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1.
The development of sustainable methods for sea urchin juvenile production is currently constrained by high mortality rates during larval growth and the high costs of larval rearing systems management. With the aim of developing a method for the production of juveniles of the purple sea urchin Paracentrotus lividus in a medium‐scale recirculating system, the present study focused on the effects of high stocking densities on larval growth. Plutei larvae were reared at three different densities (up to 7 ind/ml) in a semi‐static culture system. Larval survival and metamorphosis success were evaluated in order to identify the most effective density range. The highest metamorphosis rates (80%–95%) were obtained at 4 and 7 larvae/ml. These results are comparable with (and in some cases higher than) those reported for the same species at much lower larval densities. In conclusion, the rearing conditions tested here show for the first time that a significantly higher (4 ind/ml) stocking density than those of traditional P. lividus rearing methods (based on large volumes and low densities) can be adopted, thus supporting the feasibility of an increase in the final output of competent larvae with no increase in rearing volumes.  相似文献   

2.
The effect of stocking density on the survival and growth of pikeperch, Sander lucioperca (L.), larvae was examined in two consecutive experiments. In experiment I, 4-day-old larvae [body wet weight (BW): 0.5 mg; total body length (TL): 5.6 mm] were reared in 200-l cylindro-conical tanks in a closed, recirculating system (20 ± 0.5°C) at three stocking densities (25, 50 and 100 larvae l−1) and fed a mixed feed (Artemia nauplii and Lansy A2 artificial feed) for 14 consecutive days. At densities of 25 and 100 larvae l−1, growth rate and survival ranged from 2.7 to 1.9 mg day−1 and from 79.2 to 72.3%, and fish biomass gain ranged from 0.6 to 2.0 g l−1, respectively. There were two periods of increased larval mortality: the first was at beginning of exogenous feeding and the second during swim bladder inflation. In experiment II, 18-day-old larvae (BW: 35 mg; TL: 15.6 mm) obtained from experiment I were reared under culture conditions similar to those of experiment I, but at lower stocking densities (6, 10 and 15 larvae l−1). The fish were fed exclusively with artificial feed (trout starter) for 21 consecutive days. At densities of 6 and 15 larvae l−1, the growth rate and fish biomass gain ranged from 28.8 to 23.1 mg day−1 and from 2.0 to 3.3 g l−1, respectively. The highest survival (56.5%) was achieved at a density of 6 larvae l−1. Mortality at all densities was mainly caused by cannibalism II type behaviour (27–35% of total). In both experiments, growth and survival were negatively correlated and fish biomass gain positively correlated with stocking densities. The present study suggests that the initial stocking density of pikeperch larvae reared in a recirculating system can be 100 individuals l−1 for the 4- to 18-day period post-hatch and 15 individuals l−1 for the post-19-day period.  相似文献   

3.
The geoduck clam, Panopea generosa, is a species from the west coast of Baja California, Mexico, and the optimization of seed production systems is still a limiting factor for its aquaculture. In this study, a flow‐through culture system was designed and tested in P. generosa larvae. Survival and growth was compared in triplicate 45‐L fiberglass tanks using three larval densities (5, 10 and 15 larvae/ml). A head tank kept constant the water inflow, with a daily renewal rate of 1.8× tank volume. The food (Isochrysis spp.) was dosed according to the ingestion rate of larvae and the dilution rate. Survival decreased linearly during the first 10 days and reached asymptotic values of ca. 20% (15 larvae/ml) and 50% (densities of 5 and 10 larvae/ml) afterwards. Mean shell length at the end of the experiment (243 ± 1.8 to 270 ± 0.7 μm) was not statistically different among treatments, even though a trend towards higher gross growth rate was observed in the treatment with the lowest density (9.5 μm/day) relative to the rest of the treatments (8.5 μm/day). It is concluded that P. generosa larvae can be successfully grown in flow‐through systems at maximum densities of 10 larvae/ml without significantly affecting their survival and growth rates. The system design was reliable, kept a constant water flow with reduced maintenance, and may represent an important option in the laboratory for increasing the stocking density of Panopea species during the larval phase.  相似文献   

