The Life of Perch
Learn about perch through dissection!
Perch Dissection Pre-AP Biology March 30, 2014- Ryan Xu
Basic Information of Perch
The scientific name of perch in general is Perca. Perch is a common name for fish of the genus Perca, freshwater gamefish belonging to the family Percidae. Most Perch species are adaptable to any form of habitat. However, a Perch is best suited in clear water with moderate vegetation and lots of sand, mud or gravel bottoms.
Interesting facts about Perch
- The largest yellow perch recorded in Maryland was caught in a Harford County farm pond in 2003 and weighed 3 lbs., 5 oz.
- Their method of spawning is unique in that female yellow perch lay their eggs in long gelatinous strands, usually floating or hanging from vegetation or some other structure.
- Yellow perch are found in approximately 13,000 acres of lakes and ponds, with tributaries to Chesapeake Bay furnishing considerably more water area.
- Fish use a variety of low-pitched sounds to convey messages to each other. They moan, grunt, croak, boom, hiss, whistle, creak, shriek, and wail. They rattle their bones and gnash their teeth. However, fish do not have vocal chords. They use other parts of their bodies to make noises, such as vibrating muscles against their swim bladder.
- Fish can form schools containing millions of fish. They use their eyes and something called a lateral line to hold their places in the school. The lateral line is a row of pores running along the fish’s sides from head to tail. Special hairs in the pores sense changes in water pressure from the movements of other fish or predators.
- Since a fish’s jaw is not attached to its skull, many fishes can shoot their mouths forward like a spring to catch startled prey.
The circulatory system of the rat typifies the high-pressure double circulatory system of mammals in which the heart is a double pump and there are two circuits of blood flow, systemic and pulmonary. In this type of system, blood is pumped through the heart twice. Deoxygenated blood from the body is pumped to the lungs where it is oxygenated (pulmonary circulation). Oxygenated blood from the lungs returns to the heart whereupon it is pumped to the rest of the body (systemic circulation). Thus the heart pumps both oxygenated and deoxygenated blood.
To expose the pericardial (heart) cavity extend the ventral incision approximately 2 cm anterior to the pelvic fins. Extend this incision dorsally under the gills to the lateral line. The pericardial membrane should adhere to this flap of body wall you have cut. Gently free the membrane as you raise the cut flap.
You will notice a heavy membrane separating the pericardial and abdominal cavities. It is termed the transverse septum. The fish heart consists of four distinct parts. Posterior to anterior (in the same direction as blood flow) these are the sinus venosus, atrium, ventricle and bulbus arteriosus .parts are not arranged in a straight line, but have folded over one another to produce a S-shaped organ. The top of the S, the sinus venosus, receives blood from two common cardinal veins and the hepatic sinus. The sinus venosus is thin walled and opens directly into the atrium. The atrium is equivalent to the paired atria of higher vertebrates. It is thicker walled and larger than the sinus venosus. The ventricle itself is a thick muscular structure. Like the atrium, it has a single internal chamber. Backflow of blood from the ventricle during contraction is prevented by a valve. The last portion of the perch heart is the bulbus arteriosus. The bulbus arteriosus is really an enlarged, very muscular portion of the ventral aorta, the vessel in which blood flows away from the heart and toward the gills. Backflow of blood from the bulbus arteriosus is also prevented by the presence of valves. Figure 19 traces the flow of blood through the perch heart.The Heart and associated vessels
Be extremely careful during this portion of the dissection as the arteries and veins are extremely fragile. You will examine the heart and locate only the major blood vessels coming out of and going into the heart. Locate the thymus gland, which overlies the anterior portion of the heart. Carefully remove the thymus gland out of the way.
Taxonomy of Perch
Primarily age and body size determine the diets of yellow perch. Zooplankton is the primary food source for young and larval perch. They have been known to be predominantly piscivorous and even cannibalistic in some cases. About 20% of the diet of a yellow perch over 32 grams (1.1 oz) in weight consists of small fish. Maximum feeding occurs just before dark, with typical consumption averaging 1.4% of their body weight.
