If the threat of compulsory redundancies is not withdrawn, more strikes are possible.
The law requires the NUJ to give two weeks’ notice of any walkout.
Culture Secretary Angus Robertson spoke out against STV’s plans at Holyood on Wednesday.
The former journalist said the Scottish government would continue to urge against any decisions that would result in further reductions in news reporting or redundancies.
Roberston’s comments were prompted by a question from Labour MSP Richard Leonard who called on STV’s board to withdraw the proposals altogether.
BBC Scotland News spoke to STV executive Bobby Hain, whose responsibilities include the news service and regulation.
Hain said the company was “incredibly proud” of its news service but changes were needed to safeguard its future.
He added: “We thought very carefully about the changes we wanted to make and what’s really important is securing the future of regional journalism around the country.
“It’s really important that we change and adapt to changing media habits.
“I recognise it is challenging but we can’t do nothing.”
Historically, STV and other channel 3 broadcasters had local commercial monopolies.
In return, the regulator of the day expected them to provide regional news and a range of other local programmes which may not have been profitable.
But growing competition – from broadcasters, streamers and websites – together with a fall in advertising revenue now make it harder to subsidise loss-making public service output.