2. Pectoral fins: maintain the balance of the fish, if lost, the fish will sway from side to side. Equivalent to the forelimbs of terrestrial animals, born in the chest at the back edge of the gill cover. Fish have the function of movement, balance and mastering the direction of movement.
3. Ventral fin: keep the balance of the fish body, if lost, the fish body will sway from side to side. Equivalent to the hind limbs of terrestrial animals, it has the function of assisting the dorsal and anal fins to maintain the balance of the fish body and assisting the fish body to lift and turn.
4, dorsal fin: to keep the fish standing on its side, plays a key role in the balance of the fish, if lost, it will lose its balance and roll over on its side.
5. Anal fin: coordinates the other fins and plays a balancing role; if it is lost, the body will shake slightly.
Expanded Information
Morphology
1. Fusiform
Also known as the basic type (streamlined). It is the general body shape of fish, suitable for swimming in the water, the whole body is fusiform and slightly flattened. Among the three body axes, the cephalic and caudal axes are the longest, the dorsal and ventral axes are the second longest, and the left and right axes are the shortest, which makes the whole body streamlined or slightly flattened.
Spoked fin fishes such as bluefin tuna, Atlantic sailfish, flying fish, jacks, mackerel, and grass carp, and cartilaginous fishes such as mackerel sharks, blue sharks, great white sharks, bull sharks, and lemon sharks, as well as the entire peltate class. As well as the entire class of shield-skinned fishes.
The most common, most fast-moving fish are of this size.
2, flat type
This type of fish in the three body axis, the left and right axis is particularly long, the dorsal and abdominal axis is very short, so that the body is up and down flat, slow, not as flexible as the first two types of, more benthic life.
Anglerfish, rock-climbing loach, and flat-finned loach in the order Spoked-finned fishes, and rays, stingrays, and manta rays in the order Chondrichthyes, as well as the entire order Armoriformes. and the entire class of armored fishes.
Most of them inhabit the bottom of the water and are slow-moving.
The clubbed type is also known as the eel type. These fish have an unusually long cephalocaudal axis, while the right and left axes and the ventral axis, which are almost equal, are short, giving the whole body a clubbed shape.
Spoke fins such as eels, eels, and moray eels. as well as the entire round-mouthed order.
Fish with this body type are suitable for burrowing, good at drilling in the mud or penetrating around underwater reefs and rock crevices, but are not very
quick and slow swimmers.
3, lateral flat type
This kind of fish in the three body axis, the left and right axis is the shortest, the proportion of the head and tail axis and the dorsal and abdominal axis is not too much difference, the formation of left and right symmetry of the flattened shape, so that the whole body type is obvious and flat and wide.
This type is only found in the class of Spoke-finned fishes, such as the group of pomfrets, breams, pomfrets, silver pomfrets, and small carp.
The bony fishes are more common, mostly living in calm water, inner bays and lakes with slow currents in the middle and lower layers, and their movements are not very agile
The bony fishes are more common in the middle and lower layers.