RETURN OF THE TUNA

TUNA ARE LONG-DISTANCE SWIMMERS. NOW THEY ARE BACK IN THE ØRESUND OFF THE DANISH COAST—AFTER AN ABSENCE OF 50 YEARS

- Bernd Hauser

For more than half a century, the bluefin tuna had disappeared off the coast of Denmark.

Now, these extraordinary fish are back in the Öresund, north of Copenhagen. ARINE BIOLOGIST Jens Peder Jeppesen takes his guests on a tuna safari:

Katrine Larsen manoeuvers the inflatable boat between the leisure yachts out of the harbour of Helsingör while Jeppesen gives a lecture for the 12 guests.

"I'm sure you've all been on safaris in the African savannah," he says. "Then you know that the lions are there, but sometimes they don’t show themselves." It's the same with the tuna safari.

"The conditions today are ideal"—no wind, the sea is smooth, the surface current is leading northwards into the Kattegat." Nevertheless, we have no guarantee of seeing the tuna." But anyone going on a safari wants a thrill. A good guide knows that. continues Jeppesen. “And they are heavy. If one jumps into the boat by mistake, it can kill you. If that happens, dive into the water to save yourselves!”

The fish have a circumference like an old tree: two meters is not unusual. They can grow up to 4.5 meters long. The specimens in the Øresund are thought to be at least 18 to 25 years old and thus weigh between 200 and 500 kilograms. The largest tuna ever caught weighed 725 kilograms—almost as much as a VW Beetle. Its speed is also comparable: the tuna can accelerate its streamlined body to 80 kph.

And it swims and swims, relentlessly, day and night. Fish usually absorb oxygen in the water by means of muscular breathing movements. Tuna lack this pumping mechanism. They must keep moving to ensure that a current of water flows through their gills.

BACK IN THE ØRESUND