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1.
Successful development of planktonic copepods for use as live feed in marine aquaculture relies on optimization of environmental conditions for population growth and egg storage. This study examined strain-specific differences in egg survivorship during cold-storage-induced quiescence in four cultures of the widespread marine calanoid Acartia tonsa Dana, 1849. Experimental cultures were obtained from Øresund, Denmark (DIFRES), Kiel, Germany (KIEL), Turkey Point, Florida, USA (FL), and Mobile Bay, Alabama, USA (AL), and were shown to derive from three highly distinct mitochondrial clades. Eggs from Gulf of Mexico strains had low tolerance for cold storage, and showed very low hatching success after 10 days. In contrast, Baltic Sea strains produced eggs able to tolerate up to 150 days of cold storage, with the DIFRES strain showing the highest egg survivorship during the experiment. Eggs from the Kiel strain showed an increase in hatching over time, indicating the presence of dormant eggs. Parental rearing temperature was also found to affect egg survivorship during quiescence in the DIFRES strain, with lower hatching success observed among eggs produced at 25 °C than at 17 °C. The DIFRES strain is recommended as the optimal strain for use in aquaculture, and conditions for cold storage of eggs are discussed.  相似文献   

2.
A dual column photobioreactor (PBR) (2 × 47 L) with mixed CO2/air bubbling was tested for cultivation of the microalga Rhodomonas salina as food for live feed copepods. In the continuous growth phase, the cell density was relatively stable at 2.40 ± 0.13 × 106 cells/ml at an average dilution rate of 0.46 ± 0.02 per day throughout the 30‐day experiment. The produced algae had a high content of both total fatty acids (TFA) and free amino acids (FAA). Especially, the harvested algae contained a high proportion of poly‐unsaturated fatty acids that made up 80% of the TFA and of essential amino acids (35% of all FAA), implicating desirable components as feed for copepods. The current PBR was sufficient to feed a culture of the calanoid copepod Acartia tonsa at a density of 2,500 adult/L in ca. 500 L culture with a daily yield of approximately 17 × 106 eggs. To be able to sustain the integrated copepods production, the suggested volume of the algae cultures should be ca. 20% of the copepod culture volume.  相似文献   

3.
The use of live prey is still necessary for a large number of raised fish species. Small sized rotifers are usually used as live preys during the first days of feeding in small mouth fish. An alternative to this is the use of copepods as prey for first feeding. In this study, the sizes, weight and biochemical contents of two copepods and one rotifer species raised on similar algal food conditions were compared. Rotifers contained a higher proportion of essential amino acids in the free amino acid (FAA) fraction (43%) than copepods (30–32%). However, rotifers had lower levels of important fatty acids like DHA (7% compared with 23–32% in copepods) and their DHA/EPA ratio was lower than that in copepods (0.54 compared with 1.35–1.63 in copepods). The FAA pattern of the preys tended to be species‐specific and its implications from an aquaculture point of view is discussed. In contrast, the‐protein bound amino acids tended to be very conservative among the studied organisms. The second part of the work is focused on ‘the price’ of hatching in Acartia tonsa eggs before or after cold storage at 3°C. The fatty acid contents in A. tonsa tended to decrease with the storage time. It also decreased with hatching of the nauplii, but its proportion compared with the dry weight remained constant.  相似文献   

4.
Copepods are the optimal live feed for hatcheries and improvement of cultivation techniques, to provide a constant food source, is crucial for the expansion of the industry. However, studies based on experimental work and real observations can be labour intensive and expensive. A simple model was developed based on the well‐known life history traits of Acartia tonsa to describe batch cultures and their productivity. Model results were compared to observations from real cultures. For maximizing egg production yields, the optimal stocking density of copepods should be adapted to the design (depth) of the culture tanks. At high densities, stress due to encountering conspecifics, as well as cannibalism of eggs by adults, limits egg production yields. Using this model, the potential selection efficacy of copepod strains was also evaluated in order to increase production yields. Selecting larger copepods increases the egg production per litre of culture, but decreases the optimal stocking density and the range of densities at which egg production yield is high, and vice‐versa. Selecting copepods that are less affected by stress due to conspecifics only affect production yields at very high adult densities. However, selecting copepods with a high Specific Growth Rate (SGR), or improving their SGR, was found to be an alternative which did not affect the optimal cultivation densities but improved egg production yields.  相似文献   

