Difference between revisions of "Invasive Invertebrates of California's Central Coast Region"

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A organizational summary, by the ENVS 560/L Watershed Systems class at CSUMB.

This is a list of some of the well-known invasive invertebrate species of California's Central Coast. The intention of this page is to educate the reader on the species' identification, their harm to ecosystems, and how to report sightings. This list does not contain all invasive invertebrate species found in California's Central Coast. To see more on invasive species in California's Central Coast see Invasive Species of California's Central Coast

Aquatic Invertebrates

New Zealand Mudsnail (Potamopyrgus antipodarum)

New Zealand Mudsnails (NZMS) are extremely small snails capable of collapsing entire food webs. They are found in freshwater, but are able to survive in brackish water. NZMS are considered generalists and will eat the food that other benthic macroinvertebrates rely on for nutrients.[1] They are so generalistic that they will out-compete important species that serve as food for local fish (i.e., the larvae of mayflies, stoneflies, and caddisflies), all of which have specific feeding habits. Once these prey species are out-competed, fish will attempt to feed on NZMS, but they are incapable of being digested and simply pass through the gut of the fish without harm[1]. NZMS reproduce asexually, and can create one million clones over the course of one summer.[1] Unpublished research from California State University Monterey Bay (CSUMB) suggests that NZMS can move against currents of 74cm/s. [2]

Professors and students at CSUMB have found NZMS in the Carmel River and Garland Ranch. Their movement within the Carmel River cannot be stopped because of their small size and large populations, save for strategically draining areas of the Carmel River. It is possible to stop NZMS movement across rivers by cleaning gear thoroughly with all purpose cleaners (to kill the snails) and letting the gear dry for 72 hours[3] before it goes in the water again (to desiccate any snails that weren't killed). Dogs that go into any body of water in the California Central Coast should also be cleaned thoroughly and not allowed in water again for 72 hours to prevent the movement of NZMS across water bodies. Report the presence of NZMS to the California Department of Fish and Wildlife (CDFW) or the State Parks System immediately.

Asian Clam

The Asian Clam, found in most freshwater bodies in America, is one of the most common invasive species in America. [4] As of today it has been sighted in the Arroyo Grande Creek, the Salinas River, and the Pajaro river [5]. Asian Clams are a threat to the other organisms that occur in the water bodies they reside in because they will filter out all the plankton in the water in large groups. The lack of plankton not only reduces food for the planktivores in the water, but also encourages algal growth because of increased water clarity [4]. The algal growth promotes anoxic conditions, killing all life in the water besides the algae. Asian Clams are very dense in their growth, leading to clogging of waterways if their growth goes unchecked [6]. One of their most successful traits at being invasive is that when Asian Clams are in their infantile stage, they are nearly invisible to the naked eye and extremely easy to transport. Asian Clams lead to economic losses due to repairs of power plants and water ways. They also pose a large threat to the already endangered native clams of the areas it resides in. If Asian Clams are spotted, report them immediately to the CFDW.

Red Swamp Crayfish (Procambarus clarkii)

Red Swamp Crayfish (RSC) have been present in Monterey County freshwater since 1959[7]. RSC are a distinct dark red color and grow rapidly[8]. As juveniles, RSC are often mistaken for native crayfish, allowing them to grow into ecologically harmful adults without intervention. RSC's main impact on native crayfish is that they efficiently out-compete them because of their large size and populations[8]. Unlike their native counterparts, RSC are capable of surviving in dry climates and have been recorded traveling across dry land[8]. RSC are commonly caught by avid anglers and either used for bait or eaten. Report any sighting of a RSC to the CDFW or request permission with the land they are present on to catch and trade them with scientific research entities [9].

It is most likely that the infestation of the RSC in California has originated from aquaculture and aquarium hobbyists [10].

Terrestrial Invertebrates

Argentine Ant (Linepithema humile)

The Argentine Ant (AA) has been introduced across the country, and is common in the Central Coast because of the Mediterranean climate. There is extensive literature on this species of ant because of its prevalency [11]. Few ants, including the AA, create supercolonies :the interbreeding and co-operation of different nests of the same species[12]. Supercolonies aid in the ant's ability to dominate whatever habitat they are in by dramatically increasing its numbers [11]. AA pose no threat to humans, but they are considered both an agriculture and household pest. Most ants that invade homes are AA [13]. AA are one of many ant species that have a symbiotic relationship with pest insects such as aphids, thus the two pests work in conjunction with one another. [11] The success of the AA comes at the price of depleting the abundance of native ant species (i.e., Carpenter and Big-Headed ants). [11]

Ants serve as prey for many invertebrate predators, including other ants, but AA are so small that they are seldom sought after for food. Few species specialize in predating on the AA, including some spiders in the Zordiidae family (Zordiidae, an ant-mimic spider) but few to none occur in California. There is no current control method for AA except for the eradication from households using insecticides.

