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1.
Abstract.— Tko experiments were conducted to determine the effects of salinity on growth and survival of mulloway Argyrosomus japonicus larvae and juveniles. First, 6-d-old larvae were stocked into different salinities (5, 12.5, 20, 27.5 and 35 ppt) for 14 d. Larvae grew at all salinities, but based on results for growth and survival, the optimum range of salinity for 6-d-old to 20-d-old larvae is 5–12.5 ppt. During this experiment larvae held in all experimental salinities were infested by a dinoflagellate ectoparasite, Amyloodinium sp. Degree of infestation was affected by salinity. There were very low infestation rates at 5 ppt (0.2 parasites/larva). Infestation increased with salinity to 20 ppt (33.1 parasites/larva), then declined with salinity to 35 ppt (1.5 parasites/larva). For the second experiment, juveniles (6.1 ± 0.1 g/fish) were stocked into different salinities (0.6, 5, 10, 20 and 35 ppt) for 28 d. Juveniles were removed from freshwater 3 d after transfer as they did not feed, several fish died and many fish had lost equilibrium. However, when transferred directly to 5 ppt. these stressed fish recovered and behaved normally. Trends in final mean weight and food conversion ratio of juvenile mulloway suggest that fish performed best at 5 ppt. Although salinity (5 to 35 ppt) had no significant ( P > 0.05) effect on growth, survival, or food conversion ratio of juveniles, statistical power of the experiment was low (0.22). Based on these results we recommend that mulloway larvae older than 6 d be cultured at 5 to 12.5 ppt. Optimum growth of juveniles may also be achieved at low salinities.  相似文献   

2.
The southern flounder, Paralichthys lethostigma, is an important commercial and recreational marine flatfish that inhabits estuaries and shelf waters in the south Atlantic, from North Carolina through the Gulf coasts, with the exception of south Florida. Because juvenile and adult fish are highly euryhaline, it is a prime candidate for aquaculture. Methods for captive spawning of southern flounder are well developed; however, information on optimal culture requirements of the early larval stages is required for reliable mass production of juveniles.To determine the optimal photoperiod and salinity conditions for culture from hatching to day 15 post-hatching (d15ph), embryos were stocked into black 15-l tanks (75 l−1) under four photoperiods (24L:0D, 18L:6D, 12L:12D, and 6L:18D) and two salinities (25 and 34 ppt) in a 4×2 factorial design. Temperature was 18 °C, light intensity was 150 lx, and aeration was 50 ml min−1. Significant (P<0.05) effects of photoperiod and salinity on growth (notochord length, wet and dry weights) were obtained. Growth increased with increasing photoperiod and salinity and was significantly greater at 24L and 18L than at 12L or 6L, and at 34 than at 25 ppt. On d11ph and d15ph, significant interactive effects between photoperiod and salinity on growth (wet and dry weights) were also evident. Growth of larvae reared at 25 ppt increased with increasing photoperiod to a maximum at 24L, while growth of larvae at 34 ppt reached a plateau at 18L. While there were no significant photoperiod effects on these parameters, larval survival, body water percentage, and larval osmolality on d15ph were significantly higher at 34 than at 25 ppt (41% vs. 16% survival; 322 vs. 288 mosM kg−1; and 84% vs. 76% water, respectively), suggesting stress and nonadaptation to 25 ppt, a salinity more nearly isoosmotic than full-strength seawater. Since larvae from both salinity treatments were neutrally or positively buoyant at 34 ppt, but negatively buoyant at 25 ppt, larvae reared at 25 ppt probably allocated energy to maintain vertical positioning, compromising growth and survival.The results demonstrate that growth and survival of early-stage southern flounder larvae are maximized under long photoperiods of 18–24L and in full-strength seawater. Longer photoperiods probably extend the time larvae have for feeding, while full-strength seawater salinity optimizes buoyancy and vertical positioning, conserving energy. The results show that early larval stage southern flounder larvae are not entirely euryhaline, which involves not only the ability to osmoregulate, but to conserve energy under reduced buoyancy. This is consistent with suboptimal vs. maximal growth of larvae reared at 25 and 34 ppt, respectively, under 18L (i.e., photoperiod×salinity interaction). This is also consistent with other reports that tolerance to lower salinities in these euryhaline flatfish increases post-metamorphosis when transition from a pelagic to benthic existence alleviates the need to counteract reduced buoyancy.  相似文献   