5.
Developing methods to store copepod eggs is necessary to increase the availability of copepods as a live food for the aquaculture industry and aquarium trade, and also to allow the exchange of copepods between researchers. The present study, evaluated the effect of glucose and two antibiotics (kanamycin sulphate and oxytetracycline HCl) on extending the shelf life of cold-stored subitaneous Acartia tonsa eggs. Also, egg development effects on the survival of the eggs were tested. Glucose did not have any significant effects on the survival of the eggs. However, the addition of antibiotics to the storage vials resulted in an increase of the survival of the eggs. In the best case, the shelf life of the eggs was almost doubled. After 7 days, the kanamycin+glucose treatment led to a hatching success of 86±1% of the hatchable eggs, while the untreated eggs presented a hatching success of 47±6%. However, long exposure to high concentrations of antibiotics was lethal to the copepod eggs. After more than 30 days of exposure to 100 mg L−1 of oxytetracycline, the survival of the eggs was lower than in the untreated samples. After 45 days, oxytetracycline-treated eggs (100 mg L−1) presented a hatching success of 4–5% while the non-stored eggs still had a hatching success of 9%, and the eggs treated with a lower concentration of antibiotics (10 mg L−1) showed a hatching success up to 21–23%. The size of the nauplii in all trials tended to decrease as the period of cold storage at 1°C increased. We consider that the use of antibiotics at the right dosage to be a means to increase the storage capacity of the Gulf of Mexico strain of A. tonsa eggs, which do not show any capacity to be stored for long periods of time, compared with some other strains. In addition eggs that were between 5 and 7 h old survived longer when stored in the cold than eggs, which were freshly spawned or closer to hatching.  相似文献   

6.
Copepods are the natural food items for marine fish larvae but are still difficult to be cultured on a continuous basis. Therefore, suitable storage techniques for copepod subitaneous eggs are of great interest. Cold‐stored copepod embryos still develop and retain a physiological activity during the cold storage period. As a consequence, their nutritional quality may change over the time of storage with these changes possibly affecting both eggs viability and larval fish survival and development. In this study, the clownfish, Amphiprion polymnus, was used as an experimental model to compare, for the first time, the effects of diets based on enriched rotifers and Artemia (control), Acartia tonsa copepods of a continuous culture and A. tonsa originated from 6 months cold‐stored eggs. The effects of the different diets were tested through morphometric, molecular and biochemical approach. This study demonstrated that after a 6 months cold storage period, the quality of copepods obtained from those eggs was suboptimal for A. polymnus larval rearing. In fact, larvae fed those copepods showed lower growth and survival performances respect to the other experimental groups.  相似文献   

7.
Understanding the factors limiting copepod productivity in dense cultures is a prerequisite for the partial or entire replacement of Artemia and rotifers as live feed for finfish larvae. In dense cultures, high encounter rates between individuals may increase stress, cannibalism incidents and potentially trigger resting egg production. We conducted an experiment to evaluate the potential egg production and egg quality of Acartia tonsa stocked at densities ranging from 10 to >5000 ind. L?1. Egg Production (EP), Delayed Hatching Eggs production (DHE), hatching success (HS), egg mortality and water quality were used as end points. In the present system, A. tonsa was raised at >5000 ind. L?1 without affecting the mortality, confirming that attaining this high density in culture is possible. However, egg harvest reached an optimum of 12 000 egg L?1 day?1 at ~2500 ind. L?1 indicating that increasing stocking density above this level is not of practical interest. Calculations showed that the loss in egg harvest at stocking densities <2500 ind. L?1 is of 1.3% for every additional 100 adult copepods L?1. The increasing adult density did not affected the proportion of DHE produced (~10% of harvest) but decreased significantly the HS, though not to a point that would be problematic in a commercial production. Understanding the biology of copepods when stocked at high density is important to improve copepod culture systems and increase egg harvest yields. Technical solutions such as the continuous separation of eggs from adults in the water column, recirculation and the continuous provision of food are seen as potential solutions.  相似文献   

