Resource Management Issues: Invasive Species

Overview of the issue
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 invasive species have been summarized for the Sanctuary region. However, there has not been a systematic survey of nearshore coastal waters to evaluate the level of invasive species present.

Although the effects of introduced aquatic species on habitats they colonize is often unknown, some clearly have had serious negative influences. Impacts often include decreasing abundance and even local extinction of native species, alteration of habitat structure, and extensive economic costs due to biofouling. Probably the most important mechanism for the introduction of aquatic species is transport in ship ballast tanks, though other mechanisms such as introduction through improper disposal of aquarium materials, bait and seafood packing materials, aquaculture operations, and research activities can contribute to the issue.

How is the Sanctuary involved?
Eradication of introduced species is difficult and often impossible, 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. MBNMS has also organized an initial attempt to eradicate the invasive alga Undaria pinnatifida from Monterey Harbor.