Fish Anatomy (male) Handout 3.1a. Body cavity lining. Air bladder. Pyloric caeca. Muscle tissue. Kidney. Dorsal fin. Adipose fin.

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1 65 Fish Anatomy (male) Handout 3.1a Body cavity lining Air bladder Gill cover Kidney Pyloric caeca Dorsal fin Muscle tissue Adipose fin Nostril Gall bladder Intestine Lateral line Mandible Maxilla Gill Two-Chambered Heart Pectoral fin Spleen Stomach Liver Adipose tissue Testis Pelvic fin Vent Urinary bladder Anal fin Caudal fin Source: Wildlife Conservation in Virginia Used by permission of Virginia Department of Game and Inland Fisheries

2 General Characteristics of Fish Handout 3.1b The major body parts of all fish perform the same functions, and they are located in about the same places on any fish s body; however, the size, shape, and color are often different. These differences help tell fish apart. Also, knowing the characteristics of a healthy fish is necessary for raising fish. Fins The fish s fins provide locomotion, help in steering, and hold the fish upright in the water. All fish have a tail consisting of the caudal peduncle and the caudal fin. The pectoral fin is usually located on the sides of the fish behind the head. The pelvic fin is usually located towards the rear of the body. The dorsal fin runs along the top of the fish. This fin may be a single or double fin. The double fin is sometimes called the soft dorsal fin. The anal fin is usually located right behind the anal vent (anus) on the rear bottom end of the fish. Gills All fish breathe through gills. Gills remove oxygen and nutrients from ingested water. Fish take in water through their mouths, then pass it through their gills to strain, or filter, the oxygen and nutrients from it. The water, along with certain waste products, is then passed outside of the body through the gill slits. The eating habits of a fish may be determined by looking at its gills. Fish with many feathery gill rakers and few if any teeth eat the smaller foods in a pond. Fish with few and larger gill filaments eat the larger particles from the pond. The health of a fish may also be reflected in the gills. Healthy gills are a bright red color. If the gills do not have this red color, or if the gills have white spots, the fish is not healthy and should not be bought or placed in a pond. If the fish is already in a pond, steps must be taken to get rid of the disease before it troubles other fish. Sensory Organs Most fish have eyes, but their vision is poor. They also have mouths. Nerve cells are found in the lateral line. The lateral line runs along the length of the body about midway on the side of the body. Sometimes the lateral line is covered by a layer of scales; sometimes it is a different color from the rest of the body. In all fish, the lateral line is an area of sensitivity that helps a fish feel pressure and temperature changes in the water around it. Reproductive Organs In most fish the genital openings lead to the reproductive organs. Male and female fish are difficult to distinguish in some species. The producer needs to be aware of ways to determine the sex. For example, some fish such as the tilapia change color in the breeding season. Some fish can be classified according to the color and size of their genitals. 67

3 Handout 3.1c The Life Cycle of Fish 1. Fish life begins when an egg produced by the female is fertilized by a sperm cell produced by the male. 2. The egg grows and eventually hatches into a small fish called a fry. 3. The fry is attached to the yolk sac, the leftover part of the egg from which it hatched. The yolk sac provides food for the fry during the first few days after hatching. 4. Once the yolk sac is gone, the fry searches for food in the water. All fry eat the tiny suspended and swimming plants and animals in the water called plankton. The duration of the fry stage depends upon the species of fish, and the size of fry range from 2 millimeters to 30 millimeters in length. The growth process ranges from 2 to 8 days, depending upon the type of fish. 5. As the fry grow bigger, they are called fingerlings. At this stage of the growth cycle, they are about the size of a person s finger. Fingerlings vary in size from 4 to 10 centimeters. Above 10 centimeters, the fish is called a post-fingerling. 6. Fingerlings have different eating habits from fry; they are bigger and can eat larger pieces of food. Each kind of fish chooses its own kind of food, depending upon its needs and what is available. For example, a carp fry will eat plankton; however, as a fingerling, the carp eats pieces of decayed matter, insect larvae, worms, snails, and almost anything that is on the bottom of the pond. Common carp, for example, are called bottom feeders because they eat food from the bottom of the pond. The food preference does not always change as the fish grows. Some fish, like the silver carp, eat plankton throughout the life cycle. 7. Fingerlings eventually grow to adult fish. Adult fish range in size; some can be as large as 2 meters long and weigh as much as 22 kilograms. When the fish reach adult size, they will sexually mature in the right conditions. Brood fish are sexually mature fish that are chosen as good fish to breed (spawn), produce eggs, and begin the whole cycle again. 69

