Theodore I. J. Smith

Status and management of Atlantic sturgeon, Acipenser oxyrinchus, in North America

The Atlantic sturgeon, Acipenser oxyrinchus, consists of two subspecies distributed along the Atlantic coast of North America from Labrador to the east coast of Florida (Atlantic sturgeon subspecies -A.o. oxyrinchus) and along the Gulf of Mexico from Florida Bay, Florida to the mouth of the Mississippi River (Gulf sturgeon subspecies -A.o. desotoi). The species has been exploited throughout its range with landings peaking around the turn of the 20th century followed by drastic declines shortly thereafter. During recent years, landings in Canadian waters have increased substantially (approximately 129 metric tons in 1993) while in the United States landings are more controlled or prohibited (approximately 22–24 metric tons in 1993). Recently, the Atlantic States Marine Fisheries Commission developed a Fishery management plan for Atlantic sturgeon, and the United States Fish & Wildl]e Service and Gulf States Marine Fisheries Commission drafted a Gulf Sturgeon Recovery/Management Plan. Fishery managers in Canada are in the process of establishing more stringent fishery regulations for sturgeon. Thus, the impact on populations due to harvesting should be substantially reduced. Current research focus includes: life history and population status studies, stock delineation, and development of culture and stock enhancement techniques. Implementation of the findings of such studies may be helpful in the restoration of depleted stocks.

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.

Habitat Utilization and Biological Characteristics of Adult Atlantic Sturgeon in Two South Carolina Rivers

Abstract Thirty-nine adult Atlantic sturgeon Acipenser oxyrinchus oxyrinchus (136–234 cm total length) were caught in gill nets fished at historical sturgeon-fishing locations in the Combahee and Edisto rivers (South Carolina) during spring and fall 1998. All fish were tagged (with passive integrated transponders and darts), and radio and acoustic transmitters were surgically implanted in 29 fish. When possible, gonad biopsies were taken for sex and maturity-stage determination. Locations of telemetered fish were determined several times per week from airplanes (radio) and boats (radio and acoustic). Nominal ages, based on microscopic examination of pectoral spine cross-sections, ranged from 7 to 20 years. Of the 28 fish for which sex was definitively ascertained, 21 (aged 7–15) were male and 7 (aged 15–20) were female. All fish moved out of the rivers during the period extending from October to November. Twelve fish returned the following spring (most in March), and many took up residence at the same sit...

Possible significance of variation in the larval development of palaemonid shrimp

Abstract Time of metamorphosis and postlarval development were found to be unrelated in the palaemonid shrimp Macrobrachium rosenbergii (de Man). However, in addition to being influenced by environmental factors, the tendency of a particular palaemonid ( Palaemonetes spp.) larva to pass through a given number of larval instars may be inheritable. It is suggested that variation in the duration of the planktonic larval phase and the number of larval instars may help to ensure the dispersal of sibling larvae and thus enhances the survival of the parental genotypes. Also, such variation may increase the probability of recruitment to existing parental populations and the likelihood of successful colonization of freshwater environments.

Sturgeon Fin Ray Removal is Nondeleterious

Abstract Marginal pectoral fin rays were removed from cultured shortnose sturgeon Acipenser brevirostrum and wild Atlantic sturgeon A. oxyrinchus oxyrinchus to evaluate the impact on growth and survival. Shortnose sturgeon were examined after 98 d and Atlantic sturgeon were examined after 183 d. There were no significant differences between control (no fin ray removed) and treatment fish in growth (weight or length) or survival of either species, and all wounds had healed. Removal of pectoral fin rays for age analyses had no apparent deleterious effects on these sturgeon species.

Effect of dietary menhaden oil on growth and muscle fatty acid composition of hybrid striped bass, Morone chrysops × M. saxatilis

