首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Harpacticoid copepods are being considered as alternative candidates for live feed in aquaculture, but their benthic affinity may pose problems for pelagic fish larvae. We compared the swimming behaviour and feeding incidence of herring larvae (Clupea harengus) in the presence of harpacticoid copepods (Tachidius discipes) and rotifers (Brachionus plicatilis). Additionally, we provided T. discipes via a floating sieve to improve the prey availability. The comparison was performed at 5 and 10 days post hatch (dph) via 2D‐video observations. Quantitative analyses of larval trajectories allowed the estimation of feeding behaviour through a series of indicators: swimming speed, straightness of trajectories, turning angles and swimming activities (break, sink, slow, normal, fast). The outcomes highlighted that the prey type had no significant effect on swimming speed or straightness of the swimming path. However, at 10 dph directly copepod‐fed larvae spent less time in slow but more time in the normal swimming‐state than rotifer‐fed larvae and larvae fed with Tachidius via sieve. This suggests higher energy expenditure of directly copepod‐fed larvae. Moreover, the feeding incidence was higher in larvae fed with Tachidius via sieve than directly Tachidius‐fed larvae. Thus, providing harpacticoid copepods via a floating sieve can improve the rearing of marine fish larvae.  相似文献   

2.
The feeding selectivity of laboratory‐reared larvae of Rhamdia voulezi was assessed to investigate the preferred preys in early life stages. Three experiments were conducted at different larval development stages, starting soon after the absorption of the yolk sac (on fourth day after hatching – DAH), using zooplankton from fish ponds as food. Differences were detected in the patterns of prey selection among development stages. At first, the larvae prefer small preys, such as rotifers and cladocerans. Later, when they are more developed, they prefer to feed on large preys, such as copepods. On the fourth DAH, larvae in the pre‐flexion and initial flexion stage strongly selected rotifers and cladocerans (Diaphanosoma spinulosum, D. brevireme, Moina sp., M. micrura and M. minuta). At the other stages, cladocerans continued to be strongly selected. However, on the eighth DAH, larvae in flexion stage selected less strongly copepods Argyrodiaptomus azevedoi, Metacyclops mendocinus and Termocyclops decipiens. On the tenth DAH, larvae in postflexion stage selected more strongly copepods Argyrodiaptomus furcatus, Notodiaptomus cf. spinuliferus and M. mendocinus. As larvae grow, they tend to specialize in feeding of a particular prey. Prey selection of R. voulezi larvae was based both on species and zooplankton size. The size of the zooplankton ingested was related to the mouth gape size of larvae.  相似文献   

3.
Black catfish (Rhamdia quelen) is a species of interest for aquaculture in Brazil, Argentina and Uruguay. A feeding trial was conducted to evaluate the effect of feeding R. quelen larvae on either only an artificial diet or in combination with Artemia nauplii (AN) on larval performance and fatty acid composition. For 12 days, larvae were fed from first feeding (3 days after hatching, TL = 5.88 ± 0.23 mm) with artificial food only or a combination of artificial food and AN (co‐feeding). At the end of the trial, total length of co‐fed larvae was significantly higher than that of larvae fed solely artificial food (P < 0.001). No significant differences were found in survival rates. Co‐feeding microdiet with a small amount of AN significantly affected larval fatty acid composition. Lipid and fatty acid composition of food and larvae revealed the importance of n‐3 fatty acids for growth of black catfish larvae and that, as most freshwater fish, R. quelen larvae can elongate and desaturate linolenic acid to n‐3 highly unsaturated fatty acids. Results suggest that R. quelen larvae can be fed from first feeding on microdiets as unique food source, although better larval performances are obtained by co‐feeding with a small amount of AN.  相似文献   

