Fish Anatomy - Pennsylvania Sea Grant

Fish AnatomyAnteriorPectoral finDorsalDorsal finsLateral lineCaudal finPosteriorTypes of Caudal FinHeterocercalShapes of HomocercalCaudal FinsLunateInvASIve FishMouthGill cover (operculum)Pelvic finAnal finCaudal peduncleHomocercalForkedVentralRoundedProtocercalEmarginate(Concave)DiphycercalTruncated(Straight)86 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 87

Flathead CatfishPylodictis olivaristiny eyesflattened headprotruding lower jawsquared tail*Note: The flathead catfish poses specific management and policy challenges. It is native to the westernpart of Pennsylvania in the Ohio, Allegheny, and Monongahela river watersheds; however, it is consideredinvasive in eastern Pennsylvania.Similar SpeciesUnlike other catfish, which prey on dead organisms, theflathead feeds on live fish, eating mostly sunfish, carp, andeven other catfish. Flathead catfish are nearly double theweight of the channel catfish (Ictalurus punctatus). Thelower jawbone of the flathead extends outward from therest of the face, like an under-bite, whereas the channelcatfish’s upper jaw extends over the lower. The channelcatfish also has a forked tail instead of a squared tail.HabitatThriving in reservoirs, lakes, rivers, and large streams,flathead catfish prefer deep, still, muddy waters with logsand other debris to use as shelters.SpreadEnvironmental ImpactsThe flathead catfish poses anenormous threat to native fishpopulations because it feeds onother fish. Young flathead catfishalso feed on crayfish, darters, shad,and possibly crabs and youngAmerican eel. Species such assunfish and native catfishes havedeclined heavily in some areaswhere flathead catfish are present.Pennsylvania DistributionInvASIve FishSpecies at a GlanceThe flathead catfish is one of the largest species in the catfish family.It voraciously feeds on other fish, making it an extreme threat tonative ecosystems. It has many nicknames, including Pied Cat, MudCat, Mississippi Cat, Shovelhead Cat, Yellow Cat, and Opelousa Cat.IdentificationKey characteristics of the flathead catfish are its flattened head, tinyeyes, squared tail, and protruding lower jaw. It can grow up to 152 cm(60 in) long and weigh on average 30 pounds, although some havebeen known to reach over 100 lbs. Coloration is usually brownishyellowwith mottled speckles on the back and a cream-colored whiteto yellow belly.The most likely vector of spread is intentional stocking andrelease by anglers for game and food fishing.DistributionNative to North America, including areas of the MississippiRiver Basin and the Ohio River drainage in westernPennsylvania, flathead catfish are invasive in eastern partsof Pennsylvania, including the Blue Marsh Reservoir, theSchuylkill River in Philadelphia, the Susquehanna River,and the Springton Reservoir in Media.Green - Native Blue - InvasiveUnited States Distribution100 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 101

GoldfishCarassius auratussmall, terminal mouth,lacking barbelslong dorsal fin,15-24 raysSpecies at a GlanceThe goldfish is a freshwater memberof the carp and minnow family. It was oneof the first aquatic invasive species to reach North America, arrivingin the 1600s as ornamental fish for aquariums and water gardens.It is now one of the world’s most widespread invasive species.26-32 scales in lateral lineIdentificationIt has an elongated, stout body, which is typically 10-20 cm (4-8 in)in length and weighs 100-300 g (3.5-10.5 oz), although it can reacha maximum length of 59 cm (23 in) and maximum weight of 6.6 lbs. Ithas a long dorsal fin with 15-24 rays, and a hard serrate spine at theorigin of both the dorsal and anal fins. There are normally 26-32 scalesin the lateral line. The mouth is small, terminal, and lacks barbels.While goldfish were mostly golden in color one thousand years ago,they now come in a variety of colors, including orange, yellow, white,black, silver, olive-green or greenish-brown and combinations ofthese colors. When found in nature, goldfish are most often a shadeof green, brown, or gray.Similar SpeciesGoldfish can be distinguished from common carp(Cyprinus carpio) by the carp’s two pairs of barbels on theupper jaw, a non-serrate spine, and typically more than32 scales in the lateral line. However, they can alsohybridize with the common carp, producing individualswith both characteristics.HabitatWhile