14 CULTURE OF ESTABLISHED AND POTENTIAL SPECIES-BAIT FISH

Some references on freshwater baitfish culture are: Brown and Gratzek (1980), Giudice et al. (1982), Huner and Dupree (1984), Stickney (1986), Engle et al. (1988), Gray (1988), Pounds et al. (1992). Some specifically on golden shiners (the most valuable freshwater baitfish in the U.S.) are: Ludwig (I 989), Anonymous (1995a), and Lazur and Zimet (1995).

FAMILY ACCOUNTS Aplocheilidae-Rivulins Mangrove rivulus, a hardy easy-to-raise member of this family (related to killifish), can be used for mosquito control and laboratory research (Taylor et aI., 1992).

Cyprinodontidae-Killifishes At least a few members will readily spawn in tanks or ponds. Larvae are large, robust, and capable. Juveniles grow well and are hardy.

Gulf killifish (also called bull minnows) are popular for bait and have been raised experimentally from Texas to Florida (Tatum et aI., 1979; Trimble et aI., 1981; Tatum et aI., 1982a, 1982b; MacGregor et aI., 1983; Perschbacher and Strawn, 1983; Wass et aI., 1983; Strawn et aI., 1986). They reach a market size of 50-75 mm in 4-5 months and a maximum size of ~ 150 mm.

Gulf killifish can be raised efficiently with a three phase system of breeding ponds, hatching/nursery ponds, and grow-out ponds. Broodfish are stocked at up to 30,000/ha, with two females per male, and fed a daily ration of 3-5%. Spawning can occur in any month when temperature is 20°C or higher. Spawning mats of Spanish moss sandwiched between plastic-coated wire mesh are placed around the windward edge of breeding ponds. Every 7-13 d, the mats are transferred to hatching/nursing ponds (0.2 ha or smaller), with up to 3.75 million eggs/ha stocked. Hatching occurs in about 3 weeks at 20°C and 2 weeks at 25°C. After hatching, powdered minnow meal is provided several times a day. When the young fish reach 0.3-0.8 g, they are transferred to grow-out ponds, with stocking densities up to 400,000 fish/ha. Survival is very high.

Killifish grow well on zooplankton, worms, and insects, but for better growth, especially at high densities, supplemental feeding is needed. Almost any kind of fish feed will suffice and is preferred to single foods (e.g., cottonseed meal, wheat byproducts). A daily ration of ~ 1 0% split into two meals is suitable. At temperatures less than 20°C, Gulfkillifish grow slowly, and two or three meals a week should be enough. About 45 kg/ha of 12-12-12 fertilizer every week was used to maintain a plankton bloom in clay-bottomed ponds for Gulf killifish. Simpler systems using only one or two pond types or raceways also can be used. The two-pond system uses breeding ponds and hatching/nursing/grow-out ponds, initially stocked with up to 400,000 eggs or hatchlings/ha.

Killifish are very hardy and have wide temperature (0-35°C and higher) and salinity (0-100· ppt) tolerances. I have found mummichog escapees that survived dry under a car seat in the summer for more than an hour. Potential culture problems include broodfish predation on eggs, silt or algal smothering of eggs, fungal infections of eggs, contamination of ponds with competing or predacous species, and somtimes protozoan infestations of the gills or bacterial infections in older fish. As with other pond-cultured fish, the danger from predaceous insects and birds should be considered and avoided.

Sheep shead minnows (Perschbacher and Strawn, 1988) are eagerly eaten by game fish, but Gulf killifish, mummichogs, and striped killifish are preferred for bait because they

J. W. Tucker, Marine Fish Culture© Kluwer Academic Publishers 1998

576 Culture of Bait Fish

stay on a hook better. Sheepshead minnows are extremely hardy and will grow and reproduce in almost any container of salt or brackish water. They have been used in many toxicological studies. They can be a nuisance in ponds of more desirable species such as Gulf killifish. Sheepshead minnow males clear an area of the bottom for egg placement. In 1971, they regularly spawned, and larvae were reared to adults in 30-L aquariums on cultured (collected) zooplankton, flake feed, and minced seafoods (Tucker, unpub.). Mummichogs like to deposit their eggs intertidally in containers such as oyster shells.

Gerreidae-Mojarras Live mojarras usually are very silvery and are attractive baits for game fish. (See earlier chapters.)

Haemulidae--Grunts Live grunts are good bait for certain game fish. For example, live pigfish are a preferred natural food and bait for spotted seatrout in Florida. The pigfish's grunting sounds attract the predator. (See earlier chapters.)

Sparidae--Sea Breams, Porgies Live sparids are good bait for certain game fish such as snook. Sometimes the sharp dorsal spines are trimmed with scissors. (See earlier chapters.)

M ugilidae--Mullets Small dead whole mullet (75-200 mm TL, sometimes called finger mullet) are popular as bait in many regions; and chopped sections of larger mullet, also. Live mullet sometimes are used, but they do not survive handling and confinement in bait containers as well as killifish. (See earlier chapters.)

Other Families Depending on regional preferences, other fish can be chosen.

ENVIRONMENTAL CONSIDERATIONS Anonymous (I995b) discussed some environmental concerns with bait fish culture. If equipment such as nets, waders, buckets, and boats are used both in the culture water and in natural waters outside the farm, there is potential for transferring disease and pest organisms in either direction. Then if the bait fish are sent to another area, the unwanted organisms (e.g., zebra mussels) can be transferred with them and thus introduced to a clean area. Baitfish often are intermediate hosts for parasites. In addition, the bait fish themselves could be an exotic species or from an exotic strain; if they are released, local fish communities could be affected structurally or genetically.

SUMMARY Because of the relatively low value of bait fish, rearing costs must be kept down. When the fish are shipped alive, care must be taken in handling, sorting, and counting them, which makes the product more expensive. With correct choice of site and species plus good management and marketing, bait fish farming can be feasible. Extensive culture should be considered as an option for bait fish. Ponds provide a more natural environment and a good supply of food. If constructed well, they can be managed efficiently. Tank systems are easier to manage in some ways and alleviate predator and environmental problems, but do not provide natural food and could require more effort to manage water qualiry. For most species and purposes, the grow-out period will be in the range 2-8 months. On food fish farms, culled or surplus slow-growing fish could be sold as bait, if worth the effort.