Food For Fish Larvae Research Articles

The Advantages of Inorganic Fertilization for the Mass Production of Copepods as Food for Fish Larvae in Aquaculture.

Copepods are commonly used as live feed for cultured fish larvae, but the current mass production method using organic fertilizers cannot meet the market demand for copepods. We evaluated the feasibility of applying an inorganic fertilization method, which is currently in use in freshwater and marine larviculture, to the mass production of copepods. For 30 days, and with five replicates of each treatment, we made comparative daily measurements of various parameters of (1) copepod cultures fertilized with commercially available condensed fish solubles (organic fertilization) and (2) other cultures in which the concentration of inorganic phosphorus was maintained at 100 μg P L−1 and that of inorganic nitrogen at 700 μg N L−1 (inorganic fertilization). With inorganic fertilization, pH fluctuated over a smaller range and much less filamentous algae grew in the tanks. The mean production of copepod nauplii over the course of the study was similar between the two treatments, but the combined density of copepodites and adult copepods was significantly higher with inorganic fertilization. Compared to commercial zooplankton products, copepods cultured with inorganic fertilization were smaller, were mixed with fewer (almost none) non-copepod contaminants, were also pathogen-free, and could be produced at the cheapest cost per unit output. Based on these results, we conclude that the inorganic fertilization method can profitably be adopted by commercial copepod producers to meet the demand from fish farmers, especially for small-sized copepods.

Ứng dụng marker phân tử DNA barcode trong định danh các mẫu Moina spp. phân lập tại khu vực Đồng bằng sông Cửu Long

Species of the genus Moina (Baird, 1850) often dominate the freshwater crustacean communities. Some species of Moina are used as food for fish larvae in aquaculture and as biological indicators in toxicological studies in aquatic environments. This study is aimed to investigate the species diversity of Moina spp. in the Mekong Delta region (An Giang, Dong Thap, Can Tho, Ben Tre and Long An province) by morphological analysis method and DNA barcoding method based on the mitochondrial cytochrome coxidase subunit I (mtCOI) gene sequence. Fourty eight Moina sp. specimens from this study were successfully sequenced their mtCOI genes. Five groups of Moina sp. were identified in 48 specimens examined, and the occurrence frequency of M. micrura was higher than that of M. macrocopa. The results revealed that 4/48 Moina sp. specimens belonging to group V showed 99% nucleotide similarity with M. macrocopa, whereas 31/48 specimens of group I exhibited 99% nucleotide similarity with M. micrura. Meanwhile, the mtCOI gene sequence divergence of group II (8/48 specimens), group III (4/48 specimens) and group IV (1/48 specimen) were more than 10% in comparison with the Moina mtCOI sequences published on National Center for Biotechnology Information (NCBI) Genbank®.

DNA Barcoding Reveals High Cryptic Diversity in the North Eurasian Moina Species (Crustacea: Cladocera).

Species of the genus Moina Baird (Cladocera: Moinidae) often dominate freshwater crustacean communities in temporary water bodies. Several species of Moina are used as food for fish larvae in aquaculture, as bioindicators in toxicological studies, and as common subjects for physiological studies. The aim of this paper is to estimate biodiversity of Moina in northern Eurasia using the standard DNA barcoding approach based on the cytochrome c oxidase subunit I (COI) gene. We analysed 160 newly obtained and 157 existing COI sequences, and found evidence for 21 phylogroups of Moina, some of which were detected here for the first time. Our study confirmed the opinion that the actual species diversity of cladocerans is several times higher than is presently accepted. Our results also indicated that Moina has the second richest species diversity among the cladoceran genera (with only Daphnia O. F. Mueller having a greater diversity of species). Our study strongly supports division of Moina into two faunistic groups: European-Western Siberian and Eastern Siberian-Far Eastern, with a transitional zone at the Yenisey River basin (Eastern Siberia). Here, we refrain from taxonomic descriptions of new species, as this requires a thorough morphological and taxonomic study for each putative taxon.