4.
王涛  李琪 《水产学报》2018,42(11):1729-1736
为了得到壳型规则、大小均一的单体牡蛎,本研究采用肾上腺素对岩牡蛎单体苗种生产的诱导条件进行研究,阐明了岩牡蛎单体苗种的最适诱导浓度、诱导时间和诱导密度。结果显示,肾上腺素能显著诱导岩牡蛎幼虫的不固着变态,最适诱导浓度为5×10–5 mol/L,最适诱导时间为1 h,提高诱导浓度和延长诱导时间导致岩牡蛎幼虫的不固着变态率、稚贝壳高和存活率显著降低;肾上腺素对低于8个/mL幼虫密度的诱导效果差异不显著,但稚贝壳高和存活率在8个/mL的培育密度下显著低于0.5～4个/mL,研究表明利用肾上腺素诱导岩牡蛎单体时,可大批量处理眼点幼虫,但稚贝充气培养的最适培养密度应不高于4个/mL。  相似文献   

5.
The West Indian top shell, Cittarium pica, is an endangered vetigastropod of ecological and commercial value from the Caribbean. In order to assess the use of aquaculture as a tool for its sustainable production and conservation, embryos were produced in hatchery and experimentally cultured until juveniles under different conditions. Embryos were incubated under two temperatures (25 and 29°C) and six densities (0.3, 0.6, 1.0, 4.0, 9.0 and 37.0% of bottom‐coverage). Larvae were reared under different temperatures (25 and 27°C), densities (0.5, 1, 1.5 and 10 larvae/ml) and culture systems (static and down‐welling). Post‐larvae were obtained in three different settling conditions, and the early juveniles were cultured supplying fresh seaweed (Laurencia obtusa and Padina gymnospora), natural multi‐specific biofilm and Cylindroteca sp. biofilm. The growth and survival of embryos and larvae were not affected by temperature, but they were affected by density. Higher values were obtained at low densities (<1% of embryos bottom‐coverage and <1 larvae/ml), except for the growth of larvae, which was similar among treatments. Higher larval survival was recorded using the static culture system, and higher percent of post‐larvae recovered was associated with lower density of crawling veliger (0.2 and 0.1/ml), while its higher growth rate was related to the use of biofilms with conspecific mucus and low water‐flow (50%/h). The type of food tested did not affect the juvenile growth, but higher survival was obtained in those fed with seaweed than with multi‐specific biofilm.  相似文献   

6.
The red race of the sea cucumber Apostichopus japonicus was introduced into China from Japan for large-scale seed production because of its economic value. This paper reports the effects of stocking density, temperature, and salinity on survival and growth of early larvae before and after feeding, in order to establish conditions for optimal larval growth and production. To maximize the yield per unit of space, densities of 0.5–1 larvae/ml are recommended for non-feeding larvae, while 0.1–0.2 larvae/ml are best for feeding larvae. Higher survival and growth values were obtained for both non-feeding and feeding larvae at temperature ranges from 21 to 24°C. Larvae reared at a salinity of 30‰ always showed maximum growth and survival. Based on results of this study, a temperature range from 21 to 24°C and a salinity of 30 are considered optimal for early development of the red A. japonicus.  相似文献   

7.

The present study evaluated the effect of initial stocking density and water recirculation rate on larval yield (percent of initially stocked larvae alive at the end of the experiment) and production of competent larvae (percent of initially stocked larvae alive at the end of the experiment retained on a sieve with mesh size 239 μm) of Crassostrea gigas in a recirculation aquaculture system (RAS). Different initial larval stocking densities (80, 160 and 320 larvae mL?1) and water flow rates (100, 200 and 300 mL min?1, totalling renewal rates of 60, 120 and 180 times day?1 of water volume in culture tanks, respectively) were evaluated in 2.4-L tanks using a completely randomized design in a factorial scheme. The physicochemical parameters of the water (temperature, salinity, pH, dissolved oxygen and conductivity) were stable in all treatments during the experimental period. Our results demonstrated that the production of C. gigas larvae was feasible at the proposed densities. However, the water renewal rate affected both yield and competent larvae in the recirculation aquaculture system. Oyster cultures with densities of 160 larvae mL?1 and flow of water of 300 mL min?1 showed the best yield (89.34 ± 18.43%) and rate of competent larvae (84.09 ± 16.38%) and are therefore recommended with the aim of optimizing larvae cultivation.

