Wallace E. Jenkins

Broodstock management and spawning of southern flounder, Paralichthys lethostigma

Collaborative studies are underway in South Carolina (SC) and North Carolina (NC) to control reproduction of southern flounder, Paralichthys lethostigma. Although cultured broodstock are being developed, work to date has been with wild caught adults held in captivity for at least 1 year. Shortly after capture, wild adults should be treated to control diseases and parasites, especially Amyloodinium sp. and fish lice, Argulus sp. Induced spawning using only photothermal control has not occurred, but GnRHa implants have been successfully used to induce ovulation and allow strip-spawning. In addition, during 1997, photothermal conditioning coupled with 100 μg GnRHa implants resulted in successful tank-spawning. During a 99-day period, eggs were collected on 64 days and lowering temperature was shown to inhibit spawning. On days that spawning occurred, mean number of eggs collected was 277,844 (±177,714) and mean fertility was 32.8% (±25.2%). Total number of eggs collected was 17,782,000. Females used in the study were ≥5 years old while the males were ≥3 years old. Fish had been in captivity for ≥1.5 years. The spawning success achieved using the combination of photothermal conditioning and GnRHa implants resulted in less stress to the fish, higher egg production and an extended spawning period. Use of photothermal conditioning coupled with tank-spawning techniques should allow year-round spawning of southern flounder. This should facilitate more rapid development of a culture technology for this species.

Retention of Oxytetracycline-Induced Marks on Sagittae of Red Drum

Abstract In a pilot-scale stocking program, juvenile red drum Sciaenops ocellatus were immersed for 4 h in a 500-mg/L active solution of oxytetracycline hydrochloride (OTC) and 15-g/L salinity water at a temperature of 26.2°C to mark the otoliths before release. A portion of the treated fish was retained to determine marking success and mark retention. Retained fish were held in outdoor tanks supplied with flow-through estuarine water from Charleston Harbor, South Carolina, and fed commercial trout diets daily. During a 4.4-year period, subsamples of treated fish were regularly sacrificed, and their sagittae were removed, sectioned, and examined under an epifluorescent microscope to validate presence of a mark. Because of interference from autofluorescence, OTC marks were not detectable on sagittae from fish sampled 56 d after immersion (N = 4). However, a mark was visible on 100% of sagittae examined from treated fish sampled on nine occasions from 73 to 1,618 d after immersion (N = 46). In a blind test,...

Pond Culture of Larval and Juvenile Cobia, Rachycentron canadum, in the Southeastern United States

Abstract The potential of growing larval and juvenile cobia, Rach-ycentron canadum, in ponds was investigated. Larval cobia, obtained from tank spawning of wild-caught adults, were stocked 48-72-h post-hatch at a rate of 700,000/ha into three fertilized 0.25-ha ponds. At one week post-stocking (WPS), fish were observed consuming formulated feed. Growth was rapid, with specific growth rates (SGR) ranging from 12.5-19.2% body weight/day. At harvest (5 WPS) fish reared in two ponds weighed 7.9 and 9.3 g and total length (TL) was 118.9 and 129.3 mm, respectively (all fish reared in remaining pond died the night prior to harvest due to aerator failure). Feed conversion ratio (FCR) was 3.8 for both ponds and survival was 5.3 and 8.5%. Low survival rates were thought to be due primarily to cannibalism. Immediately after harvest, fish were restocked into two 0.25-ha ponds at a stocking rate of 14,400/ ha. Fish were fed formulated, pelleted feeds. Growth was rapid up to ∼9 WPS, after which pond water temperatures declined. Ponds were harvested at 13 and 15 WPS, respectively. Final weight of fish was 309.9 and 362.5 g. Final TL was 343.1 and 355.7 mm. FCR was 3.8 and 4.5 and survival was 27.5 and 30.5%. Major losses of fish were associated with avian predators and possibly a toxic algal bloom. Results of trials indicate that cobia larvae and juveniles can be reared in pond-based culture systems, however additional research is needed to refine this approach.

Pond nursery production of southern flounder (Paralichthys lethostigma) and weaning to commercial diets

Southern flounder (Paralichthys lethostigma) were spawned during March, 1997, and 4-day post hatch larvae (mean TL=2.0±0.1 mm) were stocked into two 0.1 ha ponds at a density of 74 m−2. At stocking, water temperature was 20°C and salinity 30 ppt. No supplemental feed provided and fish were harvested after 74 days of culture (June 9). A total of 5587 fingerlings were harvested from the ponds and average survival was 3.8%. Mean fish length in one pond was 37±7 mm (23–54 mm) while mean size of fish in the other pond was 55±8 mm (38–80 mm). Incidence of pseudoalbinism was extremely low (<1%) in both ponds. The 78-day old fish which were harvested from the ponds were converted to dry diets in 14 days. Average survival during the transition period was 80.4%. In contrast, fish harvested, during a previous pond nursery study, at an age of 220 days required 106 days to transition to dry feeds. Survival during transition averaging 58.2%.

