It doesn't require most of the fishing industry to go bust. If the price of fish is too low, the way to bring it up is less supply.

As for the farming industry, I thought they were back in the cash with the price of food going through the roof.

I don't see the haulage industry dying either. It's not as if people are gonna stop needing trucks. Again, if road freight prices are too low, uncompetitive operations may go bust, but the price will then go up as trucks become a bit more scarce. There is limited scope for international divers filling up on the continent and competing for work here, especially in Scotland.