8.
Copepods are considered high quality live feed for fish larvae due to their large within species size span, swimming pattern triggering hunting behaviour, and complete biochemical profile. In a continuous cultivation system aiming at the planktonic calanoid Acartia tonsa an intruding harpacticoid frequently appears. We experimentally evaluate how the interaction from the semi‐benthic Tisbe holothuriae is affecting our cultures and ask whether the two copepod‐species are expected to pose competitive exclusion or co‐exist long‐term. This is pursued by establishing ~40 days mono‐ and mixed copepod cultures reared in a stationary setup (S) theoretically advantageous for T. holothuriae and a rotating setup (R) with organisms kept in suspension by use of a plankton wheel, theoretically advantageous for A. tonsa. The carrying capacities of A. tonsa in either mono‐ or mixed cultures are not affected whether the copepods are subject to S or R treatment. Only exception is the S‐setup containing mixed culture were A. tonsa obtains a significantly lower carrying capacity compared with A. tonsa alone in R‐setup. The mono‐ and mixed cultures of T. holothuriae are, however, highly negatively affected by the R setup compared with S setup. A long‐term solution to limit the presence of T. holothuriae is to apply turbulence level in a classical stagnant tank setup to an extend that suppress T. holothuriae and simultaneously allow algae in suspension as food for A. tonsa, make their eggs sediment as well as minimize risk of benthic‐predation on eggs.  相似文献   

9.
Cannibalism in copepod culture may limit its production yield and therefore affect the economic interests associated with the use of copepods as live feed in aquaculture. The effects of adult density, egg density, and algal availability were tested on the calanoid copepod Acartia tonsa to understand how these parameters affect cannibalism rates on eggs. The overall cannibalism within the range of adult densities tested (120–1,000 adult L?1) was solely influenced by the egg and algal density, and not by the adult density. The increased densities of eggs lead to higher occurrences of cannibalism. Increasing the availability of alternative diets (e.g., algae) significantly diminished the adults’ cannibalistic behavior. The highest cannibalistic rates per adult were observed at low densities of adults and high densities of eggs (120 ind L?1 and 20,000 eggs L?1, respectively) and resulted in consumption rates >20 eggs ind?1 h?1. In this experiment, cannibalistic behavior reached 20 % of adult weight ind?1 h?1 under the aforementioned parameters. Additionally, the present study suggests that at high adult copepod density, the interactions between adults result in a decreased “time to feed.” Finally, it is argued that the separations of eggs from adult copepods, as well as the continuous access to an alternative food source, are necessary for decreasing the effects of cannibalism in copepod cultures.  相似文献   

10.
Ciliates in live feed cultures can be a pest that lower production yields. This could dramatically affect the management and success of copepod cultures. In this study, we investigated the effect of the ciliate Euplotes sp. on egg production, specific egg production and egg hatching success of Acartia tonsa fed with Rhodomonas salina. We found that at a concentration of 2 cells ml?1, Euplotes sp. had no effect on the production and hatching success of eggs but increased/decreased the mortality/quality of non-subitaneous eggs. Euplotes sp. had a good fatty acid profile containing high proportion of unsaturated fatty acids, but the amount of fatty acids compared to their carbon weight was very low and, therefore, it was considered as a poor food source. We propose a short-term interruption of food supply to copepod cultures in order to mitigate bloom formation of ciliates. This will force copepods to feed on them actively as prey and therefore decrease their long-term negative effects.  相似文献   

