Growth and prey selection by Atlantic salmon yearlings reared on live freshwater zooplankton

The experiment was carried out in a coastal lake near Bergen, Norway. Two experimental groups of Atlantic salmon (Salmo salar) yearlings were fed with live zooplankton in an artificial current. A third group, given commercial dry food pellets, was used as a control. The offered zooplankton biomass reached a maximum in the second week of July. The caladoceran Daphnia longispina dominated the zooplankton at this moment. A stock breakdown for this species was soon observed. The salmon yearlings preferred cladocerans. At the height of the zooplankton occurrence, Daphnia became the only prey species observed in the stomachs — and a prey selection for larger individuals was observed when food was in surplus. Earlier in the period the salmon selected the largest individuals of two cladoceran species of different shape, pigmentation and size at the same time. In the experiment live zooplankton was recognised as a satisfactory food when it occurred in sufficient amounts, compared with commercial fry food pellets. Best mean growth rate of zooplankton-fed fish was 0.92 mm/day. Negative growth rate was observed when low zooplankton densities occurred.     

The risk of parasite transfer to juvenile fishes by live copepod food with the example Triaenophorus crassus and Triaenophorus nodulosus

Natural zooplankton is a potential food resource for juvenile fish in fish farms as it is a good source of fats, carbohydrates, and protein. However, it is also a potential source of parasites and pathogens. The present study was conducted (1) to estimate the risk of parasite transfer by live copepod food under intensive farming conditions using the parasites Triaenophorus crassus and Triaenophorus nodulosus as example and (2) to look for strategies to avoid parasite infestation of juvenile fish.An easy and routinely applicable aniline blue staining method was developed to check the infestation levels of copepods with procercoids during the on-growing season of juvenile fish. From the copepod species occurring in zooplankton Cyclops spp. was infested frequently (9.4 ± 12.0%, maximum 38.7%), Diaptomus spp. infrequently (1.5 ± 1.6%, maximum 3.2%), Daphnia spp. never. Juvenile grayling, Thymallus thymallus, and corgonids, Coregonus sp., which had been fed with natural zooplankton revealed infestations rates with T. crassus of circa 5%, with T. nodulosus of circa 10%. As the occurrence of procercoids in the zooplankton was temporary limited, Triaenophorus infestation can be avoided by using artificial food instead of live copepods during the risky season.To prevent parasite infestation of juvenile fish methods were investigated to eradicate procercoids from copepods by chemical treatment (sodium chloride, hydrogen peroxide, citric acid treatment) and by freeze-thawing methods. Chemical methods failed to remove procercoids. In fish, which had been fed with frozen thawed zooplankton, no Triaenophorus spp. infestation was observed. Their survival rates were similar as in the control fed with live zooplankton, however the weight of the fish was significantly lower.     

Controlled propagation of the African catfish,Clarias lazera (C. & V.): III. Feeding and growth of fry

The suitability of some common, natural and artificial feedstuffs for the rearing of fry of Clarias lazera (C. & V.) was investigated in 2 experiments.It was found that a dry trout starter, an experimental dry feed and dried inactive yeast were not suitable feeds for rearing C. lazera fry. Neither could ground Clarias fingerlings or frozen zooplankton be used. By contrast, frozen Artemia and especially live Artemia and live zooplankton gave good results. After 4 weeks the fish thus fed had attained an average weight of 0.3 to 1 g and survival ranged from 50 to 96%.Feeding in excess of satiation and feeding 24 h/day gave the fastest growth, although the differences in comparison with feeding Artemia or live zooplankton to satiation 4 times per day were not significant. The specific growth rate (% body weight) of these fish decreased from 68% at the start of the experiment to 9% after 28 days.     

Early weaning of cuttlefish (Sepia officinalis,L.) with frozen grass shrimp (Palaemonetes varians) from the first day after hatching

The suitability of early weaning cuttlefish using frozen grass shrimp, and its effects on growth and mortality was determined in a 50‐day experiment. Three food groups were used. One group (C) was fed with live prey until 25th DAH and weaned with frozen prey until the end of the experiment. In the other two groups, weaning started at the fifth DAH (W5) and first DAH (W1), also with frozen diet. Significant differences were found between C and the remaining treatments (P < 0.05) for mean wet weight (MWW), instantaneous growth rate (IGR), biomass (B) and mortality at the 25th and the 50th DAH. Despite the lower growth (~1/3 of the achieved with live food) and higher mortality (3% obtained by C versus 23% in the W1 and W5 groups), C cuttlefish presented a similar weight gain tendency to W1 and W5 groups after weaning. This is the first record of early acceptance (at the first DAH) of frozen food by cuttlefish hatchlings. These differences could be related with digestive enzymes of cuttlefish and prey, changes in nutritional composition and amount of captured prey, etc. Future research should also address the effects of this early weaning on cuttlefish life cycle.     

