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Atlantic cod

Atlantic cod (Gadus morhua Linnaeus, 1758) is a species with a high economic value both for commercial and recreational fisheries. For decades, this species has been subjected to high fishing pressure in the entire North Atlantic region. Consequently, population levels have dropped significantly in the 1980s leading to historical low levels. Although fishing pressure is strongly reduced nowadays, recovery of the North Sea populations are slow.

Apart from fishing, North Sea fish species today have to deal with many more human activities. Marine traffic, offshore energy development, construction and exploration of the seabed are every day practice. Besides changing the marine environment, these activities also heavily impact the marine soundscape. They all produce high intensity low frequency sounds, which travels far under water. These sounds are within the hearing range of most marine fish, such as cod, that hear best between frequencies of 20-500 Hertz. Man-made noise can cause masking of other sounds that are important for feeding, mating and orientation and can, in extreme cases, even cause swim bladder rupture. Therefore, the rise in anthropogenic activities producing underwater noise has led to a growing concern about their effects on the marine fish.

Since 2009 acoustic telemetry is used to investigate both the general movement and distribution of cod and the effects of man-made noise on them. This technique offers the possibility to track animal within an area remotely. To this date, over 250 Atlantic cods have been tagged. Apart from information on the presence of cod in an area, the acoustic tag can also transmit information on depth and acceleration (overall movement activity) that the animal is experiencing, which results in a better understanding of the individual behaviour. Information on movement ecology and habitat preferences are crucial to inform and advice on efficient, long-term management plans for the recovery of Atlantic cod.  

Visualization of what telemetry data looks like, can be seen here.



Left: Internal tagging of cod (©Yoeri van Es) - Middle: Cod recovery and external flow-tag mark (©Yoeri van Es) - Right: Atlantic cod (©Jeroen Hubert)