3.
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.  相似文献   

4.
Abstract.— Three experiments investigating larval stocking densities of summer flounder from hatch to metamorphosis, Paralichthvs dentalus, were conducted at laboratory‐scale (75‐L aquaria) and at commercial scale (1,000‐L tanks). Experiments 1 and 2 at commercial scale tested the densities of 10 and 60 larvae/L, and 10, 20, and 30/L, respectively. The laboratory scale experiment tested the densities of 10, 20, 30, and 40 larvae/L. Experiments were carried out in two separate filtered, flow‐through seawater systems at URI Narragansett Bay Campus (laboratory‐scale), and at GreatBay Aquafarms, Inc. (commercial‐scale). At both locations, the larvae were raised in a “greenwater” culture environment, and fed rotifers and brine shrimp nauplii according to feeding regimes established for each location. Water temperature was maintained at 21C (± 2) and 19C (± 1) for the duration of laboratory and commercial experiments, respectively. Experiments 1 and 2 at the commercial location were terminated at 42 and 37 d post hatch (dph), respectively, and the laboratory experiment lasted 34 DPH. Larvae initially stocked at 10/L grew to an average length of 14.3 and 14.4 mm, and were significantly larger (P < 0.05) than those stocked at 30/L (13.1 mm) and 60/L (11.7 mm) in commercial scale experiments I and 2, respectively. At laboratory scale, no significant differences in length were detected, although mean total length tended to decrease with increasing stocking density (average length of 14.2, 13.3, 12.7, and 12.7 mm for treatments of 10, 20, 30, and 40/L, respectively). Final survival percentage was not affected by stocking density in either commercial experiment, and was 61 and 40% for treatments of 10 and 60/L in Experiment 1, respectively, and 62, 59, and 56% for Experiment 2, respectively. Similarly, there was no significant difference in final survival percentage among treatments in the laboratory experiment, which averaged 59, 55, 56, and 37% for treatments of 10, 20, 30, and 40L. respectively. Since larval length was not different between the intermediate densities (20 and 30 Iarvae/L), and because high‐density rearing can produce a much greater numerical yield per tank, we recommend a density of 30 larvaen as an optimal stocking density for the hatchery production of summer flounder.  相似文献   

5.
This research examined the effect of initial stocking density and feeding regime on larval growth and survival of Japanese flounder, Paralichthys olivaceus. Larval rearing trials were conducted in nine 50‐L tanks with different initial stocking densities combined with different feed rations (20 larvae/L with standard feed ration [LD], 80 larvae/L with standard feed ration [HD], and 80 larvae/L with four times the standard feed ration [HD+]). Larvae were stocked on 0 days posthatch (DPH) following hatching of the fertilized embryos. Larval total length (TL), survival rates, and final densities were observed on larval settlement (32 DPH) to evaluate larval rearing performance. At 32 DPH, there were no significant differences (p > .05) in TL or survival rates between the LD (46.5 ± 17.0%) and HD+ (40.3 ± 9.4%). The TL and survival rate of HD (23.1 ± 3.5%) were significantly lower than that of LD and HD+ (p < .05). However, the larval density of HD was significantly higher than that of LD (p < .05). HD+ achieved the best larvae production (32.27 ± 7.51 larvae/L), supported by sufficient food source, high water exchange, and proper water quality management (routine siphoning, surface skimming). The larval‐rearing protocols and larval development from hatching to metamorphosis is described in detail, with corresponding photographs taken during the experiment.  相似文献   