4 Choosing Pond Fish Handout 3.2a Pond Conditions A pond differs from a natural waterway. Usually, no water flows through a pond. Some fish thrive only in waters that have a current (flow). The food already in the pond is all that is available to the fish unless extra food is added. Fish have only a certain volume of water and pond area in which to move about. Some fish will not adapt to these pond conditions and cannot be used in pond culture; however, many fish do grow well in ponds, and cultivation in ponds is practiced in this country and in countries around the world. Exotic Fish Worldwide, producers are introducing exotic fish species (fish not native to that environment) into fish pond programs. They do this for three reasons. Some introduced fish grow better and faster than native fish. Some introduced fish are preferred over local fish for their food value. The offspring of a cross between a local fish and an introduced fish sometimes grows faster and tastes better than either of the parent fish (this is called hybrid vigor). Exotic fish must be managed very carefully. They must not escape into local waters where they compete with local fish for food. Also, exotic fish may carry diseases or parasites that are fatal to native fish species. Fish Selection The producer should consider a number of factors before selecting a fish for pond culture. The fish should be available locally able to reproduce naturally in an area able to live in a confined space relatively free of parasites and diseases known and liked as a food fish in the area fast-growing able to find the right foods. 73

5 Handout 3.2b Fish Used in Pond Culture Common Carp (Cyprinus carpio) Native to Asia and a member of the minnow family, the carp was brought to America from Germany in Carp can be distinguished by a very long dorsal fin which is preceded by a hard, saw-toothed spine. A similar spine is located on the leading edge of the anal fin. Carp also have two whisker-like barbels (small projections that hang down from the sides of the mouth). Although goldfish are closely related to carp, they do not have barbels. Common carp generally are a gray-green color. However, they also can be gold, yellow, orange, pink, blue, green, or gray. They spawn year round in warm waters, and they can be made to spawn by the pond owner if they do not spawn naturally. Common carp are good to eat when they are cooked properly. They can be grown in ponds by themselves (monoculture) or in ponds with Chinese or Indian carp (polyculture). The common carp is a favorite warmwater pond fish for many reasons. Common carp spawn easily in ponds are relatively disease resistant tolerate wide ranges of temperature and ph eat all kinds of food, from zooplankton to decaying plants have a very good growth rate accept supplementary foods. Common carp is a good species for a farmer to use for a first effort. With good management, common carp will continue to produce healthy eggs and fry until about 5 years of age. Used by permission of Volunteers in Technical Assistance. 75

6 Handout 3.2c Fish Used in Pond Culture Tilapia The Tilapia genus (family cichlidae) contains at least 14 species, all of which are good pond fish. The color of the fish differs only slightly and depends upon species; tilapia are generally dark brown to black in color. The most common species grown in ponds is the Tilapia mossambica, also called the Java tilapia. This species has been introduced throughout the world and can be found in most places. Tilapia are herbivorous. Some species eat phytoplankton; others eat plants of a higher order. Both the Java tilapia and the Nile tilapia (Tilapia nilotica) do well in very enriched waters (waters polluted by sewage). All tilapia have slightly different eating habits, depending on the species. Tilapia reproduce every month or so once they become sexually mature. They then take good care of their own eggs and fry. If the producer plans to breed and raise fry, this fish is a good choice because the fish themselves take care of the fry at a stage where many fish of other species die easily. The major problem with raising tilapia in fish ponds is that they become sexually mature at a small size and begin to reproduce instead of growing. One method of avoiding this problem is to separate tilapia by sex before they are old enough to reproduce. Another method is to introduce catfish into the pond to control the population of small fish. Tilapia species have many attributes conducive to pond culture. Tilapia are hardy fish, resistant to disease. Tilapia breed easily in ponds. Tilapia grow rapidly. Tilapia are considered a tasty fish. Tilapia withstand wide temperature ranges. First-time fish producers find tilapia a good choice. 77

7 Handout 3.2d Fish Used in Pond Culture Tilapia cont d Tilapia, Tilapia mossambica Characteristics of Male and Female Tilapia Head Male Anus Genital Papilla Tail Head Female Anus Oviduct Genital Ureter Papilla Tail Used by permission of Volunteers in Technical Assistance. 79

8 Handout 3.2e Fish Used in Pond Culture Trout The brook trout is the only trout native to the Old Dominion. The rainbow trout was found originally in Rocky Mountain streams. The brown trout was first stocked in Virginia in the Roanoke River during All three species have an adipose or fatty fin behind their dorsal fin. Brook trout have a coat of red, gray, or yellow spots rimmed in blue. They also display vivid white edges on their lower fins. In small Virginia streams, brook trout seldom grow beyond about a pound in weight. Rainbow trout have a horizontal pink-to-red-or-purple band along their sides. This band turns bright red during the breeding season and is black polka-dotted all over. As the males grow older, they become more sharp-nosed than the females. The older males protrude their lower jaws as if in defiance to a hook, thus this band of cartilage has been termed a hook or kype. Rainbow trout usually reach about two pounds in Virginia waters. Brown trout are larger than both brook and rainbow trout. They can grow to three or more pounds. Trout production requires plentiful, cold spring waters of high quality. Used waters discharged into an area of trout production jeopardize the legal status of game fish. Brown Trout Used by permission of Virginia Department of Game and Inland Fisheries. 81

