As you may or may not be aware, one of the sticking points on Brexit is that the French and the Spanish are demanding the right to continue to fish (strip mine) British waters.
What I know is that if there is no deal, and Europeans are not allowed to fish those waters, then the pressure on the fishery will be reduced, at least until the British fishing fleet is expanded.
If you have been following this, this is pretty obvious.
The thing that I know, and you probably don’t, is that if the continental fishing fleets are excluded, then the percentage of selachians, sharks skates, and rays, of the catch, will go up.
The short version is that with reduce human predation, other predators will take up the slack.
The longer version, and the one that I learned in differential equation class in college is that Lotka–Volterra equations were developed to describe the changes in catches in Italian fisheries during the First World War.
With many fishermen at the front, the total catch declined, and the percentage of sharks and related fish increased.
The instructor described this as the first application of differential equations to what could generally be called ecology, though I had to explain to him what selachians were .
So, a no-deal Brexit is a happy time for sharks in UK waters.
Now you know.