Abstract Hybrid striped bass were fed four diets in triplicate containing 0, 4, 8 and 12% menhaden fish oil (MFO) for 18 weeks to determine uptake of n−3 fatty acids and its effect on body composition and fish health during growth to market size. Fish (X = 624 ± 26 g) were stocked in 12 circular flow-through tanks (2000 liters) with 9 ppt salinity and temperature at 22°C. Fish fed the 4 and 8% MFO diets had significantly better growth compared to fish fed the 0 or 12% MFO diets. Survival ranged from 89 to 96% and did not appear to be diet-related. Fatty acid profiles in muscle tissue reflected the diet concentrations with significant increases (P ≤ 0.05) in eicosapentaenoic acid (EPA) in fish fed the 8 and 12% MFO diets. Other fatty acids demonstrating significant (P ≤ 0.05) muscle concentration increases of 1% or greater in fish fed the MFO diets were: 14:0,16:1n−7, 22:6n−3, as well as total polyunsaturates, total n−3 fatty acids, and the n-3 n-6 ratio. Fatty acids showing significant decreases (P ≤ 0.05) of 1% or greater were 16:0, total saturates and monounsaturates. Fish fed the 0% MFO diet had a decline in both EPA (6.1 to 5.4%) and docosahexaenoic acid (DHA) (12.5 to 8.6%). Thus, a dietary source of n−3 fatty acids is important in maintaining EPA and DHA levels during intensive culture. Fish fed the 8 and 12% MFO diets had twice as much n−3 fatty acids (1.0 g/100 g tissue) as those without MFO (0.5 g/100 g tissue). There were no significant (P ≤ 0.05) differences in muscle composition except lipid content which increased from 3.2% in the 0% MFO, to 3.5%, 3.9% and 4.4% in the 4, 8 and 12% MFO treatments, respectively. No significant changes were observed in serum triglyceride concentration, hepato-somatic index, and hepatic structure.

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,...

Habitat Use and Movements of Juvenile Shortnose Sturgeon in the Savannah River, Georgia-South Carolina

Abstract During 1999-2000, 28 juvenile (<56 cm total length) shortnose sturgeon Acipenser brevirostrum were captured in the lower Savannah River, Georgia−South Carolina, and acoustic transmitters were implanted in or attached to 15 of them. The juveniles were located only between river kilometers (rkm; measured from the mouth of the river) 31.2 and 47.5, in salinities of 0.1‰ to (briefly at high tide) 17.6‰, and at depths of 2.1-13.4 m. The fish used two small areas very intensively. When water temperatures were above 22°C, the fish moved upriver; they aggregated particularly at rkm 47.5 when temperatures were greatest, and the average salinity at this location was 0.1‰. When water temperatures were below 22°C, the fish moved downriver into Savannah Harbor and used approximately 2-km segments of the Front and Middle rivers just upriver of their confluence at rkm 31.5. Here they encountered higher salinities (mean, 5.4‰) than during warm months. During the period of lowest water temperatures, the fish aggr...

Effectiveness of Six Methods for Marking Juvenile Shortnose Sturgeons

Abstract The shortnose sturgeon (Acipenser brevirostrum), an endangered species, was the subject of a stock enhancement trial. Some standard methods of marking individuals for later identification as cultured fish appeared to be ineffective. Therefore, six marking techniques were tested on several groups of cultured juvenile shortnose sturgeons (mean total lengths, 115–500 mm) during 1989–1990. The methods evaluated were: (1) coded wire tags implanted in the snout cartilage, (2) dorsally implanted T-bar tags, (3) dorsally implanted dart tags, (4) abdominally implanted T-anchor tags, (5) abdominally implanted disk anchor tags, and (6) barbel clipping. After 2 years, 100% of the clipped barbels were partially or completely regenerated. Retention of coded wire tags was highly variable (70–100%) in trials of 62–410 d. Retention was greater for the T-anchor tag (92%) than for any of the other tag types. However, in most cases, tag incisions and wounds persisted for the duration of the experiment.

Communications: Tank Culture of Larval Sunshine Bass

Abstract In 1995, two studies were conducted at the Marine Resources Research Institute, Charleston, South Carolina, that focused on development of techniques to intensively rear larval sunshine bass, the hybrid of female white bass Morone chrysops and male striped bass M. saxatilis. During the first study, the rotifer Brachionus plicatilis was shown to be an acceptable first-food when fed at 10 organisms/mL in static black tanks receiving high surface illumination (mean, 600 lx). It was further demonstrated that larvae could be switched to a diet of just nauplii of Artemia sp. by at least day 8 post-hatch. At the conclusion of the 8-d study, larvae fed Artemia nauplii earlier were significantly larger (9.12 mm total length, TL) than larvae fed rotifers through day 7 posthatch (6.71 mm TL). However, there were no survival differences (mean, 67.2%). During the second study, supplementation of the Artemia nauplii diet with a commercial larval feed offered no advantage to 12-d-old larvae, which had similar s...