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1.
Flow field control via aeration adjustment for the enhancement of larval survival of the kelp grouper Epinephelus bruneus was examined. Aeration rate of 300 mL min?1 was introduced during daylight (07:00–19:00 hours) and adjusted to 0, 300 and 900 mL min?1 at night (19:00–07:00 hours). Larval sinking velocity±SD increased from 0.08 ± 0.05 to 0.26 ± 0.24 cm sec?1 from 4 to 12 days after hatching (DAH), indicating their susceptibility to sink. Larvae reared in 300 mLmin?1 attained the highest survival rate at 24.9 ± 3.4%, but remained significantly smaller in growth: 4.54 ± 0.56 mm compared with 4.82 ± 0.53 mm in 900 mL min?1. The flow field in 300 and 900 mL min?1 was at 10–20 and 15–25 cm above the bottom of the tank and 8.0 and 1.0 cm beneath the water surface. A favourable rearing condition was observed in 300 mL min?1 as larvae were away from the bottom and surface areas, thus preventing them from dying due to sinking and surface tension‐related death (STRD). Although sinking death was decreased with an increasing aeration rate, the stronger flow had increased larval susceptibility to STRD. Our findings suggest that aeration at 300 mL min?1 could enhance larval survival by reducing both sinking death and STRD.  相似文献   

2.
Success of swim bladder inflation (SBI) is crucial for early survival of Pacific bluefin tuna (PBF) larvae, because it reduces larval sinking death by enhancing buoyancy. In Experiment 1, we examined the effect of photoperiod on SBI and survival in PBF larvae by comparing photoperiods of 9L: 15D (9L), 14L: 10D (14L: natural photoperiod), 19L: 5D (19L) and 24L: 0D (24L) during 2–10 days post hatch (dph). In Experiment 2, the combined effects of photoperiod (24L and 14L) and nighttime aeration rate (enhanced night‐time aeration: ENA of 1300 mL min?1 as a countermeasure for sinking death and 130 mL min?1) on the survival and SBI were also examined during 2–10 dph. Moreover, in Experiment 3 the effect of photoperiod on vertical distribution of larvae in night‐time was examined on 3–5 dph. Photoperiod of 24L in Experiment 1 significantly inhibited SBI compared with 14L and 19L; nevertheless, it significantly improved survival compared with other photoperiods with a dark period. On the other hand, the shortened light period (9L) showed significantly reduced SBI and also survival. In Experiment 2, the countermeasure for sinking death of ENA under 24L did not further improve the survival; rather it tended to reduce the survival. In Experiment 3, larvae distributed less in the bottom layer in 24L than in 14L, suggesting the reducing effect of 24L on sinking death. The results indicate that 24L without ENA is suitable for survival which is the most serious problem in PBF larviculture.  相似文献   

3.
Early‐stage mortality due to surface water tension‐related death and due to sinking to the tank bottom was investigated for yellowfin tuna, Thunnus albacares (YFT), larvae. Different aeration rates and rearing water surface conditions were examined to evaluate the effect on larval survival, swim bladder inflation and growth. The percentage survival of yolk sac larvae was significantly higher when the rearing water surface was covered with fish oil at aeration rates of 0 and 50 mL min?1. The highest mortality occurred at the highest aeration rate of 250 mL min?1 regardless of surface water condition. A second experiment was conducted twice under different water surface conditions: the water surface was covered by fish oil (FO), skimmed of fish oil (SS), and was not treated (NC). The percentage survival was not significantly different between treatments after 7 days of feeding. In contrast to the survival, the proportion of larvae with inflated swim bladders was significantly higher for the NC and SS groups than that of the FO group. Results of these experiments indicate that the addition of oil to the rearing water surface without its removal interferes with the initial swim bladder inflation in YFT larvae. These results also indicate that YFT larvae need to obtain (gulp) air at the water surface for initial swim bladder inflation, and success of initial swim bladder inflation may be crucial for their survival.  相似文献   

