The Servicio Nacional de Guardacostas is on patrol off the northern Caribbean coast to protect green turtles that are coming ashore now to lay eggs.
The patrols have been reinforced after coast guard officers found a boat where the crew was harpooning the swimming turtles.
The green turtle is in danger of extinction.
Coast guards officers said they found six harpooned turtles cast back into the water, presumably by the four men in the suspect boat.
Turtles are caught illegally for their shells, their eggs and their meat, which find its way to the local market, frequently being disguised as some other type of meat, said the Ministerio de Gobernación, Policía y Seguridad Pública.
Officials called on the residents of the Caribbean
coast to reject purchasing turtle meat or turtle eggs. They described what is happening at sea as a massacre.
The arrival of the turtles, chelonia mydas, is a big tourist draw for places like Tortugero where the creatures dig nests in the sand. The green is one of the largest turtle in the word.
The sprawling, unkempt 22-mile beach at Tortuguero is the most important Western Hemisphere site for this activity.
The female green turtle is easily 140 kilograms (more than 300 pounds). They resemble small Volkswagens as they pull themselves from the surf, trundle 30 or 40 meters up the dark beach and begin building a nesting pit in the sand.
But at sea they are no match for humans with harpoons and outboard motors. They are air breathers that have to spend time on the surface where they are vulnerable.