A Preliminary Evaluation of Naturally Occurring Organisms,Distillery By-Products,and Prepared Diets as Food for Juvenile Freshwater Prawn Macrobrachium rosenbergii

The relative acceptability and suitability of naturally occurring pond organisms identified as likely natural food items for juvenile freshwater prawn, Macrobrachiurn msenbergii, were evaluated under controlled conditions. The potential of direct consumption of materials used as organic pond fertilizer (distillers dried grains with solubles [DDGS] was also evaluated. Growth and survival of prawn fed gastropods, oligochaetes, zooplankton, or DDGS were compared with those fed a nutritionally-complete pellcted diet (control). Groups of five juvenile prawn (average weight 1.66 ± 0.10 g) were stocked into eighteen 7.5-L glass aquaria. Dietary treatments were evaluated in triplicate aquaria for 21 days. Prawn fed live zooplankton exhibited a significantly higher rate of weight gain (P < 0.05) than drawn in other treatments, as measured by differences in slopes of regression lines for weight gain over time. There were no significant differences (P > 0.05) in rates of gain for prawn fed a complete diet and those fed DDGS or gastropods. Prawn fed oligochaetes grew significantly slower (P < 0.05) than those fed the prepared diet. Results indicate that juvenile prawn as large or larger than 2g can utilize live zooplankton and that DDGS may be consumed directly by prawn. Thus, DDGS may serve a dual role as a feed and pond fertilizer. Additional research in pond management strategies that maximize zooplankton and gastropod numbers and the potential of DDGS as a combination food/fertilizer in freshwater prawn production ponds should be conducted.     

Evaluation of Naturally-Occurring Organisms as Food for Juvenile Crayfish Procambarus clarkii1

Nutritionally important food items for crayfish have been difficult to identify and little information exists for third instar (first-feeding) crayfish. In this study, three major groups of potentially-important foods were fed to communally-reared third instar crayfish (Procambarus clarkii) and weight gain and survival were measured over a 30 day period. Mean weight gain (% increase) of crayfish fed the zooplankton Daphnia magna alone or in combination with other food items, ranged 2, 277–3, 239%, while mean weight gain of crayfish fed unidentified aquatic bacteria, the aquatic macrophyte Myriophyllum spicatus, combinations of bacteria and plant, or a negative control ranged 254–767%. No significant interaction of food items was detected. Bacteria appear to be a utilizable nutritional source for juvenile crayfish, but, using the methods employed in this study, do not support maximum rates of weight gain. Thus, pond management strategies that maximize zooplankton populations at the time of crayfish hatching might be beneficial.     

Larval rearing of African carp,Labeo parvus Boulenger, 1902 (Pisces: Cyprinidae), using live food and artificial diet under controlled conditions

This study aimed at (1) evaluating the efficacy of live food organisms (Artemia and natural zooplankton) and an artificial diet in the larval rearing of African carp Labeo parvus and (2) determining appropriate rearing conditions. After yolk sac resorption, the larvae were separated into five different feeding trials with two replicates. At the end of the larval rearing period (28 days post‐hatching), the highest (94.6%) and the lowest (53.7%) cumulative survival rates were found when larvae were fed with natural zooplankton for 7 days followed by Nippai food for 21 days, and when larvae were fed from the beginning of exogenous feeding with Nippai food only respectively. The significant highest body weight (351.6 mg), total length (34.4 mm) and specific growth rates (15.5%day^?1) were recorded when the larvae were fed with Artemia nauplii for 14 days followed by Nippai food for 14 days. The lowest growth performance (body weight and specific growth rates) were obtained when larvae were fed exclusively Nippai food. These results indicate that L. parvus can be successfully cultured in indoor nursery systems from hatching to the early juvenile stage.     