goldfish prefer a habitat with a muddy bottom andthick vegetation, they can tolerate pollution, temperaturefluctuations and high levels of turbidity. They naturallylive in freshwater ponds and slow-moving or still waters indepths of up to 19.8 m (65 ft) and prefer temperatures of4-41°C (40-106°F), although they cannot live for long athigh temperatures.SpreadGoldfish have been intentionally introduced forornamental purposes to ponds, fountains, and small lakesto which they may disperse through connecting waters.Many introductions of goldfish were also due to their useas live bait. In addition, goldfish are often released intothe wild by pet owners not realizing the environmentalrepercussions of setting the fish free.DistributionNative to eastern Asia, goldfish have been reportedinvasive in the United States by every state except for Alaska.They are established in all of the Great Lakes, and in Erie,Northampton, and Philadelphia counties in Pennsylvania.Individual specimens have also been collected in severaldrainages throughout Pennsylvania; however, it is unknownwhether these represent established populations.Environmental ImpactsGoldfish are believed to beresponsible for population declinesin many native fish, invertebrate,and plant species. They also uprootplants and create enormousturbidity due to their aggressivebottom feeding behavior.Pennsylvania DistributionUnited States DistributionInvASIve Fish102 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 103

Grass CarpCtenopharyngodon idellagrass carp fingerlingSpecies at a GlanceThe grass carp, also known as the white amur or the waan ue, is oneof the largest minnows in the family Cyprinidae. It is also a memberof the Asian carp complex, which also includes the black, bighead,and silver carp. They were introduced into the United States tohelp control the growth of aquatic weeds in aquaculture facilities;however, they also feed voraciously on other food types, includinginvertebrates, vertebrates, and algae.IdentificationThe body of the grass carp is oblong in shape but considered slenderfor most carp. They typically reach between 65 and 80 lbs, althoughindividuals as large as 400 lbs have been reported. Scales are large,with dark edges and a black spot at the base. The scaleless head lacksbarbels. Overall color is olive to silvery-white, while the fins are a clearto gray-brown. The dorsal fin is composed of three simple rays andseven branched rays.Similar SpeciesGrass carp may be confused with the common carp(Cyprinus carpio), which can be distinguished by the presenceof barbels around the mouth. Common carp are alsomore golden in color and have spiny modified rays on thedorsal and anal fins.HabitatGrass carp prefer shallow and quiet waters, typically0.91-3 m (3-10 ft) deep, such as ponds, lakes, pools andbackwaters of large rivers.SpreadOnce introduced, grass carp can spread to distant waterbodies by tributaries, waterways, river systems, canals, anddams. This carp is also still intentionally stocked in aquaculturefacilities; however, it must be stocked in the triploidform, which means it is sterile and unable to reproduce.A permit is required to stock the carp in Pennsylvania, andstocking is only permitted in ponds to prevent the spreadthrough waterways and river systems.DistributionNative to eastern Asia, including China and Russia, grasscarp were introduced in many countries for aquacultureplant control. They are now widespread in 45 states inthe U.S., including Pennsylvania. In Pennsylvania, triploidcarp, which are reproductively sterile, can be stockedwith a permit.Environmental ImpactsWhile grass carp do help to reduceunwanted aquatic vegetation,they alter the food web becausethey also voraciously feed ondesirable plant species, reducing theamount of food available to nativeinvertebrates and fish. Excretedplant material can also increasenutrient levels in the water thatcause harmful algal blooms andaffect water quality.Pennsylvania DistributionUnited States DistributionInvASIve Fish104 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 105

