Tagging bluefin tuna in Norway

Tagging bluefin tuna in 1959

How do you tag a big fish weighing over 200 kg? This was the challenge given to the Norwegian scientist Johannes Hamre. In the 1950’s fishing for bluefin tuna became an important fishery for many Norwegian fishermen. Tagging tuna should give the scientists more information about the bluefin tuna, its growth and its migration pattern.

The tuna is depended on a constant flow of water over its gills in order to get enough oxygen. While caught in a seine, the tuna will die as the seine is hauled in – preventing it to swim. Tagging tuna was therefore a difficult task; both to place the tag and then releasing the tuna before it died.

Tagging bluefin tuna

A Norwegian bluefin tuna seiner with a catch in 1959. Johannes Hamre has left his small rowboat. He is here aiming for a fish with his tagging-stick. The tuna is panicking and it was not easy to place the tag and then releasing the same fish.

Tagged bluefin tuna

A bluefin tuna is tagged and released. The lack of oxygen while caught in the seine has made the fish dizzy. 42 bluefin tuna were tagged in 1959. Some of the tunas tagged in 1957, 1958 and 1959 were later caught in foreign waters; outside Spain, Portugal, Denmark and Morocco. Most of the tagged fish were though caught by Norwegian fishermen outside Norway.

The scientific work done by Harme also included biological samples and collecting data from the fishery. His work on the bluefin tuna represents the best data we have of the bluefin tuna stock in the 1950’s. Even today his work is studied to learn more about this big fish – now suffering from decades with overfishing.

Nowegian seiner fishing bluefin tuna in 1959

All photos: The Norwegian Institute of Marine Research. Related posts:

Bluefin tuna in Norway – Some photos

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  1. Renata says —

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