Palau's fisheries minister says the country is still figuring out the balance of fishing in its waters.
On Wednesday, an amendment was passed including accommodations for Japanese fishing boats to continue operating in Palau.
The law, which comes into force next year, will restrict fishing to an area that encompasses 20 percent of Palau's exclusive economic zone.
The changes also allow for long-line exports after it was previously restricted to only purse-seine fishing.
Minister Umiich Sengebau said the government doesn't know how the sanctuary will perform yet and it will have to monitor stocks.
"It's about ensuring that the stocks remain healthy within Palau waters. Can we do this and ensure that within Palau there's always going to be a supply of fresh tuna that's for the local population and also the visitors, and then if we have surplus we can ship it off so that's revenue for Palau."
Palau's government said the concession came after consultation with Japan.