Assessment of tag loss and photographic identification of sea turtle at Chagar Hutang, Redang Island

Abstract

Sea turtle tagging enables us to obtain valuable information regarding various aspects of sea turtle biology. However, there is the problem of tag loss which causes bias in sea turtle studies. Photographic identification (photo-ID) would help alleviate this problem from occurring as it utilizes the natural facial markings to identify individuals. This study was carried out to estimate the extent of tag loss in green turtles of Chagar Hutang for both intra-seasonal and inter-seasonal, as well as to test the feasibility of photo-ID technique along-side inconel tagging. For tag loss assessment, tagging data from the Sea Turtle Research Unit (SEATRU) database was assessed using the model of Limpus (1992). Field sampling for photo-ID of the sea turtles was conducted between 13 th May 2010 and 21 st June 2010 at Cha gar Hu tang, Redang Island. The scute patterns were drawn using Adobe Photoshop CS4 and later compared manually. Assessment of tag loss was done for 951 green turtle individuals. Intra-seasonal analysis showed higher tag retention for inconel tags compared to titanium tags which could be attributed to tag design.