Recreational vessels as a vector for marine non-natives: developing biosecurity measures and managing risk through an in-water encapsulation system

Abstract

Increasing recognition of non-natives as a threat to biodiversity and the functioning of marine ecosystems has brought with it the challenge of seeking novel management solutions. Hull fouling of recreational vessels is an important non-native vector, particularly in coastal areas where it is responsible for both introduction and secondary spread. This study introduces an in-water boat encapsulation system designed to limit transfer of marine non-natives, developed in response to the introduction of the ascidian Didemnum vexillum in Wales, UK. Here we describe the “decontamination berth”, examine the chemical concentrations required to eliminate D. vexillum and review biosecurity approaches for recreational vessels. Laboratory tests of treatment chemicals showed that acetic acid and sodium hypochlorite were equally effective in reducing D. vexillum growth following exposures of <30 min. In situ trials confirmed the ability of both chemicals to decrease D. vexillum colonies growing on marina pontoons. Efficiency trials found the mean loss of chemical from the berth during each pumping cycle would be equivalent to 417 g of active chlorine. Our preliminary testing indicates that devices such as the decontamination berth may be usefully employed to contain the spread of existing marine non-native species and to prevent future introductions at marine transportation hubs.