A first quantitative assessment of seabed litter collection efficiency using bottom otter trawls and fishery...

Marine seabed litter threatens benthic ecosystems, yet the performance of conventional monitoring methods remains poorly quantified. This study evaluated the collection efficiency of single-vessel bottom otter trawl in Zhangbei Bay through repeated trawling surveys conducted in 2023 and 2024. Using two classical depletion models (DeLury and Patch), we estimated litter collection efficiency and density across different categories. Total litter collection efficiency ranged between 0.52 and 0.66 (DeLury) and 0.75 (Patch), with densities of 917-1164 items/km² (DeLury) and 474-497 items/km² (Patch). Plastic litter exhibited higher and more variable efficiency (DeLury: 0.53-0.75; Patch: 0.76-0.99) than non-plastics (DeLury: 0.43-0.61; Patch: 0.78-0.81). Numerical simulations confirmed the robustness of Patch model. By incorporating a Hit matrix to account for trawl overlap, it yielded more accurate estimates than DeLury model. Simulations indicated that high positional error and low overlap reduce accuracy, while moderate-to-high overlap improves Patch model performance. This work provides the first quantitative assessment of seabed litter collection efficiency by bottom otter trawls, offering a methodological basis for optimizing surveys and supporting evidence-based management of coastal ecosystems.