6.
ABSTRACT: A series of experiments were conducted to examine the effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage Epinephelus coioides larvae. Newly hatched larvae were transferred to 40-L aquaria at a density of 1500 individuals/aquarium. Larvae were exposed to different levels of aeration (0 mL/min per L, 0.62 mL/min per L, 1.25 mL/min per L, 2.50 mL/min per L, or 3.75 mL/min per L); salinity (8 ppt, 16 ppt, 24 ppt, 32 ppt, or 40 ppt); and light intensity (0 lx, 120 lx, 230 lx, 500 lx, or 700 lx) for 4–6 days. Twenty larvae were sampled daily at 11:00 hours to measure for total length (TL), oil globule volume, and feeding incidence. Survival rates were determined by counting the total number of larvae remaining in each aquarium at the end of the experiment. Significantly higher survival rates ( P   <  0.05) were observed at aeration levels of 0.62 mL/min per L and 1.25 mL/min per L, at salinity levels of 16 ppt and 24 ppt, and at light intensities of 500 lx and 700 lx. The influence of aeration level, salinity and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage grouper larvae are discussed.  相似文献   

7.
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.  相似文献   

8.
Two experiments were conducted to evaluate the initial stocking density in larvae of Bay snook, Petenia splendida, and Mexican mojarra, Cichlasoma urophthalmus, using a recirculation system. Five initial stocking densities (0.5, 1, 5, 10, and 20 larvae/L) were evaluated by triplicate for 45 d. Weight and total length (TL) were measured every 15 d, and fish production was calculated for each density. The larvae stocked at the lowest densities (0.5 and 1 larvae/L) presented the highest growth for both species: C. urophthalmus (0.78 g and 45‐mm TL, and 0.76 g and 45‐mm TL, respectively) and P. splendida (0.80 g and 52‐mm TL, and 0.79 g and 49‐mm TL, respectively). However, lowest fish production was recorded (35 and 69 fish per tank, respectively, for C. urophthalmus and 34 and 70 fish per tank, respectively, for P. splendida) compared with those at densities of 5, 10, and 20 larvae/L (336, 584, and 604 fish per tank, respectively, for C. urophthalmus and 341, 679, and 912 fish per tank, respectively, for P. splendida). The polynomial model for biomass production related to the stocking density shows that the optimum stocking densities for C. urophthalmus and P. splendida are 12 and 14 larvae/L, respectively.  相似文献   

