Production potential: Moderate Marketing potential: Moderate, Size: 1.5 - 3.5 lbs, Market: Food, Sport Temperature requirements: Growing: 77-86oF, Spawning: 61-68oF, Lethal: N.A. Feed requirements: Protein: 45-50%, Fat: 15%, Fry: Stocked into ponds containing rotifer and cladoceran zooplankton populations Spawning requirements: Spawns late March to May. Cross made with either female white bass and male striped bass (Sunshine Bass) or with female striped bass and male white bass (Palmetto Bass). Female striped bass average 25,000 eggs per ounce of spawn and white bass females average 100,000 eggs per spawn. Eggs hatch in two to five days. Survival of fry is low less than 50%. Most common production systems: Ponds, recycle systems and cages BIOLOGY AND LIFE HISTORY: Hybrid striped bass generally refers to a cross between striped bass (Morone saxatilis) and white bass (M. chrysops). This cross, sometimes called the “original cross,” was first produced in South Carolina in the mid-1960s using eggs from striped bass and sperm from white bass. The accepted common name of this cross is the Palmetto Bass. More recently the “reciprocal” cross-using white bass females and striped bass males was also produced. The accepted common name of this cross is the Sunshine Bass. Hybrid striped bass have gained widespread acceptance as a sportfish, particularly in the large reservoirs of the southeast U.S., where it was stocked because of the large forage base provided by gizzard shad and threadfin shad. Striped bass and hybrid striped bass, in particular, have potential for culture in the United States as foodfish. Other Morone species have since been hybridized with striped bass but none has gained the acceptance of the striped bass by white bass cross, either as a sport fish or as a culture species. The genus Morone belongs to the family Percichthyidae of the order Perciformes. Four species of Morone are found in the United States. Two species, white bass and yellow bas (M. mississippiensis) are found in freshwater. Striped bass are anadromous, but landlocked populations can be found in some freshwater reservoirs. White perch (M. americana) is a brackish water species but also does well in freshwater lakes and reservoirs. Three other marine species belong to the family Percichthyidae. DISTRIBUTION: Striped bass was originally found on he Atlantic Coast from New Brunswick to Florida and along the Gulf Coast from Florida to Texas. It was introduced to the west coast in the early 1890s and established reproducing populations. On the Pacific coast striped bass now range from British Columbia to south of the border between the United States and Mexico. Landlocked populations exist in many reservoirs throughout the United States where inflowing stream conditions meet striped bass spawning requirements. Striped bass populations are maintained by stocking programs in many reservoirs throughout the United States where striped bass do not reproduce. The species is anadromous and considered an excellent food and game fish sometimes reaching over 70 pounds. Commercial harvest of striped bass has declined drastically since 1973 when a harvest of nearly 15 million pounds was recorded. Now, less than a million pounds per year are harvested commercially, and commercial and sport fishing for striped bass is prohibited or strictly regulated. PHYSICAL CHARACTERISTICS: The appearance of hybrid striped bass is intermediate to that of the parental species. The body is slightly compressed in cross-section and scaled. Lateral stripes similar to those of the striped bass are present, but the stripes are generally broken in the area behind the pectoral fin and below the lateral line. The fish has two dorsal fins, a spinous dorsal fin near the center of the body contains 8-9 spines and a soft-rayed fin behind that contains 1 spine and 13-14 rays. A membrane does not connect the two dorsal fins. The caudal finis forked and the two lobes are pointed. The anal fin has three spines and 9-13 soft rays. The general color of the fish grades from silver and black dorsally to white underneath. The shade depends on the color of the water. Young hybrids have visible parr marks on their sides until they are several inches long. HABITAT: Hybrid striped bass are stocked into a variety of water types for recreational purposes. They do well in slow moving streams, large reservoirs, lakes and ponds. They are seldom found in extremely shallow areas or areas that contain dense growth of aquatic weeds. Because they are pelagic in nature they are generally found in open water areas. They are generally most active during periods of low light such as dawn and dusk. Beginning in late winter they