Elevage des larves de Loup (Dicentrarchus labrax, L.) a l'aide d'organismes du zooplancton congele: Resultats preliminairesRearing of sea-bass (Dicentrarchus labrax L.) larvae on frozen zooplankton: Preliminary results

Larvae (fry) of sea bass (Dicentrarchus labrax L.) were successfully reared from the mouth-opening stage to the age of 120 days being fed only on frozen zooplankton (Rotifera, Copopoda and Daphnia). This inert food is well accepted when left in the water less than 4 h after being thawed, but is rejected afterwards. The larval development can be compared to that obtained by artificial food and the survival rate is similar to that obtained by living plankton.     

A comparison of artificial and natural foods and their combinations in the rearing of goldfish, Carassius auratus (L.)

Intensive grow‐out of goldfish, Carassius auratus (L.), larvae and juveniles in closed systems requires the control of environmental conditions and feeding. This study investigates the use of different types of live food and combinations of live food and dry food in a series of four rearing experiments. Juvenile goldfish can be weaned from Artemia onto live food at about 24 days after the onset of feeding without causing a reduction in growth and survival. The replacement of Artemia by Daphnia at day 10 appears feasible, as growth and survival were not significantly affected. Fish fed decapsulated Artemia cysts grew better than fish fed live Artemia. Within the first 14 days, goldfish juveniles should be fed at least 155 cysts per fish per day to achieve fast growth and to minimize size variation.     

Review of the present knowledge of rearing whitefish (Coregonidae) larvae

Intensive fishing of whitefish (Coregonus lavaretus) and a survival rate of the early stages of the fry that is generally too low lead, at present, to the whitefish stocks not being able to utilize fully the natural food resources now produced many times in excess of the requirements by the eutrophication of lakes.Feeding experiments in aquaria have, for several years, shown very impressively, that there are two main reasons for the high mortality of the larvae in the natural environment: high sensitivity to even a short-term lack of food and specific food requirements — the necessity for the larvae to feed on the juvenile stages of certain zooplanktonic crustaceans.Artificial breeding of whitefish eggs in cold water at 1°C caused a delay in hatching of about 8 weeks compared with natural hatching, thus allowing the release of the larvae at a time when the density of zooplankton is about ten times higher and mainly juvenile stages of crustaceans needed by the whitefish larvae are present. Hence, this is one proven way of improving the survival rate of whitefish larvae in the natural environment.Young fish, after metamorphosis, have less specialized food requirements than the larval stage and can even be fed adequately with dry food. In rearing the larvae, natural zooplankton can be replaced by the nauplii of the brine shrimp, Artemia salina. Larvae have not yet been reared on dry food or even on slowly frozen zooplankton or Artemia, but Artemia nauplii shock-frozen in liquid nitrogen (at ?196°C) were found to be as acceptable as living ones and allowed metamorphosis of the larvae to take place. The substance, assumed to be present in the living Artemia, which was lost on slow-freezing but retained after shock-freezing and was shown to be essential to the whitefish larvae, was insoluble in water. Biochemical investigation and identification of this substance are urgently required in order to synthesize an artificial complete food for whitefish larvae.As long as this artificial food is not available, attention will have to be focussed on rearing the larvae in natural ponds where the specific and essential zooplankton can be encouraged.     

Effects of feeding live or frozen prey on growth, survival and the life cycle of the cuttlefish, Sepia officinalis (Linnaeus, 1758)

The effects of feeding live or frozen grass shrimp (Palaemonetes varians) to the cuttlefish, Sepia officinalis, were determined in two experiments. During Experiment I, two populations of 30 cuttlefish (aged 90 days old) were fed either live or frozen grass shrimp. Cuttlefish fed live shrimp grew larger, matured earlier, had a shorter life cycle (255 days) than the ones fed frozen shrimp (282 days), and had lower mortality. Females from the group fed frozen shrimp matured a month later but were significantly larger, 130.9 ± 38.5 g, compared to 74.2 ± 16.0 g, laid larger eggs, 0.47 ± 0.11 g, compared to 0.28 ± 0.10 g, and had higher individual fecundity (411 eggs female⁻¹, compared to 150 eggs female⁻¹). Newly born hatchlings from both groups had similar weights. During Experiment II, six replicates of 15 cuttlefish (50 days old) were used, three for each of the two diets tested. The exact same amount of live or frozen shrimp was provided to both populations twice a day. No differences in growth and feeding rates or food conversions were found at the end of the experiment. During the first week, cuttlefish fed frozen shrimp grew larger, and had higher conversion rates, compared to the ones fed live shrimp. Mortality was higher for the group fed live shrimp (36.6%) in Experiment II, mainly occurring during the last week. Mortality for cuttlefish fed frozen shrimp in Experiment II was 2.2%. Results obtained here indicate that freezing the grass shrimp only had a negative effect on the survival of S. officinalis in Experiment I. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of initial weight during the change from live to compound feed on the survival and growth of four cyprinids

