Peterson Field Guide to Freshwater Fishes, Second Edition

PREFACEThe first edition of this guide was completed in 1990 and publishedin 1991. Since then it has been a primary source of informationon identification of North American freshwater fishes. Thissecond edition increases the number of species in the guide from768 to 909, incorporates new maps and several new and revisedplates, and corrects errors. The increase in number of species isthe result of adding 114 newly recognized species native to theU.S. and Canada, 19 marine invaders commonly found in freshwater,and 16 newly established non-native (exotic) species. Eightspecies recognized in the first edition were deleted as names weresynonymized or as exotic species thought to be established disappeared.The ichthyofauna of the twenty-first century is not thatof the twentieth century, and a revision of this guide was badlyneeded. We hope we have succeeded in making it current as wellas more user-friendly. Suggestions for improvements and notificationsof errors are welcome.—LMP and BMBINTRODUCTIONHow To Use This GuideNaturalists, anglers, and aquarists derive pleasure and knowledgefrom observing and catching fishes. Ichthyologists and other scientistsstudy fishes to learn more about the evolution of life, thehistory of our continent, and how natural resources can be bettermanaged. For these interests and related endeavors, accurateidentification of fishes is essential. This guide includes all fishesin fresh waters of North America north of Mexico. Fishes are aquatic vertebrates with fins and gills throughoutlife. Currently recognized as valid are about 31,000 species, ofwhich 831 species (3 percent of the total) are native to fresh watersof the United States and Canada. Another 58 species fromelsewhere in the world have been established in our area, and 20marine species are encountered often enough in fresh water tobe included in this guide, bringing the total number of species to909. Of the 537 families of fishes, 34 (6 percent) are represented by1 or more species native to freshwater lakes and streams of theUnited States and Canada, and another 11 families have marinespecies that occasionally enter our rivers. Eight other familiesare represented by introduced (exotic) species. Although our fishfauna represents a fraction of the world’s total, it is Earth’s mostdiverse temperate freshwater fish fauna. All freshwater fishes known from North America north ofMexico are included in this guide. The Peterson Field Guide toAtlantic Coast Fishes and the Peterson Field Guide to Pacific CoastFishes provide additional information on marine and brackishwaterfishes likely to be encountered in fresh water.NamesMost names of fishes used in this guide are those in Commonand Scientific Names of Fishes from the United States, Canada,and Mexico, published in 2004 by a joint committee of the AmericanFisheries Society and the American Society of Ichthyologistsand Herpetologists. In a few instances in which the committeechanged a common name, we chose to keep the name used in thefirst edition of this field guide. Scientific names of species consist of two Latinized and italicizedwords, e.g., Lepomis punctatus. The first is the genus, whichbegins with a capital letter. The second is the “specific epithet”and is not capitalized. A subspecies has a third descriptor, e.g., Lepomispunctatus miniatus. Genera are grouped into families (withnames that end in idae), families into orders (ending in iformes),and orders into classes.IllustrationsColor plates were painted from live fishes or, more often, fromcolor photographs of live or freshly preserved fishes. Black-andwhiteplates depict fishes that lack bright colors or show littlevariation in color among closely related species. Fishes are notdrawn to scale, but much larger species usually are shown largerthan smaller species. The 57 plates (42 in color, 15 in black andwhite) show 824 individuals representing 677 species. Additionalspecies are illustrated in text figures.MeasurementsAlthough ichthyologists use the metric system, guide users remainfamiliar with inches, feet, and pounds. Measurements are givenin both systems. A short rule comparing metric and U.S. unitsappears below and on the back cover. The maximum total lengthknown (tip of snout, lip, or chin—whichever is farthest forward—to end of longer caudal fin lobe) is given for each species. Forsmall fishes, this number is given in quarter-inches and tenthsof centimeters, for intermediate fishes in inches and centimeters,and for large fishes in feet and meters. If the maximum length recorded was given originally in centimeters,it was converted to inches; if in inches, it was convertedto centimeters. Rounding from centimeters to quarter-inches cangive various results; for example, 7.4 through 7.9 cm are all givenas equivalent to 3 in.AccountsFamily accounts provide information on distinguishing characters(often anatomical) and distribution. Numbers in parentheses followingfamily names are numbers of native species in the UnitedStates and Canada; if introduced species are in our area, numberof natives is followed by number of