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Notes: The effects of four practical diets on growth, feed utilization, and body composition of wild-caught juvenile and subadult black sea bass Centropristis striata (316 ± 113 g =±± SD) were compared for 221 d in a recirculating tank system consisting of 12 2,660-L tanks. Salinity averaged 33.5 ppt and temperature averaged 20.9 C but vaned from 12 to 27.1 C. Diets differed in crude protein (CP) and crude lipid (CL) as follows: 1) low CP (44.0%), low CL (11.4%) trout diet; 2) low CP (44.8%), high CL (15.0%) trout diet; 3) midlevel CP (47.9%), midlevel CL (12.8%) Bounder diet; and 4) high CP (53.9%), high CL (15.1%) marine finfish diet. Energy: protein ratios (E: P) were 44.6, 45.3, 41.8, and 39.1 W/g.Survival to 221 d on all diets was 100%. Significant (P 〈 0.05) differences in growth rates were observed among diets. Final weights were higher for midlevel and high CP diets 3 and 4 (1,051 and 1,013 g) than for low CP diet 1 (873 g). Relative growth rate (RGR, % total increase in weight), specific growth rate (SGR, % increase in body weight/d), and daily weight gain (DWG, g/d) were higher for higher CP diets 3 and 4 (RGR = 223 and 221; SGR = 0.53; DWG = 3.28 and 3.16), than for low CP diet 1 (RGR = 181; SGR = 0.47; DWG = 2.54). There were no significant differences between initial and final whole body protein and fiber content among diets. Lipid and gross energy levels significantly increased (P 〈 0.0001) in all treatments while moisture levels significantly decreased (P 〈 0.001).Although these differences were not significant, feed conversion ratio (FCR = dry weight fed/wet weight gain) was lower for fish given midlevel CP diet 3 (1.49) and high CP diet 4 (1.52) than for those fed low CP diets 1 and 2 (1.60 and 1.62). Protein efficiency ratios (PER = weight gain/weight protein fed) (1.43 to 1.24), apparent net protein retention (ANPR = weight protein gain/weight protein fed) (20 to 25%), and apparent net energy retention (ANER = energy gain/energy fed) (53.3 to 56.8%) were not significantly different among treatments. The midlevel CP (50%), midlevel CL (12%) diet maximized growth rates and was also significantly less expensive per kg fish weight produced ($1.40) than the high CP diet ($1.94) which produced the second highest growth rates. These results demonstrated that wild-caught black sea bass can be successfully reared in recirculating tanks from juvenile to marketable sizes with high survival and with good feed conversion and growth on commercially prepared diets with a wide range of protein and lipid levels.

Notes: Abstract— Wild-caught, adult summer flounder Paralichthys dentatus (avg. wt. = 740 g; range = 264–1,540 g; N= 60), collected in northeastern US coastal waters during October 1994, were transported to Vero Beach, Florida in March 1995 and held in 2.6-m3 indoor tanks through November 1995 under two artificial photothermal regimes: (1) natural regime, simulating natural habitat conditions; and (2) accelerated thermal regime, with seasonal temperature changes advanced by one month. A third group of fish was held in outdoor tanks under ambient photothermal conditions. Under all photothermal conditions, onset of vitellogenesis was associated with declining daylength and temperature, beginning in the accelerated group, then progressing to the natural and the ambient groups. From 20 September to 28 November 1995, 23 vitellogenic stage females from the accelerated and natural regimes were implanted with a cholesterol-cellulose pellet containing LHRH-a (100 μg/kg body wt). Females with initial mean oocyte diameters ranging from 258–456 μm spawned voluntarily 2.5–5.5 d postimplantation, while no maturational response was obtained from females with mean diameters ranging from 165–231 μm. Two females were spawned twice during the study period by LHRH-a pellet implantation. Infrequent, natural spawning without hormone intervention was also obtained. Females released from 22.7–396.9 × 103 eggs on the first day of spawning, with fertilization and hatching rates of 0–93.470 and 0–81.1%, respectively.