In a series of trials, larvae of common carp (Cyprinus carpio L.), silver carp (Hypophthalmichthys molitrix Rich.), grass carp (Ctenopharyngodon idella Val.) and bighead carp (Aristichthys nobilis Rich.) were transferred directly from a diet of zooplankton to a dry, compound feed. The dry diet was based on a previously described diet of yeast and freeze-dried animal tissues. Common carp larvae showed the best growth on live zooplankton (46.3 mg individual weight after 14 days) compared to fish fed solely on dry feed (13.8 mg). Transfer of common carp larvae to dry diet when they reached 4.27 mg significantly improved growth, but no dependence was observed on two diets tested. Grass carp larvae grew equally well on live food and on the best compound diet (8.7 mg after 15 days), but fish transferred to dry diet at 4.3 mg showed significantly improved growth. The growth rate, however, depended on the diet (12.9–23.5 mg). Silver carp grew better when fed solely on dry diet (23.5 mg), compared to live zooplankton (15.8 mg after 15 days), but this was due to an insufficient supply of suitable live food. Transfer of fish at 6.8 mg to dry diet improved the growth only slightly, and dependence on the kind of dry diet was observed. Bighead carp larvae showed better growth on live zooplankton (42.2 mg after 15 days) than on the best compound diet (18.6 mg). Fish transferred at 5.6 mg to dry diets showed good growth, but high mortality was observed. It was concluded that common carp larvae are the most “difficult” to raise solely on dry diet, whereas silver carp larvae are the “easiest”. The present study has shown that the transfer of four cyprinids to dry diet improved their growth rate and that the transfer is possible at the individual wet weight of 5–6 mg.     

Rearing the spotted seahorse Hippocampus kuda by feeding live and frozen copepods collected from shrimp ponds

This study evaluated the use of live and frozen copepods collected from shrimp ponds for rearing juveniles of the spotted seahorse Hippocampus kuda. Protein and HUFA contents in frozen copepods were all higher than in Artemia nauplii, the conventional live food for seahorse juveniles. The results of this study showed that copepods can be used as feed for rearing seahorse fry and juvenile. The spotted seahorse showed obvious preference for live copepods and rarely fed on dead copepods on the tank bottom. Furthermore, the combination of frozen copepods and live Artemia nauplii resulted in highest growth and highest survival of the experimental seahorses. Further research on possible effects of DHA:EPA ratio on survival and growth of young H. kuda is recommended.     

Rearing of European grayling, Thymallus thymallus L., larvae using dry and live food

Abstract. European grayling, Thymallus thymallus L., larvae, after hatching, were fed solely on a dry food diet and compared to those fed live zooplankton. After 28 days of rearing at temperatures ranging from 15·0°C to 18·3°C (mean, 16·4°C) fish fed the dry diet reached 0·21 g individual wet weight and 31mm in total length; those fed zooplankton reached 0·13g and 27·5 mm respectively. The survival rate of fish fed the dry diet was higher (56·6%) than that of fish fed the live food (40·7%). Results are discussed in the light of the development of the alimentary tract in the early ontogeny of grayling.     

