FISH-ID 101 – LAB
OBJECTIVES:
To identify some of the common fishes located in Southwestern PA
To identify some of the common fish shapes that fishes possess
To identify some of the scale types present on various fish families
To identify the various fish fin types present on fishes
BACKGROUND:
A variety of background information has been provided for your reference. Please refer
to it for descriptions of scale, fin, and morphology descriptions. Also refer to the
dichotomous key to assist with the identification of selected PA fishes.
METHOD:
There are a variety of fish specimens scattered throughout the lab. Your assignment
today is to identify these specimens, providing a brief explanation as to why this fish is
what it is on the attached data sheet. In the column marked, reason for ID provide a
short rationale for why you called this fish what you did – i.e., what is/are the
distinguishing characteristics. To say because it looks like this, isn’t enough.
Also, examine all dissected specimens in the lab for both internal and external
morphology. Be sure to note what the structure and function is of each part labeled.
FISH-ID 101 – LAB Data sheet
Name:
Specimen #
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Family Name
Common Name
Reason for ID
An introduction to fish shape, morphology, and identification
Basic Fish Body Shapes:
Sagittiform: "Arrow-like." Example shown is a grass pickerel. Other fish with this body
type include pikes, gars, topminnows, killifish, needlefish, and barracuda. These body
shapes are good for rover predators, which depend on an ability to strike quickly--often
from a hiding place.
Depressiform: "Flattened." Flounders, halibut, rays, and skates all have this form, which
allows the fish to rest on the bottom and hide either using camouflage or by covering
itself with a layer of sand. In streams, sculpins come close to having this shape.
Fusiform: Streamlined and shaped like an airplane fuselage. The example shown is a
blue-fin tuna. Tunas, mackerel, swordfish, sailfish, and marlin are all fusiform fishes.
This shape allows them to move through the water extremely fast. In streams, most
minnows have fusiform shapes.
Compressiform: Compressed laterally. Example shown is a green sunfish. This shape is
highly versatile and is probably the most common fish shape. It combines the advantages
of several of the other fish body shapes. Many freshwater fishes have this shape, such as
bass, crappie, and sunfish.
Anguilliform: "Eel-like." Many eels, of course have this shape. Shown is a brook
lamprey. This shape allows a fish to enter and hide in very narrow openings, and also
helps the fish resist the force of current.
Fish Morphology:
Fin type:
Spines:
Spines are a late development in fishes, and many fish have them. Spines may be found
almost anywhere on the body, and are used primarily for defense. Spines may have
painful poisons in them, such as those of the catfish, or simply be annoying because they
are sharp and serrated. Some fishes have developed large spines that merely make it
difficult for other fishes to get their mouths around them, or impale the unfortunate diner.
The most common locations for spines are the first part of the dorsal fin (or in fishes with
two dorsal fins, the first dorsal fin), and the first part of the pectoral fins. Spines may be
counted and their location noted, and this often helps us tell one species from another.
Spines may also be cut and their rings counted to provide the fish's age, much like a
forester would age a tree trunk.
Pectoral fins:
Pectoral fins may be horizontal and down low, like in a salmon, trout, shark, or sturgeon,
and used mainly for gliding. Over the course of millennia they have moved upwards on
the body of many fishes. Most reef and schooling fishes have their pectoral fins up high
and oriented vertically, as in the above diagram. These are often are used for swimming,
holding position, and changing directions quickly. Some fishes have further specialized
their pectoral fins; the sculpin uses its broad, spiny pectoral fins to help it hold itself to
the bottom against strong currents. Flying fishes have lengthened their pectoral fins to
allow them to glide. Some fishes use only their pectoral fins to swim, sculling them
through the water like oars.
Pelvic fin location:
Pelvic fins are usual abdominal, meaning that they are attached midway down the belly.
Salmon and trout have pelvic fins at this location. When the pelvic fins are below the
pectoral fins, such as can be seen in the diagram of the non-existent fish above, they are
termed thoracic. When a thoracic pelvic fin is attached under the gills, it may also be
called jugular, and if under the chin or eye, mental.
General caudal fin shapes:
A. The homocercal (homo-SUR-kul) tail is a modern development. It is symmetrical. It
includes truncate, square, slightly forked, and deeply forked types. It is by far the most
common caudal fin shape, shared by most fishes.