9 Handout 3.2f Fish Used in Pond Culture Bass Two species of bass are the white bass and the striped bass. The white bass is strictly a freshwater species. The striped bass moves from tidal bays to fresh water to spawn. Kerr Reservoir (Buggs Island Lake), Smith Mountain Lake, and Lake Anna are the only land-locked waters in Virginia that contain striped bass. In these bodies of water, striped bass are considered a freshwater species. Both the striped bass and the white bass have two dorsal fins and seven black lines running lengthwise on their sides. The white perch, sometimes mistaken for bass, does not have the black stripes, and it has a smaller mouth than the other two species. The white perch is more streamlined than the deeper-bodied white bass. The striped bass is the largest member and best known sporting fish of the family. One striped bass weighing 50.5 pounds was taken by an angler in Virginia, and larger ones have been taken by commercial fishers. The white bass reaches 5 pounds; the average white bass reeled weighs less than 2 pounds. The white perch averages.5 pound. The hybrid striped bass is a large species that does well in a variety of environments and displays good hybrid vigor. This is an experimental fish that is being studied to determine if it can be raised successfully. Brood fish and fingerlings are hard to obtain, and prices may be high. Some problems with the crosses developing abnormalities have been discovered. State permits are required to grow the fish, and in some places interstate transportation is banned. Striped Bass Used by permission of Virginia Department of Game and Inland Fisheries. 83

10 Handout 3.2g Fish Used in Pond Culture Catfish Two species of catfish are frequently cultivated the channel catfish and the blue catfish. Catfish do not have scales, but rather a thick, leathery skin. They live on mud bottoms of streams and ponds, and are adapted for life in such locations. They have barbels, or feelers, to help them find their way about and to find food in the mud. Two barbels stand straight up, the two largest ones stand out on each side of the mouth, and two pairs of short ones adorn the lower lip. Catfish gill covers open below rather than at the sides of their bodies. Channel catfish found in Virginia waters do not exceed 25 pounds, and they average 5 pounds in weight. The producer considering the channel catfish for production should consider the following: Expensive site development is often required. Feed costs are high. An off flavor is easily developed. Oxygen generally has to be supplemented. Ammonia accumulation is often a problem. Fierce market competition holds prices down. Netting is a problem due to the nervous temperament of the channel catfish. Despite these problems, channel catfish have yielded excellent production results, are readily adaptable to artificial feeds, and resist crowding. The blue catfish is the second most frequently cultivated species. Blue catfish dress out at a higher weight percentage than channel catfish. Also, they readily learn to eat at the surface, they are less nervous and easier to seine, and the males are less prone to fight at breeding time. Being able to observe the fish as they feed allows the producer to determine the condition of their health. Disadvantages of raising blue catfish include a poor survival rate when shipped alive, poor conversion of artificial feed, and a greater age at maturity. Channel Catfish Used by permission of Virginia Department of Game and Inland Fisheries. 85

11 Transparency 3.2a SCIENTIFIC NAMES OF FISH Each fish has a scientific name that is always the same. Often fish also have a corresponding common name. However, the common name of a fish may vary from one region to another. Using the scientific name avoids confusion. Genus and Species Common Name CARP 1. Carassius carassius crucian carp 2. Cirrhina molitorella mud carp 3. Ctenopharyngodon idellus grass carp 4. Cyprinus carpio common carp 5. Hypophthalmichthys molitrix silver carp 6. Mylopharyngodon piceus black carp CATFISH 1. Clarias batrachus catfish 2. Clarias macrocephalus catfish TILAPIA 1. Tilapia macrochir tilapia 2. Tilapia melanopleura tilapia 3. Tilapia mossambica tilapia 4. Tilapia niloctica tilapia 87

12 Handout 3.3a Legal Issues Related to Fish Production Permits Certain fish operations require a permit. Contact the Virginia Marine Resources Commission (VMRC), P. O. Box 756, Newport News, Virginia 23607, or telephone (804) for current information on permit requirements. Certificates The sale of some species requires a certificate that they were not caught from a wild population. Regulations for Containment The following criteria are used to prevent the escape of fish into commercial waters: 1. Screens should be placed on all drains. 2. Water flows entering the pond must not originate beyond the boundaries of the pond owner s property. 3. Water leaving the pond must pass through a dry percolation system. 4. Water cannot discharge into streams that enter tidal waters. 91