I could be mistaken though.
It would appear DFO may have control over 370.4 Km from the shoreline.
More research should be done.
Exclusive economic zone
An exclusive economic zone extends from the outer limit of the territorial sea to a maximum of 200 nautical miles (370.4 km) from the territorial sea baseline, thus it includes the contiguous zone. A coastal nation has control of all economic resources within its exclusive economic zone, including fishing, mining, oil exploration, and any pollution of those resources. However, it cannot prohibit passage or loitering above, on, or under the surface of the sea that is in compliance with the laws and regulations adopted by the coastal State in accordance with the provisions of the UN Convention, within that portion of its exclusive economic zone beyond its territorial sea. Before 1982, coastal nations arbitrarily extended their territorial waters in an effort to control activities which are now regulated by the exclusive economic zone, such as offshore oil exploration or fishing rights (see Cod Wars). Indeed, the exclusive economic zone is still popularly, though erroneously, called a coastal nation's territorial waters.
Still the amount of boats brave enough to venture that far really don't even interest DFO I'm sure. Now if every boat was able to get tuna they'd probably try and find a way to capitalize.
I doubt they would also waste time, money, and resources sending out their inflatables, 60 miles offshore to catch a few boats with one or two more tuna on board than allowed, considering the Tuna isn't really a native species to BC itself. I guess it depends on the markets globally whether Harper would direct the goons to do anything, and I'm guessing the Asian markets want Tuna much larger than these.