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1.
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   

2.
The African River prawn Macrobrachium vollenhovenii is the largest of the local Palaemonidae prawns along the Cameroonian coast and an important target species for fisheries and aquaculture. A preliminary study on larviculture of this species was carried out at the IRAD-AQUASOL hatchery in Kribi, Cameroon. Berried females M. vollenhovenii were obtained from the Lobe and Lokoundje Rivers in the Southern Region, typical Lower Guinea rainforest streams. The larval rearing system consisted of a single recirculation system of four 65 L cylindrical plastic containers connected to a submerged biological filter container (65 L). Experiments were conducted three times in the same condition, with two batches of larvae reared separately in duplicate per experiment, at a density of 40/L, temperature 26°C, and salinity 16%. Larvae were fed from 1 day after hatching until metamorphosis to postlarvae (PL) with newly hatched Artemia nauplii, three times daily at the rate of 5 nauplii per mL water. The number of newly hatched larvae per female body weight unit was not affected by the female size and ranged between 531 to 1349 larvae g?1. The six batches succeeded from hatching to metamorphosis, and the 11 distinct larval stages described for M. rosenbergii were found. Larvae in all the batches developed more or less at the same pace up to stage V. However, a clear difference in the timing of appearance of the developmental stages was observed between batches and individuals of the same batch during the subsequent stages. The transition from stage V to stage VI and from stage IX to stage X was longer than the passage to other stages and seems to be the critical rearing period of M. vollenhovenii. From day 20 onward to sampling, the larval stage index (LSI) showed that larval development of the batch 1 was significantly faster than for all other batches. The time for first appearance of postlarvae was variable between batches (41–74 days), and batch 1 larvae passed through metamorphosis within a shorter span of time (41 days). Survival up to postlarvae was variable among batches, ranging between 3%–9%, and was better in batch 1 (9.31 ± 1.09). The general poor performance in terms of survival and metamorphosis rates of larvae seems to be related to the wild condition of broodstock. To improve performance of larvae, domestication of stock may be necessary. This result is the first recorded success in larviculture of M. vollenhovenii in Cameroon.  相似文献   

3.
It is not known whether rotifers or Artemia nauplii are the best first food for South African mud crab Scylla serrata larvae. In order to test this, larvae were fed with five different test diets. These were rotifers for the first 8 days and newly hatched EG® type Artemia nauplii (San Francisco Bay) from day 6 onwards (treatment R6A); newly hatched EG® type Artemia nauplii throughout the rearing period (treatment EG); newly hatched Vinh-Chau strain (Vietnam) Artemia nauplii throughout the rearing period (treatment VC); decapsulated cysts of EG® type Artemia throughout the rearing period (treatment DECAP); or decapsulated cysts supplemented with low densities of Artemia EG type Artemia nauplii (treatment MIX). Two experiments were conducted approximately 1 month apart using larvae from two different female crabs. Although results showed it is possible to rear S. serrata larvae through metamorphosis on Artemia nauplii exclusively, larval performance (development, survival and successful metamorphosis) was enhanced by the inclusion of rotifers as a first feed.No significant difference in performance was recorded between larvae fed on the two strains of Artemia nauplii. Larvae fed on decapsulated cysts in treatments DECAP and MIX performed poorly, but there were indications that decapsulated cysts and other inert diets may have potential as supplements to live food in the rearing of S. serrata larvae.  相似文献   

4.
Four separate studies were done on Southern flounder Paralichthys lethostigma larvae during first feeding and metamorphosis to determine the effects of stocking density, salinity, and light intensity on growth and survival. One study used stocking densities of 10, 20, 40, and 80 fish/L during first feeding; the second study compared the growth and survival of larvae stocked at 20 and 33 ppt; and a third experiment evaluated stocking densities of 1/L and 3/L under two different light intensities (1,600 lux vs 340 lux) during metamorphosis. The fourth experiment tested the effects of different salinities (0, 10, 20 and 30 ppt) on larval growth and survival during metamorphosis. Growth and survival (overall 6.9%) were not significantly different ( P > 0.05) for stocking rates up to 80/L. Larvae placed into 20 ppt salinity had survival through first feeding similar to that of larvae raised at 33 ppt. During metamorphosis, light intensity had no effect ( P > 0.05) on growth or survival, but fish stocked at 3/L had significantly lower ( P < 0.05) survival than fish at 1/L. Complete mortality of larvae occurred at 0 ppt. Growth and survival past metamorphosis were not significantly different ( P > 0.05) at 10, 20 and 30 ppt, but unmetamorphosed fish did not survive to day 60 at 10 ppt. Based on these results, practical larviculture of Southern flounder may require a two-step process with high stocking rates (80 fish/L) through first feeding and lower densities (1/L) through metamorphosis. Fingerling production in fertilized nursery ponds might he possible at salinity as low as 20 ppt.  相似文献   