Their microhabitat is usually along the shore among reeds and aquatic weeds, docks, and other structures. They are most dense within aquatic vegetation, since they naturally school, but also prefer small weed-filled water bodies with muck, gravel, or sand bottoms. They are less abundant in deep and clear open water or unproductive lakes. Within rivers, they only frequent pools, slack water, and moderately vegetated habitat. They frequent inshore surface waters during the summer. They are the primary prey for walleye Sander vitreus, and they consume 58% of the age zero and 47% of the age one yellow perch in northern lakes. However, in shallow natural lakes, largemouth bass Micropterus salmoides may be most influential in structuring the quality of yellow perch populations. In Nebraska sandhill lakes, the mean weight and quality of yellow perch is not related to invertebrate abundance, but is related to the abundance of largemouth bass. The three primary factors influencing quality panfish populations are predators, prey, and the environment.
The cichlid fish(Nile Perch) in the lakes of East Africa are a classic example of rapid evolution and extreme adaptation, In Lake Victoria, more than 100,000 to 400,000 species of cichlids have evolved and probably even in a much shorter period, because there are indications that 14,600 years ago the lake was completely dry.
The cichlid population has suffered heavily in recent decades as a result of major ecological changes. The Nile perch, a predator introduced into Lake Victoria in 1954, underwent explosive growth in numbers in the 1980s. In the same period, algae flourished, oxygen concentrations and the clarity of the water reduced and the food chain in the lake also changed.
Human Impact on Nile Perch
In recent history, and especially during the last one hundred years, the Nile River ecosystem has seen a radical decrease in the diversity of its fish populations (Getabu, Tumwebaze, & MacLennan, 2002). This oversimplification of the river’s and its various lake’s fish populations has, of course, ramifications that threaten not only the stability of the ecosystem, but perhaps the human populations around the river as well. This section of our research delves into what the likely causes are for this decrease in biodiversity, as well as what effects this may have further on into the future.
Biodiversity in the Past
The Nile, and especially Lake Victoria, were once home an extremely diverse population of fish species, with more than 300 different variants (Ogutu-Ohwayo, 1993). These fish were by and large haplochromine cichlids, but other species of fish including mormyrids were common as well. More than 99% of the haplochromines were endemic to the region, making this population not only diverse but unique to the area as well.
Introduction of a New Species
Despite the wide array of fish, the region’s fishing industries struggled to grow because the fish that did live in the river and lakes were predominately small-bodied and bony, not the best sort of fish for commercial enterprise (Kitchell, Schindler, Ogutu-Ohwayo, & Reinthal, 1997). A larger, more commercially viable fish was clearly needed if the fishing economy was to expand. This fish was the Nile perch, Lates niloticus. The Nile perch can grow far larger than many of the other Nile fish, and was perfect for commercial fishing purposes. In the eyes of the human fishers, it was seen as “the saviour.”
Introduced at an undetermined time during the middle of the twentieth century, the Nile perch adapted to its new home extremely successfully. Its population grew slowly at first, but soon exploded into exponential growth during the 1960s and 70s (Kitchell, Schindler, Ogutu-Ohwayo, & Reinthal, 1997). Yields for the fisheries increased up to four times their previous maximums.
Impacts on Biodiversity
The Nile perch, while a boon for the fishing industry, proved to be devastating on the varied fish population. Being a carnivorous fish, the Nile perch made the smaller native fish its prey. As the population of the Nile perch grew, the populations of the other species plummeted. Many of the endemic species went extinct entirely, with many specialists saying that 150-200 of the native species have vanished entirely (Kitchell, Schindler, Ogutu-Ohwayo, & Reinthal, 1997). The Nile perch quickly ascended to become the dominant species in the Nile by a wide margin.
Presently, this system that was once so diverse has now been simplified to an extreme degree. Nile perch constitute most of the fish population, and their growth is only encouraged by local humans. Based on the impacts of foreign species seen in other waterways worldwide, this simplified ecosystem cannot remain stable indefinitely.