B. The heterocercal tail is an ancient form, possessed by only a few primitive fishes, such
as sharks, sturgeon, and paddlefish. It was a necessary tail shape when fishes had no
swim bladders and were heavy in the front; if the fish tried to use a symmetrical tail, it
would have plunged toward the bottom. Instead, it developed a tail with a deliberately
downward-driving design and supplemented it with horizontal, plane-like pectoral fins
that transformed that downward force into a horizontal, forward-driving force. Genius!
C. This tail has a non-differentiated caudal fin. This may be found on eels of all sorts, as
well as lampreys.
D. The lunate tail is a tail that the tuna and mackerel have refined to an engineer's delight.
This tail provides powerful forward force, with very little turbulence.
Fish Scale Shapes:
Ganoid scales are found in fishes such as the bichirs (Polypteridae), Bowfin (Amia
calva), paddlefishes (Polyodontidae), gars (Lepisosteidae), and sturgeons
(Acipenseridae). Ganoid scales are usually rhomboid in shape and have articulating peg
and socket joints between them. They are modified cosmoid scales, which consist of a
bony basal layer, a layer of dentine, and an outer layer of ganoine (an inorganic bone
salt).
Placoid scales are found in sharks and rays, and can vary greatly in external appearance.
They do not increase in size as the fish grows, instead new scales are added.
Cycloid and ctenoid scales are found in the majority of bony fishes (the Teleostei). The
anterior part of each scale is usually overlapped by the posterior portion of the scale in
front, which gives the fish great flexibility.
Ctenoid scales have a variously developed spiny posterior margin (the word "ctenoid" is
from the Greek word "cteno", meaning comb, and refers to the comb-like ctenii on the
margin of the scale).
Cycloid and ctenoid scales consist of two main regions, a surface "bony" layer, composed
of an organic framework impregnated largely with calcium based salts, and a deeper
fibrous layer composed mainly of collagen. These scales are derived from ganoid scales,
which have lost the ganoine and thinned the bony embedded plate.
As a fish with cycloid or ctenoid scales grows, its scales also grow. This results in a
pattern of concentric growth rings on the scale, which look a little like the growth rings in
the trunk of a tree. These are sometimes used to determine the age of the fish.
cycloid
ctenoid
Key to Selected Families of Pennsylvania Fishes
1a. Head with jaws; no pelvic fins; body long and “snakelike”: Eel Family - Anguillidae.
1b. Pelvic fins present; body not long nor “snakelike”. (2)
2a. Upper portion of caudal (tail) fin base longer than lower portion. (3)
2b. Upper and lower portions of caudal fin base about equal in length. (5)
3a. Vertebrae extend into elongated upper portion of caudal fin; snout with four barbels on underside; body
with separate rows of bony plates: Sturgeon family - Acipenseridae.
3b. Vertebrae not noticeably extended into upper portion of caudal fin; tail somewhat rounded. (4)
4a. Jaws long and thin with many teeth; scales thick and bony; dorsal fin short: Gar family - Lepisosteidae.
4b. Jaws short and thick; dorsal fin very long: Bowfin family - Amiidae.
5a. Adipose fin present. (6)
5b. Adipose fin not present. (7)
6a. Body scaleless with chin barbels present: Catfish family - Ictaluridae.
6b. Body with small scales: no chin barbels; body distinctly spotted; thin pointed flap of skin (axillary
process) at base of pelvic fins: Trout and salmon family - Salmonidae.
6c. Body with large scales; no axillary process at base of pelvic fins: Smelt family - Osmeridae.
7a. Stout duck-bill snout and jaws with obvious sharp teeth; single dorsal fin with no spines: Pike family Esocidae.
7b. Not with duck-bill snout; dorsal fin single or double with both spines and soft rays or soft rays only. (8)
8a. Single soft-rayed dorsal fin completely forward of anal fin; mid-belly scales sharp and “saw-toothed”;
silvery body strongly flattened from side to side; no lateral line: Herring family - Clupeidae.
