The Nature, Extent and Survivorship of Biofouling Organisms at Different Hull Locations on Various Vessel Types

The importance of vessel biofouling as a vector for the dispersal of non-indigenous marine species (NIMS) is only just beginning to receive international attention. At the time of commencing this study, there was a considerable lack of knowledge surrounding which vessels, hull locations, levels and types of biofouling pose the greatest biosecurity risk. Therefore, the aim of this study was to investigate the nature, extent and survivorship of biofouling organisms on various vessel types at different hull locations and offers a pragmatic risk assessment approach for managing this threat. The results of this thesis found that the recruitment, persistence, distribution, abundance and species composition of biofouling on vessel hulls is influenced by many factors including: 1) the presence/absence, age and type of anti-fouling coating; 2) voyage duration and route; and 3) port residency period. Therefore, higher levels of biofouling (species richness, percentage cover, and biomass), including NIMS are more likely to accumulate and persist on vessels (and in hull locations) that: 1) lack and/or possess old, ineffective, damaged, inappropriate or unsuitable anti-fouling coatings; 2) spend prolonged periods stationary in ports; 3) travel at slow speeds (i.e. <10 knots); 4) have short voyage durations; and 5) remain at similar latitudes. Prevention is clearly better than a cure, hence the correct application and maintenance of suitable anti-fouling coatings to the entire submerged hull surface of vessel hulls, including niche areas is the most cost-effective way of minimising the unwanted translocation of biofouling organisms and NIMS. However, the results of this thesis demonstrate that if biofouling organisms colonise and establish on a vessel's hull, voyage speed alone is not capable of providing a reliable secondary level of defence against the unwanted dispersal of NIMS. Clearly, the survivorship of biofouling organisms was highest amongst vessels that travelled at slow and medium speeds (e.g.