SRAC Publication No. 323 r

Southern Regional Center

June, 1990 .

Red Drum Brood Stock and Production

James T. Davis*

The securing of brood stock, inducing tank, the way the fish were handled, placed into the transport container. them to , and caring for the the temperature of the water, the feed While handling the fish use wet eggs until hatching requires the most being used, and the lighting control all hands, wet towels or wet burlap sacks technical expertise of any phase of affect the time required. to carry the fish. Covering the eyes of fish production. Red drum are no ex- the fish has a calming effect. Better ception. As with most fish the selec- Capture of handling means less mucus removal tion and care of brood stock and less opportunity for bacterial in- determines the success or failure of a Before any brood fish can be cap- fections to develop. hatchery. Well cared for brood stock tured, a permit must be obtained in spawn more readily, produce more most states. This usually is issued by Handling of brood stock eggs with a higher fertilization rate, the state fish and game agency and have fewer disease problems and live may require an inspection of facilities The transport container should contain longer. and sworn statements or depositions. water of identical quality as the bay or The length of time required for this reservoir from which the fish are Broodstock collection and will vary between states but usually is taken. The temperature can be slightly 2 to 4 weeks. cooler, and the oxygen should be 5 handling ppm or higher. Do not crowd the fish. Several methods have been used to Because red drum brood stock have Crowding tends to increase fish ac- capture brooders. Most tivity with a consequent rise in am- not been reared to maturity in cap- have used sport methods, but monia levels. The transport container tivity, all brooders in use were cap- some success has been achieved using tured in the wild. As a general rule all should be as dark as possible. When purse seines, beach seines and fish are added to the container, the fish must become accustomed to the longlines. If fishing is to be done in cover should be raised very slowly to activities of humans in their vicinity. the Gulf, time of year will determine This is especially true for red drum prevent unnecessary excitement of the the most productive areas and fish already in the container. which become excited with unusual methods to be used. Some brood fish sounds or movement. As soon as the have been caught in impoundments. If The dissolved oxygen in the transport brood stock tank is prepared, arrange- fish are caught with sport fishing container should remain above 5 ppm ments should be made to secure brood tackle, use procedures that least stress but less than 9 ppm. In addition the stock. Usually a minimum of 6 weeks the fish. Most fishermen recommend a water in the container should be and up to 6 months in an indoor tank circle tuna hook 3/0 to 7/0. The line cooled to 70%, if the fish are to be in is necessary before the wild fish be- should be 30- to 40-pound test with a the container longer than 2 hours. come acclimated. The design of the light action reel and a medium action rod. Live bait is preferred. Fish should Antibiotics can be added to the water * The Texas A&M University System be landed as rapidly as possible and to reduce the incidence of bacterial in- fections. Acriflavine and Furacin have been used successfully. In addition, Spawning tanks hours of light in a 24-hour period. some hatcheries make a practice of in- Salinity of the water varies between jecting fish with tetracycline when- Spawning tanks usually are set in a hatcheries, but 32 to 34 ppt is stand- ever they are handled. recirculating system. Open water sys- ard. Considerable research has been tems are being used in some done on the red drum spawning cycle. When the fish are moved from the hatcheries, but disease and parasite For more detailed information consult transport container to the holding problems are more common. Techni- personnel at one of the commercial or tanks, they should be acclimated over cal details of both systems are dis- state hatcheries specializing in red a 2- to 6-hour period if the tempera- cussed in other SRAC publications. drum production. Table 1 includes in- ture differs more than 5% or the formation on photothermal induction salinity differs more than 3 ppt. A Preparation for spawning methods. longer acclimatization period is re- quired as the differences increase. Most hatcheries use temperature and light manipulation to condition the Spawning Quarantine of all fish brought into the fish for spawning. Generally brood After favorable spawning conditions hatchery should be a standard prac- fish are subjected to a 120-day matura- are reached in the tank, a variety of tice. This requires a separate tank for tion cycle that is intended to simulate methods may be used. Differences maintaining the new fish for at least 6 an annual cycle. (See Figure 1.) seem to occur between spawning weeks. Some hatcheries prefer to hold Spawning usually occurs at tempera- groups, due to tank size, fish size, new fish in outdoor ponds during this tures of about 75% with 10 to 11 tank shape or a variety of unknown period. After the quarantine period, the fish can be moved to spawning tanks. It is recommended that the fish be sexed and identifying marks recorded. This insures that a desirable sex ratio is established in the tanks and that individual fish can be iden- tified later when spawners are culled. Preparation for spawning Some hatcheries prefer to leave the brood fish in ponds and let them ma- ture naturally. When the fish are near spawning in the fall, they are sexed and moved to the spawning tanks. The fish are checked for gonadal condition when they are moved. The males are examined by applying pressure along the sides and belly of the fish to ex- trude milt. Females are examined by inserting a small (1 to 2 mm) diameter tube into the oviduct and then examini- ng the tissue microscopically. Con- sult any of several texts on the subject for a complete description of the developmental stages of eggs. Brooders of 15 to 35 pounds are preferred for tank spawning. Two males and two females per tank are common, but variations have been used depending on the availability of brood fish. Fish usually are fed a mix- ture of , squid and liver at about 2.5 percent of their body weight three times per week. Some evidence from wild caught fish show that the Figure 1. A 120-day induced maturation cycle is imposed under controlled photo- kind and quantity of feed is a major thermal conditions. factor in successful spawning. Table 1. Summarized methods for photothermal induction of maturation and spawning of red drum at the John Wilson Marine Fish Hatchery, Perry R. Bass Research Station, and Florida Bureau of Marine Research.

