A Perch Life
Perch Dissection Pre-Ap Biology April 07, 2014 - Guzman
The Beautiful Perca fluviatilis
Today's Objectives
Anatomy of a Perch
External
Eye - used for seeing.
Operculum - covers gill slits, water enters through mouth.
Dorsal Fin - provides stability.
Caudal Fin - swimming appendage, used to propel.
Anal Fin - located behind the anus, provides stability.
Pelvic Fin - provides stability.
Pectoral Fin - made of bone, orientation, locomotion, stopping, creates side to side movement.
Lateral Line - subcutaneous canal protruding from the body and head, detects and locates objects and animals.
Scales - small thin hard plates covering a fish's body.
Internal
Heart - two chambers: atrium and ventricle.
Mouth
Gills - feathery layers, used for respiration.
Pharynx
Esophagus - leads to the stomach.
Stomach - breakdown (mechanical and chemical) begins here, has three pouches called pyloric caeca (secretory and absorptive functions); empties into the duodenum.
Liver - situated anterior to the stomach.
Gall Bladder - drains bile (necessary for digestion of fats) from the liver.
Intestine - forms a loop (constricts and straightens at the end), extends directly to the anus. A perch's intestine is not very long because of it's carnivorous life style.
Anus - end of the digestive tract, excretes waste.
Kidneys – rid body of nitrogenous wast, help fresh water fish retain salts and excrete a copious, dilute urine.
Swim Bladder - makes the fish buoyant, as a result the fish can remain stationary without moving it's fins.
Home of the Perch
Evolution of the Perch
The Nile perch was introduced to Lake Victoria in East Africa in the 1950s, and has since been fished commercially. It is attributed with causing the extinction or near-extinction of several hundred native species, with some populations fluctuating with commercial fishing and the actual Nile perch stocks. The Nile perch's initially fed on native cichlids, but with decreasing availability of this prey, it now consumes mainly small shrimp and minnows. The fish's introduction to Lake Victoria, was ecologically negative, and stimulated meanwhile the establishment of large fishing companies. In 2003, Nile perch sales to the EU reached 169 million euro. Sport-fishing in the region of Uganda and Tanzania provided additional income for tourism. The long-term outlook is unclear, as overfishing is reducing L. niloticus populations.
Fishing of the Perch
Perch are sought-after by fishermen both for sport and for food. They can be caught with a variety of methods, but the two best methods are perhaps float fishing and lure fishing. The best way is to use a small hook and cast into the weeds just before the drop off. When fishing with a float, the angler will want to have a disgorger; perch are notorious for swallowing the hook, and will need aid of a disgorger or forceps for unhooking. In many parts of the world, they are also a favorite species among ice fishermen. They will take a variety of baits, including minnows, worms, maggots, goldfish, pieces of raw bacon, and softshell crayfish, but seem to prefer small fish, lobworms, red maggots, and lures.
The Gills of a Perch
The fish, the perch, takes in oxygen through its gills. The gills are positioned on each side of the perch's head. Gills are made up of two rows of tiny, string-like, flesh filaments that across over attached lamellas in the gill chambers. The process of breathing is basically drinking for the fish. This is because the water enters through the mouth, and it is carried into the blood vessels in the filaments and lamellas. However, at the same time, carbon dioxide is being carried through the bloodstream to exit the body. Also, the perch, along with every other fish have opercula, which is a piece of tissue that covers the gill, and stops water from escaping the fish.
gill raker -filter out dirt before the water comes in contact with the delicate gills
gill filament -used for gas exchange
gill slit -individual opening to gills, moves water out and closes to prevent reverse flow
gill cover -gives protection of gills