Notes: The southern flounder Paralichthys lethosligma is a high-valued flatfish found in estuarine and shelf waters of the south Atlantic and Gulf coasts of the United States. Wide temperature and salinity tolerances exhibited by juveniles and adults make it a versatile new candidate for commercial culture, and studies are underway in the southeastern U.S. to develop hatchery methods for this species. The objectives of this study were to establish illumination and salinity conditions that optimize growth and survival of larval southern flounder reared through the yolk-sac and first feeding stages to 15-d post-hatching (15 dph). Early embryos were stocked into black 15-L tanks under light intensities of 5, 50, 100, and 1,000 Ix and at salinities of 24 and 34 ppt in a 4 ± 2 factorial design. Significant (P 0.05) effects of both light intensity and salinity on growth and survival were obtained, with no interaction between these effects. On 11 dph and 15 dph, growth was generally maximized at the intermediate light intensities (50 and 100 Ix) and minimized at the extremes (5 and 1,000 Ix). By 15 dph, growth was higher at 34 ppt than at 24 ppt. Survival to 15 dph showed trends similar to those of growth. Survival was higher at 100 Ix (avg. = 46%, range = 41–54%) than at 5 Ix (avg. = 11%, range = 6–17%) and higher at 34 ppt (avg. = 43%, range = 3145%) than at 24 ppt (avg. = 17%, range = 8–38%). Whole-body osmolality (mOsmol/kg) was significantly lower in larvae reared at 24 ppt (avg. = 304, range = 285–325) through 11 dph than in larvae reared at 34 ppt (avg. = 343, range = 296–405). Larvae reared under the extreme light intensity treatments (5 and 1,000 Ix) at 34 ppt appeared to exhibit osmoregulatory stress, particularly on 11 dph, when a marked increase in whole-body osmolality was observed. The mid-intensity treatments (50 and 100 Ix) at 34 ppt optimized growth and survival of larval southern flounder in this study; and elicited the most stable osmotic response. These conditions appear to be consistent with those that southern flounder larvae encounter in nature during this early developmental period.

Notes: An economic analysis was performed of a proposed commercial-scale 20-ha saltwater pond culture operation for Florida red tilapia in Dorado, northern Puerto Rico. The analysis was based on actual cost and production data from a commercial-scale hatchery, pilot-scale grow-out trials conducted in six 0.2-ha saltwater (avg. = 22.7 ppt) ponds at the Dorado facility and on wholesale market prices ($4.96–5.18/kg) fetched by dressed-out (gilled, gutted and scaled) product. The proposed 20-ha growout facility is comprised of 25 0.8-ha earthen ponds, each supplied with sea water, brackish well water, drainage and aeration, which account for 60.8% of the capital costs. Ponds are stocked with fingerlings (0.85 g avg. wt.) at a density of 3.0 fish/m2 (30,000/ha), and are harvested at 160 and 220 d, at an average weight of 545 g for a total yield of 11,445 kg/ha per crop. Imported feed ($0.55/kg), processing and distribution ($0.50/kg) and sex-reversed fry ($0.11/fry) are the highest variable costs, accounting for 30.7%, 15.4% and 13.9%, respectively, of the total annual costs. Salaries and benefits, and depreciation represent the highest fixed costs, accounting for 8.4% and 5.5%, respectively, of the total annual costs. Under these conditions, a wholesale price of $4.55/kg results in a positive cash flow by year eight, and a breakeven price, internal rate of return (IRR), net present value (NPV) and discounted payback period (DPP) of $4.08/kg, 7.6%, ($235,717) and 〉10 yr, respectively, suggesting that the proposed 20-ha operation is not economically feasible under these conditions. The proposed enterprise is marginally feasible if stocking density is increased to 3.5 fish/m2 while at 4.0 fish/m2 economic outlook is favorable. Costs can be lowered considerably by targeting production and market variables most sensitive to profitability indices, using locally-prepared feeds, and vertically integrating hatchery and growout operations.

