The Life Of a Perch
by Alonso Gonzalez Ramirez . Mitcham pap bio pd.2
Perch are common freshwater game fish found throughout America. They are predator and feed on small fish and freshwater crustaceans. Perch typically spawn during the spring when females lay strings of eggs on submerged rocks or branches for males to fertilize. Perch also have two dorsal fins, one being spiny the other soft.
Young perch primarily feed on zooplankton, but as they age their diet could include smaller fish, insect larva, and crustaceans. They are usually found near the shore of freshwater bodies near vegetation or submerged objects. Perch are a major prey source for many animals in their ecosystem. Larger predatory fish like large mouth bass and birds like eagles regularly eat these fish as par of their diet. The normal breeding season is in spring when females lay strands of eggs on submerged objects and have males fertilize them. Perch are a schooling fish and are usually active during the day and inactive at night except when breeding, when they are active twenty-four seven.
Perch, like all other bony fish, evolved from cartilaginous fish. The development of bones has allowed for a more stable body structure and better protection of internal organs. American perch are thought to have evolved from moderately sized predatory saltwater fish that over time began to use freshwater to get food. Because of the lack of competition for food these early perch were able to eventually evolve and colonize these freshwater systems. Perch now have very successful breeding populations.
Today we will be dissecting a perch. Begin by cutting from the anus to the gills on the bottom side of the fish. Make sure not to puncture any organs. Then cut towards the dorsal side from the stomach. Now since you have finished the incision make sure you take note of the external features. This would include the eyes, fins, gills, lateral line, nostrils, mouth, teeth and skin. This is a bony fish so there are some features different to a cartilaginous fish. For example, the bony plate protecting the gills is only found in bony fish called the operculum. Now remove the flap you made and cut off the operculum. You will first see some feathery structures by the head of the fish, these are the gills. The gills help the fish with gas exchange like respiration. Below the gills is a small structure that is the heart. The heart helps in the circulatory system and allows blood to be pumped throughout the body. Lying next to the gills is the liver. This organ is fairly large compared to the heart and is involved in the endocrine system. below the liver is a sac like organ. That would be the stomach which is involved in digestion. Along the ventral side are the intestines. The intestines are involved in the excretory system. In females there would be a fairly large structure with small eggs inside. This would be the ovary And it is involved in sexual reproduction. There is only one ovary in the fish. Near the dorsal side of the fish is a membrane sac that might contain some gas. This would be the swim bladder that helps with buoyancy in water. Now the male gonad will be near the anus and there will be a pair of them. These are the testes and they aid in sexual reproduction.
Species: P. flavescens
Perch endocrine system
The endocrine system of the perch involves the production of hormones for the bodies use. The organs involved in this process are the testes/ovaries, the liver, pineal gland, the thyroid, pituitary, and parts of the intestines. The pineal gland controls the overall hormone production of the organism. The gonads control sexual hormones like testosterone. The liver controls hormones used to break down substances in the blood. The intestines control hormones used to help with the digestion and absorption of food. Without this vital system this organism would not be able to properly maintain homeostasis and would not be able to meet the requirements need to survive in this environment.
The perch's body systems include the endocrine (as mentioned earlier), the circulatory, excretory, reproductive, digestive, and respiratory. The circulatory system begins with the heart which is fairly small, so to supply the body with constant amounts of blood the heart has to beat at a faster average rate compared to if it was a larger heart. The excretory system includes the intestines and stomach where food is broken down into waste and passes through the intestines out the anus and into the environment. The digestive system includes the mouth and the stomach where prey is caught and killed and then digested by the stomach for use in the body. The respiratory system involves the process of removing oxygen from water in the gills through respiration. Other gas exchanges occur in the gills as well.
The perch is an acclaimed freshwater sportsman fish that is also sought after for its meat. The human impact on perch is not very great at all. The changing environment on the other hand is. Increased numbers in predatory birds and parasites along with invasive competition from fish from the aquarium trade has induced wildlife management to work on conservation of this species. This includes adding extra breeding substrate to their environment and removing excess predation. The current perch population is not in danger of extinction and thanks to our efforts it seems it will never be.