SRAC Publication No. 300

II Southern Regional Aquaculture Center

July, 1989

Hybrid Striped Bass Biology and Life History

Ronald G. Hodson*

Hybrid striped bass generally refers The genus Morone belongs to the States where striped bass do not to a cross between striped bass family Percichthyidae of the order reproduce. (Morone saxatilis) and white bass Perciformes. Four species of Morone (M. chrysops). This cross, sometimes are found in the United States. Two The species is anadromous and con- called the “original cross,” was first species, white bass and yellow bass sidered an excellent food and game produced in South Carolina in the (M. mississippiensis) are found in fish sometimes reaching over 70 mid-1960s using eggs from striped freshwater. Striped bass are pounds. Commercial harvest of bass and sperm from white bass. The anadromous, but landlocked popula- striped bass has declined drastically accepted common name of this cross tions can be found in some fresh- since 1973 when a harvest of nearly is the Palmetto Bass. More recently water reservoirs. White perch (M. 15 million pounds was recorded. the “reciprocal” cross using white americana) is a brackish water Now, less than a million pounds per bass females and striped bass males species but also does well in fresh- year are harvested commercially, was also produced. The accepted water lakes and reservoirs. Three and commercial and sportfishing for common name of this cross is the other marine species belong to the striped bass is prohibited or strictly Sunshine Bass. Hybrid striped bass family Percichthyidae. regulated. have gained widespread acceptance as a sportfish, particularly in the Distribution White bass was originally distributed large reservoirs of the southeast throughout most of the Mississippi U.S., where it was stocked because Striped bass was originally found on basin and along the Gulf Coast and of the large forage base provided by the Atlantic Coast from New has since been widely introduced gizzard shad and threadfin shad. Brunswick to Florida and along the throughout the country for recrea- Gulf Coast from Florida to Texas. It tional fishing, particularly in large Striped bass and hybrid striped bass, was introduced to the west coast in reservoirs. Although smaller than in particular, have potential for cul- the early 1890s and established striped bass, the white bass is a ture in the United States as foodfish. reproducing populations. On the popular food and game species in Other Morone species have since Pacific coast striped bass now range many areas, reaching a size of 4 to 5 been hybridized with striped bass from British Columbia to south of pounds. but none has gained the acceptance the border between the United of the striped bass by white bass States and Mexico. Landlocked Physical characteristics cross, either as a sportfish or as a cul- populations exist in many reservoirs ture species. throughout the United States where The appearance of hybrid striped inflowing stream conditions meet bass is intermediate to that of the striped bass spawning requirements. parental species. The body is slightly Striped bass populations are main- compressed in cross-section and scaled. Lateral stripes similar to ● North Carolina State University and Univer- tained by stocking programs in many sity of North Carolina Sea Grant Program reservoirs throughout the United those of the striped bass are present, However, this transition usually oc- curs 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 or- ganisms in the winter and summer. Age and growth Hybrid striped bass (striped bass x white bass). Hybrid striped bass grow when water temperatures are above 15° C. but the stripes are generally broken Water quality However, optimum growing condi- in the area behind the pectoral fin tions occur when water tempera- and below the lateral line. The fish Hybrids survive and do well in a tures are 25 to 27 C. Hybrids grow has two dorsal fins, a spinous dorsal wide range of environmental condi- rapidly during their first two years of fin near the center of the body con- tions. A temperature range of 4 to life. Growth to 275 to 375 mm in tains 8-9 spines and a soft-rayed fin 33 C is acceptable, but optimum length and 225 to 350 grams in the behind that contains 1 spine and growth occurs within a temperature first year and 450 to 550 mm in 13-14 rays. The two dorsal fins are range of 25 to 27° C. Hybrids are length and 1 to 1.5 kg in the second not connected by a membrane. The generally stocked into freshwater sys- year is common. Growth rate caudal finis forked and the two tems but they do well in salinities of declines rapidly with increasing age lobes are pointed. The anal fin has O to 25 ppt, and some can survive and is similar in males and females. three spines and 9-13 soft rays. The salinities up to full strength seawater Maximum reported weight for a general color of the fish grades from (35 ppt). Dissolved oxygen levels as hybrid striped bass is approximately silver and black dorsally to white un- low as 1 mg/l can be tolerated for a 10 kg. The typical size of hybrids derneath. The shade depends on the short period of time, but optimum caught by fishermen generally ran- color of the water. Young hybrids dissolved oxygen levels range from 6 ges from 2 to 5 pounds, but fish in have visible parr marks on their to 12 mg/1. the 10 to 15 pound range are not un- sides until they are several inches Hybrid striped bass are stocked into common. The usual life span of long. a variety of water quality situations hybrid striped bass is 5 to 6 years-- more similar to white bass than to Habitat with regard to alkalinity, hardness and pH. Alkalinity values of 100 mg/1 striped bass (30 to 40 years). or above are preferred but levels less Hybrid striped bass are stocked into The growth rate of hybrid striped than 20 mg/1 are suitable. Hardness a variety of water types for recrea- bass in production ponds is deter- and alkalinity are usually related and tional purposes. They do well in slow mined by several factors: water moving streams, large reservoirs, similar values could be given for hardness. A pH range of 7.0 to 8.5 is temperature, quality and quantity of lakes and ponds. They are seldom food, palatability of food, frequency optimum for growth, but a much found in extremely shallow areas or of feeding and water quality. Hybrid wider range is tolerated. Hybrids in areas that contain dense growth of striped bass are generally harvested culture ponds have survived aquatic weeds. Because they are at a weight of 1.5 to 2.5 pounds when repeated exposure to a pH of 2.5 for pelagic in nature they are generally they are 18 to 24 months old. found in open water areas. They are short periods of time. generally most active during periods of low light such as dawn and dusk. Feeding Beginning in late winter they tend to Hybrid striped bass is a predacious concentrate in deep areas near in- species throughout its life. Fish less flowing streams and in the spring than approximately 50 mm feed may undergo spawning migrations primarily on crustacean zooplankton into upstream areas. Hybrids are fer- such as cladocerans and copepods. tile and there are reports of success- Insects of various types and ful reproduction in a few reservoirs. 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 ap- propriate sized fish are available. deep. Females come to the surface during the spawning act and several males accompany her. The males ap- pear to bump and butt the female which may stimulate egg release. Released eggs are immediately fertil- ized by the males. 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 ad- hesive 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 Periods of no growth during cold months feed until they are approximately 5 (November to March) are omitted. days old. During this swim-up stage the relatively large oil droplet is used as a food source.

