Analysis of post mortem changes in sea turtles from the Pacific Coast of Baja California Sur using forensic techniques

Abstract

The Pacific waters of the Baja California Sur coastline host a high diversity and abundance of sea turtles. The area is considered one of the most productive areas for various fisheries. In some occasions, the fisheries techniques could affect the sea turtles populations. Fisheries bycatch and local consumption is perceived to contribute to sea turtle mortality based on thousands of dead and stranded sea turtles. Yet, few cases have been studied for other possible causes of death. In this paper, we present basic forensic techniques applied to classify the state of the carcasses according to their condition. Immediate and late post mortem changes were observed to classify cause of death. Sea turtle carcasses were evaluated from five sites along the Pacific coast of Baja California Sur totaling 187 individuals from three different species. We documented at Playa Santo Domingo: Caretta caretta (Cc) N= 56; Chelonia mydas (Cm) N=23; and Lepidochelys olivacea (Lo) N = 2.  At San Juanico: Cc N=25 and Cm N=22; Laguna San Ignacio: Cm N = 19; at Punta Abreojos: Cc N = 16 and Cm N=11; Isla Arena: Cm N=10 and Cc N=3. We classified 93 turtles as having an unknown cause of death (49.73 %) due to an advanced state of decomposition. In 53 cases, cause of death was determined as bycatch (28.34 %) and in 41 cases as direct consumption (21.92 %). Extensive decomposition limited our ability to determine cause of death between natural and anthropogenic factors. We recommend designing a basic work plan focused on constant sampling and monitoring through timely coastal and in-water surveys to identify live and dead animals.