The Cromarty Firth has become an established destination for cruises
The cruise ship industry is trying to find ways of cutting rising fuel costs.
Hull coatings, that allow vessels to slip through the waves more easily, and new means of propulsion are being used, or are now under development.
Capt Iain Dunderdale, development manager for Cruise Highlands in Cromarty, has detailed the measures.
He also said the numbers of luxury liner visitors to Invergordon and the surrounding area were rising in the face of a global credit crunch.
Four large ships were visiting the port this week.
Among them, the 100,000 tonne Grand Princess with 2,500 tourists on board and the biggest liner into the Cromarty Firth this year.
It arrived on Sunday before later departing. The vessels were due to arrive on Wednesday, Thursday and Saturday.
Capt Dunderdale said the industry was trying to adapt to operating with higher fuel costs.
He said: "Ships are slowing down slightly. They perhaps leave the previous ports slightly earlier and arrive a little later at the next port.
"They are manoeuvring ships more gently, looking at new methods of propulsion, more efficient engines and better hull coatings so the hull slides through water more easily and more efficiently with less fuel consumption.
"All these things can help save on fuel bills."
During concerns of potential shortages as a result of a strike at the Grangemouth refinery in central Scotland, ferry operator Caledonian MacBrayne suggested measures to cut fuel consumption.
These included vessels travelling at slower speeds.