STUDENT LABORATORY — Using a Dichotomous Key to Identify New York State Freshwater Fishes

Full Name: ___________________________________________ Lab Date: __________ Lab Section: _______ Lab Instructor: _____________________ Credit: 1 lab

Standards: • Common Core Standards: Reading (Grade 9): 3,4,5• Living Environment Core Curriculum: LE Lab checklist: “Designs and uses dichotomous keys to

identify specimens.”

Objectives: Students will be able to: • Use a dichotomous key to identify fish native to New York State.

Portions of this lab were adapted from dichotomous key labs from Mr. Comet, a teacher at South Lewis High School in Turin, NY and Ms. Foglia fromDivision Avenue High School, Levittown.

Pre-Lab: In taxonomy, a traditional dichotomous key (sometimes called a single-access key) is used to sort and classify the diversity of organisms by physical characteristics. Now, with scientific advancements, other characteristics such as genetic similarities can be added to a key as well. To use a dichotomous key, one answers a series of questions, each with either a yes or a no answer. Each answer leads to another numbered question where we make another yes or no decision. This continues until the last question which reveals the identity of our organism.

An example of a dichotomous key in flow-chart format is shown here. This simple guide can be used to identify an insect, dog, snail or a worm.

In this lab, you will use a dichotomous key to identify New York State freshwater fish, and first must familiarize yourself with fish anatomy. Watch the video, pause at 0:55 and see how many numbered parts you can label in the table below. Use the anatomical terms (and not the labeled fish diagram!) listed on the next page for help. Watch “A Quick Lesson on External Fish Anatomy” – https://youtu.be/CJ3GlqSVW44Un-pause the video and see how you did.Afterwards, watch https://youtu.be/eWbbSdrVaiE for another short video about fish anatomy.

Number from Video Anatomical Name

1 2 3 4 5 6 7 8 9

10 11 12

Insect Dog

Snail Worm

Image: Prime Time Aquatics

Review the anatomical terms, descriptions and the diagrams below and reference them as needed as you identify each fish using the dichotomous key.

• Anterior: towards the head • Posterior: Towards the back • Broad part of the fish: height of thickest part of the fish from top to bottom, not including the fin. Use a

ruler to measure the broad part, then use a ruler to measure the length of the fish. Compare the two numbers as a ratio. See image below.

• Hinge: Where the corners of the mouth meet; can be in front of the eye, below the eye, or in back of the eye.

• Barbel: a fleshy projection from the lip or head (like on a catfish) • Concave: curving inward • Fins: Fins can be single (separate), elongated (one type of fin, for example a dorsal fin that stretches

along part of the length of the body) or continuous (cannot distinguish separate fins, stretch along the entire length of fish as one fin)

o Adipose: a small fin on the top mid-line of the body near the tail fin (not pictured below). o Anal: a fin along the lower mid-line of the body near the tail fin. o Caudal: tail fin. Can be forked: looks like a sideways “V”, partially forked or un-forked. o Dorsal: the fin or fins along the top mid-line of the body. o Pectoral: the paired fins nearest the head, corresponding to front legs or arms. o Pelvic: the paired fins nearest the tail, corresponding to hind legs.

• Scales: overlapping outgrowths of the skin.

--------------------------------------------------------------Laboratory Exercise---------------------------------------------------------- Procedure/Observations:

1. Watch this short video to learn how to use a dichotomous key: https://youtu.be/3x7tuIZd4Sw 2. Closely examine fish 2 on the New York State Fish sheet. 3. Refer to the Dichotomous Key on the next page. Note that each numbered item on the key presents two

possibilities. 4. Read statements 1a and 1b in the Dichotomous Key. One of these statements describes a characteristic of

fish 2, while the other does not. 5. Since fish 2 has no scales (or at least none that we can see), we choose 1b which now refers us to number

12. 6. Read the 12a and 12b descriptors. This fish is not elongated or snakelike. Go to number 13. 7. Read the descriptors for 13a and 13b. The fish we are classifying has barbels growing from its lips and the

top of its head. Go to number 14 of the key. 8. 14b describes a fish having a caudal fin that is rounded with a blunt head. We see that this is the Bullhead

catfish. Go to the page with the New York State Fish Identification table. Under the column “Identified as” write “Bullhead catfish.” In the column labeled “Identification pathway” write “1b, 12b, 13a, 14b”

9. Identify the remaining fish using the dichotomous key. Terms on the dichotomous key that are in bold are defined above. Note: identification is challenging! Do your best!

