Sustainable Oceans, Livelihoods and food Security Through Increased Capacity in Ecosystem research in the Western Indian Ocean (SOLSTICE-WIO) Ten percent of the world's population depend on the ocean for a readily accessible source of protein and employment, with the majority (95%) living in developing countries. Poor coastal communities are at the frontier for climate change impacts, compounded by population growth and food demand, but are among the least resilient to the challenges of the future.  SOLSTICE-WIO will focus on coastal communities in nine developing  countries and island states in  eastern Africa, interlinked culturally and ecologically and collectively known as the Western Indian Ocean (WIO) region. All nine (South Africa, Mauritius, Seychelles, Kenya, Tanzania, Mozambique, Somalia, Madagascar, Comoros) are on the list of Official Development Aid recipients, with five identified as Least Developed Countries.  In the WIO over 100 million people live within 100 km of the ocean, with a significant proportion employed in local fisheries. This leaves the region highly dependent on the ocean for economic stability, food security, and social cohesion. These coastal communities have limited adaptive capacity to cope with dramatic reductions in fish stocks caused by overfishing, habitat destruction, and increasing environmental pressures - all aggravated by climate change. The decline of WIO fisheries has had profound socio-political ramifications, from the rise of piracy to general political instability.   A clear example of the devastating effect of a fish stock reduction is the collapse of the Chokka Squid fishery in South Africa. SOLSTICE-WIO will use this as a case study to demonstrate the strengths of a holistic approach to human-ecosystem-fisheries research and the potential solutions this can offer. The squid fishery was the 4th most valuable fishery in South Africa, bringing foreign currency into one of the poorest provinces. It was directly employing 5000 fishermen with 30,000 dependents. The 2013 crash had a devastating effect on the Eastern Cape, yet the underlying reasons are unknown: local fishermen believe the collapse was caused by environmental change. Until the mechanisms behind the collapse are understood, there is little potential for aiding recovery or guiding adaptation. SOLSTICE-WIO will provide this urgently needed understanding to help inform the fishery and Government as to the fate of the local ecosystem, whether it will recover, and whether the crash could have been predicted or prevented.   How will SOLSTICE achieve this? The key to stability of living marine resources lies in an ecosystem approach to fisheries (EAF), which sees human-natural systems as a whole, integrated entity rather than separately considering individual target species. Simply put: you cannot manage something you don't understand, nor can you adapt to change through management improvements unless you can describe, measure and understand the changes. The core strength of SOLSTICE-WIO lies in its integral approach to food security, drawing on UK expertise in physical oceanography, marine ecology, autonomous observations, environmental economics and the human dimension,and WIO expertise in fisheries, the marine economy and regional policy development.  SOLSTICE will provide the region with the state-of-the-art technology to deliver cost-effective marine research and provide the information needed to achieve maximum potential from the region's living marine resources. In the UK marine robotics, ocean models and novel data products from satellite observations have developed rapidly in the last decade, and now underpin Blue Economies and Ocean Governance in Europe. These technologies are highly agile and ready to be applied in the developing world as cost-effective ways to maximise understanding and sustainable exploitation of living marine resources. Such "technology leapfrogging" can overcome the severe lack of research ships in the WIO and save decades of effort in developing predictive modelling systems from scratch. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.