Long-term stability in modelled zooplankton influx could uphold major fish spawning grounds on the Norwegian continental shelf

Early life stages of fish spawned on the Norwegian continental shelf have long been suggested to depend on eggs and nauplii from the crustacean zooplankton Calanus finmarchicus for survival. Calanus finmarchicus overwinters in the deep basins of the Norwegian Sea, and gravid females must be advected onto the shelf prior to spawning if eggs and nauplii larvae are to serve as food for fish larvae. In this study, cross-shelf advection of C. finmarchicus is simulated over 52 years (1960–2011) using a numerical ocean model coupled with an individual-based model. The results suggest that cross-shelf transport of C. finmarchicus is surprisingly stable across years and that transport is particularly concentrated immediately upstream of the two major spawning areas for the Northeast Arctic cod (Gadus morhua) and the Norwegian spring-spawning herring (Clupea harengus), namely Lofoten and Møre, respectively. Two large topographical features, the Træna Trough and the Norwegian Trench, appear to be funnelling C. finmarchicus onto the shelf in these two areas. This could suggest that the fish spawning grounds outside Møre and Lofoten are, in part, maintained owing to stable interannual food supply in spring.

DNA identification of ciliates associated with disease outbreaks in a New Zealand marine fish hatchery

Ciliates associated with fish mortalities in a New Zealand hatchery were identified by DNA sequencing of the small subunit ribosomal RNA gene (SSU rRNA). Tissue samples were taken from lesions and gill tissues on freshly dead juvenile groper, brain tissue from adult kingfish, and from ciliate cultures and rotifers derived from fish mortality events between January 2007 and March 2009. Different mortality events were characterized by either of 2 ciliate species, Uronema marinum and Miamiensis avidus. A third ciliate, Mesanophrys carcini, was identified in rotifers used as food for fish larvae. Sequencing part of the SSU rRNA provided a rapid tool for the identification and monitoring of scuticociliates in the hatchery and allowed the first identification of these species in farmed fish in New Zealand.

Natural spawning, early development and first feeding of the semicircle angelfish [Pomacanthus semicirculatus(Cuvier, 1831)] in captivity

Successful natural spawning of Pomacanthus semicirculatus in captivity from 11 September to 18 October, 2006 is described for the first time. Each female laid an average of 230 000 eggs during the spawning period. Fertilized eggs were spherical, transparent and buoyant and had a mean diameter of 0.61 ± 0.03 mm (mean ± SD). Embryonic development lasted 18–21 h at 28.5 °C. Newly hatched larvae were 1.35 ± 0.02 mm in total length (TL) with 27 (12+15) myomeres and had an oil globule in the ventroposterior area of the yolk sac. Larvae completed yolk absorption within 3 days post hatching at 2.37 ± 0.05 mm TL. Larvae were fed either 100% microalgae (Nannochloropsis sp.), 100% s-type rotifers (Brachionus rotundiformis), 100% dinoflagellates (Gonyaulax sp.) or different combinations of the three (50%:50%:0%, 30%:35%:35%) to determine the effect of live feed on the survival rate. The survival was significantly (P<0.001) better in larvae fed a combination of diets (30%: 35%: 35%) than others. These results indicate that P. semicirculatus is a potential species for captive-breeding programmes and the use of a combination of diets (microalgae plus s-type rotifers and dinoflagellates) may be a suitable first food for fish larvae.

Evaluation of the Ciliated Protozoa, Fabrea salina as a First Food for Larval Red Snapper, Lutjanus campechanus in a Large Scale Rearing Experiment

