Growth Rates of Green Sea Turtles (Chelonia mydas) in Punta Abreojos, Baja California Sur, Mexico

Marjorie E. Howard, Gettysburg College

Environmental Studies Senior Honors Thesis

Description

Green sea turtles (Chelonia mydas) are subject to a number of anthropogenic threats including illegal hunting and incidental fisheries bycatch. These threats are particularly prevalent in coastal foraging areas essential to the growth and development of juvenile turtles, such as the coastal waters of Baja California, Mexico in the eastern Pacific Ocean. In order to better understand how anthropogenic threats might impact sea turtle populations, we must first understand green turtle demographic parameters such as growth rates. Few studies have examined growth rate of turtles in the eastern Pacific, though this information is necessary to obtain metrics such as age at maturity, model and monitor population trends, and develop effective management strategies for conservation. The objective of this study was to use sea turtle mark-recapture data collected as part of a bycatch reduction technique study from 2006-2014 to calculate growth rates for green turtles in Punta Abreojos, Baja California Sur, Mexico. Turtles were captured with monofilament gill nets, tagged on both rear flippers, measured for various body size parameters, and released at their capture site. Body size parameters included straight carapace length (SCL), straight carapace width, curved carapace length (CCL), curved carapace width, body depth, and weight. A total of 730 turtles were captured and 64 of these turtles were recaptured at least once. Intervals between recaptures ranged from one day to approximately five years. Only turtles with a recapture interval greater than 11 months were used for growth rate calculations. Recaptured turtles ranged in size from 26.6-91.4cm SCL and their mean annual growth rate was 1.57±0.29cm SCL/year and 1.71±0.26cm CCL/year. These growth rates are consistent with previous estimates from Baja California, though they are lower than those observed at warmer sites in the Caribbean. The results of this study can be used to gain valuable insights on population status and develop management strategies for the future, as well as contribute to the overall growth rate data for Eastern Pacific green turtle populations.

 
Apr 29th, 4:30 PM Apr 29th, 6:15 PM

Growth Rates of Green Sea Turtles (Chelonia mydas) in Punta Abreojos, Baja California Sur, Mexico

CUB Ballroom

Green sea turtles (Chelonia mydas) are subject to a number of anthropogenic threats including illegal hunting and incidental fisheries bycatch. These threats are particularly prevalent in coastal foraging areas essential to the growth and development of juvenile turtles, such as the coastal waters of Baja California, Mexico in the eastern Pacific Ocean. In order to better understand how anthropogenic threats might impact sea turtle populations, we must first understand green turtle demographic parameters such as growth rates. Few studies have examined growth rate of turtles in the eastern Pacific, though this information is necessary to obtain metrics such as age at maturity, model and monitor population trends, and develop effective management strategies for conservation. The objective of this study was to use sea turtle mark-recapture data collected as part of a bycatch reduction technique study from 2006-2014 to calculate growth rates for green turtles in Punta Abreojos, Baja California Sur, Mexico. Turtles were captured with monofilament gill nets, tagged on both rear flippers, measured for various body size parameters, and released at their capture site. Body size parameters included straight carapace length (SCL), straight carapace width, curved carapace length (CCL), curved carapace width, body depth, and weight. A total of 730 turtles were captured and 64 of these turtles were recaptured at least once. Intervals between recaptures ranged from one day to approximately five years. Only turtles with a recapture interval greater than 11 months were used for growth rate calculations. Recaptured turtles ranged in size from 26.6-91.4cm SCL and their mean annual growth rate was 1.57±0.29cm SCL/year and 1.71±0.26cm CCL/year. These growth rates are consistent with previous estimates from Baja California, though they are lower than those observed at warmer sites in the Caribbean. The results of this study can be used to gain valuable insights on population status and develop management strategies for the future, as well as contribute to the overall growth rate data for Eastern Pacific green turtle populations.