4.
Particle size distribution, organic content and the sinking velocity of bio‐deposits of abalone Haliotis discus hannai Ino were evaluated. The abalone was divided into three size classes according to shell length: Group B: 68.8 ± 2.8 mm, group M: 56.1 ± 2.3 mm and group S: 42.4 ± 2.8 mm. The faecal pellets had an amorphous shape, with a cross‐sectional area ranging from 0.01 to 2.64 mm2. The mean cross‐sectional area varied among the size classes: 0.59 (B), 0.21 (M) and 0.12 (S) mm2. The bio‐deposit organic content was similar among the groups (B: 18.3 ± 1.1%; M: 19.9 ± 0.9%; S: 19.3 ± 1.0%). Sinking velocity ranged from 0.5 to 2.3 cm s?1. Larger abalone tended to have larger and thus faster‐sinking faecal pellets. The median sinking velocity for groups B, M and S was 0.9, 0.5 and 0.7 cm s?1 respectively. The mean daily production rates for groups S, M and B were 2.8 ± 1.2, 3.4 ± 1.3 and 4.3 ± 1.8 g ind.?1 respectively. Bio‐deposit production rate estimated to be between 134.4 and 206.4 mg m?2 day?1 in the bay. Our results suggest that the pellet size was within the appropriate size range for filter‐feeding bivalves.  相似文献   

5.
A 12‐week feeding trial was conducted in eighteen 70 L indoor polyvinyl circular troughs provided with a water flow‐through system (1–1.5 L min?1) at 28 ± 1 °C to evaluate the dietary tryptophan requirement of fingerling Catla catla (3.45 ± 0.24 cm; 0.60 ± 0.13 g). Six casein‐gelatin‐based amino acid test diets (330 g kg?1 crude protein; 13.6 kJ g?1 digestible energy) containing graded levels of L‐tryptophan (1.0, 1.4, 1.9, 2.3, 2.8, 3.4 g kg?1 dry diet) were fed to triplicate groups of fish near to satiation at 08:00, 12:30 and 17:30 h. Absolute weight gain, feed conversion ratio, protein gain, RNA/DNA ratio, hepatosomatic index, viscerosomatic index, condition factor and haematological indices improved with the increasing levels of tryptophan from 1.0 to 2.3 g kg?1 of dry diet. Significantly higher carcass protein was obtained at 2.3 g tryptophan per kilogram of the dry diet. Exponential analysis of absolute weight gain, feed conversion ratio, protein gain and RNA/DNA ratio against dietary tryptophan levels at 95% maximum and minimum responses displayed the tryptophan requirement at 2.5, 2.3, 2.5 and 2.1 g kg?1 dry diet, respectively. Inclusion of dietary tryptophan in the range of 2.1–2.5 g kg?1 dry diet, equivalent to 6.4–7.6 g kg?1 dietary protein, is recommended in formulating tryptophan‐balanced feed for the culture of this fish species.  相似文献   

6.
Effectiveness and efficiency of frozen sperm on fertilization and hatching success of eggs from silver barb was examined in relation to cryoprotectants, freezing rate and storage period. Sperm was diluted in calcium‐free Hank's balanced salt solution, equilibrated with dimethylsulphoxide (DMSO), propylene glycol, sucrose or methanol at 5%, 10%, 15% or 20% final concentrations, and frozen in 250‐μL straws using a one‐step freezing procedure (1, 5 and 8°C min?1 from 25 to ?40°C). Highest post‐thaw sperm motility was found from a treatment using 10% DMSO and 5°C min?1 (82.2 ± 2.1%), similar to that of 10% DMSO and 8°C min?1 (87.8 ± 3.2%). Post‐thaw motility of sperm frozen at 5 or 8°C min?1 was significantly higher than 1°C min?1. Relative sperm motility declined significantly after 10 months of cryostorage while viability did not change during a 12‐month cryostorage. Average fertilization rates of sperm after 1 and 4 months of storage were 64.5 ± 4.6% and 61.3 ± 3.4%, respectively, similar to those of fresh sperm (69.6–72.3%). Hatching rates of cryopreserved sperm (45.4–51.2%) were similar to those of fresh sperm (51.8–57.8%). This study developed suitable methods for cryopreservation of silver barb sperm that can be used to facilitate hatchery operation.  相似文献   