Northern SnakeheadChanna arguslong dorsal & anal finsdark, irregular blotchessnake shaped headlarge mouth withsharp teethSpecies at a GlanceThe northern snakehead is a freshwater fish nicknamed “Frankenfish”because of its intimidating appearance and voracious appetite. An airbladder that works like a primitive lung lets this species survive out ofthe water in moist locations and wriggle over land to new bodies ofwater. These adaptations give the snakehead a competitive edge insecuring habitat and expanding its range.IdentificationThese cylindrical fish can grow over 84 cm (33 in) long. As the nameimplies, the scaled head of the fish looks like a snake. They have a largemouth with sharp teeth, a truncate, not rounded tail, and are easilyidentified by dark irregular blotches along their sides. Snakeheads alsopossess relatively long dorsal and anal fins.Similar SpeciesThe native bowfin (Amia calva) is often mistaken for thenorthern snakehead. Bowfin are distinguished by theirrounded tail, scaleless head, and an eyespot near the tail inmales. The burbot (Lota lota) looks somewhat similar but canbe distinguished by its split dorsal fin and a single barbelon the lower jaw. The dorsal and anal fins of the bowfin andburbot are also very short in comparison to snakeheads.HabitatThese fish prefer stagnant shallow ponds, swamps, andslow streams with mud or vegetated substrate. Temperaturerange is from 0-30°C (32-86°F), and they can survive inwaters that are covered in ice. As juveniles, northern snakeheadseat zooplankton, insect larvae, small crustaceans, andyoung fish. As adults, they become voracious predators,feeding on other fish, crustaceans, frogs, small reptiles,and even birds and mammals.SpreadBefore their threat was fully appreciated, live snakeheadswere sold in the United States in pet shops and live fishmarkets. Uninformed pet owners may have releasedthem into the wild when they grew too big for aquariumtanks, or as part of religious or cultural practices. In 2002,the import and interstate transport of the northernsnakehead was banned without a permit from theU.S. Fish and Wildlife Service.Environmental ImpactsWith no natural enemies, northernsnakeheads can devastate populationsof native fish and wildlife.They compete directly with nativefish, altering feeding habits, foodavailability, and behaviors of othermembers of the ecosystem.Pennsylvania DistributionUnited States DistributionInvASIve Fish106 Pennsylvania AIS Field GuideDistributionNative to China, Russia, and Korea, the first reported breeding populationin the United States was discovered in a pond in Crofton, Marylandin May 2002. In July 2004, northern snakeheads were found in a lakein FDR Park in Philadelphia, Pennsylvania. About a year later, anotherwas caught in the nearby Delaware River. In 2008, snakeheads werediscovered in the Schuylkill River below Fairmount Dam in PhiladelphiaCounty, and in 2012 a discovery was made in the John Heinz NationalWildlife Refuge in Delaware County.Pennsylvania AIS Field Guide 107

Rainbow SmeltOsmerus mordaxelongated head withpointed snoutsingle, spinelessdorsal finsSimilar SpeciesWhile they may be confused with many minnow species,rainbow smelt have an adipose fin and prominent teeththat minnows lack.HabitatHistorically, rainbow smelt have been strictly anadromous(residing in saltwater, but entering freshwater to reproduce).However, since the early 1900s the smelt has been successfullyintroduced into freshwater systems. It prefers deeper,cooler waters during the warmer seasons but will favorshallower coastal areas for feeding as winter approaches.Environmental ImpactsRainbow smelt could impact sportfishing and native fish populationsbecause they compete directly withsport fish such as perch, walleye,and lake trout for food. Smelt alsofeed on early or larval stages ofother fish.Pennsylvania DistributionInvASIve Fishlarge mouthSpecies at a GlanceThe rainbow smelt is a small fish that is eagerly pursued by anglers becauseof its fine flavor. Its Latin name Osmerus, which comes from theGreek word meaning “odor”, is fitting because when removed from thewater, they give off an odor which smells like freshly cut cucumbers.IdentificationThe rainbow smelt has a small, slender body that typically ranges from18-23 cm (7-9 in) long and weighs around 85 g (3 oz). Smelt aremostly silver, with pale olive-green backs and iridescent purple, blue,and pink sides. A conspicuous silvery streak runs lengthwise alongeach side. In the water, rainbow smelt shimmer colorfully, but whenremoved, they quickly fade to a silver white. In freshwater they aredarker, becoming almost black on the back. The head is elongated,with a relatively large mouth and pointed