Invasive tunicates and shellfish aquaculture: Assessing impacts and testing solutions



Over the past 50 years, a number of tunicate species have spread across much of the globe, posing a threat to natural ecosystems and becoming a growing concern in areas of expanding shellfish aquaculture. Tunicate infestation is currently causing significant challenges and expenses to the mussel farming industry on the east coast of Canada. While invasive tunicates have not yet proliferated along Canada's west coast to the same extent, there are at least four species in British Columbia whose adverse environmental and/or economic effects have been documented globally, and these species are known to exist at a variety of shellfish aquaculture sites and marinas around Vancouver Island. Thus, proactive solutions are needed to control the spread of these invasive tunicates to minimize potential adverse economic and environmental effects. It has generally been agreed that widespread eradication of invasive tunicates is unlikely to be feasible, but mitigation of adverse effects at smaller scales could be achieved through local control of pest density. As yet, no method has arisen as the obvious choice for controlling tunicate fouling. Several approaches have been evaluated, including air drying, water blasting (pressure washing), using fresh and hot water baths, and various biocidal agents. The challenge is to develop a methodology that is effective against target pest species, but is environmentally friendly, labour-saving, and low-cost. Also, tunicate fouling control methods should not cause significant adverse effects on the cultivated species. Despite global invasion patterns of non-native tunicates, little is known on the effects of tunicate fouling on the condition of cultured bivalves. It is essential that these potential effects be documented and quantified so that industry is aware of the impacts that these species may be having on shellfish growth and survival and, ultimately, on the economic bottom line of the business.

Program Name

Aquaculture Collaborative Research and Development Program (ACRDP)


2009 - 2010


Pacific: Vancouver Island West Coast

Principal Investigator(s)

Chris Pearce