5.
The starvation tolerance of post-larval abalone (Haliotis iris) was determined by examining post-larval growth and survival after various periods of starvation. Competent larvae (10 days old at 16°C) were induced to attach and metamorphose with 2 μM GABA. Post-larvae were either fed diatoms (Nitzschia longissima) or starved. In Experiment 1, post-larvae were starved immediately after metamorphosis for periods of 1, 2, 4, 8, 15, 20, 25 and 30 days. Starved post-larvae grew relatively well for several days after metamorphosis despite the absence of food (averages of 10.4 and 17.8 μm shell length (SL) per day after 8 days for two batches). Subsequent growth was minimal, averaging 1.7 and 0.7 μm day−1 over 6–7 days for the two batches. There was no clear relationship between period of starvation and growth rate when fed. Mean daily growth rate over 3 weeks when fed ranged from 15–22 μm day−1. However, the duration of starvation did have a significant effect on survival. Survival of post-larvae fed after 1–2 days of starvation was 90–100% after 3 weeks of feeding. Longer starvation periods gave progressively lower survival and post-larvae starved for 30 days all died within a week of being fed. In Experiment 2, post larvae were fed for 3 weeks after metamorphosis, then starved for 0, 3, 7, 14 or 21 days. Growth rates of starved post-larvae averaged only 5–6 μm day−1 in the first week (vs. 30 μm day−1 in controls), and later declined to zero. Growth resumed within a week following return to food, but the 14- and 21-day starvation treatments took 2 weeks to reach growth rates comparable to controls. The no-starvation controls and the 3- and 7-day starvation treatments all had >70% survival over 4 weeks after return to food. Survival in the 14- and 21-day starvation treatments was 15–20%, with almost all mortalities occurring in the first week after return to food. These data suggest that Haliotis iris post-larvae are relatively tolerant of starvation, so abalone farmers have a week or so to remedy food shortages before major post-larval mortality begins.  相似文献   

6.
Data on production of fingerling striped bass, Morone saxatilis, in 103 ponds at 17 hatcheries in 1988 were related to information on management practices and water qualities. Production was highly variable, with a median of 50,000/ha. No survival was evident in 12% of ponds; numbers harvested exceeded 250,000/ ha in 5% of ponds. Best survival resulted when larvae were stocked within 2 days after pond filling was started and at hatcheries with relatively low application rates of fertilizers during the prestocking interval. No survival was evident in ponds with pH >9.0 in the week after stocking. High pH's and probably toxic concentrations of un-ionized ammonia were related to water being in ponds for too long prior to stocking and to high applications of fertilizers. Examination of samples of larvae collected at stocking and the week after stocking documented a problem with swim bladder inflation. When larvae were stocked at D5 or D6 (Dl is day of hatch), inflation success averaged 91%: when stocked at ≥D7. inflation success averaged 60%. Measures proposed to improve production include: (1) Stock larvae prior to the critical period of swim bladder inflation(D4-D5). (2) Start filling ponds as close to stocking as is feasible (filling can be completed after stocking). (3) If the concentration of available nitrogen is low, apply no more than 300 µg/L of nitrogen in the prestocking interval. (4) Add phosphorus as needed, but avoid pH>8.5 until larvae are D14.  相似文献   

7.
为寻找卤虫卵的合适代用饵料,降低河蟹育苗成本,在１９９７年春季各期河蟹育苗中,进行投喂“高成”牌开口微囊配合饵料试验。结果;试验池幼体胃肠饱满度好,蜕壳时间短,变态整齐,成活率与对照组判别不五,而成本仅为对照池的４５％,经济效益显著,且不会对以后幼体发育造成不良影响。  相似文献   

8.
A need to improve larval rearing techniques led to the development of protocols for catecholamine‐induced settlement of flat oyster, Ostrea angasi, larvae. To further refine these techniques and optimize settlement percentages, the influence of salinity or temperature on development of O. angasi larvae was assessed using epinephrine‐induced metamorphosis. Larvae were reared between salinities of 15–35 and temperatures between 14.5 and 31°C. The greatest percentage survival, growth, development occurred when larvae were reared between 26 and 29°C and between salinities of 30 and 35. Larvae reared outside this salinity and temperature range exhibited reduced growth, survival and/or delayed development. Short‐term (1 h) reduction in larval rearing temperature from 26°C to 23.5°C significantly increased larval metamorphosis without affecting larval survival. Short‐term (1 h) increase in larval rearing temperature from 26°C to 29 and 31°C decreased larval survival and metamorphosis. To ensure repeatability in outcomes, tests showed that larvae sourced from different estuaries did not vary significantly in their metamorphic response to short‐term temperature manipulation and epinephrine‐induced metamorphosis.  相似文献   

