Untangling the origin of ghost gear within the Maldivian archipelago and its impact on olive ridley (Lepidochelys olivacea) populations

Abstract

There is little documentation available on the impact of abandoned, lost or discarded fishing nets (‘ghost nets’) on turtle populations. Here, we utilise data collected over a 5 year period to assess (1) if a particular net type or characteristic was identifiable as entangling more turtles and (2) if particular fishing practices (i.e. types of nets) could be managed to reduce turtle entanglement in the Maldivian archipelago. A total of 131 turtles were entangled in the 752 reported ghost nets, and olive ridley turtles Lepidochelys olivacea appeared to be the most vulnerable (making up 97% of entangled turtles). However, we estimate that the 752 nets in this study, reported over a 51 month period, could have entangled between 3400 and 12200 turtles across the Indian Ocean prior to being detected in the Maldives. Mesh size, seasonality (i.e. north east monsoon), and the presence of floats were all identified as variables significantly affecting the likelihood of turtle entanglement. The probability of entanglement increased as the mesh size increased but decreased when floats were present. Additionally, turtles were more likely to be entangled during the north east monsoon when currents flow from east to west. Cluster analysis indicated that there were at least 11 broadly assigned net types found floating in the study area, and these were dominated by trawl and gill nets. Our analyses highlight the need for a detailed database of existing gear types coupled with gear marking to improve traceability of ghost nets in the Indian Ocean.