Cefas and carried out by trained scientists. Watch a video of the tagging process below.

A person in PPE placing a tag in a fish

Once the tagged mackerel are caught by the large pelagic fishery, the battery-free tag is initiated by a detector installed in the factory which records the unique tag number for the fish. This helps us to understand the movement of mackerel between point A (release) and point B (recapture). If you imagine a keycard which is used to access your office or open your keyless car door, a similar mechanism records a unique number for that fish from the tag.  

Since 2011, the Institute of Marine Research (IMR) in Norway have released over 600,000 tags across the west of the UK and Ireland to help understand the movement of mackerel and estimate natural mortality, which is used to support sustainable exploitation through international stock assessment. In September 2023, Cefas added the North Sea to this international jigsaw puzzle. By collaborating with Norway, we mirrored their technique, so our tag returns could be recorded by more than 20 detectors across six countries.  During seven days at sea, using a Scottish commercial pelagic trawler as a platform, we released 3,207 tagged mackerel in 2023 and we have received 99 recaptures (as of 27th March 2024) across the international factory detectors.   

MAKTAG 2023 was a “proof of concept” year, and we are now exploring options for future tag deployments aiming to increase the positive impact of this work through the number of tags we can deploy and data we can collect from recaptures. By developing this work, we will be able to better understand the population dynamics of highly migratory mackerel.   

To find out more, explore the data using the Smart Fish Map which shows release squares (blue) and detection factories(green). Thank you to all our collaborators and crew for making MAKTAG 2023 a success.