Archive of Spotlight Feature Articles

Guarding Water Gardens Against Invasive Species

By Marie Zhuikov
Minnesota Sea Grant

This pond was drained in part to protect a nearby trout stream from AIS.

The University of Minnesota Duluth recently had to drain a pond to protect a nearby trout stream from potential impacts of aquarium fish released in the pond and to conduct maintenance activities. Sea Grant is working with dormitory students to inform them about alternatives to dumping their unwanted fish in the pond as part of a national campaign.

Water gardening is increasing in popularity as a hobby. The peaceful sound of trickling water and the serene gliding of goldfish spread joy and peace to water gardeners. However, if water gardeners are not careful, their gardens could also spread invasive plants and animals into the local environment.

The University of Minnesota Sea Grant Program is leading several projects that investigate release pathways posed by water gardening and methods to educate consumers about how to avoid accidentally releasing aquarium and aquatic invasive species (AIS). These species can include fish, plants, crayfish, snails, and turtles.

Sales in the water garden industry have reached approximately $1 billion per year. Leading the growth curve are mail-order sales of aquatic plants. To assess the potential for these sales to act as a vector of AIS release, Sea Grant and the Minnesota Department of Natural Resources supported a study by University of Minnesota researchers who looked at aquatic plant retailers in three categories: water garden specialists, aquarium specialists, and general garden businesses. The study, by Kristine Maki and Sue Galatowitsch with the Department of Horticultural Science, examined the issues of intentional sale of illegal aquatic plants, and unintentional shipment of such plants and other organisms.

Aquatic plants like those in this rock-strewn water garden can bring in unwanted species.

Sales of mail-order plants for water gardens are a possible pathway for the spread of invasive plants.

They placed 40 orders for plants typically used by water gardeners with vendors across the U.S. To determine whether current regulations are effective in preventing the sale of aquatic nuisance plants, they submitted orders for those classified as noxious weeds under federal law and as prohibited exotic species under Minnesota law.

When the plants arrived, they examined them for the unintentional inclusion of other plants and organisms. The 40 orders represented a total of 123 taxa and 681 individual plants, although many additional organisms were received. In fact, 93 percent of orders contained additional plants, animals, fungi, or algae.

Ten percent of the orders included other plants classified as AIS: hydrilla (Hydrilla verticillata), giant salvinia (Salvinia molesta), purple loosestrife (Lythrum salicaria) and curly-leaf pondweed (Potamogeton crispus).

"These four plants are causing problems all around the country and are some of the most destructive aquatic nuisance plants in the world," said Maki.

As for the illegal plant orders, researchers found that 13 of the 14 orders they placed were filled, reflecting a violation rate of 93 percent.

"These findings clearly indicate the need to raise awareness among riparian land owners, water gardeners, resource managers, and policymakers regarding the risks associated with the sale and use of aquatic plants," urged Maki.

This net-full of goldfish were found in a campus pond.

Goldfish found in Rock Pond on the University of Minnesota Duluth Campus. Goldfish can cause many undesirable changes to the environment when released from aquariums.

Building upon this research, Minnesota Sea Grant staff are spearheading two outreach projects that will serve different audiences and associated risk pathways. Barb Liukkonen is working with the water garden industry in Minnesota so that they don't unintentionally sell AIS plants. This summer, she is testing various marketing ideas with nurseries and garden centers and working on fact sheets they can give to customers. For example, Liukkonen is providing water garden businesses with plant markers that warn gardeners they are buying a non-native plant that could spread if used inappropriately.

On the fish front, Doug Jensen is leading a national educational project that seeks to prevent the release of aquarium fish and plants. The project will employ social marketing techniques with the intent of fostering behavioral change in aquarium owners. The project involves high-powered partners, including the Pet Industry Joint Advisory Council, the U.S. Fish and Wildlife Service, and aquarium retailers such as PetCo, PetSmart, Wal-Mart, and many private outlets. The partners represent over 90 percent of the annual U.S. aquarium fish suppliers.

Minnesota Sea Grant works with people and communities to identify needs, fund research, and translate results to help maintain and enhance the enviroment and economies along Lake Superior and Minnesots's inland waters. Research priorities include sustainable coastal communities, impacts and management of nonindigenous species, Lake Superior ecological management, economic viability, and environmental safety in biotechnology and aquaculture. Minnesota Sea Grant is associated with the University Minnesota at Duluth, MN.

[7/26/04]

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