The distribution and abundance of invasive colonial tunicates were documented at twelve sites along a ~270-km latitudinal gradient in western Newfoundland (NL), Canada. A combination of 10×10 and 15×15 cm polyvinyl chloride (PVC) panels were deployed on fixed and/or floating docks at each site between June and November 2014. The presence and abundance of invasive colonial tunicates were documented in September and November. Similar to patterns observed in 2013 (Caines personal observation), Botryllus schlosseri was found at Sites 1, 2 and 5, while Botrylloides sp. was observed at Site 2. Monthly sampling of 15×15 cm PVC panels, eelgrass (Zostera marina), rockweed (Fucus sp.), and kelp (Saccharina latissima) was conducted between September and November at Sites 1, 2 and 5 to determine spatial and temporal variation in the abundance of invasive colonial tunicates on artificial and natural substrates. Mean colony cover of B. schlosseri was 14.1 and 19.5% for panels sampled from floating docks in September for Sites 2 and 5, respectively, while mean cover of Botrylloides sp. was 3.7% on panels sampled from the fixed dock at Site 2. Interestingly, the frequency of occurrence for B. schlosseri colonies on rockweed increased from 20% in September to 100% in October at Site 2, while it decreased from 100% in September to 80% in October at Site 5. The frequency of Botrylloides sp. peaked at 50% and 70% on rockweed and kelp, respectively, in October at Site 2. The frequency of B. schlosseri on kelp specimens at Site 1 peaked at 40% in October, while kelp specimens from Site 2 had a peak colony frequency of 100% in September. Overall, the abundance of B. schlosseri on artificial and natural substrates was substantially lower at Site 1, which may be related to cooler sea temperature and increased wave exposure at this site.

Click here to read more about this report