Tolerance of the invasive tunicate Styela clava to air exposure

Abstract

Styela clava is a subtidal invasive marine species in Northern Europe, Atlantic Canada, Australia and New Zealand. It grows attached to solid substrata, including boat hulls, ropes, moorings, piers and aquaculture equipment, all of which can aid its spread to new locations. It interferes with feeding of mussels and oysters, and increases their harvesting costs. Being subtidal, it could be assumed that tunicates would rapidly die in air and thus exposure to air would be a practical method to prevent their spread on boats and equipment. This study tested their survival when exposed to air for up to (1) 120 h at a constant temperature of 10 °C, (2) shade ambient 15–27 °C, and (3) full sun ambient 15–29 °C. Humidity was consistently high (78–100%). The results indicated that survival was longer when the air temperature was cooler. Larger individuals of S. clava generally survived for longer out of seawater than smaller individuals. The results predict that two weeks of exposure to air for two weeks could be an effective management method to eradicate S. clava from marine equipment when the air temperature is 10 °C. However, drying time would be less under conditions of low humidity and under direct sunlight.

Keywords:

• pest control
• fouling
• aquaculture
• boat hulls
• alien species
• tunicate

Acknowledgements

The authors thank Jo Evans and Brian Dobson of Leigh Marine Laboratory for technical support, and Andrew Bell and Tom Hollings for helpful information.