PRODUCTION AND EXTENDED SPAWNING OF CULTURED WHITE BASS BROODSTOCK

Abstract Our research focused on the development of domesticated broodstock of white bass Morone chrysops to reduce or eliminate the dependence of public and private hatcheries on wild-caught fish. Juveniles, obtained from spawning wild white bass, were reared to a mature size in an outdoor tank system under ambient environmental conditions. At 1 year of age, a few males were mature, and by 2 years of age all males and females were mature. Females were induced to ovulate with human chorionic gonadotropin (550 IU/kg) and then strip-spawned. Mean estimated egg production was 98,273 eggs/kg for 2-year-old fish and 127,805 eggs/kg for 3-year-old fish. Holding mature fish in reduced water temperatures extended the spawning period by 3 months. The use of cultured white bass broodstock should facilitate hatchery operations for stocking public waters and for hybrid striped bass aquaculture.

Year-Class Component, Growth, and Movement of Juvenile Red Drum Stocked Seasonally in a South Carolina Estuary

Abstract Red drum Sciaenops ocellatus have been classified by the Atlantic States Marine Fisheries Commission as overfished in the Atlantic off the southeastern USA. A study was conducted to evaluate stocking hatchery-reared fish as a management tool to increase abundance of red drum in South Carolina estuaries. Multiple groups of juveniles, at mean sizes of 22–56 mm total length, were released after being marked by immersion in 15 g/L salinity brackish water containing oxytetracycline HCl (500 mg/L active). Fish were released into a small (535-ha) part of the available nursery habitat (total = 25,000 ha) in the Port Royal Sound estuary each fall and spring from fall 1995 through spring 1997. During fall 1995 and spring 1996, 347,000 fish were stocked; during fall 1996 and spring 1997, the number was 1,228,000. Movement of hatchery fish from the release site was monitored for at least 2 years after release. Overall, hatchery fish accounted for 19.0% of the 627 fish (age 0 to age 2) captured from the 1995 ...

Assessing Red Drum Juvenile Stocking in a South Carolina Estuary Using Genetic Identification

Abstract The South Carolina Department of Natural Resources has been stocking red drum Sciaenops ocellatus since 1988 to evaluate parameters critical to their successful survival and recruitment in South Carolina estuaries. From 1999 to 2002, between 600,000 and 1,000,000 juvenile red drum were stocked each year in two tributaries of Charleston Harbor. The harbor and each tributary were partitioned into three independent strata and randomly sampled monthly for two decades, allowing population trends before, during, and after stocking to be evaluated. Using microsatellite-based parentage analysis, we examined the contribution of stocked age-0 juvenile red drum (15–60 mm total length) to the local population 1 year after release by using fishery-independent sampling. Analysis of these data showed that the highest contributions (88.9%) were close to the stocking site in years with low natural recruitment, whereas in years with high natural recruitment, contributions were lower and stocking was less effective...

Small Marine Reserves May Increase Escapement of Red Drum

Abstract An experimental stock enhancement program was conducted in Port Royal Sound estuary, South Carolina, in which cultured juvenile red drum (Sciaenops ocellatus, 2–3 cm TL, ∼40 days old) were released into a system of shallow tidal creeks that flow into the Colleton River. All fish were immersed in oxytetracycline (OTC) prior to release to produce an identifiable, chemical mark on the otoliths. The release area was typical of primary nursery habitat in this region. For four years post-stocking, fish were collected throughout the sound using hook and line, spear, and trammel net. Otoliths were examined for OTC marks to determine which fish were of hatchery origin. It was found that while dispersal was substantial, many stocked fish stayed in the general area of release (1.8 × 3.2 km) until reaching the age of maturity (∼age 3) when they left the estuary, and at all ages they were mixed with wild fish. This suggests that relatively small areas containing the appropriate suite of habitat types could be...

Economic feasibility of prawn Macrobrachium production in South Carolina, USA

Abstract Cost and returns were estimated for freshwater prawn Macrobrachium rosenbergii farming as a supplemental enterprise in South Carolina in relation to the following factors: (1) existing versus new investment for ponds and water supply; (2) three stocking strategies (postlarvae alone, a 50:50 mixture of postlarvae and nursed juveniles and nursed juveniles alone) at various densities (2·15–8·61 prawns m −2 ); (3) a range of prices for seed stock (

Differentiating between Hatchery and Wild Red Drum by the Position of First Annulus on Sagitta

0–50 per thousand); and (4) two marketing alternatives (sale of product as shrimp tails only or with the large animals marketed heads-on and the rest as tails). Net revenue estimates indicate that prawn aquaculture has potential to become a source of supplemental income to farmers in the coastal plain area of South Carolina and throughout much of the southeastern United States. This is especially likely if the enterprise can utilize existing pond facilities that are already discounted into the value of the land or were constructed during a period of lower investment costs. A prawn farm is unlikely to be profitable if postlarvae alone are stocked, even in existing facilities, but if a mixture of postlarvae and juveniles or juveniles alone are stocked in existing facilities, profitability is likely at seed costs up to about