In August 2017, more than 160,000 Atlantic salmon escaped from a net-pen aquaculture facility in Washington into the Salish Sea. Although the farm was legally permitted to operate in the state, failure to properly maintain the facility led to equipment failure, thus resulting in the release of thousands of non-native fish into state waters. While many of the escaped salmon either died on their own or were eventually recovered through efforts of people in surrounding areas, the unprecedented nature of the disaster drew the nation’s attention to the challenges associated with culturing non-native aquatic species. Many of the most popular species cultivated on aquaculture farms throughout the United States are non-native to most, if not all states, including such staples as tilapia, Atlantic salmon, and Pacific oysters. As exemplified by the Washington escape, aquaculture can easily become a pathway for the introduction of non-native species to new environments. If the released animals flourish in their new environment, an invasive1 population can become established, thus imposing devastating effects on native ecosystems.
Land-based aquaculture facilities use ponds, recirculating systems, or flow. Pathways for non-native species in aquaculture through systems to grow their yield. Animals can escape from these facilities due to of a number of factors, such as: 1) a lack of suitable screening over pond outflow pipes; 2) pond overflow during flood events; and 3) the transportation and dropping of non-native animals into nearby water bodies by predatory birds. 4 Mariculture, in contrast, refers to aquaculture practiced in marine environments and in underwater habitats instead of on land. In mariculture facilities, escapes can occur because of similar, yet distinct, circumstances, such as: 1) poor facility maintenance; 2) strong storms and adverse weather events; and 3) the destruction of nets or cages by other marine life.
One well-known example of the impact aquaculture facility failures can have on native ecosystems involves Asian carp. These fish were originally imported into the southern United States from Southeast Asia to help aquaculture and wastewater treatment facilities keep their retention ponds clean. However, flooding events led to accidental releases of the fish into the Mississippi River system, where the fast-growing species now regularly out-competes native fish for food and space.
Preventing the influx of non-native, cultured species into new areas is a problem with many potential solutions, but no one “right” answer. The best methodologies vary from facility-to-facility depending on factors such as location, species, and the type of aquaculture being practiced. However, the following preventative strategies provide an important foundation for state management programs:
Species restrictions – Restricting the type of species authorized for culture helps states mitigate the risk that specific non-natives are introduced.
Permitting requirements – Permitting frameworks help states control the culture of non-natives at every stage, from import to harvest and eventual transport.
Location restrictions – Restricting where facilities culturing non-native species can operate helps diminish the likelihood that natural events, such as floods, can facilitate unintentional escapes.
Design requirements – Design standards add an extra layer of protection that can help prevent unintentional releases due to factors such as equipment failure or predation.
Biological restrictions – Restricting permitted species by factors such as gender and genetic modification provides a layer of redundancy that helps ensure non-native populations cannot become established in the event of an escape.
Financial requirements – Assuring that aquaculturists can contribute financially in the event of an escape—through tools such as bonds and liability insurance—adds to a state’s ability to prevent non-native populations from becoming invasive.
Reporting requirements – Establishing reporting frameworks helps ensure both facilities and state authorities can coordinate an effective, quick response effort in the event of an unintentional release.
The above text was excerpted from Nichols, A. 2018. Regulating invasive species in aquaculture: Common state approaches and best management practices. National Sea Grant Law Center. 12pp.