<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 />
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