ABSTRACT One of the major challenges of culturing of red snapper, Lutjanus campechanus, is providing an appropriate food source at onset of feeding. Ciliates are abundant in marine waters but their significance as a first food for fish larvae is poorly understood as many have no lorica to facilitate their identification in the gut of a larval fish. Fabrea salina is a naked heterotrich ciliate that can be mass cultured at densities up to 84 ± 10 ciliates/mL in 7 days. Its appropriateness as a first food for red snapper larvae was evaluated in a green-water setting using 1-m3 tanks. Larvae were stocked at 10/L, 36 h post-hatch, before first-feeding commenced. Larvae were fed either (1) copepod nauplii, 20–75 μm, only from days 1 to 10; (2) copepod nauplii from days 1 to 10 plus F. salina from days 1 to 5; or, (3) F. salina only from days 1 to 3 plus copepod nauplii from days 4 to 10. Copepod nauplii were added at 2/mL and ciliates were added at 5/mL. Survival after 28 days was 0.28 ± 0.15% for larvae given only copepod nauplii and 2.39 ± 2.75% for those given F. salina and copepod nauplii. Larvae given only F. salina did not survive past 4 days post-stocking. Larvae were more actively feeding in the tanks given F. salina and copepods as first foods with 34.6 ± 8.5% mean daily reduction in copepod nauplii compared to 15.8 ± 16.2% reduction when only nauplii were provided.

Preliminary trials to rear the copepod Temora stylifera as food for fish larvae

Copepods represent an important natural food supply for many fish larvae but they are not commonly used in aquaculture. The aim of this project is: 1) to set up an experimental re-circulating system to breed the copepod Temora stylifera and 2) to replace Artemia salina with T. stylifera as live food for Sparus aurata larvae. The choice of this copepod species has been based on both its abundance in the Mediterranean as well as its characteristics in terms of size and nutritional value. The re-circulating system consists of a collecting water tank of 1,000 litre of capacity, a thermoregulation system, two 500 litre tanks to rear adults and two 200 litre tanks to collect nauplii. The system allows the computerised water re-circle and to concentrate and collect nauplii through their positive response to light. It can work both in a partial re-circle way, for the thermoregulation only, as well as in a total re-circle way for the water purification through mechanic and biological filters. The culture system can host a minimum of 5,000 T. stylifera females, which will daily produce 75,000 nauplii, approximately. In a preliminary phase of this study, different uni and pluri-microalgal diets have been tested in order to maximise T. stylifera egg production rate and hatching success. Algae with high fatty acids contents were used to improve the nutritional value of nauplii and copepodids. Uni-algal diets, Prorocentrum minimum and Isochrysis galbana, were singularly provided at a mean carbon concentration of 1mg C/l. Egg production and hatching success were 19.4±11.4 eggs/female/day and 63.8% for copepods fed on P. minimum and 4.5±7.8 eggs/female/day and 42.2% for those fed on I. galbana, respectively. In the pluri-microalgal diets, P. minimum was still supplied at 1mg C/l, whereas I. galbana was given as enrichment food at high concentrations based on the size ratio of P. minimum and I. galbana. At present, the best results in terms of egg production (31.8±16.8 eggs/female/day) and hatching success (75.4%) were obtained with the mixed diet of P. minimum and I. galbana.

Influence of climate variability on whitefish (Coregonus lavaretus) year-class strength in a deep, warm monomictic lake

The year-class strength (YCS) of Blaufelchen (Coregonus lavaretus) in deep Upper Lake Constance was analysed for a 52-year period, from 1947 to 1998. Despite strong anthropogenic influences on the species' population dynamics due to cultural eutrophication and oligotrophication, intense fishing, and large-scale stocking, the influence of climate variability associated with the North Atlantic Oscillation (NAO) is apparent in the data set. This influence is significant although large-scale stocking of cold-bred larvae was performed to avoid a mismatch of larvae with their food. The importance of stocking on YCS, however, is unclear and was only detectable when analysing a subset of the data. In addition to climate variability a yet unidentified factor related to zooplankton suitability as food for fish larvae, and density-dependent mortality probably related to cannibalism do significantly influence YCS. The NAO seemed to influence YCS twofold, through temperature effects on egg development time and on larval growth rate. The first of these two mechanisms is related to the NAO via a time lag of 1 year due to the specific mixing dynamics of warm monomictic Lake Constance. Hence, a warm winter in the year before spawning results in earlier hatching of larvae, that is, hatching is decoupled from the actual meteorological conditions. This should make the larvae very prone to mismatch the dynamics of their food. However, we found no evidence for such a mismatch in this 52-year data set.

