Sky News has video of a salmon cannon in use. The device was originally designed for fruit, but engineers are using it to fire fish over dams and other obstacles at up to 40 fish a minute. The cannon is currently being tested at Roza Dam in Washington. Sky News has more on the cannon in their article.
The tube’s soft fabric forms a seal around the salmon, creating a vacuum which propels it through the pipe at speeds of up to 22mph.