The aquarium trade: A potential risk for nonnative plant introductions in Connecticut, USA

Abstract The aquarium trade has been shown to be a source for introductions of nonnative aquatic macrophyte species. Improvements are needed in identification, labeling, and retailer awareness of banned aquatic plants. In the state of Connecticut, United States, 20 nonnative macrophytes are banned from sale by state statute. At least 13 of these species are already established in the state's lakes, while the remainder are either present in near-shore wetlands or absent but thought to be capable of naturalizing. We documented the sale of banned plants in the Connecticut aquarium trade by visiting 23 retailers in 2008 and 47 retailers in 2010. Plants that resembled Connecticut's banned species were purchased and identified using standard morphological techniques. In 2010, we also employed DNA sequencing to aid in plant identification. We found that nearly 30% of stores sold banned aquatic plants including Cabomba caroliniana, Egeria densa, Myriophyllum aquaticum, and Myriophyllum heterophyllum. Cabomba caroliniana represented more than half of the banned species being sold; it was found in 17% of the stores in 2008 and 19% of the stores in 2010. Egeria densa was mislabeled 50% of the time as Egeria najas or Anacharis najas; it was sold in 11% of the stores in 2008 and 17% of the stores in 2010. In 2010, Myriophyllum specimens from 6 stores were unidentifiable using morphological characteristics. Using these techniques, one of the specimens was identified as Myriophyllum heterophyllum. Of the 29 chain stores surveyed, 7% sold banned species compared to 56% of the 27 independent stores.