John Wilson Hatchery Perry R. Bass Florida Bureau of Marine Research

Tank size (metric tons) 13 10-20 5-20

Filtration system RBC, FB, SH, S, UV PT, TF S, CB, DE

Fish/tank 4 4-6 4-6

Sex ratio (M:F) 2:2 2:2, 2:1 , 1:2 3:3, 3:2, 2:2

Mean fish size (kg) 13 11 11

Regime duration (days) 150 120 120

Max. regime temperature (°C) 30.0 30.0 30.0

Min. regime temperature (°C) 15.0 18.0 18.0

Max. regime photoperiod (HL) 14.0 14.0 16.0

Min. regime photoperiod (HL) 9.0 10.0 9.0

Spawning period (days) 22 30 100

Spawning temperature (°C) 24 26 25

Spawning photoperiod (HL) 11 10 9

Mean no. eggs/spawn period (millions) 20 20 100

Biopsy interval (weeks) 4 12 2-4

Feeding regime (% bw/day) 1.07 3.00 2.85

CB - Conventional biofilter SH - Shell DE - Diatomaceous earth TF - Trickle filter FB - Fluidized bed RBC - Rotating biological contactor PT - Packed tower UV - Ultraviolet filtration S - Sand factors. Normally a group of fish spawn naturally, other procedures Usually spawning occurs in the eve- within a tank will respond the same may be needed. Most success has nings between 1 hour before and 4 way repeatedly. Fish in other tanks been achieved by raising the tempera- hours after artificial sunset Males be- within the same room may respond ture 2 degrees per day for 5 days (up come red-brown above the midline differently. to 83 °F then lowering it 2 degrees and pronounced drumming sounds per day for 6 days (to 71°F). Repeat begin. Females show additional swell- Some groups of fish will begin to this temperature regime until spawning ing of the abdomen. Some reports indi- spawn without other stimuli. As a begins. Stabilize the temperature cate additional swimming activity by general rule wait at least 10 days for when spawning occurs. the females with the male swimming spawning to begin. If the fish do not below and slightly behind the female. Actual spawning is not very con- buoyant, skimming devices on the tank before swimming to the surface. spicuous. Most operators state that edges of the tanks are used to collect After 3 days the larvae can swim these nuptial behaviors including eggs in filter boxes or other containers. horizontally. Mouth parts are formed, change of color do not guarantee that and the eyes are pigmented. Tempera- egg laying and fertilization will occur. Hatching ture affects the rate of development. At higher temperature, the larvae Usually fish are allowed to spawn for Fertilized eggs are placed in hatching develop mouth parts within 40 hours 3 to 4 days if they spawn daily. Lower containers at a density of 1,000 to after hatching. the temperature to 70 °F over a 12- 1,200 per gallon of water. Agitation of hour period and spawning should the eggs is maintained with gentle As soon as the larvae are ready to stop . The temperature can be raised to aeration. Eggs are very fragile at this feed, they should be moved to rearing 73 or 74 °F to initiate spawning again stage. Normally 90 to 95 percent of tanks or ponds. Great care must be when more eggs are desired. Some the fertilized eggs hatch. Age of the taken in handling the larvae at this operators have been successful in ob- eggs can be estimated by the number stage. They are quite fragile and easi- taining spawns weekly using this pro- and size of the oil globules. Eggs ly damaged. Timing of the move is cedure for periods longer than 3 hatch in 24 to 30 hours at water critical. If the larvae are moved too months. temperatures of 70° to 74 °F. early they may not be able to maintain themselves in the shipping container. Handling of the eggs Handling of the larvae If they are moved too late they may not have adequate food available and Fertilization and water hardening of After hatching agitation must con- survival will be poor. the eggs occur in the spawning tanks. tinue. The larvae are negatively Because live, fertilized eggs are buoyant and drift to the bottom of the

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 Coopera- tive State Research Service and the Extension Service.