9.
The southern flounder (Paralichthys lethostigma) is a commercially important marine flatfish from the southeastern Atlantic and Gulf Coasts of the USA and an attractive candidate for aquaculture. Hatchery methods are relatively well developed for southern flounder; however, knowledge of the optimum environmental conditions for culturing the larval stages is needed to make these technologies more cost effective. The objectives of this study were to determine the effects of water turbulence (as controlled by varying rates of diffused aeration) on growth, survival, and whole‐body osmolality of larval southern flounder from hatching through day 16 posthatching (d16ph). Embryos were stocked into black 15‐L cylindrical tanks under four turbulence levels (20, 90, 170, and 250 mL/min of diffused aeration) and two salinities (24 and 35 ppt) in a 4 × 2 factorial design. Larvae were provided with enriched s‐type rotifers from d2ph at a density of 10 individuals/mL. Temperature was 19 C, light intensity was 390 lx, and photoperiod was 18 L:6 D. Significant (P < 0.05) effects of turbulence on growth (notochord length [NL], wet weight, and dry weight) were observed. On d16ph, NL (μm) increased with decreasing turbulence level and was significantly greater at 20 mL/min (64.2) and 90 mL/min (58.2) than at 170 mL/min (56.3) and 250 mL/min (57.2). Survival declined primarily during the prefeeding and first‐feeding stages from d0 to d8ph, then stabilized from d8 to d16ph. In contrast to growth trends, survival (%) on d16ph increased with increasing turbulence levels and was significantly greater at 170 mL/min (57.9) and 250 mL/min (54.0) than at 20 and 90 mL/min (21.4 and 26.2, respectively). Mean rotifer concentrations (individuals/mL) at 24 h postfeeding were significantly higher (P < 0.05) in the low‐turbulence treatments of 20 mL/min (4.48) and 90 mL/min (4.23) than in the high‐turbulence treatments of 170 and 250 mL/min (2.28 and 2.45, respectively). Under both salinities, larval whole‐body osmolality (mOsm/kg) increased with increasing turbulence levels and was significantly higher at 250 mL/min (427) than at 20 mL/min (381), indicating osmoregulatory stress at the higher turbulence levels. On d14ph, larvae in all treatments were positively buoyant in 35 ppt and negatively buoyant in 24 ppt. Results showed that growth of southern flounder larvae in 15‐L tanks was maximized under low turbulence levels of 20 and 90 mL/min, while survival was maximized at high turbulence levels of 170 and 250 mL/min. The data suggested that, in prefeeding‐ and early‐feeding‐stage larvae (which have weak swimming ability), higher turbulence levels improved buoyancy and prevented sinking. In feeding‐stage larvae (which are relatively strong swimmers), higher turbulence levels caused excessive swimming, osmoregulatory stress, and slower growth. Based on these results, we recommend that turbulence levels be maintained relatively high during prefeeding (yolk sac) and first‐feeding stages to maintain buoyancy and survival and then decreased for mid‐ to late‐feeding‐ and premetamorphic stage larvae to optimize prey encounters and feeding efficiency.  相似文献   

10.
Abstract— Alternative fish species that can be cultured together with catfish Ictalurus punctatus provide an opportunity to diversify caffish farms. A 2-yr study was conducted in 0.10-ha earthen ponds to evaluate the effect of bighead carp (BHC) stocking density on growth, yield, dressout yield, and net returns. Initially, bighead carp (average weight of 22 g) were stocked at rates of 380, 750, or 1,130 fishha in ponds with catfish. Caffish were cultured under commercial conditions by stocking caffish at a density of 12,500/ha, aerating nightly and feeding at an average rate of 82 kgha per d. Stocking rates for 2-yr-old fish were reduced to 77, 260, and 435/ha in the second growing season. There were no significant differences among treatments ( P > 0.05) in summer growth of bighead carp in either year. Bighead carp stocked at 1,130 fishha had significantly higher yields than those stocked at 380/ha, but did not reach minimum market size of 2.2 kg during the first year ( P > 0.05). There were no significant differences ( P > 0.05) in caffish growth, yield, survival, or feed conversion ratios due to the bighead carp stocking densities. Partial budget analysis indicated that net benefits were positive for all three treatments over a range of prevailing prices of bighead carp. Bighead carp production in catfish ponds is economically feasible over a wide range of prices. Given the market risk of producing smaller fish at the higher density, the medium density is the preferred stocking density of fingerling bighead carp in catfish ponds.  相似文献   

11.
The aim of this study was to evaluate the growth and survival of pacu, Piaractus mesopotamicus, larvae reared in different salinities and to determine the Artemia nauplii life span in freshwater and in saline water. First feeding 5‐d‐old pacu larvae were reared in freshwater or at 2, 4, 6, 8, 10, 12, and 14 ppt salinities. The larvae were reared in 1.5‐L aquaria at a density of 10 larvae/L with three replicates per treatment. After 10 d of rearing, significant differences (P < 0.05) were observed for growth and survival. Larval growth was higher at 2 and 4 ppt, and survival at 2 ppt was 100%. In freshwater and at 4, 6 and 8 ppt, the survival was 91.1, 93.3, 73.3, and 39.9%, respectively. At higher salinities, there was 100% mortality after 2 h (12 and 14 ppt) and 8 h (10 ppt) of exposure. The slightly saline water of at least 2 ppt increased the Artemia nauplii life span compared to the life span in freshwater. Later, in a second trial, 5‐d‐old pacu larvae were reared in freshwater and at 2 and 4 ppt salinities during the first 5 or 10 d of active feeding, and then the fish were transferred to freshwater. At the end of 15 d, larval growth was lower in freshwater (42 mg) than in treatments 2 and 4 ppt (59–63 mg). The abrupt transfer of fish from freshwater to slightly saline water and the return to freshwater did not affect the survival rates (89–97%). The larvae were able to adapt to these saline environments and handle abrupt changes in salt concentration. We concluded that salinity concentration of 2 ppt can be used for pacu larval rearing, allowing the Artemia nauplii lifetime to last longer and cause faster fish growth.  相似文献   

