Complex sentence: The use of otterhounds to hunt otters ceased in the UK in 1978 when it became illegal to kill otters, at which point otter hunts switched to hunting mink or coypu.
Split into simpler sentences: The use of otterhounds to hunt otters ceased in the UK in 1978 when it became illegal to kill otters. At that point otter hunts switched to hunting mink or coypu.