Introduced Species

an orange and white sea slug with many cerata crawls over a red bryozoan — A red bryozoan (*Watersipora subtorquata*) is non-native in California waters and has spread beyond harbors into native ecosystems. Photo: Steve Lonhart/NOAA

Invasions by non-native aquatic species are increasingly common worldwide in coastal habitats. Estuaries, in particular, harbor large numbers of introduced species. For example, there are about 250 known invasive species in the San Francisco Bay and Delta. Within sanctuary waters, there are approximately 40 invasive species in Elkhorn Slough, and another small handful of species recently reported in nearshore coastal waters. Known reports of introduced species have been summarized for Monterey Bay National Marine Sanctuary. However, there has not been a systematic survey of nearshore coastal waters to evaluate the level of invasive species present.

Impacts of Invasive Species

Although the effects of introduced aquatic species on the habitats they colonize is often unknown, some have experienced negative influences. Impacts often include:

Decliningreasing abundance and even local extinction of native species
Alteration of habitat structure
Extensive economic costs due to biofouling

How Invasives Got Here

A common way that non native aquatic species are introduced is through transport in ship ballast tanks. Other mechanisms of introduction include:

Improper disposal of aquarium materials
Bait and seafood packing materials
Aquaculture operations
Research activities

brown algae underwater attached to seafloor — Asian kelp, or "wakame" (*Undaria pinnatifida*) is an invasive species of kelp from Japan that has colonized many harbors along the California coastline, including Monterey and San Francisco. In Monterey harbor, it can grow quite large from the bottom, due to low water motion and relatively clear water. Photo: Chad King/NOAA

How is the Sanctuary Involved?

Regulations

As a result of discussions between the California State Resources Agency and NOAA’s Office of National Marine Sanctuaries, NOAA amended regulations of Monterey Bay, Greater Farallones, Cordell Bank, and Channel Islands national marine sanctuaries to reflect a single, consistent prohibition against the introduction of non-indigenous species (plant and animal) into sanctuary waters. The federal prohibition applies to both state and federal waters within national marine sanctuaries.

Eradication

Eradication of introduced species is difficult and management practices focus largely on prevention of introductions. The sanctuary has conducted some limited research and education on this issue and occasionally reviewed and provided comments to other agencies on ways to prevent introductions. Monterey Bay National Marine Sanctuary also organizes events for divers to remove the invasive alga, Undaria pinnatifida, from Monterey Harbor.