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8.
The effects of larval density, rearing media, and protein additions on fish larval survival were tested by rearing larvae in small containers. Yolk-sac larvae of Japanese flounder, Paralichthys olivaceus, were transferred 1 day after hatching to plastic dishes and cell-culture microplates by Pasture pipette at densities ranging from 0.3 to 30 individuals/ml and incubated at 16 °C without food. Dead larvae were removed and counted every 12 h. Three peaks of larval mortality were observed: the first peak appeared just after the transfer, the second corresponded to the completion of yolk absorption, and the third occurred 10–12 days after the transfer. Since about 50% of larvae survived until the third peak, it was clear that mortality at the second peak (completion of yolk absorption; equivalent to the first feeding) was not due to starvation. At the first mortality peak, better survival was unexpectedly recorded at higher larval densities (30 individuals/ml), suggesting that some material beneficial for survival is derived from the larvae. This idea was further supported by the improved survival in media previously used to rear larvae at high densities. The addition of bovine serum albumin (BSA) at 10 μg/ml effectively reduced mortality in microplates and in 30-l tanks. To reduce the larval mortality just after handling, addition of egg white at a dilution rate of 1/30,000 (vol/vol) or less is recommended as a practical alternative to BSA. Since the addition of polyethylene glycol 6000 (1 μg/ml) also effectively reduced mortality, reduction in mortality could not be attributed to a specific mechanism. The precise determination of the magnitude and timing of larval mortality was attained through the use of small containers, and a method to prevent mortality due to handling was identified in this study. These types of tests may allow the logical evaluation and establishment of better rearing procedures for seed production in aquaculture.  相似文献   

9.
A high rate of sibling cannibalism is one of the principal obstacles in the rearing of larvae and juveniles of the African catfish Clarias gariepinus. This paper examines the underlying behavioural components of agonistic behaviour under culture conditions. Ten day old catfish larvae were stocked at 30 larvae l–1 in three tank designs with different surface areas and equal volumes. Stocking densities were 1.2, 0.6 and 0.3 fish cm–2 bottom surface. Growth did not differ between treatments. The highest mortality over 30 days was recorded at the medium density (0.6 larvae l–1). Fish stocked at this density showed the highest rate of aggression, while there was no difference in aggression between the highest and the lowest stocking densities. The results indicate that stocking density should be at least as high as 1.2 larvae cm–2 bottom surface area to obtain high production at best survival rates.  相似文献   

10.
To explore which lifestages affect the stock size of young-of-the-year mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan, we investigated interannual variations in the quantitative relationships among egg production, larval density, and juvenile density. We collected adult females, larvae, and juveniles during monthly field surveys from 2004 to 2007. The interannual trend for the juvenile density index differed from those for egg production and larval density; although indices of both egg production and larval density were high in 2004 and 2007, the juvenile density index was high only in 2007, suggesting high mortality during the pelagic larval stage or the early phase of the postsettlement juvenile stage in 2004. We found that larval settlement started at the end of August and peaked in October, although larvae from the early spawning season (May–June) should have settled in August or earlier. Juveniles were found throughout the bay except in areas where bottom hypoxia occurred, suggesting that hypoxia restricts the spatial distribution of juveniles. Our results suggest that mortality during the early life history fluctuates among years, probably because of changes in environmental conditions in the bay, resulting in interannual variation in the stock size of young-of-the-year juvenile O. oratoria.  相似文献   