Summer ichthyoplankton, food supply of fish larvae and impact of invasive ctenophores on the nutrition of fish larvae in the Black Sea during 2000 and 2001

Qualitative composition and abundance of both ichthyoplankton and small forms of zooplankton were evaluated by field studies in the northern (the Crimea near Sevastopol) and southern (Sinop region and TEEZ) Black Sea during the summers 2000 and 2001. A tendency of increasing the species richness, abundance of fish eggs and larvae as well as zooplankton (which is the food for fish larvae) was observed over a period of Mnemiopsis leidyi and Beroe ovata co-existence. The eggs and larvae of the Mediterranean migrants—bonito and bluefish appeared again in the coastal waters near Sevastopol, which testified to favourable conditions for the spawning and nutrition of these fish species and their larvae. Aborigen copepod Oithona nana was found in the Crimean coastal waters although earlier in the 1990s it had completely vanished. Although rare in the 1990s copepods Centropages ponticus and Paracalanus parvus appeared in inshore waters as well as Pontellids species. Observed increases in species number and abundance of both ichthyoplankton and small zooplankton (≤500 μm), which promoted survival and development of fish larvae, were attributed to reduced predatory impact of Mnemiopsis on prey zooplankton after the arrival of Beroe in the late 1990s. However, the influence of Mnemiopsis continued to be significant during the short period of its peak occurrence in late summer. When this period coincided with the appearance of fish larvae, a negative impact on their survival could be predicted due to a low concentration of food items for larvae feeding.

Culture of harpacticoid copepods: Potential as live feed for rearing marine fish

Copepods are useful as food for marine fish cultivation, in terms of both nutrition and ease of culture. Harpacticoid copepods are favoured over calanoids, since harpacticoids, as a result of their benthic habitat, can be reared at much higher densities. However, their benthic nature also makes mass culture difficult, since large surface areas must be provided. Within Harpacticoida, Tisbe spp. seem most useful, having high overall fecundity, and positive phototaxis of the nauplii. Harpacticoids can synthesise de novo several nutritionally important essential fatty acids (EFA), making them desirable as food for rearing marine fish. However, a diet rich in EFAs (e.g. animal derived feed) improves the productivity of copepod cultures, suggesting that the synthesis of EFA is rate-limiting for their reproduction. The nature of the substratum is also important in maintaining a good population, since harpacticoid biomass is more dependent on surface area than volume of a culture. Heterogeneous substrates can support large cultures because of their high surface area, but efficient cleaning methods are necessary. Frequent harvesting of populations will maintain good water quality and an overall low density of sexually mature copepods, raising naupliar productivity overall. Over-harvesting will naturally deplete the population. Harpacticoids are generally tolerant of environmental fluctuations but they do have temperature and salinity optima, and these will be species- and strain-dependent. Harpacticoid copepods are better food for fish larvae than Artemia, because of their ability to synthesise EFAs. The nauplii of harpacticoids are energetically poor but appear to have an appetite-stimulatory effect. Uneaten nauplii grow within the fish rearing tanks and graze on the walls, building up their own nutritional value and maintaining tank hygiene.

Enrichment of Artemia nauplii in PUFA, phospholipids, and water-soluble nutrients using liposomes

Different liposome formulations, includingseveral combinations of membrane composition,type of vesicle (multilamellar and largeunilamellar vesicles), preparation method, andvehiculated nutrient, have been assayed asbioencapsulation products to enrich Artemia nauplii with nutrients for feeding fish larvae.The stability of the liposome preparationsunder conditions of use as enrichment producthas been tested using water soluble fluorescentmarkers as leakage indicators. The content ofthe fatty acids and lipid classesbioencapsulated in Artemia nauplii withliposomes has been analyzed by gas and thinlayer chromatography, respectively, andcompared with other enrichment products. Theeffect of the liposome enriched Artemianauplii used as food for fish larvae has beenevaluated in sea bass cultures. Liposomes withhigh content in polyunsaturated fatty acidsleak out more than 50% of their aqueous phasein less than 2 hours, unless they arestabilized with cholesterol and formed as largeunilamellar vesicles. Such vesicles hold70% of the encapsulated material for 8 hours.Liposome enriched nauplii in this study reflectthe influence of the enrichment products,however, they are far from the commercialemulsion (Super Selco) in terms ofdocosahexaenoic acid content, except for thenauplii enriched with liposomes made of purekrill phospholipid extract by the method ofdetergent solubilization. The liposome enrichednauplii show a higher amount of polar lipids incontrast to the feed enriched with emulsions.The larvae fed liposome enriched nauplii haveonly a slightly lower docosahexaenoic acidcontent than those fed emulsion enrichednauplii. The results obtained confirm thesuitable potential use of liposomes as foodsupplement in larviculture. Problems andadvantages are discussed.

