Debris capture during in-water cleaning of ship biofouling

Ship biofouling interferes with vessel operations and spreads non-indigenous species. While in-water cleaning (IWC) with debris capture is increasingly promoted as a management strategy, key elements remain poorly defined, including which materials must be collected, an acceptable level of capture, and how capture can be quantified. Although the processing efficacy of collected debris can be assessed, because IWC occurs in an open, dynamic system, measurement of overall capture efficiency is not feasible. Thus, ambiguous ‘capture’ requirements risk inconsistent performance, unnecessary costs, and barriers to innovation. Instead, regulations should emphasize measurable outcomes (e.g., acceptable levels of change in water quality indicators) rather than mandating specific methods. This outcome-based approach would better ensure that IWC supports ship operational efficiency while minimizing biosecurity and environmental contamination risks.