The president signed a decree Tuesday that specifies two areas in the Pacific national waters where commercial fishermen can seek tuna and similar species.
The decree invalidates one that has been signed by president Laura Chinchilla in April. That decree never took effect because it never was published.
The decree appears to keep commercial tuna fishermen 40 nautical miles from the Pacific coast. That is about 46 statute miles. The Chinchilla decree said 60 miles.
Environmentalists said they would have preferred 100 miles.
The Luis Guillermo Solís decree also put the job of drawing up details rules in the hands of the Instituto Costarricense de Pesca y Acuicultura, which generally is regarded as being pro-commercial fishery.
The new decree would require, as did the Chinchilla decree, that larger commercial boats carry a monitoring device that emits the location. There also is a provision for licensing.
A big concern with environmentalists are the circle nets that commercial tuna fishermen use. They trap dolphin and other non-tuna species, including sea turtles. Dolphins are mammals and can drown if trapped in a net.
The fisheries institute has a year to draw up detailed management plans, said the decree.