Effects of salinity, cold storage and enrichment on the calanoid copepod Gladioferens imparipes

Intensive culture techniques have been developed for the calanoid copepod Gladioferens imparipes. Despite reliable, long-term production of nauplii from these cultures, further improvements are required to maximise the number and nutritional content of nauplii available for feeding to larval fish. The effects of salinity on copepod production and prolonged algal enrichment on nutritional content of nauplii is shown. Use of cold storage for accumulating large numbers of nauplii and storing adults with minimum maintenance is evaluated. The size range of G. imparipes life history stages, particularly early nauplii, is determined. Maximum copepod production was obtained in salinities of 18–27‰. Fatty acid content of nauplii increased with prolonged enrichment. Copepod survival was poor at 4°C. At 8°C, nauplius survival was 99% after 12 days and adult survival was 90% and 68% after 21 and 42 days, respectively. Early nauplii were 67 μm in width, similar to nauplii used to rear larvae with small gapes at first feeding. Implications of these results to the use of G. imparipes as food for fish larvae is discussed.

The effect of abiotic factors on the hatching of Moina micrura Kurz, 1874 (Crustacea: Cladocera) ephippial eggs.

The roles of some abiotic factors in controlling the hatching rates of Moina micrura ephippial eggs were investigated. Determination of optimum hatching conditions would be important in developing the use of this species as a food for fish larvae in aquaculture. Ephippia were exposed to different treatments in the laboratory, and monitored for hatching over a period of seven days. Optimum hatching conditions were: pH 5-9, temperature 25 degrees C, photoperiod eight or more hours light per day and light intensity equal to or greater than 850 lux. Differences in water ionic concentrations (from deionized water to 880 mg.L-1 of selected salts) had no effect.

Influência de fatores abióticos na eclosão de ovos dormentes do rotífero Brachionus calyciflorus Pallas (Monogononta, Ploima)

The factors involved in the induction of resting eggs development and hatching are poorly understood for Brachionus calyciflorus populations of South Hemisphere. The role of some abiotic factors in controlling the hatching rates of B. calyciflorus resting eggs was investigated. Determination of optimum hatching conditions would be important in developing the use of this species as food for fish larvae in aquaculture. Resting eggs were exposed to different treatments in the laboratory, and monitored for hatching over a period of five days. Optimum hatching conditions were: pH 5-9, water ionic concentrations from 220 to 880 mg.l-1 of selected salts, temperature 25 - 30oC, photoperiod eight or more hours light per day, and light intensity equal to or greater than 850 lux.

Biochemical and enzymatic characterization of decapsulated cysts and nauplii of the brine shrimp Artemia at different developmental stages

Decapsulated Artemia cysts were used to study the factors which induce the superior performance of live organisms as food for fish larvae. The biochemical composition, the in vitro protein digestibility, and the total proteolytic and trypsin activities in cysts and nauplii of Artemia were determined at different developmental stages as a function of incubation time. Six different incubation times were studied: 1, 6, 11, 16, 21 and 25 h of development, which cover cyst and early nauplii stages. The individual dry weight of Artemia decreased through development. The individual protein and lipid content ( μg ind −1) remained constant during development until the time of hatching after which they decreased slightly. However, no significant incubation effect was found. Small changes in amino acid and fatty acid composition were found during development, but is assumed that they are too small to be of nutritional importance to fish larvae. No major changes were observed in protease activities measured at acid and alkaline pH during the first 25 h of development. From the alkaline proteases, no significant change in trypsin activity was detected during cyst and early nauplii development. From the point of view of exogenous enzyme contribution to fish larvae, there seems to be no difference whether feeding decapsulated cysts or newly hatched nauplii, since no difference in qualitative protease composition was found during the first 25 h of Artemia development. The relative contribution of Artemia proteases to the digestion of food by fish larvae is discussed.

