Fishes - Types of fish!

Clown fish are bold, because they dare to live in places where most marine animals dread to go near. Indeed, their choice of residence -- anemone (or sea anemone) - is a plant-like, immobile, underwater creature that snatches a passerby with its waving, poisonous tentacles! Yet, clown fish don't seem to mind the danger, and the anemone they co-habit with appears to enjoy their company as well. Though the living arrangement clown fish and anemones establish is out of ordinary, it benefits both animals in several ways. On the part of clown fish (or anemone fish), they know how frightened other fishes are of anemones' toxic tentacles. Hence, they capitalize on that fear by being anemones' roommates. Surely, no fish can be that hungry to chase a clown fish all the way to its dangerous dwelling. Nevertheless, if the predator continues the pursuit, it will quickly regret its decision - instead of being a hunter, the fish becomes a fallen prey of the clown fish's protector! Of course, the clown fish will never make a pact with the anemone if it doesn't have means to fend off its host's venomous stings. So, how can it avoid getting stung by the anemone? Well, it turns out that the clown fish has a special layer of mucus on its skin. Miraculously, this layer of mucus gives it immunity.

Perca is the genus of fish referred to as perch or yellow perch, a group of freshwater fish belonging to the family Percidae. Perch, of which there are three species in different geographical areas, lend their name to the largest order of vertebrates: the Perciformes, from the Greek perke meaning perch, and the Latin forma meaning shape. Many other species of fish are also called "perch." Also there is the lateral line system. Perch have "rough" or ctenoid scales. When looking through a microscope, the scale look like a plate with growth rings and 89 spikes on the top edges. Externally the anatomy of perch is simple enough. On the dorsal side of the fish, there consists a upper maxilla and lower mandible for the mouth, a pair of nostrils, and two lidless eyes. On the posterior sides are the operculum, which are used to protect the gills. Also there is the lateral line system which is sensitive to vibrations in the water. They have a pair of pectoral and pelvic fins. On the anterior end of the fish, there are two dorsal fins. The first one is spiny and the second is soft. There is also an anal fin, which is also considered spiny, and a caudal fin. Also there is a cloacal opening right behind the anal fin. All perciform fish share the perch's general morphology.

The goldfish, was one of the earliest fish to be domesticated, and is still one of the most commonly kept aquarium fish and water gardens. A relatively small member of the carp family, the goldfish is a domesticated version of a dark-gray/brown carp native to East Asia. It was first domesticated in China and introduced to Europe in the late 17th century. Goldfish may grow to a maximum length of 23 inches (59 cm) and a maximum weight of 9.9 pounds (4.5 kg), although this is rare; few goldfish reach even half this size. In optimal conditions, goldfish may live more than 20 years, but most household goldfish generally live only six to eight years, due to being kept in bowls.

The rainbow trout, also called the redband trout, is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America as well as much of the central, western, eastern, and especially the northern portions of the United States. The ocean going (anadromous) form (including those returning for spawning) are known as steelhead, or ocean trout (Australia). The species has been introduced for food or sport to at least 45 countries, and every continent except Antarctica. In some of these locations, such as Australia and South America, they have had very serious negative impacts on upland native fish species, either by eating them, outcompeting them or transmitting contagious diseases. In some cases, they have been responsible for the extinction of native fish populations.The species was originally named by Johann Julius Walbaum in 1792. In 1855, W. P. Gibbons found a population and named it Salmo iridia, however this name became deprecated once it was determined that this was a population of the already named species. More recently, DNA studies showed Rainbow Trout are genetically closer to Pacific salmon (Onchorhynchus species) than Brown trout (Salmo trutta) or Atlantic Salmon (Salmo salar), so the genus was changed.

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