Lesson XLI

The Stickleback

Leading thought—The stickleback is the smallest of our common fish. It lives in stagnant water. The father stickleback builds his pretty nest of frog-spittle which he watches very carefully.

Method—To find sticklebacks go to a pond of stagnant water which does not dry up during the year. If it is partly shaded by bushes so much the better. Take a dip net and dip deeply; carefully examine all the little fish in the net by putting them in a Mason jar of water so that you can see what they are like. The stickleback is easily distinguished by the five spines along its back. If you collect these fish as early as the first of May and place several of them in the aquarium with plenty of the algæ known as frog-spittle and other water plants they may perhaps build a nest for you. They may be fed upon bits of meat or liver chopped very fine or upon earthworms cut into small sections.

Observations—1. How did the stickleback get its name? How many spines has it? Where are they situated? Are they always carried erect? How are these spines used as weapons? How do they act as a means of safety to the stickleback?

2. Describe or make a sketch showing the shape and position of the dorsal, the anal, the ventral and the pectoral fins. What is the shape of the tail? What is the general shape of the fish?

3. What is the color of the sticklebacks? Is the color always the same? What is the color and position of the lateral line?

4. Describe the eyes. Are they large or small? Can they be moved? Do you think they can see far?

5. Describe the mouth. Does it open upward, straight ahead or downward?

6. When the stickleback is swimming what are the positions and motions of the dorsal, anal, tail and pectoral fins? Can you see the ventral pair? Are they extended when the fish is swimming?

7. When resting among the pond weed of the aquarium what fins does the stickleback use for keeping afloat? How are the other fins held? What fins does it use to move backward? Which ones are used when it lifts itself from the bottom to the top of the aquarium? How are its fins placed when it is at rest on the bottom?

8. Drop a piece of earthworm or some liver or fresh meat cut finely into the aquarium and describe the action of the sticklebacks as they eat it. How large is a full-grown stickleback?

9. In what kind of ponds do we find sticklebacks? Do you know how the stickleback nest looks? Of what is it built? How is it supported? Is there one door or two? Does the father or mother stickleback build the nest? Are the young in the nest cared for? At what time is the nest built?

Supplementary reading—Fish-stories, Chap. XXXVI, Jordan and Holder.