8b. Single or double dorsal fin; lateral line present; “saw-toothed” mid-belly scales absent; body not
strongly flattened from side to side. (9)
9a. Single soft-rayed dorsal fin (include carp and goldfish which have first ray hardened); one or more large
pharyngeal (throat) teeth on separated fifth gill arches. (10)
9b. Dorsal fin single or double with both spines and soft rays; pharyngeal teeth present or absent
(freshwater drum has teeth on fused pharyngeals). (11)
10a. Mouth directed downward with thick fleshy lips; distance from back edge of gill flap to beginning of
anal fin much greater than distance from beginning of anal fin to base of tail fin; pharyngeal teeth
more than 15 and in single row: Sucker family - Catostomidae.
10b. Mouth not with thick fleshy lips; distance between back edge of gill flap to beginning of anal fin only
slightly greater than distance from beginning of anal fin to base of tail fins; pharyngeal teeth no
more than 6 in one to three rows: Minnow family - Cyprinidae.
11a. Body largely scaleless (small prickles present); large pectoral fins; head broad and flattened: Sculpin
family - Cottidae.
11b. Body with scales. (12)
12a. Anal fin with 3 or more spines. (13)
12b. Anal fin with 1 or 2 spines. (14)
13a. Gill cover with spine: Temperate bass family - Moronidae.
13b. Gill cover without spine: Sunfish family - Centrarchidae.
14a. Lateral line ending at base of caudal fin: Perch family - Percidae.
14b. Lateral line continues to end of caudal fin; soft-rayed portion of dorsal fin longer than spiny portion;
large flat teeth present on heavy, fused lower pharyngeals; Drum family - Sciaenidae.
Description of Selected Fish Families of PA
Lampreys, Petromyzontidae: Lampreys lack the typical jaws of other fishes, in both their larval
and adult forms. Larval lampreys have a sort of oral hood. In parasitic lampreys, after
metamorphosis the hood is replaced by the adult’s concave, circular, sucker-disk mouth, with
horny teeth. In nonparasitic lampreys, the hood does not change. The patterns of the teeth help
biologists differentiate among lamprey species. Lampreys also do not have pectoral or pelvic fins,
which are found on most other fishes. The lamprey’s thin, cylindrical body is eellike or snakelike.
It has a single, low, long dorsal fin. The dorsal fin may be notched, but it is never divided in two
in lampreys, and it connects to the curved tail fin. Lampreys have no body scales, and on the
inside they have a poorly developed skeleton of cartilage. Most lampreys are gray, olive or
brown. Some species have plain sides; others are mottled. The adult lamprey’s eyes are small.
Larval lampreys have no readily visible eyes, although they are present, covered and sightless.
Behind the lamprey’s eyes, on either side, is a row of roundish gill openings.
Sturgeons, Acipenseridae: Biologists say that sturgeons are the most primitive of the bony fishes
alive today. Extinct sturgeon relatives date back more than 350 million years. Sturgeons are found
throughout the Northern Hemisphere, in both fresh water and salt water. In some parts of the
world, sturgeons are commercially valuable for their meat and for their eggs, which are used for
caviar. Although they were once a more common part of our native wildlife, nowadays
Pennsylvania sturgeons are rare. Sturgeons are elongate, with a flattened head and snout, and
seem to be five-sided. This is because they have five rows of bony plates running along the body,
one along the back, two on the sides and two on the underside. The plates are sharp in young fish,
but smooth with wear in older, larger fish. Sturgeons have four soft barbels between the front of
the snout and the toothless mouth, which protrudes to pick up food. The upper lobe of the tail fin
is much longer than the lower lobe, and the dorsal fin is set far back toward the tail. The first ray
of the pectoral fin is hardened into a bony spine. It is used by biologists to determine the fish’s
age.
Paddlefish, Polyodontidae: The paddlefish’s most distinctive feature is its snout, or rostrum. This
“paddle” is longer than the rest of the head and flattened on top and bottom, like a paddle. The
snout is thought to be an organ of touch. It may also act as a stabilizer, keeping the fish
swimming in a horizontal position when its jaw is extended downward during filter-feeding.
Paddlefish have many long gill rakers that let them strain tiny food organisms from the water.
Like the sturgeon, the paddlefish tail’s upper lobe is longer than its lower lobe, but it has no bony
scales or plates on its body. The skeleton is mostly cartilage. The paddlefish’s gill cover extends
backward in a long, flat point. The body color is generally medium to pale blue-gray. Young
paddlefish don’t have the adult’s paddle-shaped snout. Young paddlefish also have teeth, which
the adults lack.