exotics. Generic accounts are given for large genera and for small generain which all species share characters useful in identification.If a character is described in a family or generic account, it usuallyis not repeated in a species account.Species accounts begin with common and scientific names. Inthe upper right-hand corner of each account is the number of theplate or figure where the species is illustrated, or “Not shown” ifnot illustrated. A species is not illustrated if it is similar to anotherspecies. Most species accounts contain the following four sections. Asimilar Species section is omitted if a species is easily identified,and a Remarks section is added if the species has subspecies orother noteworthy characters.Identification: This section describes the most useful charactersfor identification. Usually these are color descriptions suchas “black stripe along body,” shape descriptions such as “dorsalfin origin behind pelvic fin origin,” and unusual features such as“barbel at corner of mouth.” The most prominent field charactersare italicized and usually appear early in the account. Accuratefield identifications sometimes require consideration of localityand habitat. Large specimens, especially colorful males, are easiestto identify. Positive identification of small or single individualsmay require close examination; for that reason, we give somecharacters useful in identification of preserved fishes (numbers ofscales, fin rays, and pharyngeal teeth, etc.). A color description is included unless a species is noted to besimilar or nearly identical to another species. Unless stated otherwise,the description is of an adult fish, and the fish is whitebelow (breast and belly) and has clear fins, conditions that pertainin most species. In many fishes, females retain colors similarto those of young, but males become notably brighter or darkerwith age. During the spawning season, males often becomemuch brighter in color than at any other time. When known todiffer, both “average” and “breeding male” descriptions are given.In some fishes (e.g., darters), large males retain bright colorsthrough much of the year; in others (e.g., most minnows), brightcolors are present only during the spawning season. Counts provided are those considered to be most important foridentification and are total ranges unless they are preceded by“usually” or identified as modes (i.e., number[s] occurring mostfrequently). Counts of bilateral characters are given for one sideonly, e.g., six branchiostegal rays means six on each side. Pectoraland pelvic fins come one to a side and are referred to collectively(i.e., all four of them) as paired fins. We often discuss these finsand other paired structures (e.g., eyes) in the singular (e.g., pectoralfin, eye) to simplify comparisons between species. Dorsal,caudal, and anal fins are referred to collectively as median fins. Range: A description of each species’ geographic distribution isfollowed by a comment on abundance (e.g., “Rare”). All speciesvary in abundance with locality, and the statement on abundanceis meant to apply over the species’ range or, if introduced, overits range in the U.S. and Canada. The statement is not a relativecomparison among species. For example, the Fountain Darter,Etheostoma fonticola, is common in its area but is consideredan endangered species because it occurs in only one small area.Abundant means a species is almost certain to be found in itspreferred habitat within its range (see “How to Observe Fishes”);common indicates a species is likely to be found; fairly common,may be found; uncommon, unlikely to be found; rare, very unlikelyto be found. Species and subspecies described as threatenedor endangered are those appearing on official lists of Canada(Species at Risk Act – SARA) and the United States (USFWS) asof 1 July 2010. Many species also are legally protected by states orprovinces. Habitat: Fishes vary widely in their restriction to particularhabitats. Some are extremely limited (e.g., to springs); others canoccupy habitats as different from one another as gravel riffles andswamps. For a stream-inhabiting species, a habitat descriptionincludes a statement on the size of stream the species generallyoccupies. Terms used are streams (any body of running water),headwater (a stream less than 3 ft. [1 m] wide during average condition),creek (3–15 ft. [1–5 m]), small river (15–80 ft. [5–25 m]),medium river (80–165 ft. [25–50 m]), and large river (more than 165ft. [50 m]). A basin is a major drainage unit (e.g., Arctic, HudsonBay, Great Lakes-St. Lawrence, Atlantic, Gulf, Pacific, MississippiR., Ohio R., and Missouri R. basins) or an independent endorheicdrainage unit (e.g., Bonneville basin). Component drainages maybe referred to collectively as, for example, Atlantic drainages. Adrainage is an interconnected group of streams entering an oceanor main river of a basin (e.g., Wabash R. drainage of the Ohio R.basin). A system is a subdivision of a drainage (e.g., Embarras R.system of the Wabash R. drainage). For convenience, we make a distinction between Atlantic andGulf slope drainages even though the Gulf of Mexico