snout. The lower jawprotrudes, and prominent teeth can be seen on the tongue and bothjaws. Scales are thin and easily detached. A single dorsal fin and asingle adipose fin lack spines. Spawning males are covered on thehead, body, and fins with tiny bumps called nuptial tubercles.SpreadRainbow smelt spread naturally through waterwayconnections. Other potential vectors include ballast water,bait bucket transfers, improper disposal of fish remainscontaining gametes, and intentional introduction asforage and bait fish.DistributionThe rainbow smelt is native to the Atlantic Coastaldrainages of North America and the Pacific drainages ofNorth America and Asia. It was introduced into Michigan’sCrystal Lake as a food for stocked salmon and soon escapedinto Lake Michigan. It can now be found in all of the GreatLakes, the Mississippi River, and other inland waters. InPennsylvania, rainbow smelt populations are established inLake Erie, the Allegheny and Monongahela river drainages,and Harvey’s Lake in Luzerne County.Green - Native Blue - InvasiveUnited States Distribution108 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 109

Red ShinerCyprinella lutrensishighly arched back7-8 rays ondorsal finSimilar SpeciesWhile easily confused with most other minnows, includingthe golden shiner (Notemigonus crysoleucas), the rudd(Scardinius erythrophthalmus), and the roach (Rutilus rutilus),the outstanding characteristics of red shiners are the vibrantorange fins and the orange spot between the eyes.HabitatAlthough found in a variety of habitats, the red shiner preferssilt disturbed streams and muddy riverbeds where it doesn’thave to compete with other minnows for prey.Environmental ImpactsKnown to eat small invertebrates,the red shiner is in directcompetition with native fish andinvertebrates for food. The redshiner also has adaptive advantagesover other Cyprinids because it notonly can lay eggs in tight crevices,but it can attach adhesive eggs torocks and plant life.InvASIve Fisholive-green &silver flanksSpecies at a GlanceThe red shiner is in the genus Cyprinella, which is Greek for “smallcarp”. This hardy, widespread shiner is native to the Midwest, butthrough its use as a baitfish has been introduced to habitats outsideof its native range.orange finsIdentificationThe red shiner is a deep-bodied species with a highly arched back. Itsflanks are mixed olive-green and silver, with bright orange fins and alarge orange spot that sits between the eyes on its blunt, sloped brow.Spawning males become bluish on the sides and the fins redden.There are 7-8 rays on the dorsal fin and 8-10 (usually 9) rays in theanal fin. Maximum size is only 9 cm (3.5 in) in length. The red shinercan crossbreed with other minnow species, such as the blacktailshiner (Cyprinella venusta) and the endangered blue shiner (Cyprinellacaerulea), producing hybrids that may also have a faint caudal spot.SpreadThe red shiner has infiltrated Lake Michigan through its useas bait for recreational fishing and, more recently, throughthe aquarium trade. Its extended mating season, coupledwith the versatile nature of the eggs, ensures the specieswill spread quickly throughout habitats.DistributionThe red shiner is native to a large portion of the U.S.Midwest, reaching from central North Dakota to thesouthernmost point of Texas along the Mississippi Riverand its tributaries. Currently, the red shiner is only presentin the Great Lakes region in Lake Michigan and is not yetfound in Pennsylvania.Pennsylvania DistributionUnited States Distribution110 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 111

Round GobyNeogobius melanostomusblack spot on dorsal finfused pelvic finSpecies at a GlanceThe round goby is a small, aggressive, bottom-dwelling fish thathas dramatically altered the Great Lakes food web since it was firstdiscovered in Lake St. Clair in 1990. It grows rapidly and reproducesseveral times in one season. Avian botulism outbreaks appear directlyrelated to the round goby due to its heavy feeding on invasive zebraand quagga mussels.Similar SpeciesWhile round gobies look very similar to the native mottledsculpin (Cottus bairdi), the sculpin has two separated pelvicfins and lacks the black spot on the dorsal fin. The roundgoby may also resemble the much smaller, invasive tubenosegoby (Proterorhinus marmoratus), but the tubenose hastubular shaped nostril extensions and