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Harmful Non-Native Species: Issues for CongressVII
April 8, 1999
Honeybee Mites, Varroa jacobsoni and Acarapis woodi. The honeybee, itself a non-native species, has been threatened not only by its Africanized relative (see above), but also by two invading bee parasites. These mites (not insects, but eight-legged relatives of spiders) are the tracheal mite (A. woodi) and the varroa mite (V. jacobsoni) from Europe and Asia, respectively. Tracheal mites clog the air passages of adult honeybees, eventually suffocating them. Varroa mites suck blood from adult and juvenile honeybees. Adults can be weakened to the point of death, and juveniles emerge deformed from their cells. Moderate infestations reduce pollination services and honey production, and eventually kill colonies. Costs of keeping bees escalate, thereby driving up production costs (for crops valued at about $10 billion) and food prices. 53 Hobby beekeepers are virtually eliminated, as are wild populations of honeybees. The spread of these two kinds of mites may be playing a role in slowing the spread of Africanized bees farther from the Mexican border, since they too are susceptible to these mites. Populations of native bees (mostly solitary species such as carpenter bees, sweat bees, leafcutter bees, and others, plus some social species such as bumble bees) are increasing with the increasing availability of pollen.
Commercial orchardists have relied on movable commercial beehives, to have their crop and eat it too: while bees are present and working the crop, no pesticides are sprayed, but when pollination is finished, commercial hives are easily removed, and crops can be sprayed to protect them from insect pests, blights, etc. Consequently, while the home gardener may be able to rely on increasing populations of native bees to take up the slack if wild honeybee colonies are declining, this option is more difficult for commercial growers. USDA researchers are seeking to control these pests in a number of ways: resistant strains of honeybees from areas where these parasites originated, changes in hive management, use of special foods to create greasy bees that are unattractive to mites, and chemical methods. Congressional issues have included primarily funding for research on control methods. For more information about varroa mites and tracheal mites, see: http://sun.ars-grin.gov/ars/Beltsville/barc/psi/brl/mite-vj.htm , and http://sun.ars-grin.gov/ars/Beltsville/barc/psi/brl/mite-aw.htm, respectively.
European Green Crab, Carcinus maenas. This species was introduced to the U.S. Atlantic coast from Europe's North and Baltic Seas over 150 years ago. Around 1989, this very aggressive crab was introduced into San Francisco Bay where it feeds on bivalve mollusks, and competes with native shore crabs. The European green crab also has a reputation for consuming large numbers of juvenile clams and oysters. On the Pacific coast, it is extending its range northwards mature adults have been caught in Coos Bay, Oregon and Willapa Bay, Washington. The annual estimated economic damage to shellfish production of the European green crab is about $44 million. 54 For more information, see: http://www.pac.dfo-mpo.gc.ca/OPS/fm/crab/GREENCR.HTML
Chinese Mitten Crab, Eriocheir sinensis. This native of mainland China and coastal areas along the Yellow Sea was first collected in South San Francisco Bay by a shrimper during the winter of 1993. Although mitten crabs had previously been found elsewhere in the United States, San Francisco Bay was the first place where this crab could feasibly reproduce and increase its numbers. This crab develops and lives 90% of its life cycle in freshwater and then travels to saltwater to reproduce and die. Although sometimes carnivorous, this crab eats mainly vegetation. Large numbers of burrows excavated by these crabs are causing problems with bank erosion and levee damage in the Sacramento River delta. In the summer of 1998, as many as 30,000 adult mitten crabs migrating downstream clogged the fish filtering and trash screens at the Tracy (CA) irrigation pumps every day. For more information, see: http://users.vnet.net/lizzy/mitten.htm and http://www.ansc.purdue.edu/sgnis/publicat/96Halat.htm.
Rusty Crayfish, Orconectes rusticus. This native to streams in the Ohio, Kentucky, and Tennessee region has been spread widely by anglers who use them as bait. Rusty crayfish are prolific and can severely reduce lake and stream vegetation, depriving native fish and their prey of cover and food, and reducing food for fish and waterfowl used to dining on smaller native crayfish. The decline of native crayfish species could spell trouble for an entire aquatic ecosystem, since they are a favorite meal of bass, sunfish, and other predators and thus their decline threatens healthy sport fisheries. For more information, see: http://www.great-lakes.net/envt/exotic/rusty.html.