is part ofthe Atlantic Ocean. Atlantic Slope drainages are those enteringthe Atlantic Ocean from the Arctic Ocean to the southern tipof Florida. Gulf Slope drainages are those entering the Gulf ofMexico. Composition of the stream or lake bottom (substrate) is ofmajor importance in distributions of fishes, and habitat descriptionsusually include statements on the type(s) of bottom materialmost often associated with the species. Mud refers to a softbottom (clay or silt); rock refers to a hard bottom (gravel, rubble,boulders, or mixtures thereof). More precise terms, in increasingorder of particle size, are clay, silt, sand, gravel, rubble, boulders,and bedrock.Similar species: Comparisons are made with species that appearmost similar. These species usually, but not always, are closelyrelated forms. When there are many similar species, we comparethose closest to the range of the species being identified.MapsRange maps are provided for all extant (and some extinct) freshwaterfishes native to North America north of Mexico (except afew restricted to single localities). Range maps are not providedfor introduced species or marine invaders. Production of rangemaps relied heavily on state, provincial, and regional “fish books.” A map shows the total range of a species based on historicaland recent records; that is, a map includes an area or drainageeven if that population is believed to be extinct. Within theseranges, large gaps in distribution occur in ecologically unsuitableareas. For example, the Rainbow Darter, Etheostoma caeruleum,ranges over much of the eastern U.S. but lives in rocky riffles andis absent from many areas within its range. Ranges in Mexico areshown for U.S. species that narrowly extend into Mexico. Maps for native species with transplanted populations includeareas where populations are known to be established. However,species that are continuously being stocked—notably somebasses, sunfishes, and trouts—may be found almost anywhere inthe U.S. and southern Canada. The notation “Introduced elsewhere”appears on maps for species that are likely to be foundoutside the range shown. The reader should consult a species accountfor additional information on geographic distribution.HybridizationCrosses between species occur occasionally in nature and areespecially common in sunfishes. Identifications of hybrids (asspecies A x species B) usually are difficult. In making identifications,keep in mind that hybridization occurs most often betweenclosely related species, and hybrids usually have characters intermediateto those of parental species. As aquatic environmentsdegrade, hybridization increases, presumably because of difficultyfishes have in recognizing spawning partners in turbid and pollutedwater. Intergrade zones are areas where individuals (known as intergrades)are intermediate in characters used in the recognition oftwo subspecies. Intergrades may be intermediate because of themixing of genes (“gene flow”) of two subspecies or because of variableenvironmental conditions leading to selection for charactersintermediate to those of two subspecies. Intergrades are named ashybrids between two subspecies (e.g., Percina caprodes caprodesx P. caprodes fulvitaenia).How to Observe FishesYou can watch fishes in clear water from stream banks and lakeshores,and although at first they may all look the same or at bestas “minnows” or “sunfishes,” you can identify them by knowingwhat species occur in the area and noting their distinguishingmorphological and behavioral traits. Binoculars and polarizedsunglasses that eliminate surface glare greatly facilitate fishwatching from above water. Serious fish watchers enter water and join their subjects. Witha snorkel and mask, you can view fishes at amazingly short distancesand observe their feeding, spawning, and other behaviors.Although fishes tend to swim away from humans on stream banks,they remain close to a person underwater. Often, fishes are curiousand readily approach underwater observers. In areas where many similar species occur, removing fishesfrom the water may be the only positive way to identify them.Many species can be obtained readily by seining, dipnetting, orangling, and examined while on shore or transferred to aquariumsfor long-term observation.Making IdentificationsFor most identifications, it is best to begin with the plates. Locatethe plate with fishes that look most like the one you wish to identify(see “How to Use the Plates” on page 1), and read the shortdescriptions of distinguishing features on the legend opposite theplate. Arrows on plates pinpoint these features. When you believeyou have located the correct species, go to the longer text description(page number given on legend page) and compare charactersof the fish with those given in the species account and, if necessary,in generic and family accounts. “Similar species” sectionsnear the end of each account identify the most likely alternative(s)to the species you selected and should be consulted before youdecide you have made the correct identification. At some point, you will need to refer to the distribution map.If you know from past experience that the fish you are workingwith is one of a few similar species (e.g., a sand darter), you canstart with the maps. Eliminating species outside your area willfacilitate identification.Fish MorphologyFig. 