4.
Knowledge of broodstock manipulation, gametogenesis, artificial fertilization and larval nutrition is a prerequisite to reach a large‐scale production of the polychaete Hediste diversicolor. In this study, the characteristics of oogenesis and spermatogenesis and embryonic and larval development were observed. Moreover, the effect of temperature on embryonic development and effect of diets and sediment on earlier juvenile development were tested. Mature oocytes were characterized by a spherical shape with a diameter of about 200 μm. They showed radial symmetry with a large centric nucleus surrounded by four distinctive layers. Embryo cleavage started between 4 and 10 hr after fertilization, and developed to the swimming trochophore stage after 5–6 days after fertilization at 11°C. The rate of embryonic development increased with a temperature increase from 6.1 to 21.2°C. The trochophore larvae increased in length from day 9 and commenced differentiation into 3‐setiger stage larvae at day 12. The length growth of larvae until 7‐setiger stage was 0.43 mm/day when fed with fish feed, while those fed shellfish diet and smolt sludge both grew around 0.21–0.23 mm/day. The results suggest that fish feed is a superior diet compared to shellfish diets and smolt sludge for the early larval stage of H. diversicolor.  相似文献   

5.
The present study was performed to investigate the effects of dietary lipid level on growth performance, antioxidant defense, and mRNA levels of digestive enzymes and immune genes in larval genetically improved farmed tilapia (Oreochromis niloticus). The results show that larvae fed lipid levels of 4–11.5% had greater weight gain (WG), feed efficiency, protein efficiency ratio and survival than larvae fed the other dietary lipid levels (P < 0.05). No difference whole‐body crude protein, ash or moisture contents were found between treatments (P > 0.05) but lipid contents increased as dietary lipid level was increased. The 8% and 11.5% dietary lipid levels had stimulatory effects on trypsin mRNA level compared with those of larvae fed the 15% and 18.5% lipid diets. Intestinal and liver amylase mRNA levels decreased in larvae fed the 18.5% lipid diet, following the decrease in dietary starch. Analysis of the secondary curve equation for WG indicated that the optimal dietary lipid level in larval tilapia was 8.56%. In addition, the 4–11.5% lipid levels improved superoxide dismutase and glutathione peroxidase activities and increased mRNA levels of heat shock protein70, hepcidin antimicrobial peptide‐1, and C‐type lysozyme in the liver of larvae (P < 0.05). A 192‐h Streptococcus iniae challenge study was conducted after the 35‐day feeding trial, and the results showed that post‐challenge mortality of larvae fed the 11.5% lipid level was the lowest and enhanced the immune activities.  相似文献   

6.
The time of first feeding is an important factor for establishing successful exogenous feeding in aquaculture hatcheries as it is crucial for larval survival and growth. The effects of delayed first feeding by the sea cucumber Apostichopus japonicus larvae were investigated. Groups of larvae were fed immediately after completion of the digestive tract (fed control) or starved for 24, 48, 72, 108 and 120 h post fertilization. The growth rates of A. japonicus larvae were the same as those of the control group when first feeding was delayed for less than 72 h. When the period of starvation was beyond 72 h, growth rates were reduced. The fed control group had the highest percentage of late auricularia larvae (70.0%) on day 11, followed by the groups starved for 24, 48, and 72 h, respectively, which had 35.00%, 43.48% and 41.67% of late auricularia larvae. When larvae were starved for more than 72 h, the percentage of late auricularia larvae never exceeded 12.0%. Most larvae halted in development and were deformed before reaching metamorphosis when starved for 108 and 120 h. Prolonged exposure to starvation (more than 48 h) resulted in a significant decrease in percentage of larvae reaching settlement. The point‐of‐no‐return (PNR) of A. japonicus larvae was calculated 110.4 h. Ratios of stomach length to total length, stomach width to total width were more sensitive to starvation than other larval morphometrics. To avoid mortality and obtain adequate growth and development, A. japonicus larvae in commercial culture should be fed within 48 h of the completion of the digestive tract.  相似文献   

