Abstracts Category : Other

Multidisciplinary insights into the conservation and biology of sea turtles in Mozambique

by Jessica Lauren Williams

Five of the world's seven species of sea turtles have been documented to use Mozambican habitats. While they are thought to be extensively distributed throughout Mozambican coastal waters, and the offshore waters of the Mozambican Channel, little is known about these populations. Specifically, information about the state and structure of sea turtle populations (population size estimates, species composition, age class distribution, movements of animals into and out of the study area, residency, habitat use and preferences) was scarce or non-existent for Mozambique. Therefore, my research adopted several complementary research techniques to increase knowledge on sea turtles in their foraging grounds and their exposure to human impacts.The major research aim of my thesis is to understand factors related to the distribution, abundance and use of sea turtle populations within the Inhambane region, Mozambique, and use this knowledge to inform and improve conservation and management efforts.In Chapters 2 and 3, I explore the use of citizen science and photoidentification (photo-ID) as tools to facilitate the collection of data on turtles encountered in-water. I found that citizen science is a useful tool for collecting basic biological information, particularly when coupled with photo-ID encounters. While the quality of dive log records was improved by having a few well-trained and consistent contributors, the photo-ID database benefitted from broadened public involvement. Results from the generalised linear modelling of the dive log data (Chapter 3) suggested that sightings and abundance of turtles were influenced by environmental conditions. It was also evident that factors such as visibility and diving depth lead to availability and perception bias in the citizen scientists' records. It is important to be aware of such biases since they reflect physical environmental diving conditions rather than habitat or behavioural predictors that influence sea turtles. Overall, citizen science coupled with photo-ID datasets provided the first details of Mozambique's foraging sea turtle populations. In Chapter 3, I described the use of coastal reefs by green and loggerhead sea turtles in Inhambane, Mozambique. Based on population models from the photo-ID dataset, both green and loggerhead populations were small but present year-round. Regardless of species, sea turtles favoured coastal nearshore waters and relatively shallow reef systems, which make them vulnerable to interaction with small scale fisheries (SSF). Impacts of SSF is unlikely to be consistent between species or age-classes. My findings suggest that the long-term residency of late-stage juvenile greens in these nearshore and shallow habitats make them most vulnerable to interactions with SSF.In Chapter 4, I investigated the prevalence of illegal take of sea turtles in a coastal region of Mozambique the Tofo area, Inhambane Province - and conducted a national-scale literature review. Transect- based sampling in the sand dunes demonstrated that the Tofo area