It is understood the government has since committed more funding.
Early this year the council approved Mr Dalton's expenses for the trip, estimated at about $6170, to be funded through the council's National Aquarium Expansion Project budget.
The costs for the two staff members who travelled with the mayor - council chief executive Wayne Jack and manager of visitor experiences Sally Jackson - were thought to be similar to Mr Dalton's.
When asked about expected expenses, a council spokeswoman said so far the only confirmed costs were flights - in economy - for the three, which totalled $7572.
As staff expenses were covered by the council's sensitive expenditure policy, any reasonable costs incurred would be covered if they were in line with the policy - subject to exchange rate impacts.
The trip was initially postponed from March to coincide with a celebration of 150 years of Canadian Government in Victoria, Napier's sister city. Although 11 days of celebrations begin on June 21, the council party will be returning to Napier.
The council had been invited to attend the celebrations in Victoria - with Victoria offering to fly and host them. As it had not been determined whether a council party would be going, it was not known if the council would be covering other expenses for this trip.
Reacting to the news of the trip, New Zealand Taxpayers Union executive director Jordan Williams said it had "all the hallmarks of a junket".
"Whenever politicians used weasel words like 'build relationships' and 'international partnerships' it starts to raise suspicions. Looks like a junket, quacks like a junket, let's call it for what it is," he said.
"We've asked time and time again for councils to show evidence of the alleged economic benefits of sister city arrangements. The bluff and bluster we get back points to the whole excuse being an excuse for politicians to travel the world on our dime."
Mr Dalton disputed the trip was a junket, stating "this very brief trip was nothing of the sort".
Instead, the trip had been a chance to inform plans for the development of the Marine Parade aquarium, and half the facilities they visited had already expressed interest in forming partnerships, Mr Dalton said.
"We've spent time examining the economic models of each of the aquariums, many of which receive no government support, and figured out how we can best use their experiences, both positive and negative, as we look to fund our own development and get it right," he said.
"At Monterey, they're seeing a massive US$250m ($346m) impact on the local economy annually from aquarium visits - several times over and above what they could ever have hoped for.
"We're looking closely at how that's been achieved and although we're a much smaller population, we see some great parallels to draw on here in Napier."
The expansion project includes new developments at the Marine Parade aquarium and is touted as having the potential to boost jobs, benefit economic development and grow tourism.
The council is producing a business case on the project and it was said a trip to the US would establish partnerships with international facilities considered "world leaders in the areas of marine conservation, science and research and tourism".