lacks protruding eyesand the black spot on the first dorsal fin.HabitatThis freshwater fish prefers shallow water with rocky andsandy bottoms where it likes to perch on top of rocks andhide in crevices. Round gobies can occupy a variety ofdepths, can tolerate a wide range of temperatures, waterquality, and oxygen concentrations, and can survive inbrackish water.SpreadThe round goby was most likely introduced to the GreatLakes through the ballast water of ocean-going cargo ships.Because they resemble small baitfish, boaters and fishermencan accidentally carry them from one body of water toanother through bait buckets, bilge water, and plant debris.Environmental ImpactsThe round goby is thriving at theexpense of native populations,many of which are important sportfish. It outcompetes native speciesincluding sculpin, logperch, laketrout, and darters for food sources,habitat, and spawning sites. It alsospawns more frequently and feedson their eggs and young.Pennsylvania DistributionUnited States DistributionInvASIve FishIdentificationThe two most distinguishing features of the round goby are theblack spot on the dorsal fin, and the fused pelvic fin that forms onesuction cup shaped fin. Young round gobies are a solid slate gray,whereas older gobies are mottled, with olive green, black, gray, andbrown spots. Spawning males turn almost solid black. Their soft bodyand large round head have very distinctive frog-like raised eyes.On average, they grow 10 -25 cm (3.9-9.8 in) in length.DistributionNative to Eurasia, including the Black, Caspian, and Azov seasand tributaries, round gobies were first sighted in the St. ClairRiver in 1990 and since have spread to all of the Great Lakes.They are now working their way inland through rivers andcanal systems. In Pennsylvania, the round goby is abundantin Lake Erie and its tributaries. The first Pennsylvania inlandoccurrence was confirmed in 2010 atthe Gravel Pits quarryin Erie County.112 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 113

Sea LampreyPetromyzon marinuslong cylindrical bodiesolive-brown, yellow-brown, green,red, or blue mottled to blackSpecies at a GlanceSea lampreys are primitive, jawless fish that resemble eels. Theseaggressive parasites affect Great Lakes native fish populations suchas lake trout, rainbow trout, whitefish, and walleye because they canlatch onto their victims for up to several weeks and feed on theirblood and body fluids.IdentificationSea lampreys have long, flexible, cylindrical, scaleless bodies witha deeply notched dorsal fin, separating it into two distinct parts.The body is 30-51 cm (12-20 in) long and weight can range from227-369 g (8-13 oz). Adults have a disc-like mouth that containscircular rows of over 100 sharp, hooked teeth. Larval lampreys,called ammocoetes, have a very small, undeveloped mouthhidden between folds of skin. Juveniles have white undersidesand uniformly colored blackish blue or silver backs. Adults can beolive-brown, yellow-brown, green, red, or blue mottled with a darkershade of the same color; or sometimes nearly black. The undersideis typically white or gray.deeply notcheddorsal finSimilar SpeciesNon-parasitic native lamprey species such as the Ohio lamprey(Ichthyomyzon bdellium), the American brook lamprey,(Lampetra appendix) and the northern brook lamprey (Ichthyomyzonfossor) are much smaller, lack the dark blotcheson the body, and have a single, continuous dorsal fin.HabitatSea lampreys require three distinctly different habitats connectedby free-flowing stretches of stream. Spawning adultsare found in late May or early June in shallow pits near theupper end of gravel riffles. After hatching, the ammocoetesdrift down to larger, slower moving streams and burrowinto the sediment. After several years, they transform intoparasitic adults in spring, and migrate into large bodies ofwater. They migrate back to tributary streams the followingspring to spawn and then die shortly after.SpreadIn 1921, the sea lamprey appeared in Lake Erie, arriving viathe Welland Canal. It took just 25 years for it to spread to theremaining Great Lakes.DistributionSea lampreys are native to the Atlantic Ocean, where naturalpopulations moved into the freshwater areas of Lake Ontarioand the St. Lawrence River to spawn. Now landlocked inthe Great Lakes, the sea lamprey has distributed itself intothe tributaries of those lakes. In Pennsylvania, sea lampreysare native to the Delaware and Susquehanna river basins inthe eastern part of the state, and invasive in Lake Erie andWalnut Creek in Erie County.Environmental ImpactsA single sea lamprey can destroy upto 40 pounds of fish during its adultlifetime. Under some conditions,only one out of seven fish attackedwill survive. The sea lampreypopulation explosion in the 1940sand 1950s contributed significantlyto the collapse of economicallyimportant Great Lakes fish speciessuch as lake trout.Pennsylvania DistributionGreen - Native Blue - InvasiveUnited States DistributionInvASIve Fish114 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 115