7.
Survival rates of the larvae of sutchi catfish Pangasianodon hypophthalmus are reported to be three times higher under dim conditions (0.1 lx) than those under 100 lx. In this study, larval behaviour of sutchi catfish was examined under various light intensities (<0.01, 0.1, 1, 10 and 100 lx) using a CCD camera to understand why survival rates vary under different light intensities. Five‐day‐old larvae showed significantly higher swimming activity under <0.01, 0.1 and 1 lx than those under 10 and 100 lx. On the other hand, the larvae showed significantly higher aggressive behaviour under 10 and 100 lx; swimming larvae attacked resting individuals more frequently under 10 and 100 lx than those under 0 and 0.1 lx. Aggressive behaviour was considered to induce lesions, inflicted by the sharp teeth of attacking larvae, on larval skin surfaces. It is considered that the chemical substances would generate from injured skin surfaces then acted as stimuli, causing the cannibalistic behaviour in other fish around the injured fish. This study provided evidence that the observed higher survival rates depended on lower frequency of aggressive behaviour under dark or dim conditions. It is therefore recommended that larval rearing of sutchi catfish be conducted under dim (less than 1 lx) conditions.  相似文献   

8.
Two trials were conducted to evaluate the effects of chemically synthesized astaxanthin (Ax) on growth performance, survival, and stress resistance in larval and post‐larval kuruma shrimp (Marsupenaeus japonicus). Six dietary levels of Ax (0, 50, 100, 200, 400 and 800 mg/kg diet) were added to a baseline diet. As a first study, an 8‐day feeding trial was conducted on larval kuruma shrimp, with results showing that larvae‐fed diets supplemented with different Ax levels exhibited better performance during developmental and metamorphosis to postlarvae. Broken‐line regression analysis indicated that the optimal levels for growth and stress resistance of larvae were 168.9 mg/kg and 82.1 mg/kg diet, respectively. Second, a 30‐day feeding trial was conducted on post‐larval shrimp. Supplementation with 100 and 200 mg/kg Ax yielded significantly higher final body weight, body weight gain and specific growth rate than that in a control group. A cumulative mortality index for osmotic stress revealed significantly better performance in a group fed 200 mg/kg supplementation than in controls. Broken‐line regression analysis indicated that the optimal levels for growth and stress resistance of postlarvae were 108.7 mg/kg and 178.1 mg/kg diet, respectively. Based on these results, we suggest that carefully dosed Ax supplementation is a beneficial nutritional strategy for the early developmental stages of kuruma shrimp.  相似文献   

9.
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   

10.
Southern bluefin tuna, Thunnus maccoyii, are cultured in Australia following collection of wild juveniles. Hatchery culture from egg is in the experimental stage. High early mortality has hindered the production of quality juveniles in the hatchery. This study investigated the visual capacity of T. maccoyii during early larval ontogeny in order to describe the best larval rearing conditions to produce high‐quality seed stock. Functional visual ability, determined through behavioural experimentation, identified the effect of light intensity, prey density, turbidity, tank colour and turbulence on the feeding response. Larvae were visually challenged to feed under a range of conditions in short‐duration (4 h) feeding experiments. Feeding performance was measured as the proportion of larvae feeding and the intensity of feeding. First‐feeding performance was positively affected by increasing prey density and lower turbidities and unaffected by light intensity, tank colour, turbulence, prey size and larval density. The key findings from feeding experiments on 6 and 9 dph larvae was that as T. maccoyii aged, lower light intensities and higher prey densities significantly increased feeding performance. In addition, the study has identified that high light intensity and high air‐driven turbulence induced significant mortality. The proficient first‐feeding response indicated that early mortality common in culture is unlikely to be associated with a failure to initiate feeding. Our findings show the use of low light intensity has the potential to significantly improve survival and feeding response during the first two critical weeks of culture, when the major bottleneck in hatchery production is currently experienced.  相似文献   

