Fish belongs to vertebrate group of organisms living in water bodies, either fresh or marine water. As of date, more than 25,000 fish species are identified and scientists are of the opinion that there are 15,000 more species, which are yet to be identified. The characteristic features of fish are breathing through gills, and presence of paired and unpaired fins that help them in efficient swimming. Besides fins, the body of fish is covered with some sort of protective scales. Most of the fish species are cold-blooded (or ectothermic) and depend on their surrounding environment to maintain their body temperature. Irrespective of the water chemistry, nearly all water bodies are inhabited by fish. For example, you can find various types of fish in the ocean at such a depth where there is very less or no light penetration. Likewise, several fish species are found dwelling in the streams of high mountains. As far as importance of fish is concerned, they are eaten as food and also, reared as pets in fish tanks. Fish is an important source of food for humans. Enriched with healthy proteins, they are a delicacy for people who eat animal based foods (non-vegetarians). And for aquarists, fish are wonderful pets kept in decorative aquariums. Indeed, rearing them is a relaxing hobby, which you get to enjoy watching colorful fish swimming, playing, and feeding. Since the demand of fish is very high, fish farming and fishing are sources of income for several people. Mentioned below are lists of edible fish and aquarium fish types. Types of Fish to Eat Both freshwater and marine fish are consumed as human food since time immemorial. In the market, they are sold fresh, dried, canned, or pickled. Research studies have shown that fish-derived proteins and nutrients are healthier than those of poultry and meat. What's more, many saltwater fish species contain a high percentage of omega-3 essential fatty acids, which help in treating cardiovascular diseases. Commonly eaten fish are listed below.

• Anchovy
• Abalone
• African butter fish
• Bass
• Barramundi
• Basa
• Black drum
• Bluegill sunfish
• Bream
• Brill
• Carp
• Catfish
• Clam
• Coley
• Cod fish
• Crab
• Croaker
• Crayfish
• Crawfish
• Cuttlefish
• Dab fish
• Dogfish
• Eel
• Flounder
• Grouper
• Gurnard
• Haddock
• Hake
• Halibut
• Herring
• Hoki
• Huss
• Jacksmelt
• Ling
• Lobster
• Mackerel
• Mahi mahi
• Milkfish
• Monkfish
• Mullet
• Opakapaka
• Orange roughy
• Oyster
• Perch
• Pike
• Pollock
• Pompano
• Redfish
• Salmon
• Sardines
• Scallop
• Sheepshead
• Shrimp
• Skate
• Sole
• Swordfish
• Tilapia
• Tripletail
• Trout
• Tuna
• Turbot
• Wahoo
• Weakfish
• Whitefish
• White grunt

Fish products, either canned or pickled, may contain traces of mercury and harmful chemicals. Hence, while purchasing them for consumption purpose, make sure you select those of quality brands. Last but not the least, some edible fish types (e.g. shellfish, sushi) increase the risk of food poisoning, if proper cooking is not done. Thus, correct preparation and cooking of fish is a must to avoid the risk of food poisoning. Types of Fish for Pets Depending on whether you want to keep freshwater fish or marine fish, you are required to construct an appropriate aquarium. Marine fish are more varied in color, shape, and size than the freshwater types. But, they need special care and maintenance. Hence, a freshwater aquarium is an ideal choice for a novice aquarist. In the United States, the most commonly kept aquarium fish comprises tropical fish. The list of popular aquarium fish types includes the following.

• Anemone fish
• Angelfish
• African butterfly fish
• Arowana
• Banded coral shrimp
• Barb
• Betta fish
• Biota
• Bala shark
• Bat fish
• Black knife fish
• Black-tailed dascyllus
• Blennies
• Butterfly loach
• Bumblebee goby
• Catfish
• Cypriniformes
• Cherubfish
• Clownfish
• Comet
• Copperband butterfly
• Cory
• Cichlid
• Crab
• Damsel
• Danio
• Discus
• Elephant nose
• Fantail fish
• Goldfish
• Gourami
• Guppies
• Knife fish
• Labyrinth fish
• Lionfish
• Loach
• Molly
• Mono
• Needle nose
• Oscar fish
• Pacu
• Platy
• Scat
• Seahorse
• Shark
• Shubunkin
• Silver dollar
• Spotted puffer fish
• Squirrel fish
• Swordtail
• Tetra fish
• Tiger Barb
• Upside down cat
• Yellowhead jawfish
• Yellow tang
• Yellowtail wrasse

In the present scenario, there are different types of fish that are listed in the endangered and near extinction categories. No doubt, some species are already extinct knowingly or unknowingly. But, it is never too late to conserve the extant fish. It is high time that we should stop overfishing, polluting water bodies, and destroying habitat to save this aquatic vertebrate animal. These simple conservatory approaches will surely help preserve fish and other inhabitants of the aquatic ecosystem.