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

Williams, Jessica Lauren (2017) Multidisciplinary insights into the conservation and biology of sea turtles in Mozambique. PhD thesis, James Cook University.

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Abstract

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 and greater Inhambane peninsula are a hotspot for take of sea turtles. The literature review documented year-round take of sea turtles to occur through much of Mozambique. Use of sea turtles focused on their meat, and it was rare to detect more than an empty carapace or old bones. Small scale fisheries interact with turtles in their favoured habitats (close to reefs systems) in coastal waters, particularly in the south of the primary study area, between Praia do Tofinho and Praia de Rocha. Based on interviews with fishers, the opportunistic take of turtles is prevalent and widespread (Chapter 5) in Inhambane Province. A targeted marine megafauna multi-species fishery exists in the study area. Widespread use of gillnets and long-lines occurs and these fishing gears are favoured because of their non-selectivity and ability to capture turtles and other species. Sea turtle capture in these fisheries is neither bycatch nor accidental.

Interviews with fishers (Chapter 5) indicated that the motives and drivers influencing fishers to illegally take sea turtles was variable between communities and individuals. In the two fishing communities surveyed, opportunities for alternative livelihoods were lacking or insufficient to supplement or replace their reliance on fishing activities. Five of the six major drivers identified in Chapter 5 reflect Mozambique's low socio-economic status. Similarities were evident between the drivers and motives of illegal take of turtles and the terrestrial mammal bushmeat hunting and trade. The majority of fishers had multiple motives for participating in illegal take of sea turtles. Awareness of turtle protection laws amongst fishers was high, although compliance was low. This suggests that simple campaigns to increase awareness of turtle legislation will have little impact in deterring illegal take. Future conservation efforts will need to address food security, livelihoods options and aim to minimise the number of motives an individual fisher or community may have to participate in illegal take.

I solicited opinions from local experts to quantitatively rank threats and investigate the context of conservation and management efforts underway in Mozambique (Chapter 6). Consensus of expert opinions revealed the most pressing threats to sea turtles were fisheries-related (bycatch from commercial trawling, SSF bycatch and hunting of nesting turtles). The top-ranking threat, bycatch within the commercial shallow-water prawn trawl industry, could be easily mitigated with effective implementation of pre-existing Turtle Exclusion Device legislation. This is not the case for the other two threats, which given their nature are likely to involve extensive changes/improvements to living standards and Mozambique's overall socio-economic status. Compliance with sea turtle legislation was weak throughout the country and experts identified improving enforcement efforts as critical. Parallels are evident between the issues that hamper the conservation and management of terrestrial megafauna and marine megafauna. A holistic process will be required to solve large-scale issues (e.g. governance, corruption, compliance) and strengthen overall biodiversity conservation. Given the extremely limited funding allocated to conservation of sea turtles and the marine environment, and limited access to skilled people and resources, a prioritised list of management actions for sea turtle hotspot areas is necessary.

I conclude this study by discussing my key findings relating to the sea turtle populations using the Tofo area, the impacts they face and how and where conservation management efforts could be strengthened. I also suggest specific priorities for future research to enhance knowledge of sea turtle populations, socio-economic understanding of SSF and alternative livelihoods. A balance needs to be struck between the environment, economic development and social and cultural values of coastal people in order to achieve sustainable growth whilst preserving marine biodiversity and improving living standards.

Item ID: 51516
Item Type: Thesis (PhD)
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Additional Information:

Publications arising from this thesis are available from the Related URLs field. The publications are:

Chapter 2: Williams, Jessica L., Pierce, Simon J., Fuentes, Marianna M.P.B., and Hamann, Mark (2015) Effectiveness of recreational divers for monitoring sea turtle populations. Endangered Species Research, 26 (3). pp. 209-219.

Chapter 3: Williams, Jessica L., Pierce, Simon J., Rohner, Chris A., Fuentes, Mariana M.P.B., and Hamann, Mark (2017) Spatial distribution and residency of green and loggerhead sea turtles using coastal reef habitats in southern Mozambique. Frontiers in Marine Science, 3.

Date Deposited: 17 Nov 2017 01:41
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity @ 100%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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