Silver CarpHypophthalmichthys harmandiSilver carp fingerlingSpecies at a GlanceThe silver carp is a member of the Asian carpcomplex, which also includes bighead, black, and grass carp. Althoughit is not yet found in Pennsylvania, its large size, voracious appetite,and ability to leap out of the water make it an enormous threat to theCommonwealth’s fishery and recreational economies.IdentificationThis very large filter feeder averages 40-70 cm (16-28 in) but can reachup to 130 cm (51 in) in length and weigh up to 80 lbs. Its deep body islaterally compressed, with a ventral keel that extends forward fromthe anus almost to the base of the gills. Large eyes are located lowand forward on the head. The mouth is large and terminal, and thelower jaw is slightly longer than the upper jaw. No barbels are presenton the mouth. The short dorsal fin, which lacks spines, contains7-10 rays. Scales are very small. Coloration is olive to grayish-blackon the back, with silvery sides blending to white below, with darkerpigmentation on the fins.Similar SpeciesWhile it most closely resembles the invasive bighead carp(Hypophthalmichthys nobilis), the silver carp is fairly uniformin color, whereas the bighead has irregular dark blotches onits back and sides. The bighead also has a less extensive keel,spanning from the pelvic fin to the anal fin. Silver carp mayalso resemble the common carp (Cyprinus carpio), which hasbarbels on either side of the mouth, and species of suckers(Catostomidae), which have thick lips containing smallnipple-like bumps.HabitatSilver carp are exclusively freshwater fish, preferring largeriver systems, lakes, or impoundments with flowing water,which they need to spawn. They can feed in temperatures aslow as 2.5°C (36.5°F) and can withstand low levels of oxygen.SpreadOnce introduced to open waters, silver carp readily spawnand disperse. Because the juveniles resemble some commonbaitfish species, they may be unintentionally spreadthrough the use of live bait. They can also spread in illegalshipments of live Asian carp, which is popular in the Asianfood market.DistributionNative to eastern Asia, silver carp were intentionally introducedinto the United States to control algae growth inaquaculture ponds. During flooding in the early 1980s, theyescaped into the Mississippi River and have since movedupstream towards the Great Lakes. In an effort to preventthe dispersal of Asian carp species between the Mississippiand Great Lakes watersheds, an electronic barrier is beingused in the Chicago Sanitary and Ship Canal.Environmental ImpactsThe silver carp consumes vastamounts of plankton and detrituseach day, competing with nativefilter feeders and juvenile fish forfood. In addition, when startled byboat motors or other equipment,the silver carp can leap up to 3 m(10 ft) out of the water, posing arisk of injury to boaters and watersportenthusiasts.Pennsylvania DistributionUnited States DistributionInvASIve Fish116 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 117

Tubenose GobyProterorhinus marmoratusblunt, rounded snoutdorsal fins lackspotsSimilar SpeciesWhile it may be confused with the round goby (Neogobiusmelanostomus), the tubenose goby is much smaller, hastubular shaped nostril extensions, lacks a spot on the firstdorsal fin, and has eyes that do not protrude from the topof the head. In addition, tubenose gobies do not feed onzebra mussels, and their mouths are too small to be caughton fishing lines like round gobies. Tubenose gobies may alsobe confused with native sculpins; however, sculpins do nothave scales or pelvic fins that form a suction cup.HabitatEnvironmental ImpactsWhile their impacts are not yetknown, tubenose gobies maycompete with and prey uponbenthic species in