12.
Interest in the culture of flatfishes has increased globally due to high consumer demand and decreased commercial landings. The Southern flounder Paralichthys lethostigma inhabit South Atlantic and Gulf of Mexico waters and support important commercial and recreational fisheries. In spring, 1996, a two-part larval rearing study was performed with Southern flounder to examine the effects of three larval diets and two light intensities on survival, growth, and pigmentation. The first part of the study consisted of feeding 6 d post-hatch (dph) (3.0 ± 0.1 mm TL) larvae three diets: 1) rotifers Brachionus plicatilis at a rate of 10/mL from day 1–9 and Artemia nauplii (3/mL) from day 7 through metamorphosis; 2) rotifers fed day 1 through metamorphosis and Artemia fed day 7 through metamorphosis; or 3) same diet as treatment 1 plus a commercial larval diet added day 13 through metamorphosis. The second part of the study examined the effects of two light levels: low-light (mean 457 lux) and high-light (mean 1362 lux). At 24 C, metamorphosis began on day 23 (mean fish size 8.2 ± 0.6 mm TL) in all treatments and was completed by day 30. Analysis of survival, size, and pigmentation data indicated there were no significant differences among feed treatments or between light treatments. Overall survival was 33.4% (±15.9) and mean length was 11.5 mm TL ± 1.3. Only 35% of the larvae were normally pigmented. Reexamination of the pigmentation on day 37 indicated fish reared at the low light intensity through metamorphosis (day 30) but exposed to high light intensity for 1 wk post-metamorphosis had become significantly more pigmented.  相似文献   

13.
Failing to initiate first feeding during the transition from endogenous nutrition to exogenous feeding will lead to starvation of fish larvae. However, little is known about the mechanism of first feeding selection of fish. Golden mandarin fish larvae (3 d after hatch, 2.05 ± 0.03 mg) were fed with four different foods for 7 d, including the following: M – Megalobrama amblycephala (prey fish larvae as natural food); S – surimi of M. amblycephala; A – Artemia (zooplankton); and MA –mixed M. amblycephala with Artemia (mixed food). Larvae fed with the mixed food achieved an appropriate balance between high survival and good growth through elevating the expression of growth genes (GH, IGF‐I, and IGF‐II) and fatty acid synthesis genes (FAD and ELO). Growth performance of fish fed with MA reared at different salinities (0, 5, and 10 ppt) was examined. The salinity of 5 ppt produced the best growth performance of the three salinity levels tested. Fish larvae adapted to high‐ or low‐salinity environments through increasing the expression of lipolysis genes (HSL, LPL, and HL). Therefore, both food type and salinity affect the growth, survival, and lipometabolism of golden mandarin fish larvae during initial feeding stage, and mixed food and 5 ppt salinity improved its survival and growth.  相似文献   