11.
The effects of light and short-term temperature elevation on the 48-h egg hatching success (HS) of cold-stored (2 °C) Acartia tonsa Dana (Copepoda: Calanoida) eggs were examined in the present study. The eggs can be stored for up to 7.5 months and maintain their high hatching rate under optimal conditions. Intensively produced eggs from the copepod A. tonsa may be hatched and used as an inoculum for producing copepod nauplii as live feed for fish larvae. The HS for eggs that were directly exposed to LED light declined rapidly after 1 month of storage (from 91 to 25 %), and these eggs did not hatch at all after 3 months of storage. The highest HS found was for eggs stored in complete darkness. The HS for eggs stored in normoxic (≥7 mg DO L?1) and anoxic (≤0.03 mg DO L?1) seawater was not affected by short-term temperature transitions from 2 °C up to 9 or 17 °C for a period of 12 or 24 h, when hatched 1 week post-exposure. The global mean HS for eggs stored in normoxic seawater was 85.9 % and significantly lower compared to eggs stored under anoxic conditions after 3 weeks of storage (91.8 %) (P = 0.001; SNK).  相似文献   

12.
Egg hatching and nauplii success from three euryhaline calanoid copepod species at low salinities suggest a promising alternative initial live feed for pikeperch (Sander lucioperca L.) to the conventional live feed. Acartia bifilosa and Eurytemora affinis are viable candidates with egg hatching down to zero salinity, and Acartia tonsa nauplii survive up to 2 h at zero salinity after transfer from low-salinity seawater. When offered A. tonsa and Artemia, pikeperch larvae equally consumed both prey types. We suggest that euryhaline copepods can be a supplement to or even a substitute for the normal live feed currently used as larval feed for pikeperch.  相似文献   

13.
In this study, we analysed the effect of population density and food concentration on the fecundity of a Mediterranean strain of Acartia tonsa to maximize egg production. During 4‐day feeding experiments, egg hatching success and faecal pellet production were also followed. The algae Rhinomonas reticulata was supplied at different concentrations corresponding to 250, 500, 1000, 1500, 2000 and 3000 μg C L?1 day?1 at the following adult copepod density: 40, 80 and 160 ind. L?1. Our results show a positive relationship between algal concentration and egg production under all experimental conditions confirming that the quantity of food strongly limits A. tonsa fecundity. Maximum egg production (57 eggs per female) was reached at the lowest density and at the maximum food concentration. Percentage of egg hatching success was not dependent on the quantity of food used. At the same food concentration, an increase in population density from 40 to 80 ind. L?1 induced an increase in faecal pellet production per couple which did not correspond to an increase in egg production, suggesting that higher energetic costs were shifted to swimming activity. Productivity of the A. tonsa Mediterranean strain is mainly limited by the quantity of food rather than by crowding conditions.  相似文献   

14.
Marine aquaculture facilities positioned far from the sea need access to seawater (SW); hence, commercial salts are often the chosen solution. In marine hatcheries, most fish larvae require live feed (zooplankton) that are in turn fed with microalgae. The objective of this research was to investigate the applicability of commercial salts and clarify the potential effects on the cultivation of the microalga Rhodomonas salina and the copepod Acartia tonsa. Three commercial salts were tested, Red Sea Salt (RS), Red Sea – Coral Pro Salt (CP), and Blue Treasure Salt. R. salina was cultured at salinities of 10, 20, and 30 psu resulting in equal growth rates at salinities 20 and 30 in SW and RS mixed with deionized (DI) water. The optimum salinity for R. salina was 29 psu. For A. tonsa eggs, we observed highest hatching success in 30 psu with CP or RS mixed with DI water. The egg hatching success was not affected by salinities 15–40 and optimal hatching was obtained at 27 psu. Results confirm it was possible to use commercial salts for rearing of both R. salina and A. tonsa, widening the application of these species for aquaculture facilities without access to SW.  相似文献   

