Biofouling on recreational boats on swing moorings and in berths in the Auckland region

Abstract

Hull biofouling can indicate the likelihood of a recreational boat spreading nonindigenous species. The objective of this study was to determine if boats moored on swing moorings had higher levels of fouling than those in berths, thereby posing a higher biosecurity risk in the Auckland region. The research method involved a field study using waterline visual assessment and underwater video to assess the level of biofouling. Non-indigenous species were identified from snapshots of the underwater video. Surveys of boat owners, both online questionnaires and face-to-face interviews, were used to gather information on boat movements, maintenance patterns and attitudes toward marine biosecurity. Results indicated that boats on swing moorings (regardless of whether they were yachts or launches) had significantly higher levels of fouling than those in berths (p < 0.01) using both visual and video methods, with video proving a more accurate assessment method. The questionnaire identified that swing mooring owners maintained, cleaned and applied antifouling paint on their boats more often than questionnaire respondents with boats in berths. However, all swing mooring owners who answered the questionnaire cleaned and maintained their boat themselves and high priority (niche) fouling may have been missed. The dollar amount spent on maintaining and cleaning boats on swing moorings is significantly less than those in berths (p < 0.01). Owners of both mooring types had received information about the spread of marine non-indigenous species but speed and fuel economy were the prime motivators for regular boat cleaning, as opposed to biosecurity concerns. Travel history questions found that boats generally traveled approximately once a month and usually in the summer. They typically traveled less than 30 km from their home mooring location and the majority did not travel overseas. Swing moored boats (predominantly yachts) traveled significantly slower than those in berths (predominantly launches). Survey respondents typically moored in a recipient location for only 1-9 days. Boats on swing moorings and in berths have similar travel itineraries but because those on swing moorings have higher levels of biofouling and travel at slower speeds, this makes them an increased domestic biosecurity risk compared to boats moored in berths.