MONITORING GREEN TURTLES (CHELONIA MYDAS) AND THEIR HABITAT TOWARDS MITIGATION OF FISHER-TURTLE CONFLICT IN THE LAKSHADWEEP ISLANDS - Dakshin ...
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MONITORING GREEN TURTLES (CHELONIA MYDAS) AND
THEIR HABITAT TOWARDS MITIGATION OF FISHER-
TURTLE CONFLICT IN THE LAKSHADWEEP ISLANDS
Photo courtesy: Sea Turtle Conservancy Library, Tortuguero
Nupur Kale, Muralidharan M., Naveen Namboothri & Kartik Shanker
Dakshin Foundation, Bengaluru
2018
Citation: Kale, N., M. Manoharakrishnan, N. Namboothri & K. Shanker (2018) Monitoring green turtles (Chelonia mydas) and their habitat towards mitigation of fisher-turtle conflict in the Lakshadweep Islands. Report submitted to Lakshadweep Administration. Dakshin Foundation, Bengaluru.
Acknowledgements We would like to thank the Ravi Sankaran Small Grants Programme and Rufford Foundation for funding this project. We also thank the Lakshadweep Administration, the Departments of Environment & Forest (DEF) and Science & Technology (DST) for furnishing us with the necessary permits to carry out work in the Lakshadweep Islands. Additionally, we would like to thank the Environment Wardens of Agatti, Kadmat and Kalpeni for their support during fieldwork. We would like to thank several people from Dakshin Foundation and Centre of Ecological Sciences, Indian Institute of Science for their assistance during fieldwork. NK would like to thank Anne Heloise Theo for training and guiding fieldwork in Agatti; Nachiket Kelkar, Mahima Jaini and Meenakshi Poti for providing valuable advice for fieldwork in the region; Riyaz from Department of Environment & Forest for his help with logistics in Kalpeni; Shafeeq for helping with the translations for fisher surveys and Mahaboob Khan and Ishaan Khot for their assistance and wonderful company in Lakshadweep. Fieldwork in the islands would not have been possible without the help of boatmen on the islands: Naseer uncle in Agatti, Mansoor bhai in Kadmat and Naushad in Kalpeni. Finally, we would like to thank all those who provided any form of assistance and made the field work easy and comfortable in Lakshadweep Islands.
INTRODUCTION The green sea turtle (Chelonia mydas) is classified as ‘Endangered’ by the International Union for Conservation of Nature (IUCN, 2018). However, studies in the last two decades indicate an increase in green turtle populations in the Lakshadweep islands of India (Tripathy et al. 2002; 2007). Following the increase in turtle density, it was observed that the seagrass meadows in the lagoons were overgrazed (Lal et al. 2010). The decrease in seagrass cover has begun to affect seagrass associated fish species (Kelkar et al. 2013a) and is indirectly affecting the livelihood of island inhabitants dependent on lagoon fisheries. This has resulted in a conflict with fishers resenting turtles and harming or killing turtles to conserve the fish population (Arthur et al. 2013). Our project focused on studying the green turtle population in the region and understanding their ecology. We initiated our work by monitoring the green turtles and seagrass species in the lagoon. Since the turtle-fisher conflict could have negative effects on the turtle population, we initiated a mapping exercise in areas of conflict and surveyed local fishers to document their perspectives on turtles and the conflict. OBJECTIVES Monitoring green turtle distribution and diet Mapping seagrass distribution Mapping potential conflict areas in the lagoon Understanding the history and present status of the turtle-fisher conflict
STUDY SITE
The Lakshadweep archipelago (8°N-12°N and, 71°E-74°E) is a group of 12 coral atolls
comprising of 36 smaller islands. These islands are characterised by shallow lagoons
which are suitable for seagrass species (Jagtap, 1998; 1991). A total of 8 species of
seagrass are found in Lakshadweep out of which Thalassia hemprichii and Cymodocea
rotundata are preferred by green turtles (Jagtap, 1998; Jagtap, 1991; Kelkar et al., 2013).
For our study, we chose Agatti, Kadmat and Kalpeni lagoons. According to recent
reports, Agatti has a low density of turtles, Kadmat a moderate density and Kalpeni a
high density of turtles. Additionally, Arthur et al. (2013) reported that fishers in Agatti
were resentful towards turtles whereas the inhabitants of the other two islands were
indifferent.
