Fish belong to the group Pisces, which are aquatic vertebrates. They live in freshwater (rivers, lakes) and saltwater (oceans, seas). They breathe through gills and move using fins.

Covered with scales for protection.
Have fins (dorsal, tail, pectoral) for swimming.
Streamlined body shape helps them move fast in water.
Some have bioluminescence (glow in the dark)!

Carnivores: Eat other fish, insects, or small animals (e.g., sharks, piranhas).
Herbivores: Feed on algae and plants (e.g., surgeonfish).
Omnivores: Eat both plants and animals (e.g., goldfish).
Some filter tiny plankton (e.g., whale sharks).

Short-lived: 1-5 years (e.g., guppies, betta fish).
Medium-lived: 10-20 years (e.g., clownfish, goldfish).
Long-lived: 50-100+ years (e.g., koi fish, some sharks).

Venomous fish: Have poison in spines or fangs (e.g., lionfish, stonefish).
Poisonous fish: Toxic if eaten (e.g., pufferfish).
Non-toxic: Most fish are harmless (e.g., goldfish, salmon).

Oceans: Coral reefs, deep sea (e.g., clownfish, anglerfish).
Rivers & Lakes: Freshwater habitats (e.g., catfish, trout).
Swamps & Mangroves: Muddy waters (e.g., mudskippers).
Polar Waters: Icefish in Antarctica.