How to measure the “broad” (top to bottom arrow) part of the fish as compared to the length of the fish (left to right arrow).

Dichotomous Key for Common Freshwater Fish of New York State

No. Statement Go to/Identify 1a. Body noticeably covered with scales 2 1b. Scales not covering body or too small to be seen 12 2a. Dorsal fin single 3 2b. Dorsal fins two or more, joined or separated 6 3a. Body more than four times as long as broad; front edge of dorsal fin

far back on body; mouth large, hinge of mouth in back of eye 4

3b. Body less than four times as long as broad; front edge of dorsal fin about midway between head and tail; mouth not large, hinge in front of eye.

5

4a. Dark lines forming netted design on body: fins not spotted Pickerel 4b. Body covered with yellow spots; fins spotted Northern Pike 5a. Mouth turned downward: barbels absent; dorsal fin not elongated White Sucker 5b. Mouth not turned downward: barbels present; dorsal fin elongated Carp 6a. Two dorsal fins separated, the anterior spiny and the posterior soft

(not spiny) 7

6b. Two dorsal fins united, forming an anterior spiny portion and a posterior soft portion 8

7a. Top of head concave, farming a hump in front of dorsal fin; dark vertical bars on body Yellow Perch

7b. Top of head not concave, body sloping to dorsal fin and not forming a hump; dark blotches on body Walleye

8a. Body more than three times as long as broad 9 8b. Body less than three times as long as broad 10 9a. Hinge of jaws behind the eye: notch between spiny and soft dorsal fin

deep and nearly separating into two fins Large Mouthed

bass 9b. Hinge of jaws below the eye; notch between spiny and soft dorsal fin

not nearly separating into two fins Small Mouthed

Bass 10a. Mouth large, hinge below or behind eye 11 10b. Mouth small, hinge in front of eye Bluegill 11a. Five to seven spines in dorsal fin; dark spots forming broad vertical

bars on sides, Red/orange earspot on gill covering (see picture) Pumpkinseed

11b. Ten or more spines in dorsal fin: sides flecked with dark spots Rock Bass 12a. Body elongated and snakelike: dorsal, caudal, and anal fins

continuous (cannot distinguish separate fins) American Eel

12b. Body not elongated and snakelike: dorsal, caudal, and anal fins separate; adipose fin present 13

13a. Barbels growing from lips or top of head; head large and broad 14 13b. Barbels lacking; head not large and broad 16 14a. Caudal fin deeply forked(looks like a sideways “v”); head tapering 15 14b. Caudal fin rounded or slightly indented but not forked: head blunt Bullhead Catfish 15a. Dorsal fin rounded at top: body silvery, speckled with black markings Channel Catfish 15b. Dorsal fin long and pointed at top: body bluish-gray without speckles Blue Catfish 16a. Caudal fin deeply forked; back not mottled (spotted) or with few

spots Atlantic Salmon

16b. Caudal fin square or slightly indented; back mottled or spotted 17 17a. Back and caudal fin spotted: broad horizontal band along sides Rainbow Trout 17b. Back mottled with dark lines: caudal fin not spotted; fins edged with

white Brook Trout

New York State Fish Identification Table

Fish Identified as Identification pathway 1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18 Analysis and Conclusion:

1. What did you struggle with as you used the dichotomous key to identify the NYS fish?

*Note — This lab is due at the end of the lab period or as directed by your instructor. Your instructor may modify the lab based on time.

New York State Fish

Fish 1

Fish 2

Fish 3

Fish 4

Fish 5

Fish 6

Fish 7

Fish 8

Fish 9

Fish 10

New York State Fish continued

You Have Completed the Dichotomous Key Lab!

*Important — Save this lab for your records. Upload this lab report to your Google Classroom for lab credit

Fish 11

Fish 12

Fish 13

Fish 14

Fish 15

Fish 16

Fish 17

Fish 18