Gars, Lepisosteidae: Gars are primitive, ancient bony fish. Their ancestors date back more than
100 million years, as found in fossil records. In Pennsylvania, there are currently two gar species,
the spotted (Lepisosteus oculatus) and the longnose (Lepisosteus osseus). At one time the
shortnose gar was reported to be in the Pennsylvania portion of the Ohio River and in Lake Erie,
but it has not been seen there in many years. The gar has a long, relatively thin-looking,
cylindrical body that is “armored” with large, thick, diamond-shaped scales. Its beaklike or
swordlike snout is filled with fine, sharp teeth. The single dorsal fin and the anal fin are located
far back toward the tail.
The spotted gar is usually olive-green on its back and silvery-white on the belly. There are large,
roundish dark spots on the top and sides of the head, and on the upper part of the body. The fins
have dark spots and may display orange tints. The spotted gar grows almost to four feet long.
Longnose gar are grayish to olive-green on the back and white on the belly. They may have dark
spots or blotches on their fins and especially toward the rear along their sides. The fins may show
yellow or orange tints. They can grow to about 50 inches long.
Bowfin, Amiidae: Bowfins are robust-looking fish. The body is covered with heavy scales and
the head is covered with bony plates. Their color is olive-green on the back, lighter and mottled
on the sides, and yellowish on the belly. A single long, low dorsal fin extends over half the length
of the body. It is light with lengthwise stripes. The dorsal fin is just barely separated from the
broadly rounded tail fin, which shows curving stripes. A pair of short barbels protrudes near the
nostrils. The mouth is filled with sharp, strong teeth. Male bowfins can be identified by the dark
spot on the upper side of the base of the tail fin. This spot is ringed with bright-orange or yellowgreen during the breeding season. This spot may represent a false eye that could direct predators
to the bowfin’s tail, instead of the head, thus providing it with an escape mechanism. Bowfins
grow to several feet long and nearly 10 pounds.
Mooneyes, Hiodontidae: In appearance both are quite similar to herrings, having adipose eyelids,
scaleless heads, cycloid scales and a prominent axillary process. They are distinguished from
herrings by the lack of scutes, the presence of a lateral line, prominent teeth and the dorsal fin is
inserted directly above the base of the anal fin. Both species are seldom caught or observed by
anglers.
Eel, Anguillidae: Freshwater eels are the only catadromous fishes in North America.
“Catadromous” means that they spawn in salt water and live as adults in fresh water. Anadromous
fishes, like salmon and American shad, spawn in fresh water but live as adults in the ocean. On
this continent, eels are represented by a single species, the American eel (Anguilla rostrata).
Although the eel looks snakelike, it is a fish. The American eel’s body is long and slender, and
seems scaleless. Actually, it has smooth, tiny scales that are embedded in the skin. A long, low
dorsal fin extends over at least two-thirds of the back. It blends with the caudal fin and the anal
fin, which is also long and low, on the underside. There are no pelvic fins, but the pectoral fins
are well-developed. The presence of pectoral fins can be used to distinguish an eel from a
lamprey, which has no paired fins. The head has a smallish eye. The head is long, and tapers to a
small mouth. The lower jaw sticks out a little farther than the upper jaw. Eels are yellowish
brown to dark-olive, and lighter underneath. In Pennsylvania, the maximum size is two to three
feet, although four feet or more is possible. Females grow larger than males.
Herrings, Clupeidae: The herrings have several distinct physical features that separate them from
the other fishes: a single row of sawtooth scales called scutes occur along the belly, scaleless
head, transparent eye covering that is termed an adipose eyelid, and an auxiliary process that is
located at the base of the pelvic fin.