11.
An important constraint to the commercial rearing of the marine ornamental shrimp Lysmata debelius is high larval mortality during early stages due to inappropriate procedures of larval collection and not feeding a live prey before one day elapsed after hatching. This incorrect feeding practice is commonly adopted in larval rearing of L. debelius and other ornamental marine shrimps because it is wrongly assumed that reserves of the newly hatched are enough for the first 24 h of life. Present work demonstrates that captive newly hatched L. debelius larvae ingest microalgae within minutes after hatching. When fed solely with Artemia nauplii, they have acceptable survival rates with stocking densities at or below 50 larval L–1; but when nauplii are combined with microalgae, survival is further improved to zoea 2 as initial mortality is reduced, and higher stocking densities are supported (up to 75 larvae L–1). The microalgae used were Rhinomonas reticulata, Skeletonema costata and Tetraselmis chuii. Higher survival through metamorphosis to zoea 2 was always observed for groups fed combinations of microalgae including Tetraselmis chuii. It is recommended that, larval collection methods ensure that larvae are fed microalgae within 2–3 h of release.  相似文献   

12.
Survival, growth and yield of competent great scallop (Pecten maximus) larvae were investigated during a full production season in a commercial hatchery in western Norway. Broodstock were collected from natural scallop beds and 12 groups were induced to spawn during the period December 2002 to July 2003. Larvae were reared on a large scale in 36 flow-through tanks (3500 l) at 17±1 °C and continuously fed a mixture of five algal species produced in an indoor continuous-flow system. Large variations in larval performance between spawning groups and tanks were observed, but the results were as good as earlier results using the batch system and prophylactic addition of chloramphenicol. Growth from days 3–24 averaged 4.8 μm day−1±0.8 (sd) and survival 22.4%±21.8 (sd). Mean yield of day 3 larvae was 7.1%±10.0 (sd) and 26.6%±25.9 (sd) for those surviving to day 24. Yield was significantly correlated to larval survival. Larval success was related to initial larval density, algal concentration and season. It was found that the best production regime had an initial larval density lower than 6 ml−1 and algal concentration of less than 12 μl−1 regardless of season. Seventeen tanks met these criteria and produced a mean yield of 0.5 larvae ml−1 to settlement. Flow-through systems are currently regarded as the only feasible method for viable hatchery production of P. maximus larvae in Norway.  相似文献   

13.
Studies were conducted to determine the effect of water hardness onClarias gariepinus egg hatchability and larval viability.The fertilized eggs were incubated at 28 °C and with waterhardnesses ranging from 10–700 mg/l CaCO3. Themean hatching rate fluctuated between 42.31% at hardness of 10mg/land 64.66% at 2000 mg/l. Abnormalities in the larvae were observedbeyond 200 mg/l and increased with increase in water hardness. Thehighest larval survival of 71.05% was recorded at 60 mg/l waterhardness. Based on statistics performed with analysis of variance (ANOVA) andfurther compared with Duncan's multiple range test (p = 0.05), the resultsimplythat very soft water (0–10 mg/l) and very hard water (300mg/l and above) are not suitable for Clariasegg incubation and larval rearing. A water hardness of 30–60mg/l CaCO3 is recommended for optimal normal hatching,high viability and maximum larval development of Clariasgariepinus.  相似文献   

14.
Embryonic development and larval hatching of the monogenean Diplectanum aequans, gill parasite of sea bass Dicentrarchus labrax, was studied in relation to different prophylactic treatments. Groups of eggs of D. aequans were submitted to different in vitro treatments: formalin (300 and 100 L L–1 per 1 hour), Neguvon® (trichlorphon 0.2 mg L–1 per 48 hours) and dehydration for 4 and 8 hours. Percentages of hatched larvae, aborted larvae and undeveloped embryos were estimated in comparison with the control group. Results showed that 300 L L–1 formalin and dehydration treatments were able to reduce larval hatching significantly, while Neguvon® and 100 L L–1 formalin treatments had no effect.  相似文献   

