I have no idea what Otter boarding is. I thought it'd involve Otters, but from the little I could harvest from the web, it's more about fishing.
South Africa has similar punishments for illegal fishing. Taking more than your quota, or under size fish/shellfish can lead to all your equipment used in capturing that catch being taken away. That'll include your boat, car, trailer, and the rest. We had to buy annual crayfish licenses, which also educated people on daily limits of numbers and sizes.
Whilst some people might be idiots, I suspect there are a lot of people fishing in English waters simply ignorant of the laws that pertain to it. Maybe a little emphasis on education would help?
For example, whilst I might know my Bream from my Bass, there are many other fish species I wouldn't recognise. I'll be fishing from my SOT this Summer and I expect it to be highly educational. I was thinking of trying to get my speargun in working order again but living on the South Coast of Devon, I'm not sure what I'd be likely to find. I do think spearfishing is kinder in the sense that only the fish we select are bothered, and the end is pretty quick for them.
There really is only one solution to the world's ever decreasing habitat and resources in my opinion. We need far fewer of one particular species; the invasive and prevalent homosapien.