9.
Microalgal biofilms with different amino acid profiles were investigated for their ability to induce abalone, Haliotis iris, attachment, metamorphosis, shell stage, and survival. Twenty microalgal strains, isolated from rocky shores and sandy estuaries, were grown in the laboratory to produce young and matured monospecific biofilms. Abalone larvae were exposed to the different biofilm treatments and controls (no biofilms) for 7 (attachment and metamorphosis) and 14 (shell stage and survival) d. The larvae performed significantly better in biofilms compared with controls across microalgal strains, but attachment, metamorphosis, shell stage, and survival were generally less than about 50, 35, 25, and 25%, respectively. Some microalgal strains belonging to the same species but collected from different sites had different effects on the larvae, likely due to variations in biochemical composition and activity among strains. Although no clear relationship was found between the microalgal amino acid profiles and larval processes, percentage biofilm cover and total amino acids were positively correlated with some of these processes. In addition, abalone performed significantly better when exposed to mature compared with young biofilms. These results may be due to the greater amounts of microalgal cells and their extracellular polymers within older biofilms, which may cue larvae toward more nutritionally favorable environments.  相似文献   

10.
The barber goby Elacatinus figaro is an endangered fish, endemic to Brazil and very important to the aquarium trade. One of the bottlenecks for its production in captivity is the larviculture, which is characterized by high mortality rates, especially in the first week after hatching, and prior to metamorphosis. The experiment evaluated the effect of triiodothyronine hormone (T3) on survival, growth and metamorphosis of barber goby. Larvae of 14 days after hatching (DAH) were immersed in three concentrations of T3, in triplicate: TC (control) – 0; T01 – 0.01; T025 – 0.025 and T05 – 0.05 mg/L. An additional replicate of each treatment was performed for sampling for the histological analysis of the thyroid follicles in 24 DAH larvae. The survival rates in TC, T01, T025 and T05 were 24%, 54%, 36% and 37% respectively, without significant differences between the treatments (p > 0.05). Regarding larval growth, the highest length values were obtained in TC. In T025 and T05, larval metamorphosis was anticipated in up to 11 days in relation to TC and T01. In T01 larvae, follicles were numerous with the presence of reabsorption vesicles in the colloid periphery, indicating increased production of thyroid hormones (THs), associated with the larval metamorphosis process. In T05, a follicle reduction in number and size was observed, given evidence of the end of metamorphosis. The use of 0.025 and 0.05 mg/L of T3 anticipated metamorphosis in barber goby larvae, shortening the larviculture period for this species.  相似文献   

11.
利用自然海水和天然饵料,采用无泥砂采苗方法,在天津沿海成功开展了青蛤工厂化育苗。幼虫初始壳长(120±1.28)μm,壳长平均日增长5.05μm,成活率23.0%;第19~31d为变态期,壳长平均日增长14.1μm,变态率32.9%;变态后至第53d,壳长平均日增长32.5μm,成活率82.3%。本次育苗试验充分利用天津沿海水质条件与环境特点,改进育苗方法,建立了适于天津海区的青蛤人工育苗工艺,共得到双水管稚贝约1.25亿枚。  相似文献   

12.
Southeast Asian rice farmers often manage aquatic habitats and resources on their land to increase production of aquatic animals. We introduce the concept of ‘farmer-managed aquatic systems’ (FMAS) to capture the diversity of these resource systems at the interface of aquaculture and capture fisheries and characterize FMAS in contrasting agro-ecosystems of Cambodia, Thailand and Vietnam. Cambodian and Thai FMAS yielded primarily self-recruiting species (SRS) and were managed to allow or attract them, while Vietnamese FMAS were managed more intensively to produce mostly hatchery-reared species. More than 90% of rice farming households in the study areas of Cambodia and Thailand harvested aquatic animals from their land, and about 70% created aquatic habitats such as ponds in addition to rice fields in order to increase aquatic resource production. Cambodian households created and utilized a wide variety of man-made aquatic habitats, while Thai households created predominantly trap ponds. In contrast, less than half of Vietnamese farming households harvested SRS and very few undertook FMAS management specifically for them. Vietnamese FMAS were intensively stocked and managed as aquaculture systems, with SRS accounting for less than 30% of production. Nonetheless, SRS production per area of FMAS was comparable in the three countries. Contrasting FMAS characteristics in different study areas reflect underlying differences in agro-ecosystems, aquaculture technologies, farmer livelihoods and markets.  相似文献   