Minnows, Cyprinidae: Most small fishes, regardless of species, are erroneously called
"minnows", which leads to misidentification. Cyprinids are small in size, rarely reaching more
than 12 inches in length -- even as adults. Not all members of the minnow family are small,
however; fishes such as carp, goldfish, and white amur attain a size which ranks with the largest
freshwater fishes. Cyprinids share several common taxonomic characters, which separate them
from the other fish families. External features include: scaleless head, toothless jaws, lack of
adipose fin, lack of appendages at the base of the pelvic fins, and a single, soft dorsal fin in native
species that has less than 10 rays. Internal anatomical features are: cyprinids have fewer than 10
teeth in any row on the pharyngeal arch, an enlarged intestine instead of a true stomach, and a
series of bones called weberian ossicle that form a rudimentary ear. The list of freshwater fishes
in the United States and Canada contains 754 species, of which the largest group is Cyprinidae,
and has 221 species in 43 genera.
Suckers, Catostomidae: Worldwide distribution of the sucker family is confined mainly to North
America except for two or perhaps three species that are indigenous to Asia. All fishes in the
sucker family possess pharyngeal teeth in the throat, which are tooth-like structures used for
crushing food. Many suckers are identified by the configuration of these teeth. Some species have
thin, comb-like pharyngeal teeth for filtering plankton directly from the water like Carpiodes and
Ictiobus. Others, such as Moxostoma, Catostomus and Cyceleptus, have strong, flat-topped,
molar-like structures that are used for crushing and grinding mollusks and crustaceans.
Suckers, as their name implies, are mainly bottom feeders, foraging by sucking up materials from
the bottom, separating out the indigestible detritus and ejecting it through the mouth and
operculum. At other times some members of the family, mainly the buffalofishes, filter plankton
for food directly from the water. The mouth of all suckers is located on the underside of the head
and is tipped with fleshy protrusile lips. All family members are soft-rayed fishes with toothless
jaws, scaleless heads, cycloid scales -- smooth-edged --, forked caudal fin, and a single,
continuous, fleshy dorsal fin. Many suckers look like and are often confused with minnow
species, but they differ in many features. Most of the suckers have 10 or more dorsal fin rays,
which is always one or two more than the native minnows.
Catfishes, Ictaluridae: Family members can be separated by the simplest criteria into three major
groups: the large catfishes that include channel catfish, flathead catfish and blue catfish, all of
which often reach weights of over 20 pounds; the bullheads, including black, yellow and brown,
which rarely exceed 4 pounds in weight; and the madtoms, represented by the tadpole madtom,
slender madtom, stone cat and freckled madtom, which are the smallest of the catfishes.
Catfishes are easily distinguished from the other fishes by their smooth scaleless bodies, eight
elongated fleshy barbels or "whiskers" abouth their mouth, and the strong, sharp spines that are
located at the insertion of the dorsal and pectoral fins. It is beived that the spines are adapted as
defensive structures in the catfish family. A locking mechanism allows the fish to extend the
spine outward when attacked or touched, making it hazardous for a predator to grasp it and nearly
impossible to swallow. Madtoms and small bullheads have glands at the base of the spines that
secrete a mild but painful venom when danger is threatened.
Pikes, Esocidae: The body is round-shaped and elongated with a frontal-flattened head that has a
duck-bill shaped jaw which is lined with large, canine-like teeth. The dorsal fin is inserted far
back on the body. Identification of individual pike species is another matter that demands close
observation of key characters that separate one from another.
Mudminnows, Umbridae: The banded killifish has an elongated body with flattened sides and
large, round scales. Both males and females have dark vertical lines on the sides. Lines near the
tail are shorter than those on the body. The back is olive, yellowish olive, or brownish yellow,
fading to yellowish white or silvery-white on the bottom. The fins are light-olive or yellowish
olive.
Killifish have no lateral line, and the tail is squarish. The banded killifish has rows of small, sharp
teeth in the upper and lower jaw. Adults are usually two to four inches long.
Trouts, Salmonidae: Trout and salmon have a fleshy lobe, called the adipose fin, between the
dorsal fin and the tail. Their scales are small and cycloid, or smooth, and embedded in a slimy
mucous that is most obvious in the salmons. Trout and salmon have an obvious lateral line, large
mouth and teeth. In big specimens, the teeth are caninelike. The tail may be forked or squarish,
depending on the species, and none of the fins has spines. Mature males look different from
females because they develop a long, hooked lower jaw, called a “kype.” Mature males also
deepen or gain in color at spawning time. Coloration in trout and salmon varies from dull to
intense, according to the species, where the fish lives and the time of year. Trout and salmon that
live in the sea or a large lake become silvery.
