This
week’s lab involved taking a tour through the fish families of Ohio, guided by
Dr. Sheil. We began by covering the
basics of fish morphology. The first thing emphasized was the arrangement of
fins and their proper titles, which included: the dorsal fin, caudal fin, anal
fin, pelvic fin and pectoral fin. The bony supports within fins are fin rays,
which are softer and more flexible, and spines, which are stiffer processes. The
bony plate that covers the gills is called the operculum. The line running the
length of the fish’s body is known as the lateral line, and it is a sensory
organ used to detect pressure changes in water.
Our
lecture also covered the three basic scale types: ganoid, cycloid and ctenoid
scales. Ganoid scales are the basal, or ancestral, scale type that has an upper
surface covered in ganoine, which is a mineralized tissue comparable to enamel.
Cycloid scales are a rounded type of scale, whereas ctenoid scales have more of
an irregular shape.
Another of the basic morphological characteristics discussed were the two types of
tails. The ancestral condition is a heterocercal tail, which is asymmetrical,
with the vertebral column extending into the larger lobe. Alternately, the
symmetrical homocercal tail type is derived and seen much more commonly in the
fish of Ohio.
After
learning the basics we were ready to take a plunge through the different
families of fish found in Ohio. We traveled to each of the different tables throughout
the lab and sketched the preserved representatives of the families, taking note
of particular morphological features that will aid in identification.
Petromyzontidae:
Lampreys
Lampreys
are parasites of other fish. They use their buccal funnel (mouth), which is
lined with cornfield “teeth,” and rasping tongue to feed of host fish. Although
lampreys have a mouth, they are jawless, so they lack an operculum. The
lamprey’s over all morphology resembles an eel in the sense it lacks pelvic and
pectoral fins. The dorsal fin is posteriorly displaced and is fused with the
caudal and anal fin. The dorsal fin can be undivided, have a wide notch between
the dorsal and caudal fins, or have a deep notch between the two fins. The
condition of the dorsal fin and the anatomy of the mouth are often used to
characterize species belonging to this family.
Acipenseridae:
Sturgeons
The
sturgeon is a large, prehistoric-looking fish that has an ancestral heterocercal
tail. This fish has bony plates, or scutes, that are arranged in rows running the
length of the body. Under the snout, one can see 4 distinct barbels and a
tubular mouth used for sucking food items off the substrate. There are two
species in Ohio, Acipenser fluuescens and
Scaphirhynchus platorychus. Scaphirhynchus platorychus can be
differentiated due to its long, slender tail and large, bony plates on the
caudal peduncle.
Lepisosteidae:
Gars
Gars
have a long snout that is filled with long, fang-like teeth, making them look
fierce in appearance. Typically found in slow-moving and turbid tributaries,
these fish turn right or left to grab prey as they swim through the water
column. This fish has an elongated body that is covered with rhomboid, ganoid
scales, which function as “armor-plated” protection. The dorsal fin is
posteriorly displaced, which is often associated with “sprinter” fish or fish
that swim near the surface. The operculum of members of this family has many
bones on the “cheek” rather than just one singular opercular shield. It should
also be noted the gars have an abbreviated heterocercal tail. The genus we have
in Ohio is Lepisosteus.
Clupeidae:
Herrings and Herring allies
Alewife specimens. Note the vertical eyelid and the ventral row of keeled scales that help distinguish this fish. (Photo credit) |
This
“cute” family of fish has a few unique morphological characteristics that can
help in identification. First, the dorsal fin is situated almost directly over
the pelvic fin. Secondly, this family of fish has no lateral line system. Also,
on the underside of the fish there is a row of keeled scales that resemble saw
teeth. Furthermore, the anal fin is so broad and long it almost appears to
interact with the caudal fin. A particularly interesting member of this group
is the alewife (Alosa pseudohasengus),
which has a “bizarre” eyelid that opens and closes vertically opposed to
horizontally, and is a dead giveaway for identification.
Salmonidae:
Salmons, Trouts, and Whitefish
These
fish have small cycloid scales which give them a smooth appearance. Both male
and female fish of this family possess a bilateral axillary process located
above the pelvic fin. Cameron shared that he recently completed work for a research
project that utilized this fleshy process for genetic testing. Researchers
remove the process without significant negative impact on the fish by clipping
it with a pet nail trimmer and have enough material for genetic analysis.
Another feature in this group is presence of an adipose fin which is a small
fleshy fin, comprised of fat, located between the dorsal and caudal fin. The
Brook Trout (Salvelinus frontinalis) and
the Lake trout (S. namaycush) are two
examples from this family found in Ohio.
Esocidae:
Pikes
These
fish look distinct because their snouts resemble duck bills and are filled with
large canine teeth. Similar to gars, the pike’s dorsal fin is displaced
posteriorly because this fish swims near the surface and is a “sprinter.” These
voracious predators rest in the grass, wait for prey, and then shoot out to
grab them with their sharp teeth. Esox is
the genus primarily found in Ohio. Muskellunge and Pike are typically found in
large lakes and pickerels live in small streams.
