Belt transects (BLT) are a non-invasive underwater-survey method that enumerates the diverse components of diurnally active shallow-water reef fish assemblages. At each Rapid Ecological Assessment survey site, BLT fish surveys are conducted along 3 consecutively-placed, 25m transect lines to quantify relatively small-bodied and abundant fishes. A pair of scuba diver-observers conducts parallel swims along the transect lines, recording size-class specific counts of all fishes encountered, to species-level where possible, within visually estimated but defined belt widths: 4 m wide for fishes > 20 cm TL (100 m2 area) on the initial swim-out, and 2 m wide for fishes < 20 cm TL (50 m2 area) on the subsequent swim back. Transect lines are typically set at depths of 10-15 m. Reef ledges and holes are visually searched. Stations are completed on all sides of the island/atoll, weather and sea conditions permitting. Raw survey data includes species level abundance estimates.