7.
The only known extant population of the diamond darter (Crystallaria cincotta) exists in the lower 37 km of Elk River, WV, USA. Our understanding of diamond darter habitat use was previously limited, because few individuals have been observed during sampling with conventional gears. We quantified microhabitat use of diamond darters based on measurements of water depth, water velocity and per cent substrate composition. Using spotlights at night‐time, we sampled 16 sites within the lower 133 km of Elk River and observed a total of 82 diamond darters at 10 of 11 sampling sites within the lower 37 km. Glides, located immediately upstream of riffles, were the primary habitats sampled for diamond darters, which included relatively shallow depths (<1 m), moderate‐to‐low water velocities (often < 0.5 m·s?1) and a smooth water surface. Microhabitat use (mean ± SE) of diamond darters was estimated for depth (0.47 ± 0.02 m), average velocity (0.27 ± 0.01 m·s?1) and bottom velocity (0.15 ± 0.01 m·s?1). Substrate used (mean ± SE) by diamond darters was predominantly sand intermixed with lesser amounts of gravel and cobble: % sand (52.1 ± 1.6), % small gravel (12.2 ± 0.78), % large gravel (14.2 ± 0.83), % cobble (19.8 ± 0.96) and % boulder (1.6 ± 0.36). Based on our microhabitat use data, conservation and management efforts for this species should consider preserving glide habitats within Elk River. Spotlighting, a successful sampling method for diamond darters, should be considered for study designs of population estimation and long‐term monitoring.  相似文献   

8.
A 60‐day indoor trial was conducted to study the effect of periphyton supplementation on metabolic and immune responses in tiger shrimp, Penaeus monodon. Periphyton developed over bamboo substrate in outdoor tanks (15 m2) was used as dietary supplement for P. monodon (2.02 ± 0.04 g) reared in 1000 L FRP tanks. Graded levels of periphyton were included in shrimp basal diets: 0% (P0), 3% (P3), 6% (P6), 9% (P9) and P0 diet with natural periphyton (NP) over bamboo substrate. At the end of the trial, P6 and NP showed significantly higher (P < 0.01) growth rate, 23.9% and 20%, respectively, compared with control, P0. Comparatively, lower level of metabolic enzymes, such as lactate dehydrogenase, malate dehydrogenase, aspartate aminotransferase and alanine aminotransferase, was recorded in treatments P3, P6 and NP compared with control, P0. The periphyton‐supplemented group, P3 had significantly higher (P < 0.05) superoxide dismutase (15.83 ± 0.96) and catalase activity (15.73 ± 0.69) compared to 6.88 ± 2.84 and 9.15 ± 0.67 unit mg?1 protein min?1, respectively, in P0. Similarly, higher total haemocyte counts, 32.58 ± 1.30, 28.51 ± 3.12 and 27.26 ± 4.43 × 106 cells mL?1, were recorded in P6, NP and P3, respectively, compared to P0, 23.57 ± 1.80 × 106 cells mL?1. After challenge with Vibrio harveyi, P3 recorded the highest relative percentage survival 67% followed by NP (58%) and P6 (42%) compared with control. However, treatment with highest periphyton inclusion (P9) did not differ significantly with P0 on growth and immunological parameters. This study indicates that periphyton supplementation at 3–6% level improves growth, immune response and metabolic activities in P. monodon.  相似文献   