Catastomidae:
Suckers, Redhorses and Buffalo fish
The
most obvious feature of fish in this family is the subterminal mouth. The large
and striated, sucker-like lips are used to adhere to substrate and suck up food,
such as periphyton from rocks and logs. In Ohio, we can find the red horse (Moxostoma), the buffalo fish (Carpoides),
and the common white sucker (Catastoma
commersoni). We were cautioned
not to confuse Carpoides with the
common carp, which belongs to Cyprinidae. Carpoides
superficially resembles a carp, but is distinguished by a nipple-like process
on the bottom lip and a lack of barbels.
Ictaluridae:
Catfishes, Madtoms
Madtom (left) and catfish (right) specimens. Note the small size of the madtom, as well as the unforked, rounded caudal fin. Alternately, the larger catfish displays the characteristic forked caudal fin. (Photo credit) |
Members
of this family usually have more than eight barbels around their mouth. An
interesting feature lies within the fins, with both the dorsal and pectoral
fins having a large spine. These fish lack scales, but an adipose fin is
present. Catfish (Ictalurus) and madtoms
(Noturus) can be easily confused if
one does not know what specific morphological features to compare. However, adult
madtoms do not get much larger in length than the distance between your extended
thumb and pinky finger, while catfish can grow to be quit large. Looking at the
tail can also help one decipher between the two. Madtoms have an unforked,
rounded caudal fin, whereas the caudal fin of the catfish is forked.
Cyprinidae:
Carp, Minnows, Daces, Shiners and Goldfish
Cyprinids
have a more terminal mouth and in some species, the upper jaw has fleshy barbels
that hang from it. Sometimes these barbels can be cryptic. One example of a very
common Ohio cyprinid is the common carp (Cyprinus
carpio). The goldfish (Carassius
auratus) is distinguished from the common carp due to a lack of barbels on its
upper jaw. Another group of Cyprinidae is the minnows (Campostoma), which are said to resemble “green beans” in a seine
net, and can be characterized by a large “c-shaped” upper lip that causes a
heavy overbite. Fathead minnows (Pimephales)
have only a slight overbite, but very crowded scales on the dorsum.
Anguillidae:
Freshwater Eels
The
freshwater eel has almost a serpent-like appearance, with pelvic fins absent
and a fused dorsal, caudal and anal fin. This fish has scales so small it
appears to be scaleless. On each side of the fish we find a single opercular
opening. A freshwater eel species found in Ohio is the American eel (Anquilla rostrata).
Atherinidae:
Sliversides
Sliversides
resemble a miniature freshwater barracuda. These fish have a very flat head and
back along with a “bird–beak” shaped mouth. Sliversides also have very large
eyes. Running down the length of the body is row of serrated scales that stand
out against the conspicuous cycloid scales of the rest of the body. Sliversides
also have two dorsal fins, the first of which is shorter and has six spines. In
Ohio, we find the Brook silverside (Labidesthes
sicculus). When captured in a seine net, these fish are easily recognized
by the silver flash on their side that reflects the light.
Moronidae:
White Basses
The
fish in this group have two dorsal fins, the first of which has spines that are
sharp and the second just has flexible rays. The key feature for this family is
a spine that is located on the opercular flap. Members of this family commonly
seen in Ohio are the White Bass (Morone
chrysops), the Striped Bass (M.
saxatilis) and White Perch (M.
americana). Moronids can be distinguished from members of Centrarchidae by
the condition of the dorsal fins, which as previously mentioned, are fused in
centrarchids.
Centrarchidae:
Blackbass, Crappies and Sunfishes
When
it comes to members of this family, attention to detail is critical for identification.
Counting the number of dorsal and anal fin spines as well as examining the size
of the scales is very important. In Ohio, members of this family include blackbass
(Micropterus), which have fused
dorsal fins and small scales. The sunfishes also have fused dorsal fins, but
larger scales than the blackbass. Finally there are crappies (Pomoxis), which have 5-8 dorsal spines and
5-7 anal spines.
Percidae:
Walleyes, Perch and Darters
Fish
in this family generally have large, blocky heads and the body depth tends to
be less than the head length. The overall shape of the body resembles a
torpedo. These fish also have conspicuously paired dorsal fins and a spine
associated with the anterior end of the anal fin. In Ohio, we find walleye (Stizostedion), which have a very flat
belly and two dorsal fins. We also have darters (Etheostoma), which have very blunt faces and huge pectoral fins. Finally,
we have the roughbelly darters and logperches (Percina) that have a more tapered face compared to darters in the
genus Etheostoma, as well as
significantly smaller pectoral fins.
Gobiidae: Gobies
This
invasive group of fish is distinguished by its cup-shaped pelvic fin, which
acts as a suction cup to allow them to withstand the current and sit in place
on the benthos. As we learned in a previous lab, these voracious gobies will
eat the eggs of other fish species in the time that it takes a fisherman to
pose with the caught fish for a photo. There are strict restrictions on fishing
activity due to the threat of goby predation on the eggs of native fish
species.
We
concluded the lab by helping improve the JCU Biology Department’s fish
collection by identifying and sorting unknown fish specimens. Using a
dichotomous key specific to families of Ohio fishes, we were able to organize
mixed collections of unknown fish into fresh and properly labeled preservation
jars.
In addition to basic morphological features such as fin condition, presence or absence of barbels, tail type and snout shape, it was necessary to count scales to determine finer classifications of unknown specimens.
Professors and students work together to identify this mystery fish. |
In addition to basic morphological features such as fin condition, presence or absence of barbels, tail type and snout shape, it was necessary to count scales to determine finer classifications of unknown specimens.