Spiny Water Flea, Bythotrephes cederstroemi. This native of Great Britain and northern Europe (east to the Caspian Sea) was first found in Lake Huron in 1984, probably imported in the ballast water of a transoceanic freighter. Currently, the animal can be found throughout the Great Lakes and in some inland lakes where it competes with young perch and other small fish for food. This species is easily spread when eggs and adults are transported in bilge water, bait buckets, and livewells. Also, fishing lines and downriggers can become coated with both eggs and adults. For more information, see: http://www.great-lakes.net/envt/exotic/spinyfle.html.
Zebra Mussel, Dreissena polymorpha. In the late-1980s, the zebra mussel was discovered in Lake St. Clair, between Lake Huron and Lake Erie, having arrived from eastern Europe via ballast water discharge from European freighters. This species spread rapidly to 20 states and as far as the mouth of the Mississippi River. U.S. expenditures to control zebra mussels and clean water intake pipes, water filtration equipment, and electric generating plants and other damages are estimated at $3.1 billion over 10 years. 55 For more information, see CRS Report 90-116 ENR, The European Zebra Mussel, Dreissena polymorpha, as well as http://www.nfrcg.gov/zebra.mussel/.
Brown Mussel, Perna perna. A native of Brazil, Venezuela, and South Africa, this species was introduced into the coastal waters of Texas in 1989, where it has spread from the mouth of the Colorado River 56 to Veracruz, Mexico. This species likely arrived in ballast water of a vessel from Latin America. The brown mussel is a biofouler (i.e., it attaches to exposed solid surfaces) and therefore likely to clog water and power plant intakes, similar to the zebra mussel. However, only limited damage has been reported thus far along the Gulf coast. For more information, see http://texas-sea-grant.tamu.edu/tunnell.html or http://www.mdsg.umd.edu/seagrantmediacenter/news/txmussels.html.
Asian Clam, Corbicula fluminea. This clam has a huge natural range from temperate to tropical southern Asia west to the east coast of Africa, plus the eastern Mediterranean, plus southeast Asian islands south into central and eastern Australia. This species was introduced into the United States in 1938 as a food item used by Chinese immigrants. Since its first collection along the banks of the Columbia River near Knappton (WA), it spread into major waterways of 38 states and the District of Columbia by a combination of bait bucket introductions, accidental introductions associated with imported aquaculture species, and intentional introductions by people who buy them as food. This species' most prominent effect has been biofouling, especially of complex power plant and industrial water systems, but also of irrigation canals, pipes, and drinking water supplies. It alters the floors of streams and lakes, thereby damaging habitat for a number of species, and competes with native species for limited resources. Estimated annual damage is about $1 billion. 57 For more information, see: http://nas.er.usgs.gov/mollusks/docs/co_flumi.html.
New Zealand Mud Snail, Polamopyrgus antipodarum. A native of New Zealand, but long established in Australia and Europe, this species was discovered in North America in 1987 in Idaho's Snake River. Between Shoshone Falls and the C.J. Strike Dam, population levels may exceed 100,000 snails per square meter. This species was discovered in Lake Ontario in 1991. Ballast water transfer is the suspected source of this species. However, birds and sport anglers may also be spreading this pest to additional drainages Although no effects on native species have yet been observed, scientists are concerned about competition with native mollusks for resources and habitat because of the mud snail's high reproductive capacity. For more information, see: http://rivers.oscs.montana.edu/dlg/aim/mollusca/potant.html.
Sea Lamprey, Petromyzon marinus. This species is generally marine but ascends freshwater rivers to spawn along the Atlantic Coast from Labrador to the Gulf of Mexico. This species was first reported in Lake Ontario in 1835, in Lake Erie in 1921, in Lake Michigan in 1936, in Lake Huron in 1937, and in Lake Superior in 1946. The sea lamprey may have entered Lake Ontario from its native habitat in the Atlantic drainage by migrating through the Erie Canal after the canal was opened between 1819 and 1825 or by hitching rides on boats passing through the Erie or St. Lawrence canal systems. Later, it entered the upper Great Lakes through the Well and Canal around Niagara Falls. Adult lampreys attack and parasitically feed on other fishes such as lake trout, often resulting in death of the prey, either directly from the loss of fluids and tissues or indirectly from secondary infection of the wound. The sea lamprey drove many native fish species of the Great Lakes to near extinction. Both recreational and commercial fisheries suffered major economic loss, with additional indirect losses in tourism and supporting businesses. Congress regularly considers the impacts of sea lamprey during debate on annual appropriations for the Great Lakes Fishery Commission for the U.S. share of sea lamprey control expenses with Canada (Department of State appropriations for "International Fishery Commissions"). The annual cost of international control programs for sea lamprey in the Great Lakes drainage is approximately $10 million to $15 million. For more information, see: http://nas.nfrcg.gov/fishes/accounts/petromyz/pe_marin.html.