9.
The aim of this study was to investigate the effects of different levels of Origanum onites L. essential oil as feed additives on the growth performance, antioxidant activity and disease resistance of rainbow trout. Fish (26.05 ± 0.15 g) were fed the experimental diets supplemented with four different concentrations (0.125, 1.5, 2.5 and 3.0 mL kg?1) of O. onites essential oil for 90 days. Fish fed diets containing essential oil of O. onites had significantly higher final weight than the control group. Feed conversion ratio in fish fed diets containing 1.5 and 3.0 mL kg?1 essential oil of O. onites was improved than other treatments (P < 0.05). The lowest feed conversion efficiency ratio was recorded in the 0.125 mL kg?1 group of O. onites. Antioxidant status of fish was assayed for levels of plasma superoxide dismutase (SOD) and plasma catalase (CAT) activity. Lysozyme activity in plasma was significantly higher in fish fed diet containing 3.0 mL kg?1 essential oil of O. onites (P < 0.05). After 8 weeks of feeding, fish were challenged with Lactococcus garvieae and cumulative mortality was recorded over 15 days. Dietary administration of 0.125, 1.5 and 2.5 mL kg?1 O. onites significantly reduced fish mortality (P < 0.05). The 3.0 mL kg?1 diet showed no mortality after challenged with L. garvieae. These results suggested that the essential oil of O. onites could be applied as growth promoter and also improved disease resistance when added to rainbow trout feed.  相似文献   

10.
Garlic, Allium sativum L., extract administered as a therapeutic bath was shown to have antiparasitic properties towards Neobenedenia sp. (MacCallum) (Platyhelminthes: Monogenea) infecting farmed barramundi, Lates calcarifer (Bloch). The effect of garlic extract (active component allicin) immersion on Neobenedenia sp. egg development, hatching success, oncomiracidia (larvae) longevity, infection success and juvenile Neobenedenia survival was examined and compared with freshwater and formalin immersion. Garlic extract was found to significantly impede hatching success (5% ± 5%) and oncomiracidia longevity (<2 h) at allicin concentrations of 15.2 μL L?1, while eggs in the seawater control had >95% hatching success and mean oncomiracidia longevity of 37 ± 3 h. At much lower allicin concentrations (0.76 and 1.52 μL L?1), garlic extract also significantly reduced Neobenedenia infection success of L. calcarifer to 25% ± 4% and 11% ± 4%, respectively, compared with 55% ± 7% in the seawater control. Juvenile Neobenedenia attached to host fish proved to be highly resistant to allicin with 96% surviving 1‐h immersion in 10 mL L?1 (15.2 μL L?1 allicin) of garlic extract. Allicin‐containing garlic extracts show potential for development as a therapy to manage monogenean infections in intensive aquaculture with the greatest impact at the egg and larval stages.  相似文献   

11.
Effect of various dietary protein levels on growth and nutrient utilization were studied in fringe‐lipped carp, Labeo fimbriatus fingerlings for 60 days. Five practical diets containing graded protein levels of 200, 250, 300, 350 and 400 g kg?1 with respective digestible protein (DP) contents of 192.4, 244.5, 291.6, 339.4 and 391.4 g kg?1 were evaluated as five treatments, T1, T2, T3, T4 and T5, respectively, in triplicate. Each experimental tank (80‐L) contained eight fingerlings (4.9 ± 0.1 g) and was subjected to continuous aeration and 25% water replenishment daily. The fish were fed two times daily at 8:00 and 14:00 h to satiation. Significantly higher (P < 0.05) absolute growth and thermal growth coefficient, and lower feed conversion ratios (FCR) were observed in T2–T4 than T1 and T5. Protein efficiency ratio (PER) and protein productive values (PPV) were highest in T2 and lowest in T5. Significantly higher (P < 0.05) apparent protein digestibility was perceptible in T2–T4. While specific amylase activity declined linearly with increasing DP : DE, the protease, trypsin, aspartate aminotransferase and alanine aminotransferase established polynomial relationship. Based on live weight gain, PER and PPV fitted to quadratic model optimum DP levels were estimated as 301.4, 260.0 and 273.0 g kg?1, respectively.  相似文献   