14.
In the aquaculture of summer flounder (Paralichthys dentatus), the inherent variation in growth and settling behavior during metamorphosis may lead to cannibalism and necessitate increased labor due to size grading. Our goal was to use an environmental salinity change as a cue to synchronize settling behavior and produce a larger, more uniformly sized cohort of juvenile summer flounder. Early metamorphic flounder were exposed to either a 5-day fluctuating (30–20–30–20–30 ppt; “Flux”) or a single (30–20 ppt; “20 ppt”) drop in rearing salinity. A control (continuous 30 ppt) was used for comparison. Average values for a peak settlement interval (PSI; defined as the interval beginning on the day by which the first 20% had settled until the day 80% had settled) were not affected by salinity manipulation, though the 20-ppt treatment did significantly increase percent settled per day by 54 dah. Average fish size was increased by the 20-ppt treatment (19.3±0.5 mm), but not the flux treatment (17.2±0.4 mm), compared to the control (17.6±0.5 mm). Developmental stage was significantly increased in the 20-ppt treatment (3.2±0.1) in comparison to the Flux (2.9±0.1), but not the control (3.1±0.1). However, the 20-ppt treatment reduced variance in development. To confirm the positive effects of the 20-ppt treatment, a second experiment was performed. A single salinity drop (“20 ppt”), a previously successful ([Gavlik, S., Albino, M., Specker, J.L., 2002. Metamorphosis in summer flounder: Manipulation of thyoid status to synchronize settling behavior, growth, and development. Aquaculture 203 (3-4), 359-373]thyroid hormone manipulation treatment (“TH”) and a combination of the two (“TH+20 ppt”) were compared to a control (continuous 30 ppt, no thyroid manipulation). The mean PSI was significantly reduced by both TH (7±1 days) and TH+20 ppt (8±0 days) treatments, compared to the control (11±1 days). The PSI for the 20-ppt treatment (9±0 days) was not significantly different than the control. The percent flounder settled per day was significantly increased by 20 ppt salinity and significantly modified (decreased, then increased) by TH manipulation. Flounder exposed to 20-ppt salinity were both larger (20 ppt: 18.6±0.3 mm; TH+20 ppt: 18.3±0.3 mm) and more developmentally advanced (20 ppt: 3.1±0.04; TH+20 ppt: 3.2±0.03) than flounder in 30 ppt (TH: 17.8±0.3 mm/3.1±0.3; Control: 17.9±0.3 mm/3.0±0.05). Finally, 20-ppt treatment reduced variance in development, while TH treatment reduced variance in both growth and development. Percent survival was unaffected by treatment in both experiments. In summary, a decrease in rearing salinity, from 30 to 20 ppt, increased growth, settling behavior and development of metamorphosing summer flounder. A decrease in rearing salinity, in combination with a TH manipulation, should result in larger, more uniformly sized flounder cohorts. We expect this synchronization will reduce the cannibalism and labor costs associated with size grading of cultured, metamorphosing summer flounder.  相似文献   

