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<br />In cyprinids, the fifth branchial arches are located on the <br />floor of the posterior pharynx, anterior to its junction <br />with the esophagus. To clearly view the pharyngeal teeth, <br />it is often necessary to extract the pharyngeal arch. This <br />can be accomplished by removing the operculum, gills, <br />and other surrounding tissues. Alternately, the gills and <br />operculum can be folded forward to expose the pharyn- <br />geal teeth. Much care must be exercised to extract an arch <br />without damaging the teeth and resulting in an incorrect <br />tooth count. In this guide, dorsal-view illustrations of <br />pharyngeal teeth are given in each species account. The <br />number of pharyngeal teeth is represented by a standard- <br />ized formula. For example, a count of 0,4-4,0 denotes <br />one inner row of four teeth on each arch. Alternately, a <br />count of I, I ,3-3, I, I denotes three rows on each side, with <br />three teeth in the innermost row and two outer rows with <br />one tooth each. By convention, pharyngeal teeth are read <br />from the outside of the left to the outside of the right. <br />Some species show dramatic changes with growth, and <br />young individuals sometimes have pharyngeal teeth quite <br />different from adults. The pharyngeal teeth illustrated in <br />this guide are those of adult fish. <br /> <br />Museum Specimens <br /> <br />Preserved specimens referenced in this study are <br />from the following sources: AUM (Auburn University <br />Museum Fish Collection, Auburn, Alabama); SIUC <br />(Southern Illinois University at Carbondale, Fluid <br />Vertebrate Collection, Carbondale, Illinois); TU (Tulane <br />University Museum of Natural History Fish Collection, <br />New Orleans, Louisiana); UF (Florida Museum of <br />Natural History, Department of Ichthyology, Gainesville, <br />Florida). <br /> <br />Maps <br /> <br />The U.S. distribution of each foreign cyprinid <br />species is given on a map plate in the corresponding <br />species account. Distribution information is presented by <br />drainage and by state, each coverage indicating different <br />levels of information. <br /> <br />Distribution by drainage.-U.S. Geological <br />Survey Hydrologic Unit Codes (HUCs) were used as <br />a base to build maps. This is a nationwide system that <br />delineates watersheds based on surface hydrologic <br />regions (for more information, see: http://nas.er.usgs. <br />gov/hucs.asp). Maps in this guide use a combination of <br />6-digit and 8-digit HUCs. The maps distinguish between <br /> <br />Methods 5 <br /> <br />HUCs where there is evidence of natural reproduction <br />in the wild (coded as "reproducing") and those where <br />the species has been reported, but without evidence of <br />reproduction (coded as "reported"). The distinction <br />is important. Once a non indigenous fish establishes <br />a reproducing population, it may persist indefinitely, <br />becoming a permanent addition to the fauna. <br /> <br />(1) Reproducing species,-A species is coded as <br />"reproducing" within a HUC if a naturally repro- <br />ducing population is present. These drainages are <br />color-coded red on the maps. Usually, evidence for <br />reproduction is based on presence of adult fish as <br />well as reports that eggs, larvae, or small juveniles <br />have been collected within the HUe. Sometimes <br />reproduction is inferred by persistence of a species <br />in a particular water body over an extended period <br />of time. Persistent reproduction is usually habitat <br />dependent. Some of the species in this guide are <br />capable of reproducing in still waters, such as <br />lakes and ponds (Common Carp, Goldfish, and <br />Tench). Other species, such as the Chinese carp <br />(Grass Carp, Silver Carp, Bighead Carp, and Black <br />Carp), naturally spawn in rivers. <br /> <br />(2) Reported species,-HUCs are coded as "reported" <br />if the species has been collected, stocked, or <br />observed in one or more parts of a drainage, but <br />no evidence exists that the species is successfully <br />reproducing. These drainages are color-coded pink <br />on the maps. Failed historical introductions (that <br />are known to us) are included in this category. <br /> <br />(3) Eradicated species.-Eradication is the complete <br />elimination of all individuals in a given popula- <br />tion. Many eradication attempts fail, as aquatic <br />organisms are especially difficult to completely <br />remove from a system despite vigorous and costly <br />efforts to eliminate them. Years of monitoring are <br />usually required to assure no survivors persist. In <br />some cases, the source of introduction is never <br />identified, consequently individuals continue to <br />repopulate the area. In general, the only success- <br />ful eradication projects are ones directed at fish <br />confined in small, relatively closed systems, such <br />as a pond or smaller, somewhat isolated reservoirs <br />or drainages (see account on Ide, LellcisclIs idlls). <br />In larger and unconfined water systems (rivers, <br />canal networks, estuary complexes) the possibil- <br />ity of successful eradication is extremely low (or <br />impossible) and the cost of such projects high. <br />There is little hope of completely eradicating some <br />widely-ranging nuisance fishes, especially with the <br />techniques currently available. <br />