By Stephen Beech & Rom Preston-Ellis A giant prehistoric salmon had tusk-like teeth it used to fight off predators, reveals new research. The species that grew up to nine feet long lived in the North American Pacific North West millions of years, say scientists. It sported a pair of front teeth that projected out from the sides of its mouth – similar to a warthog’s tusks. Palaeontologists believe the teeth may have been used for defence, competitive fighting, or even as digging tools. But they weren’t used for hunting as the species was vegan – feeding on plankton, say scientists. Study lead a…