Perciformes are the largest vertebrate order. These "perch-like" fish are found among the cold-blooded vertebrates. With more than forty-thousand species of these perciformes, they make up about 40% of all fish ranging from the Atlantic Wolffish to the Angelfish. These fish branch off into about 150 different families that separate the animals into closer categories based upon their appearance and behavior. The full separation into suborders of these perch fish is located on perciform taxonomy. 
Perciformes will generally have either one or two dorsal fins - the topmost fin located on the back of the fish. A common feature of the dorsal fin on these fish is that it is seemingly pushed forward to make it appear to have sharp spines on its back. Some people believe that the spines that the fin comes to evolved for defense purposes.
The pelvic fins on these fish are used for transportation to short distances. Some fish in this order do not have these fins, but some, however, have unique functions for their pelvic fins. The gobbie's fins, for example, are used as suckers to capture prey.
The mouth of the perciformes varies with each species. The type of mouth the fish has generally has to do with its type of eating habit. Some are filled with tiny sharp teeth, such as the perch fish. Others, however, such as the barracuda, have long sharp teeth used for piercing prey. Still, others have teeth which are located in the throat to aid in the consumption of foods containing hard shells.
These fish are oviparous, meaning that the young they produce is encased in an egg. Up to as many as six million eggs may be laid at one time by the mother. Instead of growing inside the mother, these creatures develop inside of the egg after the male fish fertilizes them externally. As the fish hatches from its egg and learns to swim, the yolk stays attached, giving it the nourishment it needs to survive. However, after the yolk is fully consumed, the fish needs to teach itself to hunt for its food. 
Perciformes can be found in the shallow waters of freshwater, but they may also be located as far as 2,300 meters into the depths of the ocean. Most, however, are found within the salt water shores. The fish that live in the open water often migrate to other areas of the ocean, whereas the ones that live in freshwater stay in one area. Some perciformes, however, live in freshwater and head for the sea to spawn and lay their eggs.
These fish are very protective of their territory. For example, the male fish, and sometimes the female, will guard the the new eggs once they are laid and protect them until they are hatched. Species that do this include the daters and sunfish. The Tigerfish, at a length of over 9 cm, will protect its territory by using its entire body to block off the small hole it calls home. 
Some of the perch-like fish live off of other animals. The Labridae, for example, aids in cleaning the parasites off of certain carnivorous fish, such as the shark. They venture toward the gills and the mouth to collect the leftover food. The shark, however, does not eat these helpful creatures because they rid it of its parasites.
Perciformes are aggressively harvested from fresh and saltwater bodies and shipped to many different parts of the world for human consumption. Aggressive mechanized fishing techniques are posing a serious threat to Perciforme populations. Fishing areas for these fish include the Mediterranean Sea, Atlantic Ocean, and the "Indo-Pacific" where they are most plentiful. Because many have brilliant and beautiful colors, they are also being captured and sold as pets or for use in tourist aquariums.
Another treat to Perciformes is the growing scarcity of green seaweed (Caulerpa taxifolia). The reason for its depletion is again due to human activities. It has been systematically removed from the north-west basin area of the Mediterranean Sea where certain types of perciformes would feed upon them.
Though we have threats to these fish, they also have their threats to humans. For example, the barracuda is known mainly for its attacks on swimmers and divers in the ocean. The injuries it leaves on them can be extremely serious. Another fish which causes threats to humans is the Weever fish, which can result in incredibly painful stings when touched. 
Red-Spotted Hawkfish: Superfamily Cirrhitoidea
Bicolour Parrotfish: Suborder Labroidei
Atlantic Wolffish: Suborder Zoarcoidei
Blue Tang: Suborder Acanthuroidei
Kissing Gourami: Suborder Anabantoidei
Betta: Suborder Anabantoidei
Gourami: Suborder Anabantoidei
Wrasse: Suborder Labroidei
Goby: Family Gobiidae
- Perciformes Wikipedia
- Order Summary For Perciformes Fishbase
- Perciform Britannica
- Perciform Fish Solaster-mb
- Fish Wikipedia