European Ruffe, Gymnocephalus cernuus. This fish species is native to Northern Europe and Asia. The ruffe was first observed in 1986 in the St. Louis River along the border between Minnesota and Wisconsin. It has since spread into Duluth Harbor in Lake Superior and several tributaries of the lake. By 1994 the ruffe had spread eastward along the Lake Superior shoreline as far as Michigan's Ontonogan River, and was observed in Lake Huron in 1995. The ruffe was probably introduced from ship ballast water as early as 1982-l983. Ruffe have the potential to compete with native fishes, such as yellow perch, and could consume large quantities of eggs of commercially important lake whitefish and similar species. Thus, the major effect of this species may be on sport and commercial fisheries as well as indirectly on tourism. For more information, see: http://nas.nfrcg.gov/fishes/accounts/percidae/gy_cernu.html and http://www.fws.gov/r3pao/ashland/ruffe/index.html.
Walking Catfish, Clarias batrachus Walking catfish were imported to Florida, reportedly from Thailand, in the early 1960s for the aquarium industry. The first introductions apparently occurred in the mid-1960s when adult fish imported as brood stock escaped in Broward County. Additional introductions in Florida, apparently purposeful releases, were made by fish farmers in the Tampa Bay area in 1967-1968, after the state banned the importation and possession of this species. The species can migrate overland at night or during rain, which has allowed it to spread to 20 counties in southern Florida. Although aquarium releases are apparently responsible for subsequent discoveries in California, Nevada, Georgia, Massachusetts, and Connecticut, this species is not believed to have become established outside Florida. In Florida, walking catfish have invaded fish farms, where they enter culture ponds and prey on fish. However, no studies are known to have measured the ecological or economic impacts of this species. For more information, see: http://nas.nfrcg.gov/fishes/accounts/clariida/cl_batra.html.
Alewife, Alosa pseudoharengus. The alewife may have been native to Lake Ontario or could have reached the lake in the mid-1800s. Subsequently, this fish has spread through the Great Lakes via the Welland Canal, with first reports from Lake Erie in 1931, Lake Huron in 1933, Lake Michigan in 1949, and Lake Superior in 1954. The alewife was intentionally stocked in other inland waters. The disappearance of native plankton eating fish, such as whitefish, in the Great Lakes has been attributed in part to the introduction of alewives, which reduce zooplankton populations. Some attribute the extinction of the lake herring and the decline of chub species in the Great Lakes to the alewife. Today, the alewife is the dominant fish in Lake Michigan, where it accounts for 70-90% of the fish weight (biomass). Pacific salmonids were introduced to the Great Lakes in the mid-1960s, in part to control the alewife populations. Alewives have damaged sport and commercial fisheries in the Great Lakes by eliminating certain species and have damaged tourism by undergoing periodic large-scale die-offs that litter beaches with rotting fish, posing both a nuisance and a health hazard. Costs of cleaning beaches have declined in recent years with reduced populations of alewives. For more information, see: http://nas.nfrcg.gov/fishes/accounts/clupeida/al_pseud.html.
Round Goby, Neogobius melanostomus Native to Eurasia including the Black Sea, Caspian Sea, and Sea of Azov and their tributaries, the round goby was first discovered in Michigan's St. Clair River in 1990. This fish species probably arrived in freighter ballast water. The species appears to be undergoing a population explosion in Lakes Erie, Huron, and Michigan. The round goby was first observed in Lake Superior in 1995. The round goby is aggressive, feeding voraciously upon bottom dwelling fishes (e.g., sculpin, darters, and logperch), snails, mussels and aquatic insects. Abundance of native fish species has declined in areas where this goby has become abundant, with sculpins particulary affected. Thus, there is concern that the round goby may harm sport and commercial fisheries in the Great Lakes as well as indirectly affect tourism. The Army Corps of Engineers is constructing an underwater electric barrier in the Chicago Sanitary and Ship Canal to prevent the round goby from spreading into the Mississippi River drainage. For more information, see: http://nas.nfrcg.gov/fishes/accounts/gobiidae/ne_melan.html.