11.
Morphological development and allometric growth patterns of Seriola lalandi larvae were assessed to characterize normal growth patterns under culture conditions. Early ontogenetic stages of yellowtail kingfish exhibited an exponential growth in terms of standard length as a function of age. Five development stages were characterized from hatching to the juvenile stage: larval stage I (0–2 days post hatch, dph) with endogenous feeding, characterized by a small yolk sac, unpigmented eyes, primordial finfold surrounding the body and a closed mouth; larval stage II (2–15 dph) characterized by mouth opening, complete pigmentation of eyes and the beginning of the exogenous feeding; subsequently, in the larval stage III (15–25 dph) the posterior tip of notochord of the larvae bended upward and the first rays appeared in fins, concomitant with a change in swimming behaviour; thereafter, larval stage IV (post‐flexion stage; 25–30 dph) began when larvae resembled in morphology to a juvenile organism; however, caudal and dorsal fins were not completely development. Lastly, the juvenile stage was reached 30 dph characterized by a morphology and fin structures similar to those of the adults. Growth and development of structures and organs associated with vital functions such as feeding, sensorial and breathing systems seemed to be more critical previous to 23 dph, which was reflected with a positive allometric growth of head and eyes during this period. The results from this study can be used as a tool‐guide to assess normal development in larval research with S. lalandi to improve existing rearing protocols in hatchery production.  相似文献   

12.
Muscles play important roles in feeding, respiration and swimming during not only adult stage but also larval stage in fish. However, there is no information of the muscle development in larval greater amberjack, Seriola dumerili (Risso). Here, we investigated muscle development in the greater amberjack, focusing primarily on the cranial muscles from 0 days post hatch (dph) to 12 dph using a modified whole‐mount immunohistochemical staining method. We found that the muscles required for feeding develop by 3 dph, when the larvae begin to feed. Subsequently, muscle composition in the dorsal branchial arches changes to the adult form between 5 and 8 dph. At 8 dph, all the muscles required for feeding and respiration appear, whereas the dorsal, pelvic and caudal fin muscles required for swimming develop later. This report provides fundamental information on larval greater amberjack muscle development, which will enable the detection of abnormal larval muscles and improve larval rearing techniques by modifying environmental conditions.  相似文献   

13.
This study aimed to establish feeding strategies covering the whole larval period of the forktail blenny, Meiacanthus atrodorsalis, based on the standard hatchery feeds of rotifers and Artemia. Three purposely designed experiments were conducted to determine the appropriate times and techniques to transition larvae from rotifers onto Artemia nauplii of a Great Salt Lake (GSL) strain, and a specialty AF strain, as well as subsequent transition onto enriched metanauplii of GSL Artemia. With a 3‐day co‐feeding period, larvae adapted well to a transition from rotifers to newly hatched GSL Artemia nauplii as early as 5 days posthatching (DPH), and as early as 3 DPH when fed the smaller AF Artemia nauplii. However, prolonging the rotifer‐feeding period up to 11 DPH did not negatively affect survival. Larvae fed Artemia nauplii of the AF strain showed 17–21% higher survival, 24–33% greater standard length and body depth, and 91–200% greater dry weight, after 20 days relative to those fed nauplii of the GSL strain. Meanwhile, enriched Artemia metanauplii of the GSL strain were shown to be an acceptable alternative to AF Artemia nauplii for later larvae, producing similar survival and growth when introduced from 8 DPH. Based on our findings, we recommend feeding M. atrodorsalis larvae rotifers as a first food between 0 and 2 DPH, introducing AF Artemia nauplii from 3 DPH, followed by enriched GSL Artemia metanauplii from 8 DPH onward, with a 3‐day co‐feeding period between each prey change.  相似文献   

14.
This study was carried out to evaluate the effects of feed restriction on the performance and feeding behaviour of Brycon orbignyanus. Ten‐day larvae (72.84 ± 8.61 mg) were distributed in 36 aquariums (density of 15 larvae/L) in a completely randomized design consisting of six treatments and six replicates. The treatments were determined according to the number of feed restriction days: 0, 2, 4, 6, 8 and 10 days (F0, F2, F4, F6, F8 and F10, respectively), totalling 10 days. The results for final weight, weight gain and specific growth rate were significant (p < .05), and F2 and F0 presented the highest values among all experimental groups. The adopted feeding strategies did not influence final survival (p > .05), and no cannibalism behaviour was observed in any of the treatments. F2 and F0 treatments also displayed higher swimming speed (p < .05) among the assessed groups. The time spent searching for and capturing prey was significantly lower in the F0 treatment. Muscular atrophy for the F10 group was observed, and F2 animals presented no significant difference (p > .05) in muscle fibre diameter when compared to F0. Thus, dietary restrictions can be applied as a strategy for B. orbignyanus reared in intensive laboratory systems for 2 days without compromising performance, muscle growth and feeding behaviour.  相似文献   

