Fish scale in the context of Sturgeon

Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and lift, which help the fish swim. Apart from the tail or caudal fin, fish fins have no direct articulations with the axial skeleton and are attached to the core only via muscles and ligaments.

Fish fins are distinctive anatomical features with varying internal structures among different clades: in ray-finned fish (Actinopterygii), fins are mainly composed of spreading bony spines or "rays" covered by a thin stretch of scaleless skin, resembling a folding fan; in lobe-finned fish (Sarcopterygii) such as coelacanths and lungfish, fins are short rays based around a muscular central bud internally supported by a jointed appendicular skeleton; in cartilaginous fish (Chondrichthyes) and jawless fish (Agnatha), fins are fleshy "flippers" supported by a cartilaginous skeleton. The limbs of tetrapods, a mostly terrestrial clade evolved from freshwater lobe-finned fish, are homologous to the pectoral and pelvic fins of all jawed fish.

Salmonidae (/sælˈmɒnɪdiː/, lit. 'salmon-like') is a family of ray-finned fish, the only extant member of the suborder Salmonoidei, consisting of 11 extant genera and over 200 species collectively known as "salmonids" or "salmonoids". The family includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), char, graylings, freshwater whitefishes, taimens and lenoks, all coldwater mid-level predatory fish that inhabit the subarctic and cool temperate waters of the Northern Hemisphere. The Atlantic salmon (Salmo salar), whose Latin name became that of its genus Salmo, is also the eponym of the family and order names.

Salmonids have a relatively primitive appearance among teleost fish, with the pelvic fins being placed far back, and an adipose fin towards the rear of the back. They have slender bodies with rounded scales and forked tail fins, and their mouths contain a single row of sharp teeth. Although the smallest salmonid species is just 13 cm (5.1 in) long for adults, most salmonids are much larger, with the largest reaching 2 m (6 ft 7 in).

Fish go through various life stages between fertilization and adulthood. The life of fish start as spawned eggs which hatch into immotile larvae. These larval hatchlings are not yet capable of feeding themselves and carry a yolk sac which provides stored nutrition. Before the yolk sac completely disappears, the young fish must mature enough to be able to forage independently. When they have developed to the point where they are capable of feeding by themselves, the fish are called fry. When, in addition, they have developed scales and working fins, the transition to a juvenile fish is complete and it is called a fingerling, so called as they are typically about the size of human fingers. The juvenile stage lasts until the fish is fully grown, sexually mature and interacting with other adult fish.

In sport fishing, a spoon lure is a fishing lure usually made of lustrous metal and with an oblong, usually concave shape like the bowl of a spoon. The spoon lure is mainly used to attract predatory fish by specular reflection of light, as well as the turbulences it creates when moving in water.

The design of the spoon lure is simple: the oblong, concave blade shape of the spoon will cause it to wabble randomly when towed or sinking through water, creating sparkles of light reflection that resemble those of a swimming bait fish's scales when looking from afar. The spoon wabbling also stirs up turbulences that can entice the fish to stalk and strike it. Fish normally use their lateral line system to follow the vortices produced by fleeing prey, and the oscillating movements of the spoon lure can imitate these. Different color variations and materials can be added to the classic spoon lure may also help catch fish. Silver- or gold-plated or dyed finishes can give the lure a more vibrant or brilliant appearance. Most spoon lures have at least one hook at the end, which tethers the fish's mouth when the fish swallows the spoon.

The Mexican tetra (Astyanax mexicanus), also known as the blind cave fish, blind cave characin or the blind cave tetra, is a species of freshwater ray-finned fish belonging to the family Acestrorhamphidae, the American characins. This fish is found in the lower Rio Grande, and the Nueces and Pecos Rivers in Texas, into the Central Plateau and eastern states of Mexico.

Maturing at a total length of about 12 cm (4.7 in), the Mexican tetra is of typical characin form, albeit with silvery, unremarkable scalation, likely an evolutionary adaptation to its natural environment. By comparison, the species' blind "cave" form has scales which evolved a depigmented, pinkish-white color, somewhat resembling an albino, as it inhabits pitch-black caverns and subterranean streams and has no need for a colorful appearance (i.e. for attracting mates, camouflage, UV protection).

Clupeiformes /ˈkluːpiːɪfɔːrmiːz/ is the order of ray-finned fish that includes the herring family, Clupeidae, and the anchovy family, Engraulidae and sardines. The group includes many of the most important forage and food fish.

Clupeiformes are physostomes, which means that their gas bladder has a pneumatic duct connecting it to the gut. They typically lack a lateral line, but still have the eyes, fins and scales that are common to most fish, though not all fish have these attributes. They are generally silvery fish with streamlined, spindle-shaped bodies, and they often school. Most species eat plankton which they filter from the water with their gill rakers.

Desquamation, or peeling skin, is the shedding of dead cells from the outermost layer of skin.

The term is from Latin desquamare 'to scrape the scales off a fish'.