Māui dolphins are critically endangered, with only an estimated 63 left in New Zealand waters.
The move was welcomed as the first step by the Green Party, but its fisheries spokesman Gareth Hughes added that "the rollout in its current form is too generous with taxpayers' money, too narrow and too slow".
Nash said the roll-out would be monitored as "a wider camera programme is considered across more of the commercial fleet".
"Commercial trawlers and set netters working in Māui dolphin habitat will be required to carry cameras because their fishing methods pose most risk to dolphins," Nash said.
"It will affect up to 28 vessels, although the final number requiring cameras will depend on whether they continue to fish in the area using trawl or set nets.
"Other vessels that work the area use methods like long-lines, purse seine nets and potting that pose a lower risk and they will not be required to carry cameras at this stage."
An independent Fisheries NZ observer will continue to be on board vessels to monitor activities.
Nash said the camera roll-out was one step in a wider programme that included having all commercial fishing vessels reporting their catches and positions electronically in close to real time by December this year.
The Government released a discussion document in February that looked at tightening the rules that allow commercial fishers to throw small fish back to the sea.
"Legislation is also likely to be introduced later this year after public consultation on the rules that govern commercial fishing," Nash said.
"We sought feedback on practices around what fish can be brought back to port and what fish can be returned to sea, as well as penalties and offences.
"Greater protection for Hector's and Māui dolphins will be achieved through a review of the Threat Management Plan to be released for public consultation shortly."