June July Aug. Sept. Oct. Apr. May June July Aug. Sept. Oct.

Months

Figure shows increase in weight through two growing seasons of hybrid striped bass x white bass under culture conditions. (From UNC Sea Grant research.)

Spawning Natural spawning of hybrids has been verified in a few instances. Hybrid striped bass, unlike some They may participate in spawning other hybrids, is fertile. It is runs with striped bass or possibly oviparous (egg-laying) like the white bass. There are also confirmed parental species and produces eggs cases of reproduction in reservoirs and sperm in the spring when that contain only hybrid striped bass. temperatures are 15 to 20° C. Some Hybrid striped bass produce sperm males mature at the age of 1 year and eggs during the spring when (approximately 250 mm long and 500 water temperature is between 55 to grams), and all are mature at 2 years 70° F. Temperatures of 65° to 68° F of age. A few females are mature at are ideal for spawning hybrids and 2 years of age, but all are mature at 3 the parental species. Spawning oc- years. Females produce an average curs from mid-March through May of 160,000 eggs per pound of body depending on location. Spawning weight and spawn once a year. season in any one location usually Males may spawn many times over lasts 4 to 5 weeks. Hybrids have been the spawning season. observed participating in spawning acts in areas that contain clear shal- low rocky shoals that are 1 to 3 feet 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.