It comes amid controversial plans to scrap parts of the post-Brexit deal on Northern Ireland.
The EU has threatened to retaliate with “all measures at its disposal” if the UK proceeds with new legislation overwriting sections of the Northern Ireland Protocol, as announced on Tuesday.
Salmon Scotland previously wrote to Prime Minister Boris Johnson to raise concerns about the impact of a "trade war".
Chief executive Tavish Scott said: “Any deterioration in relationships between London and Brussels which leads to friction at the border, delays and queues for hauliers crossing to France or extra costs for our exporters could put us back to where we were at the start of last year when exports were in chaos."
Liberal Democrat MSP Beatrice Wishart said disruption to trade would have knock-on effects for workers and local economies.
Giving evidence to Holyrood's rural affairs, islands and natural environment committee, Mr Eustice said: "All this speculation around trade wars we think is deeply unhelpful and, in fact, I think what we're seeing is a more measured tone from the European Union and indeed from ministers in Ireland as well.
"People recognise that there's a challenge here that we need to resolve, and there's nothing that we are proposing that breaches international law.
"It's consistent with our obligations.
"But we also do need to try to get politics restored in Northern Ireland, and the UK Government has got an obligation to the Belfast Good Friday Agreement.
"We have a responsibility to ensure that it is respected and that's why we have to take this action in order to deal with that very delicate political situation in Northern Ireland.
"So there is absolutely no need or justification for any changes to the way that the European Union approaches these matters.
"And it would be a very extreme step if they were to give notice to abandon the whole trade and co-operation agreement when we are only seeking to correct the approach on things like Scottish seed potatoes having access to the Northern Ireland market, which is a perfectly reasonable thing for us to do."
Asked to confirm there will be no disruption to exports and trade if there are changes to border controls, Mr Eustice said: "There's nothing that we are proposing that would cause any problems at all for Scottish exporters, be they salmon or anything else, since there's nothing that we're proposing that should affect the TCA, the trade and co-operation agreement.
"Now obviously I don't control what the European Union might do on the other side of the border, but I can confirm that we're proposing nothing that would change their approach."
Mr Eustice said talk of a trade war was a "media narrative".
Foreign secretary Liz Truss has said she wants the EU to “come to the negotiating table” so a “pragmatic solution” can be agreed together.
She told Sky News: “But if that doesn’t happen we do need to move ahead delivering this solution for the people of Northern Ireland.”