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Marine Turtle Newsletter 32:3-4, © 1985

Atlantic Ridley Project 1984 Prelininary Report

Rene Marquez M.
C.I.P. Manzanillo, c/o Delegación Federal de Pesca, Manzanillo, Col. 28200 Mexico

This was the l8th year of the Mexican project at Rancho Nuevo and the 7th year of cooperative work with the US Fish and Wildlife Service towards the restoration of Lepidochelys kempi in the Gulf of Mexico. Work in the turtle camp began on 8 April and continued until the second week of September; the US team was present from 12 April until 11 August. The first turtle was seen laying on 13 April and the last on 17 July. Out of a total of approximately 1036 nests, 798 were translocated; 70,878 eggs were transferred to corrals, 8188 were transferred to styrofoam boxes and 26 nests (ca. 2500 eggs) were left in situ. Only around 7.3% of the eggs were lost to predation and poaching. Preliminary estimates of hatching success are 72.9% for corrals and 80.3% for styrofoam boxes at Rancho Nuevo. Well into the season (19, 20 June) there was a storm, and heavy rain lowered the incubation rate to 49.2% in the second corral holding 199 nests. Even so, this season's overall hatching rate of 73.4% was high as compared to 49% in 1983 (Márquez 1983, MTN 26:3-4). This was due to improved work, better weather and moving one of the corrals to a safer location. More than 58, 100 hatchlings were released onto the beach. An additional 438 hatchlings emerged from undisturbed nests. Of note this year was the first ridley nest at Isla Aquada, Campeche; more than 60 hatchlings were released near there.

Between 13 April and 17 July there were 51 grouped or solitary emergences, including several "arribazon" included 322 turtle tracks and resulted in 255 nests being relocated and reburied in the same day; 20 more nests were left in situ for incubation studies. Monel tags were applied to 33 females, while 241 others received titanium tags and 7 received plastic tags. Fifteen other females were double-tagged on opposite front flippers-8 with two plastic tags and 7 with one Monel and one titanium tag each. Sixty-nine females nested twice and ten nested three times. Possible tag scars were detected on 86 turtles, which were retagged. One hundred six turtles tagged in previous years nested again this year-31 of these nested twice and 4 nested three times in 1984.

Temperatures were monitored in 14 coral clutches and in 19 styrofoam box clutches for studies of the effect on sex ratio; 24 temperature probes were also placed along the beach profile, and weather was monitored throughout the season. More than 200 dead hatchlings were retained for sex determination.

Nineteen boxes with 2000 eggs were shipped to Padre Island, Texas (USA) for incubation and imprinting. The hatching rate from this group of eggs was 89.6%. From Padre Island, 1547 imprinted hatchlings were sent to the Galveston Laboratory for headstarting. They will be released into shallow waters of the Gulf of Mexico at between 9 and 12 months old.

Over the past six years, 8191 headstarted ridleys have been released. Some 96 have been retained for study or as a potential breeding stock in several laboratories and US aquaria, and another 100 were sent to the Cayman Turtle Farm for the same purpose (Mexus-Gulf's Sea Turtle Working Group's Accomplishment and Plans for 1978-1985 ms. Veracruz, México, 1982). Of those sent to the Cayman Turtle Farm, two females produced eggs this year (Wood and Wood 1983, MTN 29:12).