15.
The free amino acids (FAA) profile was determined for newly fertilized eggs and resultant larvae from wild-caught red snapper Lutjanus campechanus induced to spawn with hCG. Yolk sac and oil globule volumes of eggs and larvae were monitored over time from digital photographs. FAA profiles of the eggs and larvae were measured in picomoles (pmol) of FAA/mg of eggs by HPLC. Newly fertilized eggs had a mean total FAA content of 21.72 ± 3.55 nmoles/egg (92.81 ± 9.71 nmoles/mg eggs). Leucine, valine, lysine, and isoleucine were the most abundant essential FAA comprising 35.9% of the total FAA. Alanine, serine, asparagine, and glycine were the most abundant non-essential FAA comprising 34.2% of the total FAA. At 24 h post-hatch (hph) the mean total FAA had decreased by 81% since egg fertilization. The bulk of the FAA decrease was between the time of hatch and 12 hph. Only 8.5 ± 1.5% of the initial concentration in fertilized eggs of isoleucine, 9.7 ± 2.5% of arginine, and 9.9 ± 2.0% of threonine remained at 12 hph. Among the non-essential FAA, alanine dropped the most by 12 hph with 4.6% of the concentration found in a recently fertilized egg remaining, while cysteine had increased 254.7 ± 26.2%. The yolk sac volume decreased rapidly in the first 12 hph and was further reduced 77.0 ± 2.5% from 12 to 24 hph. The oil globule depletion rate was a more linear decline from fertilized egg to 36 hph.  相似文献   

16.
The aim of this study was to compare the nutritional composition and effects of short periods with cultivated copepod nauplii versus rotifers in first‐feeding. Atlantic cod (Gadus morhua) and ballan wrasse (Labrus bergylta) larvae were given four different dietary regimes in the earliest start‐feeding period. One group was fed the copepod Acartia tonsa nauplii (Cop), a second fed enriched rotifers (RotMG), a third fed unenriched rotifers (RotChl) and a fourth copepods for the seven first days of feeding and enriched rotifers the rest of the period (Cop7). Cod larvae were fed Artemia sp. between 20 and 40 dph (days posthatching), and ballan wrasse between 36 and 40 dph, with weaning to a formulated diet thereafter. In addition to assessing growth and survival, response to handling stress was measured. This study showed that even short periods of feeding with cultivated copepod nauplii (7 days) had positive long‐term effects on the growth and viability of the fish larvae. At the end of both studies (60 days posthatching), fish larvae fed copepods showed higher survival, better growth and viability than larvae fed rotifers. This underlines the importance of early larval nutrition.  相似文献   

17.
It is well established in Denmark to rear calanoid copepods in outdoor tanks for use as live feed during turbot (Scophthalmus maximus) larval production. However, the copepod assemblages, composed of a mixture of all development stages and therefore body sizes, vary over time and do not always match the larval needs. When turbot larvae reach metamorphosis and are transferred indoor for weaning, the outdoor tank sediments may reveal vast amounts of copepod eggs undergoing dormancy. Here, we report a copepod species succession firstly among Centropages hamatus and then Acartia spp. both with resting eggs as part of their life cycles as a result of two different nutrients treatments and a control. We found a tendency to a higher egg production and indeed more eggs in the sediment of nutrient amended tanks. In fact close to 5 million eggs per square meter, making up to 400 million eggs per tank was found in the sediment after one production. Instead of discarding the sediment between production batches, we propose to collect it and generate an egg bank. These eggs can be stored for months to a year, however, according to the results, a large loss rate occurred, which could be potentially decreased by the optimization of storage conditions. Those procedures will enable hatchery managers to apply newly hatched copepod nauplii exactly when the turbot larvae start feeding which would potentially solve the, often occurring, mismatch between the time of start-feeding turbot larvae and actual available prey field.  相似文献   