Notes: Two 10-day hatchery experiments were conducted to evaluate s-type (Hawaiian strain) and ss-type (Thailand strain) rotifers Brachionus plicatilis and cryogenically preserved oyster Crassostrea gigas trochophores as first feeds for larval Nassau grouper Epinephelus striatus. Newly hatched grouper larvae were reared at densities of 11.2–20.8/L in 500-L tanks at 36–38 ppt salinity, 25–26 C, and under a 11-h light: 13-h dark photoperiod. Beginning on day 2 posthatching (d2ph), prey were maintained at a density of 20 individuals/mL, while phytoplankton (Nanochloropsis oculata) was maintained at 500 × 103 cells/mL. In experiment 1, survival and growth were higher (P 〈 0.05) for fish fed small s-type rotifers (mean lorica length = 117 μm; fish survival = 7.96%) selected by sieving than for fish fed non-selected rotifers (mean lorica length = 161 μm; fish survival = 2.13%). These results demonstrated the advantage of small prey size and suggested that super-small (ss-type) rotifer strains would be beneficial. In experiment 2, three feeding regimens were compared: 1) ss-type rotifers (mean lorica length = 147 μm); 2) oyster trochophores (mean diameter = 50 μm) gradually replaced by ss-type rotifers from d5ph; and 3) a mixed-prey teatment of 50% oyster trochophores and 50% ss-type rotifers. Survival was higher (P 〈 0.05) for larvae fed mixed prey (15.6%) than for those fed rotifers (9.73%) or trochophores and rotifers in sequence (2.55%), which also showed the slowest growth. Oyster trochophores, although inadequate when used exclusively, enhanced survival when used in combination with rotifers, possibly by improving size selectivity and dietary quality. In a pilot-scale trial, larvae were cultured through metamorphosis in two 33.8-m3 outdoor tanks. Fertilized eggs were stocked at a density of 10 eggs/L and larvae were fed ss-type rotifers from d2ph-d20ph, newly hatched Artemia from d15ph-d18ph, 1-d-old Artemia nauplii from d18ph-d62ph. Survival on d62ph was 1.17%, with a total of 5,651 post-metamorphic juveniles produced.

Notes: Laboratory experiments were conducted to determine the effect of salinity on embryonic development and hatching in Neobenedenia melleni, a monogenean ectoparasite of seawater-cultured (37 ppt) Florida red tilapia (Oreochromis urolepis hornorum × O. mossambicus). Eggs, collected from adult monogeneans at 37 ppt, were exposed to different salinities (0, 6, 12, 18, 24, 30 and 37 ppt) for 48, 72 or 96 h. Varying degrees of post-treatment development and hatching occurred when natural seawater conditions were restored. Hatching success generally declined with decreasing salinity and increasing duration of exposure. Under all durations of exposure, hatching success remained relatively high (≥ 69.6%) at salinities of 24 ppt and above, but declined markedly (≤ 32.5%) at lower salinities. Hatching did not occur in eggs exposed to fresh water (0 ppt) for 72 and 96 h. The most effective treatments in preventing hatching, other than prolonged exposure to fresh water, were 96 h exposures to low-salinity brackish water. Percent hatch after 96 h exposure to 6, 12 and 18 ppt was 5.5, 11.9 and 5.8%, respectively.

Notes: Growth of juvenile Florida red tilapin (1.57 g average weight) spawned and sex-reversed (monosex male) at salinities of 4 ppt and 18 ppt was compared at rearing salinities of 18 ppt and 36 ppt in 200 L aquaria under controlled photoperiod (12 L:12 D) and temperature (28 C). Growth was significantly higher for progeny spawned at 18 ppt than those spawned at 4 ppt under both rearing salinities with no difference observed between 18 ppt and 36 ppt.In another experiment, growth of juvenile progeny (0.98 g average weight) spawned and sex-reversed at salinities of 2 ppt and 18 ppt was compared in 24 m3 outdoor pools at 36 ppt. When water temperatures exceeded 27 C, growth and survival were not significantly different between these groups. However, when temperatures fell below 25 C, growth and survival were significantly higher among progeny spawned at 18 ppt.The results showed that progeny spawned and reared through early ontqenetic development in brackishwater are better adapted for growth in brackish and seawater and suggested that these fish may have higher resistance to cold-stress in seawater than progeny spawned in freshwater.

