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Higher water temperature is usually accompanied by the factors of more sunlight, advantageous 
nutrients and other aspects linked to species’ richness (Morrisey et al. 2013). 
In addition to water salinity and temperature, depth of the water and distance to shore is 
affecting the risk of biofouling growth on ship hulls and niches. The deeper the water, the more 
species typically disperse (Yebra et al. 2004). 
To keep the level of biofouling as low as possible, the ship-based factors of age and condition 
of coating, idle time and utilisation rate of the ship the ship’s speed and the maintenance 
history or surface treatment at last dry docking or during the last in-water cleaning 
procedure as well as the hull roughness should be considered (BIMCO 2021). 
There are different types of coatings (going further into detail in chapter 2) that all have different 
ifetime spans. There is no threshold yet on when a specific type of coating’s age is considered 
new”, “medium” or “old”, but it is clear that once expired, IWC is not recommended (Department 
of the Environment and MPI 2015). In hull areas where the coating is damaged, protection against 
biofouling growth may no longer be given (MEPC 2011). This is why also the cleaning method 
applied is of high importance. It should always be in accordance with the advice given by the 
coating manufacturer to avoid damage of the AFS or decrease of a coating’s service life. 
Prolonged idie periods and lower utilisation rates increase the biofouling risk of hull and niche 
areas. Some types of coatings are depended on a waterflow over the hull surface (polishing or 
water friction) to maintain the coating’s surface condition and prevent biofouling sufficiently 
(BIMCO 2021). 
Anti-fouling coatings should be individually selected to meet a ship’s operation profile. Preferably, 
coating manufacturers declare certain specifications on an accurate speed, which, once met, 
prevent biofouling growth. Niche areas may be exposed to different water flows than the ship’s 
hull and should therefore be considered separately (IMO Biofouling Guidelines). 
Specifications for AFS with regard to the optimal operating conditions needed to achieve the 
highest antifouling effectivity are therefore essential. The same counts for information on cleaning 
methods, which may be applied to keep the AFS in a proper condition and minimize the input of 
Diocides and particles during IWC (for more detail see section 2). Therefore, provision of adequate 
detailed information by AFS manufacturers are urgently needed. 
The different levels of biosecurity risk (release of non-indigenous species) by in-water cleaning 
(IWC) are based on the type of fouling (micro/macro or soft/hard; see section 1.1), the percentage 
af coverage of fouling on the hull and whether the trading ports of a ships voyage (see chapter 
1.2) contain the same species or not (MEPC 2011). The level of risk can be divided in low, medium 
and high. This categorization bases on our literature research and discussions within the 
stakeholder group. In our opinion, a smaller-sized division is hardly assessable and the benefit is 
rather low. Furthermore, a fast and certain identification of AIS within the biofouling community is 
not possible.