A new method to describe seagrass habitat sampled during fisheries-independent monitoring

We explain a new method of quantifying seagrass cover and describing seagrass species composition during fisheries-independent monitoring. This new method is similar to a point-intercept method developed to estimate arboreal crown cover, but it uses an aquascope designed for shallow water. The method does not require a diver. Seagrass cover (cover ratio) distinguished different percentage cover categories in 0.25-m² seagrass plots. Estimates of species composition determined by using the new method were most similar to those obtained by using estimates of aboveground biomass. Within each 141-m² area sampled with a 21.3-m fish seine, we accurately estimated seagrass cover ratio and species composition with six observations that typically required less than 6 total minutes. Within such areas, 42 trials were conducted to evaluate the precision with which different observers estimated seagrass cover ratio and species composition. In 98% of the trials, observers attained statistically similar estimates of cover ratio, and in 100% of the trials in areas with multiple seagrass species, observers attained statistically similar estimates of species composition. We conclude that the new method provided efficient and reasonably accurate means to quantify seagrass cover and species composition.