18.
The copepod Cyclopina kasignete is a potential live food in aquaculture and its fatty acid components and digestive enzymes were investigated. Three dry algal products (mixed algae, Melosira sp. and Nannochloropsis oculata) and two fresh microalgae (Tisochrysis lutea and N. oculata) were fed to the copepod for 30 days. The essential fatty acids (EFA) in copepods were altered by feeding different types of dry algae. The copepod fed dry Melosira sp. or fresh T. lutea contained higher eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (ARA), protease and trypsin than fed on other algae. The copepod contained a similar fatty acid profile and digestive enzymes by feeding either dry or fresh N. oculata. Between fresh algal species, the copepod fed T. lutea contained higher EPA, DHA and ARA than that fed fresh N. oculata. The amounts of EPA and DHA in copepods were more concentrated than those in the dietary algae, suggesting that the copepod has the ability to accumulate some EFA. This study indicates that dietary algae can modify the nutritional composition and in digestive enzymes copepods, which in turn may be able to transfer suitable nutrients and digestive enzymes to fish larvae in aquaculture.  相似文献   

19.
The biological benefits of copepods as live feed for marine finfish larvae have already been well established in the literature. Copepods have better biochemical compositions that improve growth, reduce malpigmentations and allow successful farming of ‘new’ marine finfish species. However, their current usage is quite limited. One of the reasons has been lack of economic knowledge concerning the cost‐effectiveness of copepod application compared to other commonly used feed items such as the brine shrimp Artemia. In this study, a cost‐effectiveness analysis is made on two alternative live feed items (copepods and Artemia) in juvenile turbot farming. Unit cost of production and profit are compared between the two feeding regimes using a unique data set from an existing turbot fry production facility in Denmark. The result reveals that copepods are not only biochemically superior but they are also economically a cost‐effective alternative. Thus, a commercial use of copepods will significantly reduce the production costs for turbot. Furthermore, the unexploited economic potential can be utilized for the successful farming of other high‐valued marine finfish species such as tuna, flounders, cod, sole and halibut. Generally, the biochemical superiority coupled with economic benefits can lead to the commercial utilization of copepods as complementary live feed in the short run and in some situations as a substitute in the long run.  相似文献   

20.
Interest in the commercial production of cobia Rachycentron canadum continues to rise as additional insight is gained into the hardy and fast growing nature of this species. However, research regarding the biochemical composition of captive-spawned eggs and egg and larval quality remains scarce. Such data is essential as a common bottleneck to production is a steady supply of fingerlings for grow-out. This study quantified the biochemical composition and quality of cobia eggs produced over 2 spawning seasons by broodstock on a traditional ‘trash fish’ diet which is commonly fed to tank spawning cobia. Throughout the study, batch fecundity, proportion of floating eggs and percent hatch averaged > 1 million eggs,  0.8 and 70%, respectively. Batch fecundity was significantly higher during the second spawning season as a result of the increased size of the females which weighed 18/22 kg and 22/26 kg at the beginning of each season. A positive correlation was found between the proportion of floating eggs and hatch rate for both spawning seasons. No correlations were found between egg composition (total lipid (30.0 ± 1.1% dry wt), protein (25.4 ± 2.2% dry wt), carbohydrate (2.4 ± 0.3% dry wt), vitamin E (10.2 ± 0.6 μg/g wet wt) or dry weight (119.1 ± 5.5 μg/egg)) and egg quality (proportion of floating eggs, hatch rate, larval growth and larval survival). Further, no differences in egg composition were noted between seasons or over the course of each season. The fatty acid composition of cobia eggs varied between seasons possibly due to changes in the quality of frozen feed (fish, shrimp, squid) given to the broodstock. The only correlation between the fatty acid profile and egg quality was a decrease in the proportion of floating eggs as the total amount of n-3 highly unsaturated fatty acids increased. No relationship between egg quality and amino acid content was noted with the most prominent amino acids being glutamate, leucine, alanine, proline, lysine and aspartate nor were any differences detected between spawning seasons.  相似文献   

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