Distribution of Brachionidae (Rotifera, Monogononta) in Inner Mongolian Waters

AbstractTwo‐hundred and fourty‐six freshwater and saline‐alkaline waters in Inner Mongolia, P.R. China were surveyed for Brachionidae. Twenty‐nine brachionid morphospecies (33 taxa) are recorded, four are new to China. Some data on their distribution, and comments on selected taxa are provided. Brachionus asplanchnoides (stat.nov.) is reinstated at the morphospecies level. We suggest that this taxon may be used in aquaculture, considering that, by its large size, it extends the size range of brackish‐water Rotifera potentially available as food for fish larvae.

Diel vertical distribution of fish larvae their prey in nearshore waters of southern California

Ichthyoplankton was sampled with bongos and microplankton was sampled with a pump at 3 to 5 discrete depths over isobaths of 8, 22 and 30 m, during a winter cruise in Santa Monica Bay, California. Although no thermocline was present, fish larvae were significantly stratified (p 6 mm in length) did not. Only 9% of northern anchovy larvae contained at least 1 food particle (i.e. 9 % feeding incidence), compared to 76 % for white croaker larvae. Early life stages of copepods were important foods for both fish species. Bivalve veligers and tintinids occurred relatively frequently in the guts of white croaker but not northern anchovy. There was little relation between daytime feeding distribution of fish larvae and esculent microzooplankton, except that distributions of white croaker and bivalve veligers were significantly correlated (p < 0.05). The low densities of bivalve veligers in samples (2 = 3 I ' ) , and paradoxically, their frequent occurrence in the guts of white croaker, are discussed in relation to their availability as food for fish larvae. The die1 vertical positions of neritic fish larvae may, in part, be an expedient strategy for their retention in shallow waters.

The suitability of frozen and freeze-dried zooplankton as food for fish larvae: A biochemical test program

Total protein, nitrogen and lipid as well as calorific content, ash content, inorganic ions and amino acids were measured in various types of zooplankton, Artemia salina nauplii and Moina sp, including summer and winter samples from Austrian lakes. The activities of three enzyme systems, L-lactate dehydrogenase (LDH), proteases and NADH 2-dependent dehydrogenases, in zooplankton are not affected by freezing or freeze-drying, or by storage below −18°C. The half-life time of LDH in freeze-dried material is 280 days at room temperature, and 3 h at 80°C. When frozen or freeze-dried zooplankton material is introduced into water, enzyme activity is rapidly lost. After 10 min at 9°C, only 27% of the original LDH activity remain in the plankton material, whereas the rest can be recovered in the incubation medium. Nearly all the free and about one-third of free plus protein-bound amino acids are lost from plankton samples incubated for one hour. The leaching experiments suggest the presence of unknown, non-protein sources of “bound” citrulline and histidine in the plankton. During the process of leaching nearly all of the bound lysine and arginine are liberated from plankton proteins by the action of the still viable proteases. Pelleting freeze-dried plankton reduces the rate of leaching considerably. After 10 min in water at 9°C, about 85% of the original LDH activity can still be found in the potential food material.

A simple and inexpensive system for continuous monoxenic mass culture of marine microalgae

A continuous monoxenic culture system for marine phytoplankters was set up utilizing low-cost and easily available materials. It consists of one or more 50-l polyethylene bags equipped with novel closing devices and tubing attachments. Supply of culture medium and air is automated, a culture-density feed-back being the controlling parameter. Illumination is obtained with a vertical series of fluorescent lamps of two types: Osram Fluora and Daylight. The intensity is about 5 klux at the bag surface. Routine operations are limited to harvesting which is achieved by periodic removal of algae suspension. The system is intended to produce adequate algae inoculum for large-volume batch cultures in hatcheries using microalgae as food for fish larvae or for invertebrates.