12.
We used a 50‐year (1961–2010) daily record of precipitation and evaporation in a hydrological model to simulate ground water withdrawal for the foodfish grow‐out phase of ictalurid catfish culture in northwest Mississippi, USA. The model quantified the effects of seepage, reusing water for multiple years, and managing water levels to capture rainfall (drop‐fill water management). Selecting sites with relatively impervious soils and reusing water for multiple years had large impacts on annual water use, and combining those practices with drop‐fill water management reduced simulated groundwater withdrawal to less than 60 cm year?1 compared with more than 450 cm year?1 for the least conservative scenario. Water conservation measures reduced estimated costs of pumping ground water from ~$1150 ha?1 year?1 for the least conservative set of water‐use variables to less than $110 ha?1 year?1 for the best set of water conservation practices. Efficiency of pumped water use was dramatically improved by intensifying production in the foodfish grow‐out phase. Combining water‐conservation practices with production intensification improved the water use index from 9.18 m3 kg?1 for foodfish grow‐out ponds with the least conservative set of practices to 0.28 m3 kg?1 for ponds built on soils with negligible seepage, managed with a 22.9‐cm drop/7.6‐cm fill, drained every 10 years, and producing 15 000 kg of catfish ha?1 year?1. When simulated ground water use for the best set of water conservation practices in foodfish grow‐out ponds was combined with estimates of ground water used for fingerling production and water used in producing grain‐based feedstuffs, total consumptive water use index for catfish culture was estimated at ~2.7 m3 kg?1. This index is competitive with most other types of animal agriculture. Efficient water use in catfish farming is easily achieved under commercial conditions using existing simple technologies.  相似文献   

13.
This study aimed to test the efficacy of 17 α‐methyl testosterone (17 α‐MT) alone and in combination with letrozole, an aromatase inhibitor, for the induction of sex reversal in protogynous greasy grouper, Epinephelus tauvina. Further, the long‐lasting effects of these treatments and spawning performance of sex‐reversed males were also investigated. Greasy grouper with oocytes in the perinucleolus stage were implanted with 5 mg 17 α‐MT kg?1 body weight (T1), 5 mg 17 α‐MT and 0.2 mg letrozole kg?1 body weight (T2) and 5 mg 17 α‐MT with 0.4 mg letrozole kg?1 body weight (T3) and no androgens/enzyme inhibitor implanted (C). The 17 α‐MT alone and in combination of letrozole‐induced sex reversal in greasy grouper, whereas untreated control fish (C) showed normal ovarian development. However, T2 and T3 group showed 100% sex reversal and completion of spermatogenesis up to functional male phase in 2 and 3 months, respectively, whereas T1 group resulted in only 66.67% functional male with motile spermatozoa after 4 months. Sex‐reversed males successfully fertilized the eggs during induced spawning. There were significant differences on fertilization and hatching rates between T2 group (79.00 ± 4.36%; 77.67 ± 2.87%, respectively) and T1 group (57.67 ± 3.17%; 63.87 ± 2.91%, respectively). The result suggested that 17 α‐MT (5.0 mg kg?1 BW) in combination with letrozole (0.2 mg kg?1 BW) has the potential to produce 100% sex‐reversed male in short period in greasy grouper, which might greatly help in seed production of greasy grouper.  相似文献   

14.
By introducing recirculation aquaculture systems (RAS) in the nursery phase of the blue mussel (Mytilus edulis) (17–18 mm), we aimed at a similar growth and survival and a similar water quality compared to the commonly used flow‐through systems (FTS). To calculate water flow and size of the biofilter, a series of experiments were done to determine clearance rate (9.26 mL min?1), pseudo faeces threshold (60 000 cells Pavlova lutheri mL?1), nitrogen production (0.00065 mg TAN h?1 ind?1 and 1.6 × 10?5 mg NO2–N h?1 ind?1) and oxygen consumption (0.03 ± 0.01 mg O2 h?1 ind?1). RAS showed no significant differences in water quality (0.06 mg TAN L?1; 7.7 mg O2 L?1) and growth performance of mussel seed specific growth rate (SGR = 5% day?1) after the experimental period of 4 weeks compared with FTS. The low water refreshment, 10% per day, as well as the constant chlorophyll concentrations (9.76 ± 1.06 μg L?1), suggests the potential of RAS as culture system for mussel seed.  相似文献   

