Fish Fins Morphology

Fish Fins Morphology
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Fish fin morphology
Fish, as many people reason, are scaly animals that have fins and live in water. Their body shape, fins and swimming mode are correlated and are the main determinants of swimming performances. Usually, the varied structures of fish body and fins suit different swimming specialisms CITATION Kar16 \l 1033 [1]. For example, slender-bodied fishes such as sharks, eels, lampreys swim in anguilliform mode, while fishes with broad tails and caudal peduncle swim in a carangiform manner. However, the success of any structure is hooked on the hydrodynamic relationship between the fins and body CITATION Kar16 \l 1033 [1]. In reality, fishes have a substantial variety of body shapes and fin morphologies that are suited for locomotion in different environments. Thus said, fins are the most essential elements in a fish and help in stability, swimming, and maneuverability, protection, propelling, and stopping.
Most of the fish have two types of fins; the paired and median fins. Paired fins include pelvic and pectoral and are arranged in pairs similar to the arms and legs of a human being CITATION EMS08 \l 1033 [2]. On the other hand, median fins comprise of caudal, anal, dorsal fins and run down the centerline of a fish. While early research on fish propulsion show caudal fin motion and body created thrust during swimming, most recent studies show that anal, median dorsal, paired pectoral fin aid in swimming CITATION EMS08 \l 1033 [2]. These fins work simultaneously allowing the fish to swim and uphold balance. During swimming, the shape of fish fins frequently changes due to hydrodynamic loading and muscular control CITATION Bro131 \l 1033 [3].
The dorsal fin is a single fin and is located at the back of a fish or the top. Dorsal fins can be grouped into three; central, distal, and proximal dorsal fins, as shown in figure 1. While some fishes have only one dorsal fin, others have two or three where the distal and ventral fins are combined. Dorsal fins help fish to turn quickly, stop and cushion against rolling CITATION Kar16 \l 1033 [1]. Usually, dorsal fins move in a multifaceted and dynamic way, contrary to the body, producing their wakes, thus, changing the caudal fin bump into and feasibly improving fish thrust CITATION Eri10 \l 1033 [4]. Typically, the average force is generated by each fin is determined by the movement of their vortices CITATION Eri10 \l 1033 [4].
Dorsal and anal fin generate force equivalent to caudal fin, thus enhancing locomotion. Movement using body waves, often entails the concurrent and active use of fins, particularly median fins such as dorsal and anal fins CITATION Lau14 \l 1033 [5]. Similarly, dorsal fin help in stabilizing the fish just as the feathers of an arrow. In bony fish, many dorsal fins have stout spines in the front that helps support the fin. Besides, dorsal fins help a fish to swim and protect itself from predators. That is, the fish can erect itself, thus making it hard for predators from eating it CITATION Eri10 \l 1033 [4]. For example, the triggerfish and filefish have welt stout dorsal spines that protect them from predators CITATION Kar16 \l 1033 [1].
Pelvic fin also known as the ventral fin is a pair of fins set ventrally beneath and after the pectoral fins. However, in some fishes such as the cod family, pelvic fins are located in front of pectoral fins CITATION Lau14 \l 1033 [5]. In others, pelvic fins are situated to the front near the throat, while in others they are located close to anal fish. Commonly the pelvic fish are used in slowing down and stabilization of the fish CITATION Dru02 \l 1033 [6] CITATION EMS08 \l 1033 [2]. Most species of fish use paired fins in balancing torques and generating thrust CITATION Lau14 \l 1033 [5] CITATION Eri10 \l 1033 [4]. Pelvic fins aid the fish in sculling, moving upwards and downwards in the water. Usually, these type of fins have a restricted three-dimensional movement during low-speed swimming and maneuvers CITATION EMS08 \l 1033 [2]. During swimming, pelvic fins move erratically but appear to act as trimming foils that help to alleviate and return the fish to stable swimming position every time a fish start moving CITATION EMS08 \l 1033 [2]. Usually, these fins move on the opposite direction, thus creating asymmetric motion CITATION EMS08 \l 1033 [2] CITATION Taf08 \l 1033 [7]. In some species like clingfishes, pelvic resembles a suction cup which helps hold the fish to the rocks. On the other hand, when a fish spots a prey, they cautiously approach it using the pectoral and pelvic fins CITATION Taf08 \l 1033 [7] CITATION EMS08 \l 1033 [2]. As such, they move simultaneously forward and back, thus transferring the body weight to the pelvic fins while moving the pectorals fo...