Abstract
The invasive colonial ascidian Didemnum vexillum (Kott, 2002) was initially discovered in the fall of 2013 near Parrsboro, Nova Scotia. A rapid response survey was conducted in April 2014 to confirm the presence of the species and to determine its distribution near the original detection site. Subsequent surveys between May and August 2014 examined the dredge contents collected during sea scallop stock assessment surveys on German Bank, northern Browns Bank, eastern Georges Bank and in the Bay of Fundy region. The presence of D. vexillum was confirmed at 22 of 30 stations sampled in four areas of the Minas Basin and Minas Channel region in the northern Bay of Fundy during the rapid response survey. The scallop surveys confirmed the presence of D. vexillum at 9 of 829 stations sampled in the Bay of Fundy region, including 7 in the Minas Basin, 1 off Digby Gut and another off the coast of Yarmouth. Due to the presence of a native species, D. albidum, in the region, a PCR assay was developed to distinguish D. vexillum from all other species in the region. Once the PCR assay was validated this assay was used to confirm all positive identifications in this study. Colonies overgrew rocks, bivalve shells and seaweeds or were retrieved as large dislodged fragments. They were in an overwintering state in April, but healthy, and observed to grow into dense mats in summer. In other regions of the world, D. vexillum has been reported to foul shellfish and aquaculture gear, smother benthic organisms such as the sea scallop (Placopecten magellanicus), and overgrow substrates, suggesting this new colonial invasive ascidian poses a potential threat to Eastern Canada aquaculture and commercial benthic fisheries.
Highlights
Biological invasions are increasing in frequency and continue to cause unwanted effects to ecological and economic systems (Simberloff et al 2013)
We suggest that regional control of biological invasions can be successful, and requires collective effort by all affected resource managers and stakeholders
We present the history of AIS management and policy development and describe the use of an “implementation plan” as a sciencebased, decision-support tool for on-the-ground aquatic invasive species control actions
Summary
Biological invasions are increasing in frequency and continue to cause unwanted effects to ecological and economic systems (Simberloff et al 2013). Despite the utility this regional AIS management plan provided, Tahoe Basin managers tasked with control or removal of AIS remained burdened with uncertainty about which taxa and locations to prioritize their control efforts. Through the recent development of a comprehensive AIS control strategy in Tahoe, including regional level programming and localized implementation plan, we provide the following recommendations for natural resource managers and invasion scientists who are faced with the creation of a sustainable AIS control program. We believe these recommendations are applicable to multiple aquatic ecosystem types with various management and stakeholder infrastructures. These recommendations should be relevant to those systems in which the lake, reservoir, or other waterbody is multi-use (e.g., drinking water supply, recreational, commercial), and where there are a diverse group of stakeholders ranging from water purveyors, local users, visitors, conservationists, and those with commercial or residential interests
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