The dolphin sale sparked a wave of protests by groups claiming the mammals would not survive the long flight. The fears were backed up when photographs were published of four dolphin carcasses found near the animals' holding pen in the capital Honiara.
"Now they have a 30-hour flight and I'm concerned some of them just won't make it - they'll die on the way," said the Pacific Director of the San Francisco-based group, Earth Island Institute, Lawrence Makili, adding that he had seen the "dead dolphins."
The Australian daily Herald Sun said the dolphins, which were sold for more than $1 million, would be housed at the new Palm Atlantis resort hotel.
Australia's Environment Minister Malcolm Turnbull has already voiced opposition to the shipment.
Meanwhile, the Earth Islands Institute threatened to boycott Solomon Islands tuna if the dolphins were exported.
Locals said one of the men involved in the deal had previously been accused of killing dolphins for their meat.
Four years ago a shipment of 28 dolphins from the Solomans to Mexico forced the government to put a ban on live dolphin exports, but a year later it was overturned.
