A preliminary investigation of biosecurity risks associated with biofouling on merchant vessels in New Zealand

Biofouling on international vessels is an important mechanism for the inadvertent transfer of non-indigenous marine species around the globe. This paper describes the nature and extent of biofouling on 30 merchant vessels (ranging from 1400 to 32 000 gross registered tonnes) based on analysis of hull inspection video footage collected by two New Zealand commercial diving companies. A new method for measuring biofouling communities is applied, which aims to incorporate the potential for various hull locations to house non-indigenous marine species. Our analysis revealed that out-of-service vessels and vessels plying trans-Tasman routes possessed greater levels of biofouling than more active vessels. Dry-docking support strips and sea-chest gratings generally had the highest levels of biofouling and may pose relatively high biosecurity risks. Any future biosecurity surveillance should target these hull locations for non-indigenous species.