13.
The study evaluated productive performance of larvae Nannostomus beckfordi submitted to feeding management (Experiment one) and different stock density (Experiment two) in captivity conditions. The first experiment evaluated feeding rate (100 and 200 nauplii of artemia larvae?1 day?1) and feeding frequency (2 and 4× per day). Second experiment evaluated different stock density (1, 5, 10, 20, 40 larvae per litre). At the end of 15 days, for both experiment, the survival and productive performance such as total length (TL), final weight (FW), specific development rate (SDR), specific growth rate (SGR), uniformity for weight (UW) uniformity for length (UL) and relative condition factor (Kr) was determined. For the main results, there is no significant difference to the rate and feeding frequency. The stock density has no significant difference for UW, Kr and survival. Nonetheless, a reduction in the TL, FW, SDR, SGR and FW with the increase in density (20 for 40 larvae per litre) was observed. Thus, for this species Nannostomus beckfordi during to initial stage using exogenous feeding, it is recommended 20 larvae per litre fed with 100 nauplii per larvae having two meals per day.  相似文献   

14.
Mature Brazilian flounders Paralichthys orbignyanus were captured in coastal southern Brazil and their reproduction in captivity was studied. Brazilian flounder will spawn naturally in captivity when the water temperature is around 23 °C and 14 h of light is provided daily. Females were induced for ovulation and hand stripping using human chorionic gonadotropin, luteinizing hormone‐releasing hormone analogue or carp pituitary extract. There was no need to inject males, as running milt was observed during the spawning season. Fertilization and hatching rates were above 80% independent of the hormone used. Notochord length at hatching was 2.18±0.07 mm for larvae hatching from naturally spawned eggs. Larvae were reared in salt water (30–35 g L?1) at 24 °C and under continuous illumination. Larviculture was with green water (Tetraselmis tetrathele 50 × 104 cells mL?1). Rotifers (10–20 ind mL?1) were offered as first food 3 days after hatching and gradually replaced by Artemia nauplii (0.5–10 ind mL?1). Larvae settled to the bottom 20 days after hatching and completed metamorphosis within a week after that. The total length for newly metamorphosed juveniles was 12.9±2.2 mm and the mean survival was 44.8%. The results demonstrate the feasibility of producing Brazilian flounder fingerlings for stock enhancement or grow‐out purposes.  相似文献   

15.
近十年来,越南将南海的金枪鱼资源作为其＂外向型＂渔业的重要支撑,不断增加捕捞强度,产量逐年升高。本文总结了越南发展南海金枪鱼渔业的过程,分析了南海金枪鱼资源的开发趋势。越南现代化的金枪鱼捕捞技术主要来自日本,使用的渔具主要有金枪鱼延绳钓、手钓、刺网和小型围网,捕捞的种类主要为鲣鱼、黄鳍金枪鱼和大眼金枪鱼,主要作业区域在西沙群岛南部海域和南沙群岛海域。越南2009年金枪鱼的产量已达到5.9×104t,计划2015年达到30×104t。根据越南海洋渔业研究所（RIMF）的评估,南海中西部的金枪鱼资源量为66~67×104t,可捕量23.3×104t,其中鲣鱼的可捕量21.6×104t,黄鳍金枪鱼和大眼金枪鱼的可捕量1.7×104t。随着全球金枪鱼捕捞配额的缩减和越南＂外向型＂渔业经济的发展,越南将继续加强对南海金枪鱼资源的开发。  相似文献   

16.
The effects of photoperiod and water exchange rate on the larvae of gilthead sea bream, Sparus aurata, from hatching to metamorphosis, 60–70 days later, were tested. Survival, growth rate and condition factor were determined with photoperiods of 12 and 24 h, and water exchange rates of 0 and 25%/day.Continuous light supported the highest mean survival (3.25%), with a maximum of 7.8% from hatching to metamorphosis. Growth rate in dry weight was best under continuous light in a water system with no exchange, up to 20 days post-hatching. Highest growth rates of larvae 40–60 days old were obtained in tanks with 25% of their water exchanged daily, along with a 12-h photoperiod. Condition factor was directly correlated with larval age. For the first 30 days after hatching, condition factor was affected by photoperiod and was highest for larvae exposed to continuous light.  相似文献   