tend to concentrate in deep areas near inflowing streams and in the spring may undergo spawning migrations into upstream areas. Hybrids are fertile and there are reports of successful reproduction in a few reservoirs, WATER QUALITY: Hybrids survive and do well in a wide range of environmental conditions. A temperature range of 4 to 33 C is acceptable, but optimum growth occurs within a temperature range of 25 to 27° C. Hybrids are generally stocked into freshwater systems but they do well in salinities of O to 25 ppt, and some can survive salinities up to full strength seawater (35 ppt). Dissolved oxygen levels as low as 1 mg/l can be tolerated for a short period of time, but optimum dissolved oxygen levels range from 6 to 12 mg/1. Hybrid striped bass are stocked into a variety of water quality situations with regard to alkalinity, hardness and pH. Alkalinity values of 100 mg/1 or above are preferred but levels less than 20 mg/1 are suitable. Hardness and alkalinity are usually related and similar values could be given for hardness. A pH range of 7.0 to 8.5 is optimum for growth, but a much wider range is tolerated. Hybrids in culture ponds have survived repeated exposure to a pH of 2.5 for short periods of time. FEEDING: Hybrid striped bass is a predacious species throughout its life. Fish less than approximately 50 mm feed primarily on crustacean zooplankton such as cladocerans and copepods. Insects of various types and zooplankton continue to be a major part of the diet until the fish are 100 to 125 mm long. Hybrids switch to fish diet at a very small size if appropriate sized fish are available. However, this transition usually occurs when the hybrids are larger than 100 mm. Threadfin shad and gizzard shad are the most common fish prey species. However, many species of forage fish have been found in stomachs of hybrids. There is seasonal variation in feeding habits with a shift towards larger organisms in the winter and summer. AGE AND GROWTH: Hybrid striped bass grow when water temperatures are above 15° C. However, optimum growing conditions occur when water temperatures are 25 to 27 C. Hybrids grow rapidly during their first two years of life. Growth to 275 to 375 mm in length and 225 to 350 grams in the first year and 450 to 550 mm in length and 1 to 1.5 kg in the second year is common. Growth rate declines rapidly with increasing age and is similar in males and females. Maximum reported weight for a hybrid striped bass is approximately 10 kg. The typical size of hybrids caught by fishermen generally ranges from 2 to 5 pounds, but fish in the 10 to 15 pound range are not uncommon. The usual life span of hybrid striped bass is 5 to 6 years-- more similar to white bass than to striped bass (30 to 40 years). The growth rate of hybrid striped bass in production ponds is determined by several factors: water temperature, quality and quantity of food, palatability of food, frequency of feeding and water quality. Hybrid striped bass are generally harvested at a weight of 1.5 to 2.5 pounds when they are 18 to 24 months old. SPAWNING Hybrid striped bass, unlike some other hybrids, is fertile. It is oviparous (egg-laying) like the parental species and produces eggs and sperm in the spring when temperatures are 15 to 20° C. Some males mature at the age of 1 year (approximately 250 mm long and 500 grams), and all are mature at 2 years of age. A few females are mature at 2 years of age, but all are mature at 3 years. Females produce an average of 160,000 eggs per pound of body weight and spawn once a year. Males may spawn many times over the spawning season. Natural spawning of hybrids has been verified in a few instances. They may participate in spawning runs with striped bass or possibly white bass. There are also confirmed cases of reproduction in reservoirs that contain only hybrid striped bass. Hybrid striped bass produce sperm and eggs during the spring when water temperature is between 55 to 70° F. Temperatures of 65° to 68° F are ideal for spawning hybrids and the parental species. Spawning occurs from mid-March through May depending on location. Spawning season in any one location usually lasts 4 to 5 weeks. Hybrids have been observed participating in spawning acts in areas that contain clear shallow rocky shoals that are 1 to 3 feet deep. Females come to the surface during the spawning act and several males accompany her. The males appear to bump and butt the female, which may stimulate egg release. The males immediately fertilize released eggs. The eggs of striped bass x white bass hybrids are intermediate in size to those of the parental species. They are semi-buoyant like striped bass eggs, although they seem to be heavier