Myoporum Thrips (Klambothrips myopori)

Thrips are small, thin insects that can range from yellow to black, depending on their life stage. Myoporum thrips feed on plants in the genus, Myoporum; specifically M. laetum [14] and M. parvifolium [15]. These two plants are used in gardens and for soil stability, respectively [16]. Californians, including those in the Central Coast, use these plants because they are drought-resistant[14][15][16]. K. myopori is common in the Central Coast and some populations have been recorded from Marin to Santa Barbara counties[17]. The thrips cause galling in the plant tissue (mainly leaves) they infest, which can lead to severe undergrowth and death[17]. K. myopori, like most herbivorous insects, has wings and is capable of dispersing to new host plants, but they are mainly distributed as eggs when infested plants are distributed[17]. Management practices for keeping K. myopori numbers down are biologic controls, such as predatory mites and lacewings. No pesticide research has proven useful in reducing K. myopori numbers, but as more Myoporum plants are being introduced as weeds, K. myopori may be reclassified from "invasive" to "beneficial"[17]. Report any sightings of galling on Myoporum plants to the CDFW, but there will likely be no action taken because of the lack of resources to control K. myopori[17]. Most ecologists will be interested in having a large data set of this thrip's range.


False Widow, "False Brown Widow", "European Spider" (Steotada nobilis)

The False Widow (FW) is a species that is common in European countries. Medically, their venom is not harmful to humans, causing no more harm than a bee sting, but there is a slim chance some people may have an allergic reaction similar to anaphylactic shock or a high fever. There have been no records of this reaction in California currently[18]. FW are similar in color to the common Brown Widow, but can be identified by the house shape on their abdomen[18]. FW pose little to no threat to humans, but they do invade niches that other native spiders currently fill, but because spiders are so widespread as a whole, ecologists are not particularly concerned with ecological effects FW may have[18]. FW are believed to have been introduced in a Southern California county, and spread North. FW have been recorded in Monterey, Santa Cruz, and San Luis Obispo[18]. Arachnologists are interested in FW's range[18]. Submit any images of the FW to websites such as iNaturalist and BugGuide.


  1. 1.0 1.1 1.2 https://www.wildlife.ca.gov/conservation/invasives/species/nzmudsnail
  2. https://sites.google.com/a/ucsc.edu/symposium-for-undergraduate-research/past-symposia/2018/program-book
  3. https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev3_015233.pdf
  4. 4.0 4.1 https://en.wikipedia.org/wiki/Corbicula_fluminea#As_an_invasive_species
  5. https://nas.er.usgs.gov/viewer/omap.aspx?SpeciesID=92
  6. https://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=92
  7. https://nas.er.usgs.gov/queries/CollectionInfo.aspx?SpeciesID=217&State=CA&HUCNumber=18060000
  8. 8.0 8.1 8.2 https://en.wikipedia.org/wiki/Procambarus_clarkii
  9. http://www.seagrant.umn.edu/ais/redswampcrayfish
  10. https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=217
  11. 11.0 11.1 11.2 11.3 http://www.antwiki.org/wiki/Linepithema_humile
  12. http://www.antwiki.org/wiki/Supercolonies
  13. <https://cisr.ucr.edu/argentine_ant.html
  14. 14.0 14.1 https://en.wikipedia.org/wiki/Myoporum_laetum
  15. 15.0 15.1 https://en.wikipedia.org/wiki/Myoporum_parvifolium
  16. 16.0 16.1 http://ipm.ucanr.edu/PMG/PESTNOTES/pn74165.html
  17. 17.0 17.1 17.2 17.3 17.4 https://cisr.ucr.edu/myoporum_thrips.html
  18. 18.0 18.1 18.2 18.3 18.4 https://cisr.ucr.edu/european_spider.html


This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessarily reflect the opinion or policy of CSUMB, its staff, or students.