Effects of Food and Temperature on Survival and Development in the Peppermint Shrimp Lysmata wurdemanni

Abstract— The effects of four kinds of foods ( Artemia nauplii, rotifer, and microalgae Chaetoceros gracilis and Isochrysis galbana ) and four temperature regimes on survival and development of larval Lysmata wurdemanni , a marine ornamental shrimp, were determined. The larvae fed with Chaetoceros or Isochrysis only survived for a maximum of 17 d, before developing to zoea IV. The survivorship of the larvae fed with Artemia nauplii or rotifer from zoea II to post-larvae was 66.7% and 68.9%. respectively, without significant difference ( P > 0.05). But larvae fed with Artemia nauplii grew significantly ( P < 0.05) faster than those fed with rotifer. Larvae fed with Artemia nauplii reached postlarvae in 29–32 d, compared with 32–36 d in the rotifer treatment. Artemia nauplii are also suitable food for the postlarvae and juveniles of L. wurdemanni . The 30 postlarvae fed on Artemia nauplii all survived to reach sexual maturity in 50 to 70 d, growing from about 7 to 28 mm in total length. The effects of four temperature regimes on larval development of L. wurdemanni was also investigated. The duration (mean ± SD d) to the postlarvae at temperatures of 26 C (37.4 ± 5.4) and of 26–30 C daily (40.2 ± 5.8) was significantly ( P < 0.05) longer than that at 28.5 C (29.3 ± 4.8) and at 27–29 C daily (28.7 ± 3.5).     

Survival and growth of larval and juvenile tench, Tinca tinca L., fed different diets under controlled conditions

Abstract. Tench, Tinca tinca L., larvae were reared under controlled conditions at water temperatures of 28°C and 31°C during a 15-day period. Feeding with exclusively live Artemia nauplii gave best results, irrespective of rearing temperature (total length 13·6mm; average weight 31 mg; survival rate 83–85%). High survival rates of 81–88% were found also in all groups fed mixed diets, whereas growth rate of tench larvae was significantly influenced by the frequency of supplemental feeding with Artemia. When applied alone, the tested carp starter feed turned out to be insufficient for rearing the larval tench.     

Ingestion of Artemia nauplii by Chinese mitten crab Eriocheir sinensis zoea larvae

A series of ingestion trials were conducted to determine the ingestion rate of Artemia nauplii by Eriocheir sinensis zoea larvae with increasing densities of Artemia and with or without rotifers as a co-feed. At each zoeal stage, 10 groups of 10 larvae were reared individually in glass beakers and fed with increasing densities of newly hatched Artemia nauplii (0.5, 2.5, 5, 10 and 20 individual (ind.) mL⁻¹) with or without rotifers (15–25 ind. mL⁻¹) as a co-feed. The average number of ingested Artemia was measured over 24 h. In addition, the average larval development rate (Larval Stage Index, LSI) over a longer period (time needed for the best treatment to reach 100% moult or metamorphosis to the next larval stage) was compared. The results showed that Artemia ingestion rate of E. sinensis larvae increased with increasing prey densities and larval development, and had a significantly negative correlation with rotifer consumption for all zoeal stages. Rotifers as an alternative prey significantly affected the intake of Artemia at early larval stages (Z1 and Z2) and promoted LSI at a lower Artemia density. Further experiments are needed to clarify the effect of prey density on survival and larval development when larvae are reared communally.     

Effects of developmental stage, seawater concentration and rearing temperature on cryopreservation of Pacific oyster Crassostrea gigas larvae

ABSTRACT: For the development of a stepwise cryopreservation technique for larvae of the Pacific oyster Crassostrea gigas , various conditions were examined. Larvae at 9, 12, 15, 18 and 21 h after insemination were cooled at a rate of −1°C/min (seeding at −8°C for 15 min) and then plunged into liquid nitrogen at −35 or −40°C using 1.5 M dimethyl sulfoxide (DMSO) and 250 mM trehalose as cryoprotectants. Among these larvae, 15 h after insemination (the trochophore stage before formation of the shell gland) showed the highest motility and the best external appearance after thawing. Trochophore larvae were cryopreserved in preservation media containing different dilutions (1/4, 1/6, 1/8, 1/10 and 1/30) of seawater. Larvae preserved in the 1/4 seawater medium showed the highest appearance of shelled larvae 4 days after thawing. Trochophore larvae reared in seawater at 21, 25 or 29°C were cryopreserved for 8 months and then reared at 26°C after thawing. Larvae reared at 25°C showed the highest survival rate and normal larval ratio at day 6 after thawing, although larvae reared at 21°C showed the highest rates until day 4. One larva developed at 25°C succeeded to settle.     