Dietary essentiality of ascorbic acid in rohu larvae: Quantification with ascorbic acid enriched zooplankton

Carp larvae, like any other fish larvae dependon natural food during first few days of theirlife. In nursery conditions, high mortality andslow larval growth are of common occurrence;sub-optimal nutrition might be a possiblereason for such consequences. To improve thesituation the effect of feeding ascorbicacid-enriched live food on survival, growth,tissue biochemical composition includingascorbate level was evaluated in first feeding(3 days old) larvae (av. wt. 2.2 mg) of therohu carp, Labeo rohita (Ham.) for aperiod of 15 days (temp. 28.6 ± 1 °C)under natural photoperiod. The larvae (stockingdensity 10 l^–1) were offered enriched andnon-enriched zooplankton ad libitumfollowing a rigid schedule with four feedingregimes, each having 3 replicates. In treatmentT₁, non-enriched zooplankton (Moina,Daphnia, Cyclops, Diaptomus) and in T₂,T₃, T₄ ascorbic acid enriched (12 henrichment) zooplankton [@10%, 20% and 30%ascorbyl palmitate (AP) inclusion in diet ofzooplankton] were offered. Highest survival(90%) and growth (9563% live weight gain)could be seen in T₃ group and the lowestin T₁ (62% survival and 805% live weightgain), thus confirming the dietary essentialityof ascorbic acid for rohu larvae. Therequirement has been shown to be 1409 µg/gdry diet. Whole body tissue analyses for crudeprotein, total lipid and RNA: DNA ratiofollowed the same trend as that of growthresponse and percent survival. Significantpositive correlation (r = 0.949 and 0.861) couldbe found with muscle RNA/DNA ratio and muscleRNA content with specific growth rate indifferent treatments. Significant differencewas found in tissue ascorbate levels betweenenriched plankton fed groups, being highest in T₃. Such live foodmediated vitamin transfer might be an effectivemeans to provide higher plane of nutrition forhigh survival and rapid growth for rohu larva.     

Successful culture of larvae of Litopenaeus vannamei fed a microbound formulated diet exclusively from either stage PZ2 or M1 to PL1

In three separate experiments, harpaticoid copepods Tisbe monozota (alive and dead) and a microparticulate microbound diet were evaluated as alternatives to live Artemia nauplii as food, beginning at either stage PZ2 or M1, in the larval culture of Litopenaeus vannamei. Larvae were cultured in 2 L round bottom flasks at a density of 150 L^− 1 (Experiment 1) and 100 L^− 1 ( 3.2 and 3.3) at 28 °C, 35‰ salinity and 12:12 LD photoperiod, and fed 4×/day^- 1. Larvae were initially fed a mixture of phytoplankton to stages PZ2 or M1 and then fed either live Artemia, live or dead copepods, or a microparticulate microbound diet. The experiments were terminated and all larvae were harvested when more than 80% of larvae had molted to postlarvae 1 (PL1) within any flask representing any of the treatments. The comparative value of the different diets and feeding regimes was determined by mean survival, mean dry weight and total length of individual larva, and percentage of surviving larvae that were PL1. Trypsin activity of samples of larvae from each treatment was also determined. The microparticulate microbound diet effectively served as a complete substitute for Artemia nauplii when fed beginning at stage M1. When fed at the beginning of the PZ2 stage, survival was comparable to that of larvae fed Artemia, but mean dry weight, mean total length, and percent of surviving larvae that were PL1 generally were significantly less. Responses to the feeding of copepods, whether fed dead or live, as a substitute were generally significantly less than those of larvae fed either the Artemia nauplii or the microparticulate diet. Values of trypsin activity (10^− 5 IU/μg^- 1 dry weight) corresponded to the relative proportions of the different larval stages within a treatment, with higher activity being characteristic of early stages. Previously demonstrated successful results with another species of crustacean suggest that the microparticulate microbound diet has characteristics that should be effective in the culture of the carnivorous stages of other crustacean and fish larvae that are currently fed live Artemia nauplii.     

Effect of diets on growth and reproductive development of juvenile pikeperch, Stizostedion lucioperca (L.), reared under intensive culture conditions

Juvenile pikeperch 3.66 ± 0.23 cm total length (TL) and 0.32 ± 0.05 g were reared in water at 22 ± 0.5^°C and fed with live zooplankton or alternatively a commercial trout feed. Fish fed with dry diet grew faster and had higher condition factor than fish fed live zooplankton. Sex differentiation in pikeperch was visible at different stages of ontogenesis, but was related to the fish growth rate. The gonads offish that were 3.43-5.69 cm TL revealed undifferentiated characteristics. Clear indication of oogenesis in females was observed in pikeperch at 7.9 cm TL and 3.47 g, whereas evident spermatogenesis was not observed till the end of the experiment.     

