Hull husbandry practices and biofouling management of vessels operating in California

Commercial shipping has been recognized as the primary vector for the introduction of nonindigenous species (NIS) into coastal environments in California, North America, and across the globe. These shipping-mediated introductions occur primarily through two mechanisms, ballast water and vessel biofouling (i.e. the attachment or association of organisms to a vessel´s wetted surfaces). In California, vessel biofouling is believed to be responsible for up to 60% of the 257 nonindigenous species currently established in California´s coastal waters. Most vessel operators manage the biofouling on their hulls because of the impact biofouling has on drag, fuel consumption, and operating costs. However, the biofouling associated with a vessel´s remaining underwater surfaces, including the “niche areas” that are more susceptible to biofouling because of variable hydrodynamic flow or inadequate antifouling protection (e.g. bilge keels and sea chests), are often undermanaged or unmanaged and may pose a greater risk of species introduction. Biofouling management options vary depending on factors such as vessel type and speed. Because of this, there are many varied biofouling management strategies implemented across the global fleet of vessels. The patterns of these management schemes, along with patterns of voyage characteristics that influence biofouling accumulation, are important tools in assessing risk of species introduction. The California State Lands Commission´s Marine Invasive Species Program has been collecting, on an annual basis, detailed information on these management strategies and voyage characteristics from every vessel operating in California since 2008. These data are currently being used to assess the risk of biofouling-mediated species introductions to California and to inform the development of mandatory management requirements to reduce NIS introduction risk to California.