Oceans and Coasts

Turf Wars

Understanding turtle-fisher conflicts in Lakshadweep seagrass meadows

Fishers in the seagrass meadows of the Lakshadweep associate a decline in fish catch with increases in green turtles over the last two decades. Our work has been exploring the ecological and economic drivers of this conflict in these lagoons 

Troubled Waters

Seagrass meadows form important habitats for lagoon fishers in the Lakshadweep Islands for regular small-scale, subsistence-level fishing. Fishers have, however, been reporting declines in fish catches from seagrasses over the last decade or so, and many fishers attribute this decline to an increase in green turtles numbers. Although easy to discount this as just another disaffected fisher tale, fishers in the Lakshadweep propose a series of very believable mechanisms linking turtles to fish decline which are much more difficult to dismiss offhand. Apart from turtles breaking nets and driving away fish by swimming, fishers we interviewed were adamant that the herbivorous turtle overgrazed seagrass, driving a decline in adult fish that used the meadow as well as reducing recruitment by many lagoon fish. In 2005, conflicts between local lagoon fishers of the Agatti Island and green turtles escalated, resulting in clandestine killing of turtles by angry fisher folk. 

Problems of plenty

Over the past few years we have been trying to validate the complex ecological pathways hypothesized by local fishers, through both observational and experimental research on turtle herbivory itself. We first estimated the magnitude of turtle herbivory in the Lakshadweep Islands, and established that the current levels of herbivory do represent a significant overgrazing, and that the herbivory rates and turtle densities in the Lakshadweep meadows are indeed among the highest in the world. We used seagrass clipping experiments to show that turtles can cause population and biomass declines in seagrasses and explore the mechanisms by which turtle herbivory causes  species shifts in seagrass meadows from long-lived, hardy species to short-lived, sediment-tolerant seagrasses. In this process of changing meadow succession, turtles are also seriously affecting the capacity for seagrass recovery. 

Many paths to conflict

We have also been tracking fisher perceptions about the turtle problem on these islands, and set out to validate these hypotheses through studies on both turtle herbivory affecting seagrass structural complexity, and most importantly, the response of fish populations to this change across a gradient of differentially grazed meadows. Our results provide considerable support for the fact that the fishers, for the most part, appear to have gotten it right in ‘blaming’ the turtles for their declining catch. We also show, through a basic economic evaluation of the costs incurred by fishers due to turtle conflict, that indirect and unobvious pathways of conflict might be far more serious than direct mechanisms such as breakage of nets, which, despite having smaller costs, are generally the focal point of conflict mitigation measures.