TRACKING PREDATORY FISH THROUGHOUT EUROPE

Tracking predatory fish throughout Europe. Which areas use sea bass, sea trout and cod along the Norwegian coast – and possibly on the continent?

Author:  Erlend Astad Lorentzen

Norwegian and international researchers will find out in the MOVE project.

The goal in Norway is to track a number of predatory fish in Raet National Park to find out how they use the coast – and whether human activity is causing trouble for them. 

If the fish make sudden trips to the Norwegian Trough or Portugal, the researchers will also be notified.

New knowledge about new species

“We have tagged a number of fish species with acoustic tags that are tracked by listening buoys in Raet National Park and the sea outside. But we also get data from similar listening buoys throughout Europe if our fish strike them,” says researcher Inge Elise van der Knaap.

This may be particularly relevant for the 12 sea bass the researchers tagged last fall at Tromøya, Arendal.

“Sea bass have established themselves in southern Norway, and there is little research on the species here. They are mostly caught in the summer – but we don’t know whether they go south in the winter or just take it easy in deep water,” says van der Knaap.

Where do cod go on a weekend trip?

The Institute of Marine Research has done a lot of research on fish tagged with acoustic transmitters in fjord areas. But this is the first time the researchers have placed listening buoys out in the Skagerrak and the North Sea, on the slope of the Norwegian Trough.

It should fill knowledge gaps – because predatory fish can swim far.

“Other tagging experiments show that fjord cod are generally very stationary. Except when they suddenly swim out of our coverage area. Then they can be gone for a few days before they return home. We don’t know what they’ve been doing,” says van der Knaap.

Important for protected areas

The information is relevant for management, especially in connection with marine protected areas.

“The goal of a protected area may be to protect cod. Then it is very interesting to know whether it takes weekend trips to other areas with intensive fishing,” she explains.

In one year of tracking, the researchers have already been surprised by the behaviour of several species.

“We see that the lyre patrols long stretches of coastline in a fixed rhythm. It often returns to the same place after a few days. The lyre also goes much deeper than expected – often down to 60 metres,” says van der Knaap.

Next, the researchers will map out what dangers these fish encounter on their journey.

Cod makes 40-kilometre trips

“When it comes to cod, we see that they can make short trips from the coast all the way to the outermost listening buoys, 40 kilometres from land at a depth of 400 metres, where they cross areas with a lot of fishing,” says van der Knaap.

“This is incredibly interesting.”

The researchers plan to further expand the network of listening buoys in the North Sea, particularly to include potential wind power areas.

“We will also tag more fish and look forward to gaining new knowledge about predatory fish migration in the years to come,” says researcher Inge van der Knaap.

Image: Sea bass has become a more or less common sight along the coast. This specimen is from Western Norway and is not part of the study. Photographer: Erlend Astad Lorentzen

Source