Fishy Relationships!

Transcription

1 Fishy Relationships! Outcome: : 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 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 of 7

2 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 of 7

3 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 teeth eye caudal fin 3 of 7

4 4 of 7 Adaptation Adaptations in Fish Purpose Example(s) Mouth Terminal (at the end of the snout) Feeds throughout the water walleye, sauger, northern pike Under the snout / longer upper jaw Feeds on prey it sees below it; usually feeds off the lake or river bottom bullhead, whitefish, carp, sucker Angled upward / longer lower jaw Feeds on prey it sees above it; small fish or aquatic insects goldeye, rock bass, smallmouth bass, often at the surface of the water tullibee Ventral (under the head) Feeds off the bottom sturgeon Sucker-shaped "Vacuums" up food off the bottom; eats aquatic insects and/or vegetation sucker, sturgeon Strong jaws and well-developed teeth Feeds on other fish northern pike, walleye With barbels Feeds off the bottom; can sense food in murky water catfish, bullhead, stonecat, sturgeon Eyes Large Feeds by sight walleye, perch, goldeye Small Likely feeds off the bottom and relies on barbels to detect food catfish, bullhead, stonecat, sturgeon Spines For protection or to stiffen fins for swimming catfish, bullhead, stonecate, perch, walleye, bass, sturgeon Body Shape Rounder, flat-bellied Feeds off or rests on the bottom; less conspicuous to predators sucker, catfish, sturgeon Oval, fairly long Prefers more open water or a few weeds walleye Oval, very long, eel-like Fast-moving in quick bursts; agile around rocks and weeds northern pike, burbot Thin, shorter, disc-shaped Agile around rocks/weeds; round shape harder for predators bass, perch to swallow Torpedo-shaped Stream-lined for high speed or swimming in currents brook trout, rainbow trout, arctic char Scales Large Used for protection; speed not needed to catch food carp, sucker Small or non-existent Fish more stream-lined or fast-moving to catch prey northern pike, catfish, burbot Colouration Fairly uniform, no markings Swims in open water walleye, goldeye Stripes Hides in weeds for protection or to ambush prey perch, smallmouth bass, rock bass Mottled Hides in rocks or on bottom northern pike Dark on top Less visible to predators above it catfish, sturgeon, carp Light-coloured belly Less visible to predators below it perch, walleye, sturgeon, sucker, carp

5 5 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

6 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 Where do you think this fish feeds? Fish No. 1 Fish No. 2 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

7 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