Illegal harvest of nesting green turtles in Tortuguero National Park, Costa Rica

Sebastian Troëng and Thomas A. Rankin González
Caribbean Conservation Corporation, Apartado Postal 246-2050, San Pedro, Costa Rica

Tortuguero National Park (TNP), situated on the Caribbean coast of Costa Rica, hosts the largest green turtle rookery in western Caribbean (Carr et al., 1978). Tagging and monitoring of the nesting population was initiated in 1955 by the late Dr. Archie Carr and has since been conducted every green turtle nesting season (Carr 1956). A major issue in the early days of the green turtle monitoring program was the harvest of green turtle females from the beach (Carr 1969). Nesting turtles were turned and slaughtered mainly for their calipee which was exported to Europe and U.S.A. to be used as the main ingredient in turtle soup (Parsons 1962). Better protection for nesting females was provided in 1970 when 18 miles of the Tortuguero nesting beach became part of Costa Rica’s first national park. Park rangers and Caribbean Conservation Corporation researchers and volunteers patrolling the nesting beach have since contributed to limit the illegal take of females from the nesting beach.

However, Costa Rican authorities currently allow a green turtle fishery. Permits are issued to fishermen in Limón, 55 km south of TNP, allowing a total annual catch of 1, 800 green turtles. The permits only allow fishermen to catch turtles in the sea and not within protected areas. Green turtles are caught entirely for the domestic Costa Rican meat market and consumption is mainly limited to Limón. The legal quota system is not strictly enforced which makes it easy for opportunistic fishermen to exceed their quota and sell green turtles caught on nesting beaches and in protected areas. Inadequate beach patrols by park rangers caused by lack of funding for Tortuguero Conservation Area (ACTo) have also contributed to an increase in illegal harvest of female turtles from the nesting beach in TNP.

A study was carried out during Caribbean Conservation Corporation’s 1997 Green Turtle Program with the objective to quantify the illegal harvest of green turtles from the nesting beach in Tortuguero.

The study period extended from 6 July to 26 September 1997. Track surveys were conducted weekly to determine the level of nesting and the number of turtles illegally harvested from the beach. The study area includes three beach sections. A total of twelve track surveys were conducted from Tortuguero rivermouth to 8 km south of the rivermouth (=beach section A). Eleven track surveys were conducted from 8 km south of Tortuguero rivermouth to Jalova lagoon (=beach section B=22 km), the most inaccessible beach section. Also, three track surveys were conducted from Parismina rivermouth to 8 km south of the rivermouth (=beach section C), outside of TNP. Green turtles nest only sparsely on this stretch of beach (<4 nests/night) but reports of extensive illegal harvest in this area rendered surveys necessary.

Track surveys were conducted in the early morning and only tracks from the previous night were recorded. The number of illegally harvested green turtles was determined by recording the drag marks from flipped-over turtles. Drag marks often covered each other. In such cases, the track surveyor would estimate the total number of turtles taken by poachers.

Ample evidence of illegal harvest was found during the course of the study. Relatively low levels of illegal harvest (0-3 females/night) occurred in beach sections A and C, throughout the study period. A large part of this harvest is likely to be for local consumption in Tortuguero and Parismina villages. However, turtles found flipped-over but alive in the morning indicate that part of this harvest was for commercial purposes.

Only live turtles are bought for slaughter in Limón, to ensure that the turtles are freshly caught. No illegal harvest was observed in beach section B during the first part of the study period. However, extensive illegal harvest began in beach section B in late August. Large-scale illegal harvest was first observed on the night of 27 August when Caribbean Conservation Corporation staff encountered poachers and flipped-over turtles in a remote part of beach section B. The start of the intense illegal harvest coincided with the onset of calm seas that allowed boats from Limón to approach the beach at night.

The limiting factor for the illegal harvest in beach section B during the second part of the study period was the capacity of the poachers’ boats to carry turtles. This was confirmed one morning when the track surveyor encountered 15 turtles still flipped-over on the beach. The turtles were most likely left by poachers who had filled their boat to the brim and would return to collect the turtles after they had off-loaded their first shipment To estimate the total illegal harvest, we assume a constant harvest regime in beach section A and C, and two harvest regimes, 6 July-26 August and 27 August-26 September, in beach section B. A total of 1, 720 (90% C. I. =601-2, 939) green turtles were illegally harvested from the nesting beach (sections A, B, and C) during the study period.

The estimate of the illegal harvest presented here should be considered conservative for two reasons. Firstly, only drag marks visible on the beach in the morning were recorded. Drag marks from turtles turned over close to the water’s edge had by then already been erased by waves. Secondly, the study period did not encompass the entire green turtle nesting season (late Junelate October 1997). Illegal harvest was observed before 6 July and after 26 September in conjunction with other monitoring activities.

The full effects of the illegal harvest on the nesting population are not known. However, consequences may be serious given the long time green turtles take to become sexually mature and the sensitivity of sea turtle populations to exploitation of adult females. It should be added that the population of green turtles that nest at Tortuguero is also heavily exploited in the main feeding pastures in Nicaragua. Lagueux (1998) estimates that at least 10, 166 green turtles were harvested in Nicaragua in 1996.

The illegal harvest in Costa Rica is made possible by lack of enforcement of the legal quota system and lack of enforcement of protected area legislation. Caribbean Conservation Corporation and other Costa Rican conservation organizations therefore urge the newly elected Government of Costa Rica to address the problem by:

A) increasing the number of beach patrols by Tortuguero Conservation Area (ACTo) staff; and either:

B) enforcing the legislation that controls the sale of turtle products, particularly in Limón; or:

C) ending the legal harvest since the quota system renders the enforcement of legislation controlling turtle trade difficult.

This study was entirely funded and conducted by Caribbean Conservation Corporation as part of the 1997 Green Turtle Program.

Carr, A.F. 1956. The Windward Road. New York.
Carr, A.F. 1969. Survival outlook of the West-Caribbean green turtle colony. IUCN Publications New Series Supplementary Paper No. 31: 13-16.
Carr, A.F., M.H. Carr, and A.B. Meylan. 1978. The ecology and migrations of sea turtles, 7. The Western Caribbean green turtle colony. Bull. Am. Mus. Nat. Hist. 162: 1-46.
Lagueux, C.J. 1998. Marine turtle fishery of Caribbean Nicaragua: Human use patterns and harvest trends. Doctoral dissertation. University of Florida. Gainesville, Florida.
Parsons, J. 1962. The Green Turtle and Man. University of Florida Press. Gainesville, Florida. 126pp.

Abstract of paper presented at 18th International Symposium, 1998