15.
Spiny lobsters are highly valuable seafood species that are captured and marketed in more than 90 countries. After more than 30 years of stable catches, spiny lobster fisheries in many parts of the world are declining due to decreased recruitment. The planktonic larvae spend up to 2 years in offshore waters, accumulating energy stores to fuel the non‐feeding post‐larva, or puerulus, to actively migrate onshore and settle. The total energy required by spiny lobster pueruli for cross‐shelf migration has not been accurately determined. Recent advances in larval culture have provided the opportunity for the first detailed examination of the swimming performance, respiratory metabolism and nitrogen excretion of spiny lobster (Sagmariasus verreauxi) throughout the puerulus stage. The routine and active metabolic rates of pueruli were lower than for most other decapod larvae, probably to provide greater energy efficiency. However, pueruli were found to have limited time, swimming ability and fuel for active cross‐shelf migration. It is estimated that S. verreauxi pueruli require at least 13.8 mg of stored lipid to provide sufficient energy (18.4% DW) to complete the puerulus stage and recruit to coastal habitats. The ability of the preceding phyllosoma larvae to accumulate these reserves, and the presence of favourable oceanographic conditions during the limited time available to the migrating puerulus, are both crucial to subsequent successful recruitment. Spiny lobster recruitment processes appear to be particularly vulnerable to changes in oceanic climate which is likely to contribute to the recent large‐scale declines in recruitment to valuable fished populations.  相似文献   

16.
To study the transport of plaice (Pleuronectes platessa L.) eggs and larvae in the eastern Irish Sea, we constructed a 3D‐baroclinic physical model and coupled it to a particle‐tracking scheme that allowed aspects of larval behaviour to be simulated. Starting positions for eggs were based upon data from a series of ichthyoplankton surveys and final positions were compared with results of settled plaice distributions from two beam trawl surveys conducted on beaches around the eastern Irish Sea. If simulated larval behaviour was limited to passive drift or horizontal swimming, the particles diffused away from the spawning areas but failed to reach nursery grounds in significant numbers (85–90% remaining offshore). In contrast, switching on circatidal vertical swimming significantly increased the numbers of larvae reaching the coast (only 23–30% remained offshore). Particles tended to accumulate in bays and estuaries and this pattern compared well with the distribution of settled plaice from the field surveys. Studies in the southern North Sea (where spawning and nursery grounds are widely separated) have also demonstrated the importance of selective tidal stream transport for successful recruitment of settling plaice to nursery grounds. Although our understanding of the ontogeny of this behaviour is still poor, the model results presented suggest that this aspect of behaviour is a key factor influencing plaice settlement success.  相似文献   

17.
Data from stock assessment surveys, published research and climate sensors were linked to model the interaction between fishing, physical‐oceanographic processes and spatial patterns of larval settlement for western king prawn [Penaeus (Melicertus) latisulcatus]. This information was used to evaluate the trade‐off between larval recruitment and catch during fishing periods that demand high prices but coincide with spawning. Total rates of larval settlement were maximized when tidal currents and atmospheric physical‐forcing components were coupled with simulations of larval swimming behaviour under average gulf temperatures. Average gulf temperatures sustained longer larval durations and increased larval settlement rates by over 12% compared with warmer gulf conditions simulated under a scenario of global warming. Reproductive data coupled with outputs from the biophysical model identified consistent inter‐annual patterns in the areas contributing to larval settlement success. Areas located in the north‐east, and central‐west of the fishery, consistently contributed to over 40% of all larvae reaching a settlement in each year. Harvest sensitivity analyses indicated that changes in the spatial patterns of pre‐Christmas fishing could lead to improvements in overall rates of the larval settlement while maintaining or improving the levels of catch. Future studies to refine the model inputs relating to physical processes, larval behaviour and mortality rates for P. latisulcatus coupled with surveys of juvenile prawn abundance to ground truth the modelled predictions, would allow stock recruitment relationships to be more closely examined and inform adaptive management of the fishery in the future.  相似文献   