Notes: An economic analysis of a hypothetical small-scale marine recirculating aquaculture system (RAS) is conducted for ongrowing small, wild black sea bass Centropristis striata at the University of North Carolina Wilmington, Center for Marine Science (UNCW-CMS) aquaculture facility in Wrightsville Beach, North Carolina (NC). The analysis is based on production data from field trials and marketing data from the sale of tank-grown product. The growout facility consists of four 16.7-m3 (dia. x ht. = 5.58 × 1 m) fiberglass tanks supported by state-of-the-art RAS components, including particle traps and swirl separators, drum screen filter, trickling biological filter, UV sterilizer, heat pump, protein skimmer, and oxygen cone. Wild-caught, above minimum legal size black sea bass (24.2 cm TL, 350 g, 0.77 lb) were purchased from a commercial fisherman for $3.14/ kg ($1.4011b), stocked at a density of 21.1 kg/m3, and grown to a final weight of 1 kg (2.24 lb) in 200 d at 23 C resulting in 1.8 production cycles per year. Fish were fed a commercial pelleted diet ($0.94/kg; $0.42/Ib) with a feed conversion ratio of 1.5. Final harvest density was 60 kg/m3 (0.50 lb/gal), and total harvestable weight was 3,982 kg (8,919 Ibs) of fish per cycle, or 6,760 kg (15,022 lb) per year. The economic analysis assumes that the facility owner manages and operates the system on coastal property zoned commercial/industrial, where full strength seawater is available on demand from natural sources. Under the base case scenario, initial investment in construction and equipment is $84,506 (10-yr life), fish are grown to a harvestable weight of lkg/fish (2.24 lb/fish), product price (farm gate basis) is $10.10/kg ($4.50/lb), and breakeven price is $7.02/kg ($3.13/lb). Depreciation, fingerlings, interest paid, electricity, and feed, account for 19.6%,17.4%, 16.9%, 16.6%, and 12.3%, respectively, of total annual costs. Measures of financial performance for the base case, 10-yr scenario are: annual return to management, $18,819; net present value (5% discount rate), $145,313; internal rate of return on initial investment, 37%; and discounted payback period on initial investment, 3.2 yr. Sensitivity analysis showed that product price changes have the largest impact on annual returns, while changes in daily growth rate, initial weight, and survival have a strong impact on financial performance. Moderate effects are seen with changes in fingerling costs, feed costs, feed conversion ratio (FCR), final weight, and interest rates.

