Fishy Relationships!
Outcome:
6-1-13: Compare and contrast the adaptations of closely related vertebrates living in
different habitats, and suggest reasons that explain these adaptations.
Materials:
?
scissors
?
writing utensil
Teacher’s Instructions:
1. Make a class set of pages 4, 6 and 7. Make several copies of the fish cards on page 5
(enough so that each student will have one fish card).
2. Cut out the fish cards, shuffle them and place them face down in a pile.
3. Hand out page 4 to each student. Using the chart for reference, discuss with students
the various physical adaptations of fish and their possible benefits or purposes,
including mouth shape, body structure/shape, and colouration.
4. Ask each student to draw a fish card from the pile. Next ask students to choose a
partner. Partners cannot have the same fish card.
5. Hand out pages 6 and 7 to each student or pair of students.
6. With their partners, students will examine the fish they have drawn and discuss their
features. Based on the features they have observed and using the chart on page 4,
they will guess what kind of habitat their fish prefer and what kind of food they eat.
7. Ask students to record their observations and guesses using the chart on page 6.
8. Next, ask students to fill in the Venn Diagram on page 7, comparing and contrasting
the similarities and differences between the two fish.
Teacher Background Information:
An adaptation is a structural or behavioural change in an organism which improves its
ability to survive in the environment.
There are many different species of fish, all varying in body shape and structure, and
colouration and markings. These differences in appearance - along with differences in
behaviour - have evolved over time (in some cases, millions of years) as different fish
species adapted to different environments. The Key to Manitoba Fish Species shows the
more obvious similarities and differences among our fish.
Continued on page 2...
1 of 7
Teacher Background Information (Cont’d.):
Most fish have scales, which may be very large or barely visible to the naked eye,
depending on the species of fish. Scales help to protect fish from injury and small
predators. They overlap to reduce friction through the water, however fish with larger
scales give up some flexibility and speed for the added protection. The prehistoriclooking sturgeon is unusual. While ancient sturgeon had a heavy, armour-like covering of
hard, shiny, interlocking scales, modern sturgeon have lost their scales and retain only a
bony plate over their skull and five rows of bony plates, called scutes, that run the length
of their body. The sharp, hooked scutes protect young sturgeon from predators and adult
sturgeon from injury while feeding or reproducing in rocky areas.
A fish's body shape also reflects its "lifestyle". Suckers and sturgeon have round bodies
that are flat on the bottom and suit their bottom-feeding existence. Northern Pike are
more slender (laterally compressed) which allows them to rapidly pursue their prey. Other
fish that lurk in the weeds or rocks, such as bass, tend to be shorter and thin or discshaped. This allows them to make quick turns around the rocks. The narrow, disc-shaped
goldeye can "slice through" the water with little resistence. Its narrow profile, when
viewed from head-on, also makes it less detectable to predators. Trout and arctic char
are streamlined and elongated, for high-speed swimming or prolonged swimming against
strong currents.
The fins of different fish species can also differ. They may be soft or have spines.
Spines can be used for protection from predators (e.g. in catfish or walleye). Spines not
only discourage predators but also make their prey more difficult to swallow. Spines can
also be used to stiffen fins to assist in swimming (e.g. in sturgeon). Fins are used for
locomotion, stability or balance, and steering. They can also be used for braking and
aggressive displays.
The tail is actually a fin also called the caudal fin. It helps to propel the fish forward as it
moves side to side - the actual forward thrust coming from the pressure of the fish's tail
against the surrounding water. Fish with smaller caudal fins undulate their bodies to
move forward. Their tail may be lobed or club-shaped. The sturgeon's shark-like
(heterocercal) tail or caudal fin contrasts with the homocercal (symmetrical) tail of all
other Manitoba fish species, and is considered to be the most primitive of tail forms
today.
The shape of a fish's mouth reflects what it eats and how it consumes its food. Fish that
feed on the bottom of a river or lake, such as a sucker or carp, have "sucker-shaped"
mouths under their head which they use to "vacuum" up their food, including aquatic
insects or plant material. The sturgeon's tube-like mouth can actually protrude for
maximum sucking action. Generally, fish that feed off the bottom do not have any teeth,
or only have small teeth. A carp's molar-like teeth are used to grind up vegetation.
Fish that are carnivores or piscivores (i.e. they eat other fish) will have large mouths
with strong jaws and well-developed teeth (like a northern pike or walleye). They will
likely have mouths at the end of their snout, or even above it, which helps them seize
their prey. Some fish, such as bass, feed on prey that they see from below so their lower
jaw is actually longer than the upper jaw. Other fish, such as catfish, have a longer upper
jaw than bottom, because they tend to see and feed on their prey from above.
Continued on page 3...
2 of 7
Teacher Background Information (Cont’d.):
Some fish, including sturgeon, channel catfish, bullheads, and stonecats, have barbels
or fleshy feelers ("whiskers") that hang in front of their mouths. Barbels are sensory
structures that help the fish detect its food as it swims along the bottom of a river or lake.
In the dim light and murky water, these bottom-feeding fish rely more on their sensitive
"whiskers" to detect their food than their eyesight, so their eyes are very small. Fish that
are piscivores tend to have big eyes, to better see their prey. A walleye's large eyes are
actually sensitive to bright sunlight. For this reason walleye tend to feed at twilight or dark
periods. Fish do not have eyelids; the water bathes them constantly so they do not need
tears.