© Google Earth © Google Earth
Kadmat Agatti
© Google Earth
Kalpeni
Fig 1. Maps of the islands surveyed in this study. (Images from Google Earth)
Island Survey Period
Agatti 20-29 March 2018
Kadmat 9-18 April 2018
Kalpeni 25 April- 8 May 2018
METHODS
1) Monitoring green turtle distribution
The lagoons were divided into two different regions based on their orientation
(North, Central and South) and proximity to the reef (Shore, Mid Lagoon and
Reef). A total of 8, 12 and 12 boat transects (1km long) were surveyed in Agatti,
Kadmat and Kalpeni respectively (Fig 2).
(a) (b) (c)
Fig 2. Turtle survey transects in (a) Agatti, (b) Kadmat and (c) Kalpeni
2) Mapping the seagrass distribution
The entire lagoon was divided into grids of 500x500m in which 28 points were
randomly chosen using QGIS© to survey for seagrass presence (Fig 3). The points
were then classified as Shore, Mid Lagoon and Reef region in the Northern,
Central and Southern part of the lagoon. The chosen points were surveyed in four
directions: North, South, East and West by snorkelling. After every 8 fin strokes,
a sub-point was counted and the substrate was noted. Similarly, 10 sub-points
were collected from each transect. On encountering seagrass, a 0.5x0.5m
quadrant was laid to measure seagrass density.
(a) (b) (c)
Fig 3. Points selected for seagrass transects in (a) Agatti, (b) Kadmat and (c) Kalpeni
3) Mapping potential conflict areas in the lagoons
In order to locate conflict points in the lagoons, commonly used fishing sites and
turtle foraging/sighting spots were marked on maps of the islands. These maps
will be useful tools in locating regions which turtles commonly use and can thus
be avoided by fishermen. Moreover, overlapping the two regions will provide
potential areas where conflict occurs.
4) Understanding the history and present status of the turtle-fisher conflict
Questionnaires were used to collect initial data from lagoon fishers. A total of 30
fishers were surveyed from Agatti, Kadmat and Kalpeni. Snowball sampling was
used to determine interviewees. The purpose of this survey was to understand the
local knowledge with respect to history of turtles, turtle behaviour and fisher
perception of turtles.
ANALYSIS AND RESULTS
1) Monitoring green turtle distribution
In Agatti and Kadmat, the turtle encounter rate was low while Kalpeni had a
higher rate than the other two. Turtles were mainly observed in the northern part
of Agatti and Kadmat lagoons whereas the southern region of Kalpeni lagoon
showed high turtle occurrence.
Studies by Kelkar et al. (2010) and Lal et al. (2010) showed higher densities of
turtles in Agatti, followed by Kavaratti and later Kadmat. Meanwhile Poti et al.
(2016) and our present study show that the turtle densities are now higher in
Kalpeni (Fig 4).
Turtle encounter
180
160
140
No. of turtles
120
100
80
60
40
20
0
North
Central
North
North
North
North
Central
Central
Central
Central
South
South
South
South
South
2016 2018 2018 2016 2018
Agatti Kadmat Kalpeni
Fig 4. No. of turtles observed in Agatti, Kadmat and Kalpeni by boat transects in 2016 (Poti et al. 2016) and
2018
2) Mapping the seagrass distribution
Seagrass surveys in Agatti showed presence of patches of Thalassia, Cymodocea,
Syringodium and Halophila sp. whereas only Cymodocea and Thalassia were seen in
Kadmat (Fig 5). Apart from Thalassia, Syringodium was also observed in Kalpeni
lagoon. Kalpeni lagoon showed high densities of Thalassia in the southern part of
the lagoon with few patches in northern region (Fig 6). We also found evidence of
washed up seagrass on the eastern side of Agatti during beach surveys.
