The structure and function of the different fins of the Rainbow Trout, Oncorhynchus mykiss
The Rainbow trout, belonging to the family Salmonidae, Class Actinopterygii (ray finned fish), inhabitscold streams, rivers and lakes in North America. Ones living in lakes have silver scales apart from those on their back which are dark green. They are covered in dark spots that usually go no further than the lateral line. The lateral line is a line of sense organs found on the side of the Rainbow trout. It is used to detect vibrations (and therefore movement) in the water surrounding it. A pinkish red band often runs the length of the lateral line. The shape of the Rainbow trout is a characteristic shape not uncommon from that of salmon. (Guidekenairriver.com)
Fish fins developed around 500 million years ago. A fin is a thin appendage attached to the body of an organism that causes either propulsion, stabilization, or the ability to steer and brake. The median caudal, dorsal, and anal fins are possessed by most fish species. The rainbow trout has six different types of fins- an anal fin, an adipose fin, a dorsal fin, a caudal fin, a pair of pelvic fins, and a pair of pectoral fins.
The anal fin is situated between the anus and the tail fin, on the ventral surface of the fish. In Rainbow trout, the anal fin is bordered by a black margin. This is one of the fish’s features which help to identify it. Its function is to stabilise the fish whilst it’s swimming. Due to the dorsal fins being located above the rolling axis of the Rainbow trout, the movement of the dorsal fins would cause the fish to roll whilst swimming if not for the anal fin which counteracts this movement and stabilises the fish. (Journal of experimental Biology).
The dorsal fin is situated on the middle dorsal surface of the Rainbow trout. The base of the dorsal fin is supported cartilaginous bones called pterygiophores. There are three pterygiophores present in the dorsal fin; proximal, middle, and distal. (Wikipedia). Its function is as an ancillary force generator around the axis of the body of the trout. This means providing the support needed when the force, in the case the propulsion of the Rainbow trout through the water, is exerted. The dorsal fin is used in thrust production when the fish starts to increase speed rapidly. However as the Rainbow trout further increases its swimming speed, the dorsal fins sweep amplitude and height decrease, becoming less involved in the momentum of the fish’s movement. (Journal of experimental Biology 2005). At high speeds the dorsal fin is used as a stabiliser to control roll and yaw. The yaw is the vertical axis through the Rainbow trouts centre of gravity, and therefore a yaw motion is when the nose of the fish tilts side to side on this axis. The roll axis is the horizontal axis through the trout running from nose to tail, and therefore the roll...