15.
The aim of this experiment was to determine the effects of dietary inclusion with mannan oligosaccharide (Bio‐Mos, Alltech, Nicholasville, KY, USA) on growth, survival, physiological and immunological conditions and gut morphology of the black tiger prawn (Penaeus monodon). Five diets supplemented with MOS at 0 g kg?1 (control diet), 1, 2, 4 and 8 g kg?1 were fed to the prawn juveniles (0.4 ± 0.06 g, total weight) for the duration of 63 days. Growth was the highest (P < 0.05) when the prawns were fed the 1 g kg?1 MOS included diet. Wet tail muscle index (Tw/B), dry tail muscle index (Td/B) and tail muscle protein (Tmp) were higher (P < 0.05) in the prawns fed MOS included diets MOS compared with the prawns fed the control diet. Total haemocyte counts (THCs) of the prawns fed MOS included diets were higher (P < 0.05) than THCs of the prawns fed the control diet. Epithelium layer and epidermal cell density of the gut of the prawns fed 1 g kg?1 and 2 g kg?1 MOS diets were better than the prawns fed the control and other MOS diets. The results imply a positive effect of dietary supplementation of 1–2 g kg?1 MOS in the culture of black tiger prawns.  相似文献   

16.
The summer flounder, Paralichthys dentatus L., is a high‐value species and considerable research has been conducted to determine practices conducive for its culture. As milt can be limited in this species, experiments were conducted to develop a practical sperm cryopreservation protocol for hatchery use. Two dilution ratios (1:2 and 1:4; sperm:extender), 2 diluents (saline and sucrose‐based), 2 cryoprotectants (10% DMSO and 12% glycerol) and 3 freezing rates (?5, ?10 and ?15°C min?1) were evaluated using differential staining to assess post‐thaw sperm survival. Seven combinations of the factors examined reduced post‐thaw viability by less than 30%. The average viability of sperm from fresh, pooled flounder milt (67.2 ± 2.9%) was not different from that of thawed milt diluted 1:4 with sucrose diluent (10% DMSO) frozen at ?5°C min?1 (38.4 ± 7.7%) and fertilization and hatch success were not different in trials using fresh or thawed, cryopreserved sperm. From these experiments a practical sperm cryopreservation method was developed, but further refinement of the freezing protocol is necessary to optimize results.  相似文献   

17.
Knowledge on apparent digestibility coefficients (ADC) is necessary to maximize the feed efficiency, thus lessening dietary nutrient and energy losses. This study tasks the determination of apparent digestibility of selected feedstuff to striped surubim Pseudoplatystoma reticulatum, a carnivorous, South American catfish of economic importance for fisheries and fish culture alike. Juvenile striped surubim (82.4 ± 17.7 g and 23.0 ± 1.6 cm) was distributed in 21 cylindrical, plastic cages (80 L), housed in seven 1000 L feeding tanks under constant water flow and aeration and conditioned to a two daily meals (20h00m and 22h00m) feeding regimen on a practical, reference diet (RD) (460.0 g kg?1 crude protein (CP); 19.23 kJ g?1 gross energy (GE)]. Test diets were obtained by adding of 1 g kg?1 chromium III oxide and 300 g kg?1 of one the following feedstuffs: fish meal (FM), meat and bone meal (MBM), poultry by‐product meal, feather meal, blood meal, soybean meal, wheat bran, corn and corn gluten meal to the RD. After the last daily meal, fish were transferred to cylindrical, conical‐bottomed aquaria (200 L) under aeration and continuous water exchange, coupled to refrigerated plastic bottles for faeces collection by sedimentation. Best ADC of protein (99.36%) and energy (86.25%) were recorded for poultry by‐product meal and MBM, respectively, which are thus deemed ideal surrogate feedstuffs to FM in the formulation and processing of diets for striped surubim.  相似文献   