Notes: Pilot-scale trials were conducted to evaluate growout performance of hatchery-reared summer flounder fingerlings in a state-of-the-art recirculating aquaculture system (RAS). The outdoor RAS consisted of four 4.57-m dia × 0.69-m deep (vol. =11.3 m3) covered, insulated tanks and associated water treatment components. Fingerlings (85.1 g mean initial weight) supplied by a commercial hatchery were stocked into two tanks at a density of 1,014 fish/tank (7.63 kg/m3). Fish were fed an extruded dry floating diet consisting of 50% protein and 12% lipid. The temperature was maintained between 20 C and 23 C and the salinity was 34 ppt. Under these conditions, growth, growth variation (CVwt), feed utilization, and survival of fish fed to 100% and 82% of a satiation rate were compared.Due to clear changes in growth patterns during the study, data was analyzed in three phases. During phase 1 (d 1–d 196), fish showed rapid growth, reaching a mean weight of 288 g ± 105 and 316 g ± 102, with a CVwt of 0.36 and 0.32 and FCR's of 1.38 and 1.36 in the subsatiation and satiation groups, respectively. During phase 2 (d 196–d 454), fish displayed slower growth reaching mean weights of 392 g ± 144 and 436 g ± 121, with a CVwt of 0.37 and 0.28, and increasing FCR's of 3.45 and 3.12 in the subsatiation and satiation groups, respectively. During phase 3 (d 454–d 614), fish showed little growth reaching mean weights of 399 g ± 153 and 440 g ± 129, with a CVwt of 0.38 and 0.29 in the subsatiation and satiation groups, respectively. Over the entire growout period (d 1–d 614), feed conversion ratios were 2.39 and 2.37 and survival was 75% and 81 % in the subsatiation and satiation treatments, respectively. The maximum biomass density reached during the study was 32.3 kg/m3.The satiation feed rate was superior to the 82% satiation rate, since it maximized growth rates, with no effect on FCR. The higher CVwt in the subsatiation group suggests increased competition for a restricted ration led to a slower growth with more growth variation. The decrease in growth in phases 2 and 3 was probably related to a high percentage of slower growing male fish in the population and the onset of sexual maturity.This study demonstrated that under commercial scale conditions, summer flounder can be successfully grown to a marketable size in a recirculating aquaculture system. Based on these results, it is recommended that a farmer feed at a satiation rate to minimize growout time. More research is needed to maintain high growth rates through marketable sizes through all-female production and/or inhibition of sexual maturity.

Notes: Growth and feed utilization of juvenile, hatchery-reared mutton snapper Lutjanus analis (mean weight = 12.2 g) were compared for 40 d in laboratory aquaria on four isonitrogenous diets (45% crude protein) of varying lipid content (6, 9, 12 and 15%) with energy:protein ratios (E: P; kJ/g protein) of 33.9, 36.3, 38.8, and 41.2, respectively. Growth on these diets was compared under temperatures of 25 and 30 C. Final weights (Wtr) and specific growth rates (SGR) were higher (P 〈 0.05) at lower dietary E: P ratios of 33.9 and 36.3 (Wtr= 20.3–22.0 g; SGR = 1.25–1.35%/d) than at E:P ratios of 38.8 and 41.2 (Wtr= 17.2-17.7 g; SGR = 0.84–0.85%/d). Growth at 30 C (Wtr= 21.5 g, SGR = 1.35%/d) was higher (P 〈 0.05) than at 25 C (Wtr= 17.3 g; SGR = 0.82%/d). Feed consumption (FC) was higher (P 〈 0.05) at a dietary E: P ratio of 33.9 (1.57%/d) than at 36.3 (1.27%/d) or 38.8–41.2 (0.89–0.98%/d). Growth was highly correlated (P 〈 0.01) to E: P ratio and to feed consumption. Feed conversion ratio (FCR = 2.17–3.98), protein efficiency ratio (PER = 0.58–1.03) and apparent net protein retention (ANPR = 15.8–20.0%) were not significantly (P 〉 0.05) affected by dietary E: P ratio. Apparent net energy retention (ANER) was higher (P 〈 0.05) at E: P ratios of 33.9 and 36.3 (9.50–9.98%) than at E: P ratios of 38.8 and 41.2 (7.15–7.10%). Feed utilization parameters were significantly (P 〈 0.05) better at 30 C (FC = 1.36%/d; FCR = 2.6; PER = 0.88; ANER = 10.2%) than at 25 C (FC = 1.03%/d; FCR = 3.38; PER = 0.69; ANER = 6.72%), with the exception of ANPR (17.0–17.8%). Maximum growth and energy retention in juvenile mutton snapper using a diet containing 45% crude protein was obtained at dietary lipid levels of 6–9% and E: P ratios of 33.9–36.3 kJ/g protein. Studies which determine optimum protein levels and the effects of reducing E: P ratios below 33.9 kJ/g are needed to improve feed conversion and growth.