a mannersimilar to the larger round goby.However, because it is small andnot as aggressive, the tubenosegoby may not be as detrimentalas the round goby.InvASIve FishSpecies at a Glancefused pelvic finsThe tubenose goby is a small, bottom-dwellingfish that gets its name from its tubular-shaped nostrils. It feeds mainlyon aquatic insects, and although females can live for up to five years,males die immediately after spawning.IdentificationIts cylindrical body has small scales and a somewhat flattenedunderside, measuring 6-11 cm (2.4-4.3 in) in length. It has a blunt androunded snout with a wide mouth and large lips. Tubular shapednostrils extend just beyond the tip of the snout. Two pelvic fins arefused into a single suction cup shaped fin, and two dorsal fins lackspots. The body is light brown, with darker brown blotches that canform vertical bars on the rear half of the sides. A triangular black spotis present at the base of the caudal fin, followed by two white spots.The tubenose goby lives in slightly brackish to fresh waterand defends nest sites created under rocks, logs, and shellsin shallow areas of lakes and rivers with plenty of plant cover.SpreadThe tubenose goby was most likely introduced to the GreatLakes in the ballast water of ocean-going ships. Since theyoften resemble small bait fish, they can also be spread byboaters and fishermen who accidentally carry them fromone body of water to another through bait buckets, bilgewater, and plant debris.DistributionNative to the Black and Caspian seasin Europe, the tubenose goby wasfirst found in Lake Erie around 1990and can now be found in lakes St. Clair,Erie, and Superior.Pennsylvania DistributionUnited States Distribution118 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 119

White PerchMorone americanasteep slope fromdorsal origin to nosedeep notch separating spinyand soft dorsal finsSimilar SpeciesThe white perch is most similar to the white bass (Moronechrysops), which grows larger, is more uniformly silver withprominent dark horizontal stripes, and lacks the connectedmembrane between the first and second dorsal fins. Hybridizationbetween the two species has been documentedin Lake Erie, which has resulted in mixed characteristics.HabitatThis predacious and opportunistic feeder thrives in brackishand freshwater rivers, streams, and lakes. It exploits shallowand deep water, and can overpopulate quickly.Environmental ImpactsThe diet of the white perch, whichincludes zooplankton, insect larvae,and other fishes, puts it in directcompetition with native gameand forage species for food. In thespring, white perch feed heavily onthe eggs of other fish species suchas walleye and white bass, limitingrecruitment and causing declines inspecies numbers.InvASIve FishSpecies at a GlanceThe white perch, also called the silverperch and the stiffback, is not actuallymouth extendsbelow the eyea perch but rather a member of the temperate bass family. It is aprolific competitor of native fish species and is believed to have thepotential to cause declines of Great Lakes walleye populations.IdentificationIts deep, laterally compressed body, which averages in length from13-18 cm (5.1-7 in), is steeply sloped from the dorsal origin to thenose. The mouth is large and extends just below the eye, and thetongue lacks teeth. The dorsal fin is made up of a spiny and softportion separated by a deep notch and a small membrane. Color issilvery-gray to greenish-brown above, fading to silvery-white belowand paler on the sides, with no lateral line.SpreadSpread has occurred through natural dispersal, unauthorizedstockings, and recreational activities. Additional spread mayoccur as the white perch is stocked as a sport fish in manyareas of the Mississippi River Watershed.DistributionThe white perch is native to the Atlantic coastal regions ofthe United States, including the Lower St. Lawrence Riversouth to South Carolina. It invaded the Great Lakes throughthe Erie and Welland canals in 1950 and is now found in allof the Great Lakes. In Pennsylvania it is established in LakeErie, the Monongahela and Allegheny rivers, and has beenfound in several inland lakes throughout the state. Thisspecies is native in the lowerDelaware and lowerSusquehanna rivers.Pennsylvania DistributionGreen - Native Blue - InvasiveUnited States Distribution120 Pennsylvania AIS Field GuidePennsylvania AIS Field Guide 121