The Commons Leader was responding to criticism from the SNP after the party’s Commons leader Tommy Sheppard raised the “Brexit fishing disaster” and asked for a debate on compensation for Scotland’s fishing industry.
“What is happening is that the government is tackling this issue, dealing with it as quickly as possible, and the key thing is we've got our fish back,” Mr Rees-Mogg said.
"They're now British fish and they're better and happier fish for it."
The speaker Sir Lindsay Hoyle intervened and said: "Obviously there's no overwhelming evidence for that."
Earlier, Mr Sheppard had said: "Boats confined to harbour, lorry loads of seafood destroyed, the industry losing £1m a day as firms go bust – all as a result of Brexit red tape imposed by this government.
"Yet when asked about this yesterday, the prime minister refused to answer."
Scottish Conservative leader Douglas Ross said one skipper in his Moray constituency had found the value of his catch had fallen to “half of what he needs to cover his costs” as a result of the trade deal.
Other MPs complained of an “avalanche of paperwork” and “cumbersome red tape” faced by fisheries firms.
Mr Rees-Mogg also defended Boris Johnson’s seven-mile bike ride after shadow Commons leader Valerie Vaz raised the issue.
“It seems that the prime minister doesn't take his own advice to stay local, exercise locally,” Mr Vaz said.
"I don't know if it was the letters from the backbenchers that said what a terrible prime minister he was. They must have said, 'on your bike' and he actually took it literally."
Mr Rees-Mogg responded: "As regards the prime minister's exercise, he was clearly exercising reasonably within all the rules, both the spirit of the rules and the letter of the rules.
"I think this sort of game of trying to pick holes in what people are doing when they're obeying the rules is undignified.
"And I think there is clarity in the rules, I think people know what they're supposed to do, and people are allowed to exercise and they are allowed to at the moment meet one person whilst they're exercising, these rules are absolutely clear."