Monitoring Fishmeal & Fish Oil production near Gunjur (The Gambia) with 3m PlanetScope Imagery: An Exploration

Artisanal fishers in Senegal and The Gambia are increasingly caught between offshore industrial fishing and a fast-growing shore-based fish meal/fish oil (FMFO) industry. While the impact of the former has been the subject of numerous studies that have tried to detect and quantify the scale of fish stock depletion it is responsible for, the latter has so far received far less attention. Even if the disastrous effects of FMFO production in The Gambia – and more generally along the West African coast – have been amply denounced by local populations as well as international organizations and journalists. In the absence of any official data monitoring FMFO production in The Gambia this study sets out to develop a model for detecting and documenting the activities and locations of artisanal fishing fleets, upon which the FMFO factories depend. This preliminary study focuses on in the Gambian coastal village of Gunjur, where the Golden Lead FMFO factory opened in 2016. The study employs remote sensing techniques to detect the presence of artisanal fishing vessels gathering to land their catch in the Bay of Gunjur during the 6 months of FMFO factories activity, between November and June. This framework allows for the study of changes in the activities and numbers of artisanal fishing brought about by the factory’s operations. Whilst providing insights into practices of temporary migration between Senegal and The Gambia driven by FMFO production. We present an open, reproducible workflow that applies simple spectral indices to fourteen PlanetScope scenes (2018–2024, 3 m spatial resolution) to detect small wooden and fiberglass boats operating in Gunjur Bay. A scene-specific Normalised Difference Water Index (NDWI) threshold, morphological cleaning and 4 connected component analysis isolate vessel footprints. Early counts illustrate the potential for community-led oversight while underscoring the caution required when drawing conclusions from single and isolated snapshots. This methodology lays the ground work for further in-depth studies with increased access to satellite imagery, providing deeper insights changes in artisanal fishing practices following the emergence of West Africa as a crucial FMFO global exporter. Conversely, it must be noted that the number of boats provides only an indirect—and imperfect—proxy for estimating the volume of fish stock consumed by factories, as vessel presence alone does not reflect catch size, fishing effort, or ultimate usage.