18.
We investigated the first‐feeding success of two species: southern bluefin tuna (Thunnus maccoyii) and yellowtail kingfish (Seriola lalandi) to determine if similar culture parameters can be used for both, especially when S. lalandi are held in the same tanks as prey for T. maccoyii. The feeding performance (proportion and intensity) was examined in three short‐duration (4 h) experiments: prey density, prey size and larval density. Increasing prey density from 0.5 to 25 rotifers mL?1 increased the proportion of T. maccoyii and S. lalandi larvae feeding. Prey size alone did not affect feeding in either species. Seriola lalandi had a decreased proportion of larvae feeding when larval density reached 50 larvae L?1 concurrent with a gradual increase in feeding intensity between 2 and 50 larvae L?1. In T. maccoyii, there was no pattern to the effect of larval density on the proportion of larvae feeding. The overall feeding performance of larvae was higher in T. maccoyii than S. lalandi. Increased prey density improved the first‐feeding ability of T. maccoyii and S. lalandi larvae. The effect of larval density on S. lalandi feeding requires further investigation, to ensure that they remain feeding when provided as prey in T. maccoyii culture. The identification of factors in this study, which increase first‐feeding success, will improve the culture of both species.  相似文献   

19.
A series of experiments were conducted to obtain an efficient larval rearing protocol for Megabalanus azoricus. The first part of this study investigates the effect of microalgae‐based diets on survival and larval development. Mono and mixed‐diets were tested at 20 ± 1°C, in a sequence of 11‐day feeding experiments. The second part presents a preliminary study on the influence of a biofilm on recruitment and use of oyster spat collectors in a mass rearing system. A photographic record of larval development and a brief reference to the diagnostic features that enable quick larval staging are also presented, along with morphometric measurements. Of the microalgae tested (Chaetoceros sp., Chloromonas sp., Dunaliella sp., T‐Isochrysis sp. and Skeletonema sp.) the mixed‐diet Skeletonema sp. with T‐Isocrysis sp. showed the highest survival percentages: total survival ranged from 79.7 to 85.7% and 69.7–80.0% of nauplii were in stage VI after 11 days of rearing. Cypris were also present, but only represented 5.3% of the survivors at most. In the mass rearing system juveniles were found settled in the collectors after 25 days, at 20 ± 1°C. However recruitment was less than 1%. Preliminary results showed no settlement preference towards collectors with biofilm. Nevertheless, this study provides the first record of M. azoricus settlement under laboratorial conditions and represent a starting point for future larval rearing studies.  相似文献   

20.
Problems of limited number of dry feeds as supplement or replacement of live feeds have led to poor larval nutrition in many species of fish. Therefore, the suitability of co‐feeding 8‐day‐old African catfish (Clarias gariepinus) posthatch larvae using live feed (Artemia salina) and formulated dry diet containing freshwater atyid shrimp (Caridina nilotica) during weaning was investigated. The experiment ended after 21 days of culture and respective groups compared on the basis of growth performance, survival, feed utilization and nutrient utilization. Larvae co‐fed using 50%Artemia and 50% formulated dry diet resulted in significantly (P < 0.05) better growth performance, food gain ratio (FGR), protein efficiency ratio (PER) and productive protein values (PPV) than other treatments. The lowest growth performance occurred in larvae weaned using 100% formulated and commercial dry diets. Better survival of over 90% was obtained in larvae weaned using 50%Artemia and 50% dry diet, while abrupt weaning using 100% dry diets resulted in lower survival (<75%). These results support a recommendation of co‐feeding C. gariepinus larvae using a formulated dry diet containing C. nilotica and 50% live feed when weaning is performed after 8 days posthatching period.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号