This video is called Behind the Mediterranean Bluefin Tuna Trade.
From Wildlife Extra:
Tuna spotted off the Hebrides
Tuna sighted west of Lewis
The Lochlann went to investigate, fully expecting to find the usual dolphins feeding on a shoal of herring. We told the passengers to get their cameras ready for the spectacle of diving birds and jumping dolphins and possibly Minke whales. It is common to see diving gannets in a feeding frenzy as they can spot the fish from a great height. The gannets are helped by dolphins, which herd the fish to the surface.
Murray Macleod of Seatrek takes up the story.
“The leading edge of the diving gannets was unusually fast moving at 5 knots, and as we closed in we could see the fast moving splashes among them. We were amazed to see the characteristic upright, thin forked tails of tuna darting through the water. Some were coming to within 10m of us and you could see they were about 6/7 ft long, maybe more. The sight was amazing. The furiously diving gannets were accompanied by fulmars, skuas, Manx shearwaters, sooty shearwaters, black backed gulls and herring gulls, all looking for a piece of the action.
We watched them enthralled for some time and thought they were possibly Bluefin tuna; such an unusual wildlife sighting we had never experienced before so close at hand.”
A second shoal was moving much faster, at about 10 knots and zigzagging with birds showing their whereabouts when near the surface. The tuna were about the same size.
Earlier in the day those on board the Lochlann had also seen a handful of smaller Bonito, 2ft long, just East of Gallan Head, Uig, Lewis. These were fast moving along the surface just beside the boat but were unaccompanied by birds.
Murray added “The rare sighting of tuna so far north of their normal habitat was a memorable experience. Unusual also was the distinctive spectacle of the exceptionally large number of gannets that were following the shoal of fish. We have never seen such a large flock in such a small area; they could be seen from many miles away.”
An Australian fisherman caught a 600-pound monster tuna near Greymouth, New Zealand, but scientists fear fish caught there may be contaminated with radiation from the March 2011 Fukushima nuclear meltdown: here.
Overfishing pushes tuna stocks to the brink: experts: here.