a Marine megafauna interactions with East African small-scale fisheries

Abstract

Small Scale Fisheries (SFF) in the developing southwestern Indian Ocean (SWIO) region employ half a million fishers, contribute over 70% of marine fisheries catch and their importance to coastal communities for food and income cannot be overstated. However, SSF may also have substantial negative impacts on marine ecosystems, reflecting the global challenge of balancing conservation goals with the needs of communities reliant on natural resources. Marine megafauna (here referring to elasmobranchs, marine mammals and sea turtles) are particularly vulnerable to fisheries impacts, due to their classically k-selected lifehistories, and play important roles in the structure and function of marine ecosystems. Yet, little is known of the interactions between SWIO SSF and these species. This thesis provides the first independent regional assessment of elasmobranch catch volume and composition based on fisheries landings data and provides evidence for the ongoing catch of marine mammals and sea turtles across SWIO SSF. Elasmobranch catches were estimated at 73% more than reported to the Food and Agriculture Organization of the United Nations in 2016 and 129% more than the 10-year average (2006-16). However, subsequent vulnerability assessments of species is restricted by limited, or absent, life-history data. The thesis provides the first life-history data for the recently described Baraka’s whipray (Maculabatis ambigua), an important component of the ray catch. The life history results suggest a species of potentially high resilience to fisheries exploitation, although the observed SFF catch demographics indicate a potentially unsustainable catch pattern. The thesis also explores for the first time the dependence of fishers on elasmobranch resources, their use and value. It provides evidence of a specialised livelihood strategy exacerbating elasmobranch dependent fishers’ vulnerability to external shocks and highlighting them as a potential target group for livelihood diversification programmes. Lastly, the thesis compares rapid interview-based assessment methods for marine megafauna fisheries catches with data derived from observed fisheries landings and finds that the outputs of these methods show little evidence of equivalence. It indicates the need for a multi-method approach in assessing marine megafauna interactions with SSF in data-poor regions. The thesis demonstrates the challenges of understanding the interactions between small-scale fisheries and marine megafauna and highlights the need for rapid yet effective approaches toward generating priority baseline data for fisheries effort and catch to provide a basis for evidence-based management and feasible solutions