Background for Teachers

Cool Schools...of Fish! 

If you don't have Texas Parks & Wildlife magazine, try printing this copy of Cool School (PDF).

One fun twist on going back to school: fish schools! Find features on freshwater fish (in Texas streams, rivers and lakes) and saltwater fish (in the Gulf). Fun facts are strewn throughout the story about fish adaptation, the differences between fish species, and the importance of conservation.

Fishing for "Sport"

Did you ever go fishing with a grandparent? Were you ever curious about what you tried to catch? Does a relaxing day on a river or lake, with the occasional excitement of a fish on the line, sound like fun? 

Texans love to fish! With miles of coastline, bays, rivers, lakes and streams, we care for a rich diversity of saltwater and freshwater species. Check out these sport fish species, whose populations are protected. Scientists monitor their quantities and qualities to set fair rules for how many, what size and when they can be caught and kept, for recreational and commercial uses. After careful study, with surveys in many waterways, fisheries staff recommend rules. Regulations are then proposed and approved by the Parks and Wildlife Commission. Some fish populations are replenished by state and federal hatcheries. Texas Freshwater Fisheries Center, Sea Center Texas and other hatcheries don't just raise and stock fish populations; they also welcome visitor groups for special tours!

Other Fishes

Some species, like the San Marcos gambusia and the Comanche Springs pupfish, are found nowhere else in the world. Texas also has endangered or threatened fish species. One interesting and threatened fish, the paddlefish, is a relic from pre-dinosaur times. Some fossils are over 300 million years old! These amazing fish can grow 7 feet long, and like sharks, they have cartilaginous skeletons and no scales. Unlike sharks, these gentle giants eat plankton, which they filter from the water as it flows over their gill rakers. Students love learning about these fish, which are currently being raised and reintroduced to some east Texas rivers.

Life History

Because fish can adapt to survive, they can engage students' interest and stretch their understanding of the natural world. How do different kinds of fins and body shapes make some fish speed through water like a bullet to attack prey, or help them dart quickly in a short space to elude a predator? Why do different species  have different mouth shapes? Every mouth shape is adapted to the food it eats. A fish whose mouth slants upward might attack prey from underneath. A fish whose lower jaw is flat probably feeds on or near the bottom.

How can coloration camouflage a fish to help it survive? Southern flounder, for example, can change coloration to blend in with muddy or sandy bottoms of bays. Bright silvery fishes live in areas where light reflects off their bodies, making them harder to see and confusing predators. Many fish have two-tones or "counter-shading." Their lower bodies are lighter, so when seen from underneath, they blend in with the sun shining into the water. They are darker on their upper bodies so when seen from above, they blend in as the water gets deeper. Some fish have "disruptive coloration" of stripes or spots to blend in. The bright red color of some fish, such as a red snapper, actually make it harder to see under water. Red is barely visible in deep water!

Fish have a protective coating called "slime" that covers their bodies and helps prevent infection. When handling live fish, it is important to wet your hands to minimize any disturbance to their slime coating and gently return them to water.

How long do fish live? Determining age can be difficult, but research is producing some answers. Similar to reading tree growth rings, biologists have learned to read growth rings formed in scales, fin spines, ear bones (otoliths), and vertebrae of fish to determine age. During periods of rapid growth, rings are farther apart. When growth is slower, such as during winter months,  rings are close together. By counting areas of concentrated rings, biologists can tell how many winters have passed. This method is more accurate in northern states, where winter temperatures are cooler and longer-lasting. However, it is still not completely accurate, because other conditions besides winter can sometimes slow growth.


Species (Common Name)  Lifespan (Years)
Carp 50
Crappie 6
Flounder 10
Goldfish 25
Perch 11
Pike 24
Seahorse 6
Sturgeon 50
Trout (Rainbow) 4


The world of fish is fascinating and vital as a resource for people. Fish health and human health are intricately tied together. People must consider how their actions affect water. Did you know it could take up to 50 years for a styrofoam cup to dissolve in water, and up to 600 years for fishing line? Tin cans take 50 years. Plastic six-pack rings take 400 years. In addition to careless trashing of our water, debris can enter through runoff from rain, or it can be blown in by wind. Fertilizers can run off land, down storm drains and into waterways. These "nutrients" can overfeed algae and plants in water and eventually choke out fish and other biotic life. Our actions, intentional and unintentional, impact fish and wildlife. What about people in cities and towns, who need water to drink and clean and bathe? What is good for fish is usually good for people. What is bad for fish is usually bad for people. Each person is responsible for keeping our natural waters as clean and healthy as possible.