Silversides, Atherinidae: Silversides are distributed from tropical to temperate waters. Two
widely separated dorsal fins, the first with flexible spines and the second with one spine followed
by soft rays; anal fin with one spine followed by soft rays; pectoral fins high on body; mouth
small and terminal; no lateral line; broad silvery lateral band (black in preserved specimens);
pelvic fins usually abdominal; scales relatively large
Sculpins, Cottidae: Sculpins are small, camouflaged fish reaching four or five inches in length.
Their dark-and-light mottled color pattern helps them hide on the stream bottom. The broad head,
fleshy mouth and upward-peering eyes look large for the rest of the body. Sculpins are
compressed top to bottom, tapering quickly from a robust head to a narrow tail. The large, fanlike
pectoral fins and the sculpin’s flattened body shape allow it to stay pressed against the stream
bottom, maintaining its position when in swift water–a hydrodynamic adaptation. Sculpins have
no swim bladder, so they are nonbuoyant and move over the bottom in short spurts. There are two
dorsal fins. The front fin is spiny and the rear one is soft. Both are held erect. The pelvic fins have
a single spine and soft rays. The sculpin’s body is scaleless, except for some scattered areas that
have small, sharp scales called “prickles.” The tail is straight or rounded.
Temperate basses, Percichthydae: The fishes in this family were historically referred to as the sea
basses, since most of the members were saltwater inhabitants, except for a few species that were
found in freshwater environments. Most ichthyologists acknowledge that all of the temperate
basses originated in the sea and that some became landlocked during geological land-mass
changes. For that reason it was proposed and adopted by fish taxonomists that the Percichthyidae
family be expanded to include all temperate freshwater basses along with the giant sea basses and
the ocean striped bass.
Sunfishes, Centrarchidae: All are characterized by having at least one spine at the front part of the
dorsal fin, which is continuous with the rear portion. Their body is deeply compressed laterally,
and the attachment of the pelvic fins is far forward, nearly beneath the pectoral fins. There are
three or more spines at the front of the anal fin, and the scales are ctenoid, which means they have
rough edges.
Perches, Percidae: The perch family includes the yellow perch, walleye, sauger and many darter
species. Members of the perch family are characterized by rather slender, elongated bodies and by
a large bone on the gill cover which ends in a flat spine. The dorsal fins are a very distinctive
characteristic of the family with a definite separation evident between the anterior spiny portion
and the soft portion to the posterior. The mouth of walleye and sauger is filled with formidable
canine teeth on the jaws, the roof of the mouth and palate, teeth that are absent in the perch and
darters.
All members of the family are strictly carnivorous. The large species are piscivorous, eating
mostly other fishes, while the smaller darter species prey mostly on minute aquatic insects and
planktonic crustaceans. A wide range of forage and habitat preference is primarily responsible for
the distribution of the family throughout Iowa.
Drums, Sciaenidae: The freshwater drum (Aplodinotus grunniens) is Pennsylvania’s only
freshwater representative of a large group of 210 marine species found in temperate and tropical
coastal waters around the world. The lower pharyngeal (throat) arches are heavy and fused, and
they bear flat, molar-like teeth. The spiny and soft-rayed portions of the dorsal fin are narrowly
joined. The spiny-rayed portion is shorter that the spinous section. The lateral line continues to
the end of the tail fin. In Pennsylvania, the freshwater drum occurs in Lake Erie, and in the
Allegheny, Ohio and Monongahela rivers. The freshwater drum is dark-green to olive-brown on
the upper part of the head, back and sides, shading to silvery on the sides. The belly is white. The
anal fin has two spines, the first, very small and the second, quite large. The body is sharply
arched.
IDENTIFICATION OF THE
TEMPERATE BASS
White Bass, Striped Bass and their Hybrid
Yellow bass can be identified because they do not have a tooth patch on their tongue and the
second spine of the anal fin is longer than the base of the anal fin. White bass can be identified
because they have a single center tooth patch, and their stripes are faint. On a white bass, the first
stripe below the lateral line is not distinct nor complete to tail. Some striped bass may have
broken lines, but the stripes of a fresh hybrid are distinct and definitely broken. The shape of the
head can be a distinguishing characteristic between the striped bass and the hybrid bass (wiper).