Similar concerns with this to the EU water directive. Will it be watered down to suit commercial interests, will good legislation fall by the wayside etc. I will still say its not a given and equally, good laws and legislation could come through and some bad ones ditched. Given the chance to tailor laws and legislation to specific UK needs , species/marine environment, sea anglers and commercial interests (it is just as important); might just be a good thing and its not going to be done in isolation to the EU.
Only time will tell but ever an optimist.