15.
A study to determine the effects of four stocking densities on growth and feed utilization of wild‐caught black sea bass Centropristis striata was conducted in a pilot‐scale recirculating tank system. The outdoor system consisted of 12 insulated fiberglass tanks (dia. = 1.85 m; vol. = 2.17 m3) supported by biological filters, UV sterilizers, and heat pumps. Subadults (N= 525; ×± SD = 249 ± 16.8 g) were stocked at densities of 4.6 fish/m3 (1.18 kg/m3), 16 fish/ m3 (3.91 kg/m3), 25.3 fish/m3 (6.83 kg/m3), and 36 fish/m3 (7.95 kg1m3), with three replicate tanks per treatment. Fish were grown under 35 ppt salinity, 21‐25 C, and under ambient photoperiod conditions. A commercial flounder diet containing 50% protein and 12% lipid was hand‐fed twice daily to satiation for 201 d. Mean (range) total ammonia‐nitrogen, 0.61 (0‐2.1) mg/L, nitrite‐nitrogen, 0.77 (0.04‐3.6) mg/L, and nitrate‐nitrogen 40.1 (0‐306) mg/L were significantly higher (P < 0.0001) in the 25.3 and 36 fish/m3 treatments than in the 4.6 and 16 fish/m3 treatments [0.19 (0.05‐0.5), 0.1 (0.24‐0.63), and 11.9 (1.3‐82.2) mg/L, respectively]. However, there were no significant differences (P > 0.05) in growth (RGR = 196.8‐243.1%; DWG = 2.55‐2.83 g/d; and SGR = 0.55‐0.61%/d), coefficient of variation of body weight (CwtV., = 0.24‐0.25), condition factor (K = 2.2‐2.4), feed consumption (FC = 1.45‐1.65%/d), and feed conversion ratio (FCR = 1.45‐1.52) among stocking densities. Final biomass densities on day 201 reached 3.48, 12.0, 21.1, and 27.2 kg/m3 at stocking densities of 4.6, 16, 25.3, and 36 fish/m3, respectively. Survival (83.8‐99.1%) did not differ among treatments. Apparent net protein retention (ANPR) was significantly higher (P < 0.005) for fish stocked at the lower densities of 4.6 and 16 fish/m3 (22.5‐23.7%) than for those stocked at 25.3 and 36 fish/m3 (21‐20.1%). There were no significant differences (P > 0.05) in apparent net energy retention (ANER = 55.9‐59.1 %) among stocking densities. Final whole body protein (15.3‐16.3%) and lipid (23.1‐26.4%) levels did not differ significantly (P > 0.05) among treatments. The results demonstrated that growth, survival, and feed utilization were not impaired under stocking densities ranging from 4.6‐36 fish/m3 (3.48‐27.2 kg/m3), despite a slight reduction in water quality at the higher densities. In addition, growth variation and final whole body protein and lipid levels were not influenced by these densities. The results suggest that black sea bass are tolerant of crowding and moderate variations in water quality during intensive culture in recirculating tank systems and that higher stocking densities are possible.  相似文献   

16.
Abstract.— In South Carolina, studies have been conducted to develop rearing techniques for southern flounder Paralichthys lethostigma a candidate for aquaculture development and stock enhancement programs. To help define environmental tolerances, a variety of salinity studies were conducted with the early life stages of this species. Eggs were buoyant at 32 ppt and sank at 29 ppt with salinities of 30–31 ppt providing varying levels of suspension in the water column. Eggs incubated at 0 and 5 ppt all died, whereas 82.5% hatched at 10 ppt but larvae died shortly thereafter. At 63 h post-fertilization, there were no differences in hatch level for eggs incubated at salinities of 15 to 35 ppt (mean hatch level 98.5%). In a 72-h study, fish 3 wk post-metamorphosis (13.7 mm TL, 50-d-old) were acclimated to seven salinities ranging from 0–30 ppt. Fish held at 0 ppt salinity exhibited a statistically (P < 0.05) lower survival (20.0%) than those exposed to 5–30 ppt salinity concentrations. No differences were detected in survival (mean 99.1%) among fish held in the higher salinities. A second study examined the tolerance of older juveniles to lower salinities. Juvenile flounder (95.2 mm TL, 220-d-old) were acclimated to 0, 1,5 and 10 ppt salinities and reared for 2 wk. Results showed that fish could tolerate salinities of 0–10 ppt (100% survival). These data indicate that salinity tolerance of southern flounder increases with age. In addition to the short duration studies, a replicated 11-mo duration tank grow-out study was conducted at mean salinity 5.4 ppt and mean temperahue 22.6 C with an all male population. Flounder grew from a mean length of 100 mm to 213 mm TL and weight from 8.9 to 104.3 g. Growth of the cultured fish approximated that observed among male flounders in the wild.  相似文献   

