Kathryn E. Dawson

Recreational fisheries in remote regions often operate under limited regulation and data availability, presenting challenges for sustainable management. Diego Garcia, located within the Chagos Marine Protected Area, hosts a unique recreational reef fishery embedded within a highly protected environment. We assessed the stock status of five key species— Lutjanus bohar , L. gibbus , L. monostigma , Caranx melampygus , and Variola louti —using the Length‐Based Spawning Potential Ratio (LB‐SPR) approach and length composition data collected through stereo‐video surveys. The average spawning potential ratio (SPR) across all species appears to be operating above 30%, a common threshold below which a stock can be considered overfished. The SPR of L. bohar and L. gibbus remained above 30% across all bootstrap iterations indicating confidence that these species are exploited at a sustainable level. L. monostigma , C. melampygus , and V. louti exhibited greater uncertainty in their estimated SPR, spanning all possible values with at least 50% of bootstrap iterations remaining above 30% SPR; for these species, caution should be applied until additional sampling can improve the resolution of these estimates. These findings suggest that the recreational fishery is operating within sustainable limits, likely due to access restrictions and diffuse fishing pressure across species. However, uncertainty in model outputs for data‐limited species underscores the need for continued biological sampling and catch monitoring.

In a time of ever‐increasing pressure on the coastal ocean and rising costs, the development of effective and efficient methods for assessing the health of marine ecosystems is becoming essential for continued conservation efforts. Taking advantage of technologies such as remotely operated vehicles (ROVs) may be a way of achieving this, but a quantitative check on the quality of ROV‐derived data is necessary. Here, using coralline algae reefs (maerl beds) as a model habitat, we compared 3D seabed reconstructions obtained from structure‐from‐motion photogrammetry surveys from diver‐held and ROV‐mounted camera systems. We found that both approaches achieved satisfactory alignment and mm‐scale resolution, allowing small‐scale features and individual organisms in the maerl bed to be resolved. The higher quality camera system available to divers resulted in generally lower modelling errors, but the spatial extent of surveys was highly restricted. In contrast, although associated with a slightly higher error, we show that much larger areas can be surveys by ROVs—we reconstructed 11,285 m² of seabed in just 400 min of ROV deployment time. Moving forward, we recommend that a hybrid survey approach is adopted: utilising ROV surveys for large‐scale monitoring and diver surveys for higher detail insights that are informative for areas with highly complex and fine‐scale morphologies (like coralline algae reefs). Here, even small changes in complexity can be indicative of habitat change, and associated species can be small in size so multiscale visual assessment is beneficial.