than striped bass eggs. Eggs of this cross are generally not adhesive like white bass eggs and must be buoyed up by the turbulent water flow till they hatch. Other hybrid crosses such as striped bass x white perch have adhesive eggs. Eggs hatch in approximately 2 days at water temperatures of 65 to 68° F. At colder temperatures eggs may take over 72 hours to hatch. Newly hatched fry do not have fully developed mouth parts and do not feed until they are approximately 5 days old. During this swim-up stage he relatively large oil droplet is used as a food source. This publication was supported in part by a grant from the United States Department of Agriculture, Number 87-CRSR-2-3218, sponsored jointly by the Cooperative State Research Service and the Extension Service. HATCHERY PHASE: BROODSTOCK COLLECTION: Broodstock to produce fingerling striped bass and hybrid striped bass must be collected from the wild during their spring spawning run because the species has not been domesticated. Spawning runs for striped bass species occur from late March to late May depending on location. Spawning grounds for striped bass are usually found near deep, swift and turbulent sections of a river, well upstream from lakes, reservoirs and sounds. Males begin their spawning run 1 to 3 weeks before the females when water temperature is less than 15° C. Female striped bass begin their spawning migration when water temperature is around 15° C. For any given population of striped bass several periods of spawning may occur during a 4- to 5-week period when water temperatures are 16 to 20° C. Periods of spawning activity during this time frequently follow sudden temperature increases of 1 or 2° C. White bass, although restricted to freshwater, also make spawning migrations from lakes and reservoirs to inflowing streams. They generally spawn in rocky areas where water flow is turbulent. Their peak-spawning season usually occurs from late March to late May depending on location. As with striped bass, male white bass usually arrive at the spawning grounds before the females. Peak spawning activity occurs when water temperatures are 18 or 19° C. There is usually more than one period of activity for a specific population. COLLECTION METHODS: Methods of collecting broodstock vary with the species, type of habitat and local laws and regulations. The most commonly used methods for collecting striped bass and white bass are hook and line, gill nets, pound nets and electro fishing. Hook and line collections work well for white bass males and females because these relatively small fish are easy to catch in spring as schools of fish migrate toward the spawning grounds. This method is also effective for collecting striped bass males because relatively few fish are needed and the stress of capture is less likely to affect their ability to produce viable gametes than in the case of striped bass females. However, this method is less desirable to collect striped bass females because of the high mortality rate associated with the stress of capture. These large fish must be played to near exhaustion during the capture process. Females that do survive are often difficult to ovulate, probably because the blood supply to the ovaries was shut down during capture. However, hook and line collections are frequently the only means for private culturists to collect striped bass broodstock because other methods are restricted by law. HORMONE INJECTIONS: Human chorionic gonadotropin (HCG) hormone is used to induce final maturation and ovulation of eggs and to enhance sperm production of striped bass and white bass. The hormone is injected intramuscularly below the dorsal fin. Striped bass females are usually injected as soon as possible after capture to improve the chances of successfully spawning the fish. They receive an injection of 275 to 330 International Units (IU) per kilogram (125 to 150 IU per lb) of body weight to induce ovulation. An injection of 110 to 165 IU per kilogram (50 to 75 IU/lbs) of body weight is given to males to enhance sperm production. An egg sample is taken 20 to 28 hours after injection with a 3 mm (outside diameter) glass or plastic catheter. The tube is inserted through the urogenital opening and into the ovary to take a small sample of eggs. Eggs are examined under a microscope to determine how long before ovulation will occur. Ovulation usually occurs in 25 to 50 hours depending on water temperature and stage of gonadal maturation. White bass females are injected with 1,100 IU per kilogram (500 IU per lb) of body weight to induce ovulation. This quantity of hormone is probably well over the threshold level for induction of ovulation. Because studies