The Prime Minister on Monday let slip the details just hours after furious Scottish shellfish exporters drove a dozen lorries to the steps of Downing Street in protest.
Trucks with slogans such as “Brexit carnage” and “incompetent government destroying shellfish industry" were parked near Number 10, but the protest ended with those involved being fined.
Asked what compensation the industry could expect, Mr Johnson finally appeared to put a figure on it.
He said: “Well, I’m also saying that is where businesses through no fault of their own have experienced bureaucratic delays or difficulties getting their goods through where there is a genuine, willing buyer on the other side of the channel, and they’ve had a problem, then there’s a £23 million pound compensation fund that we set up and we’ll make sure that they get help.”
Exports of fresh fish and seafood have been severely disrupted by delays since the UK’s transition period ended on December 31.
Some Scottish fishermen have been landing their catch in Denmark to avoid the “bureaucratic system” that exports to Europe now involve, according to Scotland’s rural economy secretary Fergus Ewing.
On land, lorries transporting freshly-caught produce have been held up at distribution hubs and many have struggled to enter into France – a situation that First Minister Nicola Sturgeon described as “shameful and disgraceful”.
Under a deal reached last month, British trade with the EU is tariff free, but fish exporters say their businesses are now suffering due to a series of new document demands.
Mark Moore, manager of the Dartmouth Crab Company, explained his business and others were protesting to "raise awareness" of the impact of new border checks.
He said: "It's not about the increased documentation per se.
"We have taken that on board, and we ourselves – and I know many others – have had no issues with producing the actual paperwork.
"It's the volume required and the timeframe in which to produce it, which doesn't lend itself to live shellfish and fish generally."
It was earlier claimed that protestors intended to dump unsellable seafood cargo in the streets around Westminster.
Lib Dem MP Alistair Carmichael said the anger should come as "no surprise".
He said: “Boris Johnson was told by Scottish fishermen last week that he knew that his claims about controlling all the fish in UK waters were not true.
"Despite that, he is repeating them today.
"This will only fuel the growing anger of fishing communities where everyone now knows that the Prime Minister dropped the ball and broke just about every one of the promises he had made.
“I had hoped that after Brexit the Prime Minister would stop trying to blame other people for his failures. Unfortunately that doesn’t seem to be the case.
“Boris Johnson used fishermen, betrayed their trust and now seeks to blame them for his failings.”
On Sunday, foreign secretary Dominic Raab insisted the issues were just "teething problems".