17.
Larvae of Metapenaeus monoceros (Fabricius) at protozoea 1 (PZ1) stage were stocked in 2‐L glass flasks to investigate the effects of various salinities (25, 30, 35, 40, 45, 50 and 55 ppt) on growth and survival until the post‐larval (PL) stages. The PZ larvae were not able to tolerate a sudden salinity drop of over 10 ppt. Yet, an abrupt salinity increase of over 10 or even 15 ppt did not cause mortality. The PZ larvae were successfully acclimated to different test salinities at a rate of 4 ppt h?1. The larvae displayed better tolerance to high rather than low salinities. The lowest and highest critical salinities appeared to be 22 and 55 ppt respectively. Taking into account survival, growth and development results, the optimal salinity for the larval culture of M. monoceros inhabiting the Eastern Mediterranean was 40 ppt. At this salinity, the PZ1 larvae were successfully cultured until PL1 stage within 11 days with 68% survival on a feeding regime of Tetraselmis chuii Kylin (Butcher) (20 cells μ L?1), Chaetoceros calcitrans Paulsen (50 cells μ L?1), Isochrysis galbana Parke (30 cells μL?1) and five newly hatched Artemia nauplii mL?1 from M1 onwards at 28 °C.  相似文献   

18.
The performance (growth and survival) of diploid and triploid jundia, Rhamdia quelen, was evaluated at six different stocking densities (10, 60, 110, 160, 210, 260 larvae/liter) during 31 days after rearing in an intensive larviculture system. Triploid fish exhibited a significantly higher survival rate than diploids at all stocking densities (27.1 ± 4.3% vs. 12.1 ± 3.3%; P < 0.01). Survival was not affected by stocking density (P > 0.05). Length gain was not affected by either ploidy or stocking density. Diploid fish gained more weight than triploids (P < 0.05), though this difference could result from lower fish densities in diploid treatments resulting from the higher mortality rate of diploid fish. This hypothesis is strengthened by the higher biomass present in triploid treatments (P < 0.01).  相似文献   

19.
Two experiments were conducted in order to determine the appropriate age and stocking density of vundu catfish Heterobranchus longifilis at the weaning time. In the first experiment, five triplicate groups of 100 larvae (initial mean weight=3.4 mg) per aquaria were stocked from first feeding [day 3 post‐hatch (p.h.)] to day 30 p.h., and then weaned, on days 3 (W3), 5 (W5), 8 (W8) and 14 (W14), and an unweaned group (An). Significant differences were observed in growth, survival, cannibalism, coefficient of weight variation and body composition among larvae weaned at different ages and the control group. The later the larvae were weaned, the better were the growth performances [final mean weight: from 65.1 to 201.1 mg and specific growth rate (SGR): from 11.0 to 15.2% day?1] and the survival (from 36.5% to 74.3%). The experiment with stocking densities of 5, 10, 25 and 50 larvae L?1 showed that increasing the stocking density decreased growth performances and weight variation but improved the survival rate of larvae. The best growth performances (SGR=13.4 and 11.4% day?1) with the lowest survival rates (70.3% and 77.3%) were observed in larvae stocked at densities of 5 and 10 larvae L?1 respectively.  相似文献   

20.
Juvenile largemouth bass Micropterus salmoides , trained to accept artificial diets, were stocked into six 0.04-ha ponds at stocking densities of either 6,175 or 12,350 fish/ha. Fish were fed a floating custom-formulated diet, containing 44% protein, once daily to satiation for 12 mo (May 1994–May 1995). At final harvest, the total yield of fish was significantly greater (P < 0.05) and feed conversion ratio (FCR) was significantly lower, for bass stocked at the higher density (4,598 kg/ha and 2.3, respectively) than when stocked at the lower density (2,354 kg/ha and 3.3, respectively). There was no significant difference (P > 0.05) in average weight, length, or survival of bass stocked at the two densities. Averaged over the study period, there were no significant differences (P > 0.05) in total ammonia-nitrogen (TAN), nitrite-nitrogen, or un-ionized ammonia concentrations in ponds in which bass were stocked at the two densities. These data indicate that largemouth bass of the size used in this study are amenable to pond culture at densities of at least 12,350 fish/ha and that higher stocking densities may be possible.  相似文献   

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