In 1957 the Thames was so polluted it was declared “ biologically dead ” by the Natural History Museum. But a new State of the Thames report shows the river is now home to a range of wildlife, some of which seems surprisingly out of place. Shark species present in the river include tope, spurdogs and starry smooth-hound. Tope grow up to 6ft and are known to be aggressive while spurdogs release a venom from their fins which can cause swelling in humans. The sharks are born in the Thames’s shallow