15.
First feeding performance of the milletseed butterflyfish (Chaetodon miliaris) was evaluated using three experiments examining prey type, microalgal cell density and prey density. To ensure no size bias existed between trials, morphometric measurements, fertilization and hatch rates were recorded for each trial. The proportion of larvae feeding and feeding intensity were measured in each experiment. To evaluate prey type, larvae were offered small size Brachionus plicatilis and Parvocalanus crassirostris nauplii in clear water and water greened with Tisochrysis lutea (Tiso). In trial 1, green water and P. crassirostris nauplii had a significantly higher proportion of larvae feeding and feeding intensity. In trial 2 no differences were detected between P. crassirostris treatments. Microalgae experiments evaluated six treatments ranging from 0 cells/ml to 8 × 105 cells/ml. Feeding response increased as microalgae was added to the environment, but no statistical differences were discerned between treatments besides the highest cell density (8 × 105 cells/ml) and lowest cell density in both trials (0 cells/ml). To determine if prey density had an effect on first feeding response P. crassirostris nauplii were added to tanks at 1 to 15 nauplii/ml. No significant differences in the feeding response were found between prey densities of 1–15 P. crassirostris nauplii/ml in either trial. This study revealed that C. miliaris larvae had the highest first feeding response, measured by the proportion of larvae feeding and feeding intensity per larvae, with the prey item P. crassirostris nauplii in green water and prey densities between 1 and 15 nauplii/ml.  相似文献   

16.
A flow-through (FT) culture system is described for calico scallop, Argopecten gibbus, larvae. Its performance was assessed by larval survival rate, shell growth, settlement rate and post-larval shell growth for the duration of larval life (13 days). Comparisons were made with larvae reared in standard static system (S). Effect of increased larval density on FT performance was also investigated. With comparable larval densities, survival rate of Day 2 larvae to pediveliger stage was similar in both larval rearing systems. Shell growth for FT-reared larvae was comparable or significantly higher than in the static system (P < 0.01). Settlement rate of pediveligers was comparable for both systems, averaging 30.7%, and no significant difference was seen in shell growth of FT- and static-reared pediveligers. Increased initial larval density did not affect survival rate in FT, but did negatively affect larval shell growth, settlement rate and post-larval shell growth yielding lower growth and minimal settlement rate (10.9 ± 2.8%) compared to the static system. This FT system was successful as larval rearing system, optimising space allocation in the hatchery, reducing labour, and eliminating the use of antibiotics. Optimising initial larval density within the system needs to be investigated in association with food ration.  相似文献   

17.
The combined effects of stocking density (0.2, 0.5, 1, 2, 4 and 8 inds/ml) and dietary microalgal ration (20,000 and 40,000 cells/ml) and the sole effect of temperature (10, 12, 14, 16, 18 and 22°C) on the specific growth rate (SGR), per cent survival and per cent metamorphosis of auricularia larvae of the California sea cucumber, Parastichopus californicus, were evaluated in two separate experiments. The SGR was not significantly affected by stocking densities in the range of 0.2 to 4 inds/ml, but was significantly reduced at 8 inds/ml. The SGR of larvae fed 20,000 cells/ml was significantly reduced in comparison to those fed 40,000 cells/ml. Larvae had significantly higher per cent survival and per cent metamorphosis when reared at densities of 0.2 and 0.5 inds/ml compared with those reared at 2–8 inds/ml. Microalgal ration level did not significantly impact survival or metamorphosis. Larvae reared at 16 and 18°C had significantly higher SGRs and per cent metamorphosis than those held at all other temperatures, while per cent survival was highest at 16°C. Based on these results, we recommend rearing auricularia larvae of P. californicus at a stocking density at or below 0.5 inds/ml, a dietary ration of 40,000 cells/ml, and a temperature of 16°C.  相似文献   