Colouration in fish helps them to blend into their surroundings so they can stalk their
prey. The yellowish-brown walleye prefers to hunt in open water that is slightly turbid or
murky. The mottled markings of a pike help it to hide in the weeds or rocks where it lays
in ambush for unsuspecting smaller fish. The vertical striping on a yellow perch also
helps this carnivore hide in the weeds. The greyish-brown or olive colour of the rock bass
helps it to hide in the rocks, of course!
Colouration can also be used for protection. These same stripes and spots on fish help
them hide from predators as well as from potential prey that they hope to ambush. Some
fish are darker on top while being pale or white underneath. The dark colour on top is not
easily seen by predators viewing them from above while the light colouring on the bottom
help them blend in with the light background when viewed by a predator from below.
Juvenile fish often are mottled or have spots to help them blend in with the bottom or
rocks where they are hiding.
Colouration can also be used to attract a mate for reproduction. Fish, particularly the
males, often become much more brightly coloured in the spring when they are
reproducing or spawning. However, this colouration is temporary and sometimes
confusing to someone trying to positively identify a fish.
For more information about fish adaptations, see the chart on page 4.
Walleye
spines
eye
caudal fin
teeth
3 of 7
Adaptations in Fish
Adaptation
Mouth
Terminal (at the end of the snout)
Under the snout / longer upper jaw
Angled upward / longer lower jaw
Ventral (under the head)
Sucker-shaped
Strong jaws and well-developed teeth
With barbels
Eyes
Large
Small
Spines
Purpose
Example(s)
Feeds throughout the water
Feeds on prey it sees below it; usually feeds off the lake or
river bottom
Feeds on prey it sees above it; small fish or aquatic insects
often at the surface of the water
Feeds off the bottom
"Vacuums" up food off the bottom; eats aquatic insects
and/or vegetation
Feeds on other fish
Feeds off the bottom; can sense food in murky water
walleye, sauger, northern pike
Feeds by sight
Likely feeds off the bottom and relies on barbels to detect
food
walleye, perch, goldeye
For protection or to stiffen fins for swimming
bullhead, whitefish, carp, sucker
goldeye, rock bass, smallmouth bass,
tullibee
sturgeon
sucker, sturgeon
northern pike, walleye
catfish, bullhead, stonecat, sturgeon
catfish, bullhead, stonecat, sturgeon
catfish, bullhead, stonecate, perch,
walleye, bass, sturgeon
Body Shape
Rounder, flat-bellied
Oval, fairly long
Oval, very long, eel-like
Thin, shorter, disc-shaped
Torpedo-shaped
Scales
Large
Small or non-existent
Colouration
Fairly uniform, no markings
Stripes
Mottled
Dark on top
Light-coloured belly
Feeds off or rests on the bottom; less conspicuous to
predators
Prefers more open water or a few weeds
Fast-moving in quick bursts; agile around rocks and weeds
Agile around rocks/weeds; round shape harder for predators
to swallow
Stream-lined for high speed or swimming in currents
sucker, catfish, sturgeon
walleye
northern pike, burbot
bass, perch
brook trout, rainbow trout, arctic char
Used for protection; speed not needed to catch food
Fish more stream-lined or fast-moving to catch prey
carp, sucker
northern pike, catfish, burbot
Swims in open water
Hides in weeds for protection or to ambush prey
Hides in rocks or on bottom
Less visible to predators above it
walleye, goldeye
perch, smallmouth bass, rock bass
northern pike
catfish, sturgeon, carp
perch, walleye, sturgeon, sucker,
carp
Less visible to predators below it
4 of 7
Walleye
Perch
Rainbow Trout
Brook Trout
Manitoba Fish
Manitoba Fish
Manitoba Fish
Manitoba Fish
Sturgeon
Catfish
Bullhead
Carp
Manitoba Fish
Manitoba Fish
Manitoba Fish
Manitoba Fish
Sucker
Goldeye
Rock Bass
Northern Pike
Manitoba Fish
Manitoba Fish
Manitoba Fish
Manitoba Fish
5 of 7
Fishy Relationships!
Do you think these two fish eat the same food? Yes _____ No _____
Do you think these two fish feed in the same area of the water?
(i.e. along the bottom, in the middle or throughout the water, near
the surface of the water)
Yes _____ No _____
Fish No. 1
Where do you think this
fish feeds?
How does it find its
food?
What do yo think this
fish eats?
Is this fish a fast or slow
swimmer?
How does this fish avoid
predators?
6 of 7
Fish No. 2
Fishy Relationships!
What do these two fish have in common? Where do they differ?
Look at the clues at the bottom of the page and write them in the
appropriate spot in the circles.
Fish No. 1
Adaptations
Fish No. 2
Adaptations
Similar
Adaptations
Clues
Mouth: sucker-shaped, underneath the snout, at the end of the snout, angled upward
Body Shape: oval, flat-bellied, thin, disc-shaped, torpedo-shaped
Colouration: stripes, mottled, no markings, dark on top, light underneath
7 of 7