have not been performed to determine the appropriate levels for white bass females, culturists tend to inject excess hormone. Sexually mature female white bass will usually ovulate within 25 to 50 hours after injection depending on water temperature. Eggs samples are generally not taken from white bass because the fish are small, relatively easy to handle and ovulation is less likely to be affected by handling stress. Egg samples can be taken from white bass using a 1.5 mm outside diameter catheter and staged under a microscope in the same manner as striped bass. SPAWNING: Striped bass females can be spawned by using one of two methods. The tank spawning method can only be used to produce pure line striped bass because female striped bass will not ovulate in the presence of white bass males. When this method is used the fish spawn “naturally” in tanks. The fish are injected with HCG and placed in tanks 12 to 15 hours before the female is expected to spawn. Usually two females and four males are placed in a circular tank and left undisturbed. The tanks may be 1.2 to 2.4 m in diameter and about 1.2 m deep. Water is supplied at a rate sufficient to create a circular velocity of 10 to 15 cm per second at the perimeter. The center standpipe must be screened and a bubble curtain used to prevent loss and impingement of eggs. When males have participated in spawning, the water will appear milky. The broodfish are removed after spawning and the eggs are incubated in the tank. Some culturists install a device to collect the eggs after they are water-hardened and the eggs are collected and incubated in McDonald jars. The production of hybrid striped bass must be accomplished by manually stripping the eggs and sperm from the ripe fish into a container. Sperm from two or more white bass or striped bass males is used to ensure fertilization of the eggs. Fertilization of striped bass eggs is accomplished by using either a wet or a dry method. There appears to be little difference in the percent fertilization between the two methods. Wet fertilization is accomplished by stripping the eggs from the female into a small amount of water. Sperm are added periodically as the eggs are being stripped because sperm are motile for only 1 to 2 minutes, and the eggs begin to water-harden as soon as they come in contact with water. Water-hardening may prevent the sperm from entering the egg. This technique is best accomplished with 2 or 3 workers to efficiently remove eggs and and mix in sperm at the same time. The main advantage of this method is that urine and drugs may be diluted before contact with eggs, minimizing any deleterious effects. MARKET OF HSB: Recently one study was done to assess market of HSB. Of the 208 full-service restaurant fish buyers that participated in the survey, exactly one-half indicated that they did not know that farmers raised hybrid striped bass as a food fish, and an additional 8% indicated that they were not sure. Of the 147 supermarket fish buyers that participated in the survey, 73% of single-unit supermarket buyers and 47% of chain buyers indicated that they were not aware that farmers raised hybrid striped bass as a food fish. An additional 16% of single-unit buyers and 17% of chain buyers indicated that they were not sure. When compared to restaurant buyers, single-unit supermarket buyers quoted offer prices that were 39% lower for whole hybrid striped bass and 37% lower for hybrid striped bass fillets. Supermarket chain buyers quoted offer prices that were 13% lower for whole fish and 18% lower for fillets. The focus group with 10 Illinois fish consumers consisted of a sensory evaluation of hybrid striped bass fillets and a discussion of participants’ perceptions of fish and their fish purchasing activities. The sensory evaluation allowed participants to taste and evaluate three cooking methods and two recipes found on the Internet. The overall results indicated that participants generally liked hybrid striped bass, but that the preparation method was an important factor in determining the degree to which participants liked or disliked the fish. The focus group discussion revealed that participants were unfamiliar with hybrid striped bass as a food fish, and they commonly associated the words “striped bass” with sport fishing. The results of this study suggested that the success of large-scale marketing of hybrid striped bass in the North Central Region would depend on extensive product promotion and education of both retailers and consumers. Full-service restaurants were more likely than supermarkets to offer prices that covered farm production costs. REFERENCES:
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