17.
This study examines the larval development, metamorphosis and postlarval stage of Venerupis pullastra in relation to growth, lipids content and fatty acid composition, specifically those believed to be essential for most bivalves (i.e. 20:5n‐3 and 22:6n‐3). Clam larvae were fed with two species of microalgae supplied individually or mixed –Isochrysis galbana and Tetraselmis suecica–species normally used in bivalve hatcheries. Larvae fed with T. suecica showed a progressive accumulation of lipids and fatty acids but did not survive to metamorphosis. Contrarily, larvae fed with I. galbana or mixed diet showed a progressive decline in lipids and essential fatty acids (20:5n‐3 and 22:6n‐3) from the pediveliger stage onwards, and a survival rate of 95% until the start of metamorphosis. The lower content in n‐6 and the absence of 22:6n‐3 in T. suecica diet might contribute to the massive mortality observed for larvae fed with this diet. That diet seems to fail in the supply of some particular nutrient that allows energetic transformation of reserves for growth and metamorphosis. Nevertheless, larvae fed on mixture diet showed higher weight growth values at postlarval stage than those larvae fed on I. galbana diet.  相似文献   

18.
This study aimed at evaluating the effects of two starvation modes (fasting‐feeding mode and feeding‐fasting mode) on survival, growth and development of mysis larvae of Exopalaemon carinicauda. It showed that food restriction significantly affected the survival, growth and development in both starvation modes. With the extension of initial starvation period, a significantly reduced survival rate during metamorphosis was observed. In the fasting‐feeding mode, the duration of metamorphosis was extended and the body lengths of the individuals, which experienced successful metamorphosis to the post‐larval stage 1, were much shorter. In the feeding‐fasting mode, the extension of initial feeding period led to dramatically increased survival rate and body lengths, while there was no significant difference in duration of metamorphosis of those groups that reached to post‐larval stage. The 50% point‐of‐no‐return and the 50% point‐of‐reserve‐saturation were 3.85 days and 4.81 days respectively. The results of this study indicate that E. carinicauda mysis have the ability to withstand or recover from relatively extended starvation, but to ensure the success of commercial seedling, timely and adequate feeding is necessary. The information obtained from this study could provide a basis to optimize the feeding schedule of artificial seedling of E. carinicauda.  相似文献   

19.
Onset and development, and diel rhythm of aggressive behavior were observed in the early life stages of Japanese flounder Paralichthys olivaceus . The frequency of nip was counted as an index of aggressive behavior. No aggressive behavior was observed during the larval stage until day 39 after hatching (when fish were 13.2 mm in standard length (SL)) in the experimental tanks. The onset of aggressive behavior was observed on day 39, coinciding with completion of metamorphosis from the larval to the juvenile stage, and it developed until day 46. During the metamorphosing stage, typical shivering behavior (Ohm (Ω)-posture) was observed, and it showed a peak on day 19 (SL 7.6 mm) and decreased thereafter. Ω-Posture disappeared in the juvenile stage. Aggressive behavior and Ω-posture were only observed in the daytime. Settlement was first observed from day 19 in less than 30% of larvae and all individuals settled from day 39. As Ω-posture was observed regardless of the presence or absence of food and the peak of frequency in Ω-posture was observed in a specific stage of metamorphosis, this behavior is not related to feeding behavior, and it is possibly a precursor to aggressive behavior in this species.  相似文献   

20.
The spatial and temporal occurrence of pelagic fish stages and their biological variability may affect their dispersal and survival, and ultimately fish recruitment. We collected Atlantic cod larvae at one station inside and at one station outside the Gullmar Fjord, eastern Skagerrak, in order to investigate small-scale larval group differentiation. Rectangular midwater trawl hauls were taken every 6 h (during 24 h) from three separate depth intervals between the surface and 70 m depth. About 80% and 20% of all larvae occurred above the halocline at the Fjord station and the Coastal station, respectively. Hatching (at both stations) occurred from the 3rd week in February to the 1st week in May, indicating that cod larvae were present for at least 5 months (from late February to early August). The length and hatch date frequency distributions of larvae from the surface layer were unimodal inside the fjord but bimodal outside the fjord. Analyses of seven microsatellite DNA loci indicated that larvae collected inside the fjord (where local spawning occurs) were genetically distinct from larvae sampled on the outside (FST = 0.0026). The two age cohorts outside the fjord were not, however, genetically different, nor were larvae collected at different depths. We conclude that small-scale variability of vertical concentration and larval life history variability should have consequences for interpreting models of larval dispersal and survival, and subpopulation structure analyses.  相似文献   

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