Assessment and Management of Risks from Biofouling

Vessel biofouling is a well recognised modern-day pathway for the transfer of nonindigenous species (NIS). However despite awareness of these risks, marine incursions as a result of vessel biofouling continue to occur at a growing rate. The objective of this thesis is to provide underpinning knowledge to improve pre- and post-border management strategies for vessel biofouling. Chapter 2 provides a baseline assessment of the biofouling extent and assemblage composition on slow-moving vessels arriving at New Zealand's border. Slow-movers were targeted because their operational profile is widely considered to favour the accumulation of extensive biofouling communities (i.e., potentially high risk vectors of NIS). Interestingly, this research revealed low fouling levels and a low incidence of NIS. Highest levels of fouling were observed in areas where antifouling paint condition was poor or absent (e.g., dry-docking support strips and niche areas), which is consistent with recent studies of biofouling on other vessel types. Despite these findings, there have been several documented examples where heavily fouled slow movers have had high risk NIS on them. As such, risk profiling of slow-moving vessels is recommended. This should be based on operational characteristics such as maintenance history, exposure to regions where pest species are known to be present and intended vessel movements in the recipient region, and should ideally be undertaken on a case-by-case basis prior to arrival from international or distant source-regions. There are limited biofouling risk mitigation options available upon the discovery of NIS at the border, particularly for large vessels (e.g., barges) or towed structures (e.g., oil rigs) where removal to land is often not feasible and in-water defouling may be the only option available. Chapter 3 provides a conceptual framework that identifies biosecurity benefits and risks posed by in-water defouling. Among the latter are the survivorship of de