Effect of different forms of Artemia biomass as a food source on survival,molting and growth rate of mud crab (Scylla paramamosain)

An experiment was conducted to evaluate the effect of different forms of Artemia biomass as a food source on survival, molting and growth rate of mud crab Scylla paramamosain. Instar 1 crablets with a mean weight of 0.0082 ± 0.0007 g were reared both individually and communally and fed with different diets consisting of fresh shrimp meat (control feed), live Artemia biomass, frozen Artemia biomass and a dried Artemia‐based formulated feed for 40 days. The highest survival was obtained for crablets receiving live Artemia (92.5% and 75.8%) followed by the groups fed with frozen biomass (90.0% and 47.5%), the control feed (72.5% and 24.2%) and the dried Artemia‐based diet (60.0% and 21.7%) for individual and communal cultures, respectively. The intermolt period, the total number of moltings and the growth rate, which were determined on individually reared crabs, showed the same pattern as for survival. The results suggest that crab performance decreased in the following order: live Artemia>frozen Artemia > fresh shrimp meat > dried Artemia‐based formulated feed. Live Artemia biomass proved an ideal feed for nursery of Scylla paramamosain crabs. Frozen Artemia biomass may be an alternative in times of shortage. Our findings illustrate the high potential for local utilization of Artemia biomass in Vietnam for reliable production of mud crab juveniles.     

Frozen mysids as an alternative to live Artemia in culturing seahorses Hippocampus abdominalis

This investigation examined the effects on growth and survival of seahorses Hippocampus abdominalis Leeson 1827 fed a 25% body weight (wet weight) daily ration of live Artemia sp. enriched with Algamac‐3050, frozen mysids Amblyops kempi or a combination of live enriched Artemia and frozen mysids. After 3 months there was no difference in seahorse length, wet weight, condition factor (CF), or food conversion ratios (FCR) between the treatments. Mean daily specific growth rate (SGR) was higher for the Artemia‐only treatment than for the mysid‐only treatment (P<0.05). FCRs ranged from 6.14 g to 8.72 g dry weight of food required to give a 1‐g dry weight increase in seahorses. There was no difference in survival between treatments. Fatty acid analysis revealed that mysids had a higher percentage composition of EPA, 20 : 5n‐3, and DHA, 22 : 6n‐3, but a lower composition of AA, 20 : 4n‐6, than enriched Artemia. Percentage n‐3 highly unsaturated fatty acids (HUFAs) in mysid levels were approximately twice that of Artemia. Proximate analysis revealed mysids to be higher than the enriched Artemia in protein and fats, and lower in water content. This experiment demonstrates that, although no growth advantage was derived from the use of frozen mysids, they can be used successfully as an alternative food to live enriched Artemia for H. abdominalis. The use of frozen mysids is highly recommended in commercial seahorse culture if the seahorses are to be sold into the live aquarium trade, as this may increase their chances of survival after sale.     

Determination of the optimum transfer time of kutum (<Emphasis Type="Italic">Rutilus frisii kutum</Emphasis>) larvae from live food to artificial dry feed

Kutum Rutilus frisii kutum is known as a valuable commercial species in the southern part of Caspian Sea. Artificial rearing of fry has been introduced as an alternative to supply kutum fry in order to restock the kutum population in the Caspian Sea. The aim of this study was to find the suitable time to transfer kutum larvae from live food to artificial feed. The experiment began on day 3 post- hatching and lasted for 21 days. Mean initial weight of larvae was 4.5 mg. Five experimental groups including Group A (zooplankton alone for 21 days), Group B (12 days zooplankton + 9 days artificial feed), Group C (8 days zooplankton + 13 days artificial feed), Group D (4 days zooplankton + 17 days artificial feed) and Group E (artificial feed alone for 21 days) were considered for this experiment. According to the obtained results, the specific growth rate of kutum larvae varied from 8.01 to 13.58% day⁻¹, and the highest and lowest specific growth rate were found in A and E treatments, respectively. The lowest mean body weight (24.6 mg) was found in larvae fed on artificial feed for 21 days. However, survival rates of kutum larvae fed mixed zooplankton for 8 and 12 days (85.83 and 89.33%, respectively) were comparable with those of larvae fed live food during the entire experiment (91.6%). The lowest survival rate (69.16%) was found in larvae fed artificial feed during the entire experiment.