1 illustrates various structures, counts, and measurementsused to identify fishes. Most are self-explanatory. The followingcomments and the Glossary explain others. Fishes have median fins (dorsal, caudal, and anal) and pairedfins (pectoral and pelvic). The dorsal fin in more ancient fishesis supported by flexible, segmented “soft” rays. In more recentlyevolved fishes, the front section of the dorsal fin contains only inflexiblespiny rays (“spines”) and may be contiguous with or separatedfrom the soft-rayed part; when the front section is separated(or nearly separated) from the soft-rayed part, the fish is said tohave two dorsal fins. Likewise, the anal fin may be spineless orhave spines (usually only one to three) preceding rays. Throughout the evolution of fishes, pelvic fins have tended tomove forward on the body, and their position is a quick way tojudge whether a fish belongs to a more ancient or a more recentgroup. If pelvic fins are abdominal, the fish is a member of an ancientgroup (e.g., sturgeon), and you can expect to find it near thefront of this guide. If the pelvic fins are thoracic (on the breast)or jugular (on the throat), you will find the fish (e.g., a sunfish)closer to the rear of the guide. The mouth is described as terminal if it opens at the front endof the head with the upper and lower jaws being equally far forward;upturned if it opens above that point; and subterminal if itopens on the underside of the head. You can see the rakers on thefirst gill arch by lifting the gill cover (Fig. 2); a gill raker count isthe total for the entire first arch unless upper or lower limb only isspecified. The largest bone in the gill cover is the opercle (Fig. 1). Measurements and counts used in this guide are shown inFig. 1. Measurements of body parts (e.g., snout length) or finsoccasionally are used to separate similar species. These measurements,which are always made in a straight line (not along abody contour), usually are compared with another measurement(e.g., total length). A comparison such as snout length into totallength is made by dividing one measurement into the other, or byphysically “stepping off” one measurement into the other usingdividers. Lateral-scale count (also known as lateral-line scale count)begins just behind the head and continues along the lateral line(or along the midside if the lateral line is absent) to the originof the caudal fin (which is located by bending the caudal fin toeither side and noting the crease between the body and caudalfin). Scales on the caudal fin are not included in lateral-scalecounts even if they are pored. Scales above and below the lateralline begin at the origin of the dorsal or anal fin, respectively, andcontinue diagonally to the lateral line (but do not include thelateral-line scale). A transverse-scale count is a continuation ofthe count of scales below the lateral line diagonally upward (includingthe lateral-line scale) to the dorsal fin. Scales around thecaudal peduncle are those around the narrowest part. Predorsalscales are those along the nape from the rear of the head to thedorsal fin origin. Fig. 3 shows how dorsal and anal rays are counted. In pectoraland pelvic fins, all rays are counted. Branchiostegal rays are longslender bones supporting branchiostegal membranes; all (shortand long) rays are counted. To examine pharyngeal teeth, it is necessary to remove the firstpharyngeal arch by placing the fish on its side and lifting the gillcover (if necessary, slit the skin along the bottom to loosen thegill cover from the body). The arch lies just to the rear of the gills.Insert a scalpel or strong forceps between the arch and shouldergirdle, beginning at the upper angle of the gill opening and cuttingdown along the shoulder girdle. Carefully sever the fleshy tendonsthat hold the upper and lower ends of the arch in position, then liftout the arch and remove the attached flesh to expose the teeth.ConservationPets, bait, and other fishes should never be released into a stream,lake, or pond other than from where they were originally taken.Non-native fishes and their offspring may outcompete or feedon fishes or other organisms and do tremendous harm to nativepopulations. No objective of this guide is more important than that of increasinghumanity’s appreciation of fishes and their environments.We often fail to give adequate consideration to the vast and variedforces over millions of years that have forged our present-day biodiversity.Each species on Earth is the product of millions of yearsof evolution and is fine-tuned to its environment. To conserve thediversity of life, we must reduce our own population, reduce ourconsumption, and set aside large ecosystems as preserves. We willbe able to accomplish those changes only through education andan awareness of the value of diversity. It is our sincere hope thatthis guide to the rich diversity of North American fishes will contributeto that goal.