Did you think the days of arguments between the UK and the European Union over fishing were gone? Think again. 

"There's a broad problem with exporting fresh fish and shellfish into the EU as the UK is now a third country and so is facing non-tariff barriers at the border," according to Barrie Deas, the CEO of the UK National Federation of Fishermen's Organizations. 

Live shellfish, or more precisely "bivalve mollusks," which include oysters, mussels and scallops, from certain areas of UK waters have been banned from export to the EU.

Previously, the UK fishing industry had exported shellfish that weren't yet ready to be eaten, which were then "purified" in the EU country that bought them. Now the EU says the fishing companies must purify the mollusks before exporting them.

"The issue surrounding bivalve mollusks is very technical and seems to involve a conflict of interpretation over two aspects of all of the rules, the EU's own rules," Deas explained.

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It's a very specific restriction affecting a small number of shellfish, but it has caused ripples at the highest levels of government. UK Environment Minister George Eustice has already written to Stella Kyriakides, the European commissioner for health and food safety, to complain. 

He said the UK had very high food safety standards and the uncleaned produce in question should not cause future problems as it is intended for processing in the EU. 

"This development is … of grave concern to the UK and businesses that rely on this trade.

"We accept that there is a distinction between mollusks that are already fit for human consumption and those that require purification beforehand. The point is that the animals in question are alive, destined for further treatment. The parallel might be with livestock as they leave the farm gate," the minister wrote on Monday. 

He said the UK government was "surprised" the European Commission "changed its position."

DEFRA, the department in the UK government responsible for fishing, did not comment when asked to confirm if the minister had received a reply. 

In a statement, the department said the EU "must recognize the existing high standards and history of trade between the UK and the EU."

The export of live shellfish, including oysters, mussels, clams, cockles and scallops, is worth approximately $27.3 million to the UK economy, according to the Shellfish Association of Great Britain.

But until a solution is found, Deas said it would be the smallest UK producers who would lose out the most. 

"This particular problem ... starts when small buyers have small amounts grouped together to put a consignment into the EU. If one of those buyers gets this paperwork wrong, then the whole consignment is delayed. And, of course, we're talking here about a highly perishable commodity that is losing value by the hour. And so there's a lot at stake."