18.
The effects of saline-dissolved or Freund's incomplete adjuvant (FIA)-emulsified GnRHa treatment on the induction of ovulation in rainbow trout, Oncorhynchus mykiss, were examined. The FIA-emulsified GnRHa was first diluted in 0.25 ml physiological saline and then mixed with an equal volume of FIA. Fish were selected in the beginning of the spawning season and were allocated into four groups and were treated intraperitoneally with (a) 0.5 ml of emulsified GnRHa (GnRHa–FIA), (b) 0.5 ml saline-dissolved GnRHa in a single injection (GnRHa-1), (c) 0.5 ml saline-dissolved GnRHa in two injections spaced 1 d apart (GnRHa-2) and (d) 0.5 ml of saline (Control). The GnRHa dose in all hormone treatments was 25 µg kg− 1. All fish in the FIA–GnRHa and GnRHa-2 groups ovulated within 10 and 11 d after treatment, respectively. In contrast, only 75% in the Control fish and 60% of the fish in the GnRHa-1 group ovulated within 36 d after treatment. None of the treatments caused any pre- or post-spawning mortality in the broodstock. Fertilization, eyeing and hatching percentages of the produced progeny were normal in all the treatment groups and did not differ significantly among them. In conclusion, FIA-emulsified GnRHa can be effective in advancing the onset of and synchronizing the ovulation of rainbow trout within a two-week period, thus shortening the egg collection period, without affecting broodstock survival and egg quality.  相似文献   

19.
Land-based aquaculture facilities often utilize additional bicarbonate sources such as commercial sea salts that are designed to boost alkalinity in order to buffer seawater against reductions in pH. Despite these preventative measures, many facilities are likely to face occasional reductions in pH and corresponding reductions in carbonate saturation states due to the accumulation of metabolic waste products. We investigated the impact of reduced carbonate saturation states (ΩCa, ΩAr) on embryonic developmental rates, larval developmental rates, and echinoplutei skeletal morphometrics in the common edible sea urchin Lytechinus variegatus under high alkalinity conditions. Commercial artificial seawater was bubbled with a mixture of air and CO2 gas to reduce the carbonate saturation state. Rates of embryonic and larval development were significantly delayed in both the low and extreme low carbonate saturation state groups relative to the control at a given time. Although symmetry of overall skeletal body lengths was not affected, allometric relationships were significantly different between treatment groups. Larvae reared under ambient conditions had significantly greater postoral arm and overall body lengths relative to body lengths than larvae grown under extreme low carbonate saturation state conditions, indicating that extreme changes in the carbonate system affected not only developmental rates but also larval skeletal shape. Reduced rates of embryonic development and delayed and altered larval skeletal growth are likely to negatively impact larval culturing of L. variegatus in land-based, intensive culture situations where calcite and aragonite saturation states are lowered by the accumulation of metabolic waste products.  相似文献   

20.

The Catarina scallop Argopecten ventricosus is a highly valued resource. Although its hatchery spat production has already been reported, the effects of initial larval stocking density have never been reported for production purposes. This study evaluates A. ventricosus growth and survival in triplicate using three stocking densities: low (LD; 2 larvae mL?1), medium (MD; 4 larvae mL?1), and high (HD; 6 larvae mL?1). Three-day old larvae were reared in 18-L plastic carboy at 25.6?±?0.5 °C and fed with a microalgal blend of Isochrysis galbana and Chaetoceros calcitrans (1:1 cell number ratio) for 7 days, equivalent to 10 post-fertilization days (PFD). Higher specific growth rate was recorded at LD (15.8?±?0.2%) after 8 PFD of culture compared to MD (1.6?±?0.5%) and HD (4.1?±?1.8%) densities. The least time required for 60% of the larvae to reach the pediveliger stage was recorded at LD condition (10 PFD). Higher survival was recorded at HD (58.8?±?3.1%) at 8 PFD compared to MD (53.5?±?3.1%) and LD (43.9?±?3.0%). After 8 PFD, stocking density was highly related to larval growth and survival. To increase production and growth, and reduce the time required to reach pediveliger stage, stocking density should start with 6 larvae mL?1 and be reduced to 2 larvae mL?1 at 7 PFD.

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