Common Carp, Cyprinus Carpio. Native to Asia, this species was an early introduction to Europe, from where it was introduced into the United States as a sport fish in the 1850s. Carp are currently found in every state except Alaska. Carp are bottom-feeders, destroying aquatic plants and increasing suspended sediments as they feed. Overabundant carp can severely deplete lake bottom food sources needed by species sought by sport anglers, such as yellow perch, bluegills, and channel catfish. Although carp are sought by some recreational fishermen, others see carp as damaging sport fisheries for a variety of native species. For more information, see: http://www.und.nodak.edu/org/ndwild/carp.html and http://www.seagrant.wisc.edu/Communications/Publications/Fish/carp.html
Lake Trout, Salvelinus namaycush. In 1993, lake trout were discovered in Yellowstone Lake in Yellowstone National Park, where they pose a significant threat to native cutthroat trout. Lake trout probably entered Yellowstone Lake by illegal human introduction as early as the late 1970s or early 1980s. The lake trout's native range includes most of the northern-tier states from Maine to Minnesota and across Canada into Alaska. Sport fisheries for native trout and tourism are likely to be harmed by this introduction. Cutthroat trout in Yellowstone National Park support a recreational fishing industry valued at $36 million annually, as well as supporting many species such as grizzly bears and bald eagles during the cutthroat's spring spawning season. For more information, see: http://www.npca.org/np/98-05/mj98-fea2.html and http://www.aqd.nps.gov/pubs/yr_rvw96/chapter1/laketrou.htm
Brown Tree Snake, Boiga irregularis. The brown tree snake was introduced to Guam where it is now extremely abundant and has damaged the electrical and telephone grids, as well as eaten several endemic Guamanian birds to extinction in the wild. Estimated losses due to power outages alone on Guam cost are at least $1 million per year. 58 It poses a serious threat to Hawaii and its tourism industry, since snakes are not hesitant to enter homes or hotels; though their venom is weak, over 200 Guamanians have been bitten, usually when snakes crawled into sleepers' beds. Native Hawaiian birds, having evolved in a snakeless environment, would also be at serious risk (and Hawaiian non-native birds would enjoy yet another advantage over the native birds). The problems caused by this species are covered in CRS Report 97-507 ENR Non-Indigenous Species: Government Response to the Brown Tree Snake and Issues for Congress
Indian Mongoose, Herpestes auropunctatus. In the late 1800s, sugar cane growers in Hawaii and Puerto Rico sought ways to control the damage that introduced rats were causing to the crops. In what would prove to be a misguided attempt at biological control, they imported the Indian mongoose, a small predatory mammal native to Asia. The mongoose failed to control the rats but instead decimated native birds and other species, probably causing the extinction of some. In Puerto Rico and other Caribbean islands, mongooses are a major vector for rabies, and in some parts of Hawaii, they damage papaya and banana crops. They now occur on four of the five major Hawaiian islands, Kauai being the only exception. Control efforts costing millions of dollars per year have sof ar not succeeded in eliminating the mongoose from any of those islands. 59
Nutria, Myocastor coypus. Nutria (relatives of beavers) were introduced to the United States from South America in 1899 to stimulate the fur industry. When the industry failed, surplus animals were released. The highly prolific, semi-aquatic species is now established in 22 states, and has been sighted in many more. It has no natural enemies, and remaining fur trappers have not kept pace with its exploding population growth. It has severely damaged marsh vegetation which causes conversion of heavy vegetation to open water, thereby removing nesting or overwintering habitat for many birds, and eliminating habitat critical to the juvenile stages of important commercial species such as shrimp, crabs, oysters, many species of young fishes, and others. It has been very destructive in Gulf Coast states and the mid-Atlantic states, primarily on the Delmarva Peninsula. After a hearing before the House Resources Committee (Ser. No.105-97), Congress passed legislation (P.L. 105-332) to assist Maryland in controlling nutria populations. For more information, see: http://www.nfrcg.gov/nas/mammals/mammals.htm.
53 Pollenation services represent only a very small fraction of the cost of producing most crops. Shortages of hives will have to become severe to have substantial effects in supermarkets. In the meantime, the beekeeping industry itself suffers most.
54 K.D. Lafferty and A.M. Kuris. "Biological Control of Marine Pests." Ecology, v.77, no. 7 (1996): 1989-2000.
55 OTA Report, p.68.
56 The west has two major rivers called "Colorado" ("Reddish" in Spanish). This one has its mouth on the Gulf coast of Texas, southwest of Galveston.
57 Balcom, N. C., 1994. Aquatic Immigrants of the Northeast, No.4: Asian Clam, Corbicula fluminea", Connecticut Sea Grant College Program.
58 Pimental report.
59 Pimental report.
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