18.
During April to June 2009, a large bolus of Amazon River water impacted the northeastern Caribbean Sea. Shipboard observations collected near Saba Bank, the U.S. and British Virgin Islands, and the Anegada Passage showed low surface salinity (35.76 ± 0.05 Practical Salinity Unit (PSU)), elevated surface temperature (26.77 ± 0.14°C), high chlorophyll‐a (1.26 ± 0.21 mg m?3) and high dissolved oxygen (4.90 ± 0.06 mL L?1) in a 20‐ to 30‐m thick surface layer in the riverine plume. The water was ~1°C warmer, 1 PSU fresher, 0.3 mL L?1 higher in oxygen and 1.2 mg m?3 higher in chlorophyll‐a than Atlantic Ocean waters to the north, with Caribbean surface waters showing intermediate values. Plankton net tows obtained in the upper 100 m of the water column revealed larval fish assemblages within the plume that were significantly different from those of the surrounding waters and from those encountered in the area in previous years. The plume waters contained higher concentrations of mesopelagic fish larvae from the families Myctophidae and Nomeidae, which as adults typically inhabit offshore, deep water habitats. Concentrations of larvae from inshore and reef‐associated families such as Scaridae, Serranidae, Labridae and Clupeidae were lower than those found outside the plume in similar shallow areas, particularly in near‐surface waters. An event like the one observed in 2009 had not been documented in at least the past 30 yr, and yet it was followed by another similarly extreme event in 2010. The ecological implications, including any long‐term consequences of such recent extreme events, are important and merit further study.  相似文献   

19.
Scaling up the hatchery production of juvenile sandfish Holothuria scabra is constrained by limited hatchery space and the associated high operational costs. To shorten the hatchery rearing phase, ocean nursery systems like floating hapa nets have been used with good prospects but with limitations during rough sea conditions. In this study, the potential of bottom‐set trays (0.14 m2) as an alternative ocean nursery system for early sandfish juveniles (0.5 ± 0.1 cm) was evaluated. The effects of stocking density and presence of artificial substrates (AS) on the growth and survival were determined in a 60‐day field experiment. Average length and growth rates at lower stocking density treatment (100 individuals tray?1) were significantly higher (1.45 ± 0.22 cm; 0.03 ± 0.01 cm day?1) than at higher stocking density treatments (400 and 500 individuals tray?1) 0.95 ± 0.06 cm; 0.03 ± 0.004 cm day?1) with or without AS (p < .05) respectively. The coefficient of variation in length (CV) at high stocking densities were significantly higher than at low densities (p < .05) and growth rate was strongly negatively correlated with density. Survival was significantly higher (55% ± 9%) in trays with AS across all stocking density treatments than in trays without AS (34% ± 2%). Results suggest that AS may have reduced intra‐ and interspecific interactions, resulting to significantly lower growth variations and higher survival. The bottom‐set tray with AS can be a practical alternative ocean nursery unit for rearing early sandfish juveniles particularly when the sea surface condition is rough. With improved design and density management, survival and growth may be further enhanced.  相似文献   

20.
The effects of delayed first feeding on the survival and growth of tiger grouper, Epinephelus fuscoguttatus (Forsskål 1775), larvae were examined under controlled conditions. The total length, yolk sac volume, oil globule volume, yolk sac absorption time and nutritional transition period (NTP) of the larvae fed at different first times (0, 6, 12, 18 and 24 h after the mouth opening stage; h AMO) were compared. Larval first feed intake was observed at 54 h after hatching (h AH) at 27.5 ± 0.5 °C. The yolk sac was consumed more rapidly with an increase in delayed first feeding and was significantly different among treatments (P<0.05). Larvae first fed at 0 h AMO had the longest yolk sac absorption (72 h AH) and NTP (20 h) times and had the highest survival and growth rates at the end of the experimental period (360 h AH), being significantly higher (P<0.05) than the other treatments. First mortality was observed at 69 h AH, approximately 2 h after point of no return (PNR) occurred. This study suggests that first feeding of tiger grouper larvae should commence at 0 h AMO for enhancement of larval survival and growth.  相似文献   

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