Seafloor litter has become a growing environmental concern to marine ecosystems and coastal economies. To better understand the environmental behavior of seafloor litter, it is important to characterize its spatial patchiness at local scales. However, the local-scale patch size of seafloor litter has rarely been quantified. Thus, a patch size spectrum method was developed to estimate local-scale patch size from bottom-trawling survey data. The method utilized geostatistical simulations to relate observed area-normalized catches with simulated area-normalized catches under varying potential patch sizes. Cross-validation demonstrated predictive accuracy with a typical relative error of ∼20% and 31% in worst-performing cases. Application to experimental bottom-tow data collected from Tokyo Bay showed the local-scale patch size of 134 m, substantially smaller than the trawling transect length (∼2.8 km). Moreover, the local-scale patch size remained temporally stable between two survey periods. This method provides a novel framework for quantifying local-scale heterogeneity in seafloor litter distribution, and it is broadly applicable to other forms of integrated line transect sampling, such as benthic organism surveys and environmental monitoring where within-transect spatial resolution is limited.
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