Help us keep watch for the two dozen “least wanted” invaders! Familiarize yourself with these unwanted aliens, and help us to better protect the rich native coastal biodiversity of central California!

If you represent a coastal organization that would be interested in involving your members or staff in this program, contact Kerstin Wasson to receive a free shipment of booklets, flyers, and a CD providing background on aquatic invasions.

Download the Aquatic Invaders booklet (.pdf file, 811KB).

Keeping watch for “least wanted” invaders

The Elkhorn Slough National Estuarine Research Reserve, in partnership with the Elkhorn Slough Foundation and the Monterey Bay National Marine Sanctuary, and with funding from California Sea Grant, has established an early detection program for aquatic alien invaders. The goal of this program is to detect new invasions of problematic non-native aquatic organisms early enough to allow for successful eradication.

Background on aquatic invasions

“Alien,””non-indigenous,””non-native,” or “introduced” species are those moved far beyond their natural ranges by human activities. Aquatic species are transported between bioregions by activities such as commercial shipping and oyster culturing, and can spread within a region due to local boat traffic and dispersal of larvae on currents. Aquatic invasions have been extremely common in recent decades, and are continuing at a rapid pace. Estuaries are particularly highly invaded; those with big ports often have hundreds of non-native species established in them. Many non-native species may have relatively minor influences on the communities they invade. Some, however, have dramatic negative impacts. Our early detection program focuses on such species, whose negative effects have been demonstrated elsewhere. These non-native species may have impacts at a variety of scales. Invaders have been shown to cause local extinction of native competitors or prey organisms, alteration of community composition or food webs, change in physical habitat structure, and even alteration of energy or material flux through whole ecosystems.

Green Crab - Elkhorn Slough Invasive Species

This European green crab species is already established
in the slough. Help us keep out other aquatic invaders.

Biological invasions of marine habitats, and particularly estuaries, are occurring at an accelerating rate. The ecological threats posed by some alien species rival those of pollution or anthropogenic habitat destruction, and are among the greatest resource management challenges for estuarine ecosystems. Once widespread and abundant, aquatic invaders are extremely difficult, if not impossible to eradicate. However, if they are detected soon after initial establishment, removal efforts can be successful. Such management depends on early detection of new invasions within this window of opportunity.

What can be done about aquatic invasions? On the one hand, prevention of further invasions is critical. Public support for regulatory measures decreasing human transport of invasive propagules will help prevent invasions. On the other hand, control of existing invasions is sometimes possible. Once a non-native aquatic species has become abundant and widespread, it is difficult or impossible to control it. However, there is a window of opportunity soon after invasion when eradication efforts may be successful. In order to intervene during this early establishment phase, early detection of new invasions is essential.

Development of an early detection program

In order to accomplish such early detection during the window of opportunity for eradication, we have developed this new program. We began by assessing existing non-native species composition in the region to establish a baseline, and then chose “least wanted” invaders for the area. From a potential pool of hundreds of known aquatic invaders, we chose a subset of two dozen species that: 1) are not yet present in the Monterey Bay area, 2) have a high potential to be transported there (especially from nearby sources such as San Francisco Bay), 3) are relatively large and easy to identify, and 4) are likely to have a significant ecological impact if they invade.Each of the two dozen “least wanted” species is described in booklets we have prepared and published. We provide information on diagnostic features for identification, and information on habitat, native origin, invaded areas, and ecological concerns. The booklets also contain instructions on what to do if a putative invader is sighted: individuals are directed to note their exact location, collect a single voucher specimen, and immediately make an “urgent invasive alert” to us. We will then confirm the identification and inform the appropriate agencies (which vary by species and habitat). We will help to coordinate interagency efforts to plan the most appropriate response strategy, and will support rapid response efforts to contain or eradicate the new invasion, if appropriate. The target areas for this early detection program are Elkhorn Slough and Monterey Bay, central California, because the coordinators of this program are based there, because we have good baseline information for these areas and because there are many citizens active in aquatic habitats there. However, we welcome reports from as far south as Morro Bay to as far north as Moss Beach.

The success of this program depends on having as many pairs of eyes as possible on the lookout for new aliens. Toward this end, we are attempting to provide booklets to all citizens in the Monterey Bay area who frequent aquatic habitats and are likely to notice alien species. By holding a training workshop and providing free materials, we have involved about 50 regional coastal organizations (kayaking, fishing, diving, conservation groups; harbormasters; government agencies; aquaria; universities and research organizations) in this effort, resulting in broad dissemination of nearly 4000 booklets to their constituents. By involving the community in this effort to look for and report new invasions of “least wanted” species, we are increasing the likelihood of detecting new invasions in time to take action. Familiarize yourself with these unwanted aliens, and help us to better protect the rich native coastal biodiversity of central California!