Science Centres: Aquatic Biodiversity and Biosecurity

NIWA divers Crispin Middleton and Matt Smith inspect a yacht hull in an Auckland marina. (Photo: Nicola Rush, NIWAL)

While this study focussed on yachts, yachts are not the only vessel types bringing non-native species into the country. The results reported here form part of a larger MAF Biosecurity New Zealand study to identify the types and quantity of marine organisms that are transported to New Zealand from overseas on the hulls of all major vessel types. Between August 2005 and January 2007, 182 international yachts were surveyed soon after their arrival at the four main ports of entry: Opua, Whangarei, Auckland, and Nelson.

Results suggest that a large proportion of recreational yachts arriving in New Zealand carry small quantities of fouling organisms on their hulls. Non-native species were common, particularly where fouling was heavy. Fouling was heaviest and non-native species most prevalent in niche areas – such as keels, propellers, and rudders – which were probably missed during hull cleaning.

An index of the levels of fouling made by surface observers generally corresponded well with the actual biomass and number of fouling species recorded by divers, although surface observers often missed very low levels of fouling. Until better predictive tools have been developed for hull fouling assemblages, we recommend that divers be used to identify yachts posing a biosecurity risk.

The study in numbers:

• 182 yachts surveyed, 149 (82%) had fouling
• 78% of fouled yachts carried less than 1 kg of fouling organisms
• 957 samples collected, amounting to 2373 species records
• 202 taxa identified, of which 111 were identified to species level
• 75 (68%) of the identified species were non-native, of which 45 were not known to be established in New Zealand.