Research ProjectRecreational vessels transport marine organisms

Quantifying the transport of non-native species by recreational vessels

  • Recreational vessels in a marina

    Recreational vessels can transport nonnative species if their hulls are not cleaned prior to leaving their home port.

  • divers survey the hull of a recreational vessel

    Divers conducting a survey of the hull of a recreational boat in Alaska. 

Affiliated Labs

Project Goal

To understand the patterns & processes of non-native species transport by recreational vessels, including factors such as seasonal boating trends, the influence of hull husbandry, antifouling paint effectiveness, and the impacts of the organisms themselves.


Recreational vessels are an important vector for the transport of marine non-native species. This occurs primarily because of biofouling accumulation on boat hulls and submerged surfaces, which is moved from harbor to harbor. Evidence suggests there is a strong link in non-native species spread between bays with large commercial ports and smaller bays without commercial ports.

Using in-water surveys and boater survey data, we identify biofouling organisms on boats and quantify their abundance to determine what species are being transported among bays in the United States. We also collect information on the history and husbandry of each vessel surveyed, including previous voyages, boater maintenance schedules, and the age and type of antifouling coating (paint) on vessels. This information is paired with data from published literature on the location, identity, and timing of species introductions. We also use historic vessel traffic analyses to understand how changes in recreational boating patterns (temporal and spatial) contribute to the spread of introduced species.  

These data show that recreational boaters may be the most important link between large bays, such as San Francisco Bay, and smaller bays in the surrounding area. The spread of nonnative species can magnify their impact and make it extremely difficult, if not impossible, to control or prevent any damage they cause. Maintaining a clean hull reduces fuel costs and is an important contribution individual boat owners can make to prevent the spread of nonnative species. So please maintain a clean boat, especially before traveling to a different harbor!

Feature Stories

North to Alaska: the Spread of Marine Invaders into the New Frontier. By Monaca Noble and Ian Davidson. March 2014

From Big Ships to Small Boats – the Secondary Spread of Introduced Species. By Monaca Noble, July 2014

Boaters Beware: Hitchhikers May Be Slowing You Down. By Ian Davidson, October 2012


Zabin CJ, Ashton GV, Brown CW, Davidson IC, Sytsma MD, Ruiz GM (2014) Small boats provide connectivity for nonindigenous marine species between a highly invaded international port and nearby coastal harbors. Management of Biological Invasions 5:97-112

Ashton GV, Davidson ID, Ruiz GM (2013) Transient small boats as a long-distance coastal vector for dispersal of biofouling organisms. Estuaries and Coasts 37:1572-1581

Williams S, Davidson IC, Pasari J, Ashton GV, Carlton JT, Crafton RE, Fontana RE, Grosholz ED, Miller AW, Ruiz GM, Zabin CJ (2013) Managing multiple vectors for marine invasions in an increasingly connected world. Bioscience 63:952-966

Davidson I, Zabin C, Chang A, Sytsma M, Ruiz G (2008) Characterizing the risk of species transfers on recreational boats in marine systems via hull fouling: A pilot study. Report submitted to the U.S> Fish & Wildlife Service.

Ashton GV, Boos K, Shucksmith R & Cook EJ (2006) Risk assessment of hull fouling as a vector for marine non-native species in Scotland Aquatic Invasions 1 (4) 214-218