140
120
Seagrass presence (Encounter rate)
100
80 Syringodium isoetifolium
Thalassia hemprichii
60
Halophila ovalis
40 Cymodocea rotundata
20
0
Central North South Central North South Central North South
Agatti Kadmat Kalpeni
Fig 5. Seagrass encounter rate
Density of seagrass
4000
3500
3000
2500
2000
1500
1000
500
0
Central North South Central North South Central North South
Agatti Kadmat Kalpeni
Fig 6. Density of seagrass
3) Mapping potential conflict areas in the lagoons
Fishing and turtle occurrence spots were marked upon observation of the two
activities. Additionally, fishers were asked to mark these sites on maps. In case of
accidental capture, fishers would lift the net to release the turtles. However,
during fisher interviews, they said sometimes they would hit turtles with sticks to
scare them away or tie floats/plastic bottles on their flippers to keep them on the
water surface. Given below are the turtle observation points and lagoon fishing
sites that were marked in Agatti, Kadmat and Kalpeni. Circled areas mark
common sites where turtles and fishing occur (Fig 7(a), 7(b) & 7(c)).
Fig 7(a). Observed fishing sites and turtle sighting points in Agatti (F: Fishing, T: Turtle)
Fig 7(b). Observed fishing sites and turtle sighting points in Kadmat (F: Fishing, T: Turtle)Fig 7(c). Observed fishing sites and turtle sighting points in Kalpeni (F: Fishing, T: Turtle)
4) Understanding the history and present status of the turtle-fisher conflict
Fisher responses indicated that there is currently very little to no resentment
towards turtles in Agatti and Kadmat while Kalpeni fishers were unhappy due to
the high turtle density in the lagoon. Previously, conflict was observed in Agatti
and Kadmat (Arthur et al. 2013). Now, it appears that the turtle densities in
Kalpeni have increased resulting in negative attitudes towards turtles.
The common grievance was accidental capture of turtles in nets which
resulted in destruction of nets or release of turtles by lifting the net due to which
fishes would escape too. Some fishers mentioned that they would check their
fishing site for presence of turtles before casting nets. The fishers gave the
following reasons for an increase in turtle numbers: a) Turtle hunting ban b)
Increased turtle nesting c) Increased amounts of seagrass in the lagoons.DISCUSSION In order to facilitate conservation and management, it is crucial to study all ecological aspects of a species (Hirth, 1997). Similarly, although the green turtle populations are recovering, the resentment of local communities makes it imperative to manage the turtle population in Lakshadweep Islands. Not only does this conflict threaten the recovery of green turtles but also the livelihoods of the local fishing community. It was observed that tide influenced turtle encounters in the lagoons as more turtles were encountered during low tide. Additionally, fisher responses indicated that in addition to Kalpeni, Bangaram and Suheli also have high number of turtles. There was also seagrass found growing on the eastern side of the islands in Agatti and Kalpeni. Cymodocea was mainly identified as the seagrass species growing on the eastern side. However, detailed surveys are required to determine if there are other seagrass species found in the eastern shores of the two islands. Results from this study reflect the need to understand more aspects of green turtle ecology. Tracking studies are required to discern their inter-island movements and in turn, varying turtle densities between islands. It also indicates that the foraging ecology of the green turtles must be studied as the seagrass sources are slowly depleting. This could cause a shift in the diet of the green turtles as they adapt to a lack of foraging resources. The change in diet could also affect the growth rates in green turtles which will then affect their reproductive ability. Moreover, it would also result in change from seagrass dominated to an algal dominated habitat in the lagoons. Hence, it is important to study green turtles, conserve seagrass meadows and associated fish species to manage the turtle population as well as protect the livelihood of fishers.
FUTURE STEPS In the upcoming seasons, the project will proceed to study aspects of green turtle biology such as past and current diets using stable isotope analysis (SIA). This information will be useful in planning management of the population and understanding their recovery. Other behaviour such as inter-island movement and linkage with other green turtle populations in the region will be determined by initiating a tagging program and collecting genetic material respectively. Knowledge about their movements will be crucial in resolving conflict with the fishers and developing tools to conserve seagrass and lagoon fish populations. Moreover, experimental exclosures will be set up in some parts of the lagoon to test their efficiency in conserving patches of seagrass. These approaches will not only provide insights into turtle ecology in the region but also aid in management of the population. It will also provide means to conserve the green turtle habitat, the seagrass meadows, and consequently, lagoon fish populations. This, in turn, will help in resolving the persistent fisher-turtle conflict that threatens the fisher livelihood.
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