Effect of vitamin E and highly unsaturated fatty acid-enriched Artemia urmiana on growth performance, survival and stress resistance of Beluga (Huso huso) larvae

A 44-day rearing trial was conducted to examine the enrichment of Artemia urmiana nauplii with vitamin E and highly unsaturated fatty acid (HUFA) and its effects on the growth performance, survival and stress resistance of great sturgeon, Huso huso , larvae. Cod liver oil (EPA 18% and DHA 12%) and α-tocopherol acetate were used as lipid and vitamin E sources. Beluga larvae at the first exogenous feeding with 69±5.9 mg body weight were randomly distributed into four treatments and three tanks were assigned to each diet. The test treatments were as follows: larvae fed with HUFA+20% and HUFA+50% (w/w) vitamin E-enriched Artemia nauplii (E1 and E2 groups, respectively), HUFA without vitamin E (HUFA group) and non-enriched Artemia (control group). All treatments fed non-enriched Artemia for the initial 5 days after first feeding and then fed enriched Artemia for 7 days. After the period of enrichment, larvae were fed with daphnia from the 13th to the 40th day. At day 40, submersion in salt water (6 ppt for 4 days and 12 ppt for 2 days) and warm water (33 °C for 2 days) was performed to evaluate larvae resistance to salinity and temperature stress. Final weight, daily growth rate, specific growth rate and weight gain were higher in beluga fed with enriched Artemia . The highest growth rates were observed in E1, whereas survival was not significantly different between groups. Use of vitamin E and HUFA significantly increased fish resistance to a salinity of 12 ppt and the lowest stress resistance was observed in the control group. Stress tolerance was not significantly different at 6 ppt and 33 °C between groups. There was no comparable difference in the haematocrit index under stress conditions. These results indicated that the enrichment of Artemia with essential fatty acids and vitamin E can affect some growth and stress tolerance factors in great sturgeon, Huso huso , larvae.     

The effect of vitamins C and E in (n-3) highly unsaturated fatty acids-enriched Artemia nauplii on growth, survival, and stress resistance of fresh water walleye Stizostedion vitreum larvae

This study aimed to evaluate the effect of enriching Artemia nauplii with vitamin C (ascorbyl-6 palmitate) or vitamin E (α-tocopherol acetate), 20% w/w, together with a mixture of concentrated eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3) on the growth, survival, and stress resistance of fresh water walleye Stizostedion vitreum larvae. Either cod liver oil (CLO) or EPA/DHA ethyl esters concentrate was used as lipid sources in the Artemia enrichment. Walleye larvae were fed ad libitum for 40 days. At day 40, submersion in salt water (25 g L⁻¹) was performed to evaluate larvae resistance to stress. EPA and DHA levels in walleye juveniles fed EPA/DHA-enriched Artemia increased significantly, by an average of 650% compared with fish fed non-enriched Artemia . A significant increase was found for vitamins C (71.8 ± 1.0 and 42.7 ± 1.2 μg g⁻¹ wet weight (WW)) and E (17.0 ± 3.7 and 6.5 ± 0.9 μg g⁻¹WW) concentrations in fish fed enriched and unenriched Artemia , respectively. Growth was comparable throughout treatments, whereas survival was significantly higher in fish fed CLO-enriched Artemia nauplii compared with fish fed Artemia nauplii enriched with EPA/DHA concentrate. The addition of vitamin C increased fish survival by 1.4-fold compared with fish fed Artemia enriched with only EPA/DHA concentrate. The survival of the latter was similar to control fish ( Artemia without enrichment). The supplementation of vitamin E did not affect fish survival significantly. Stress tests revealed that the resistance of walleye larvae to salinity changes increased when Artemia enrichment was supplemented with vitamin C. However, walleye larvae fed CLO-enriched Artemia had the best performances in the stress test.     

Japanese nephropid lobster <Emphasis Type="Italic">Metanephrops japonicus</Emphasis> lacks zoeal stage

ABSTRACT:   Larvae of the Japanese nephropid lobster Metanephrops japonicus hatched in the laboratory were reared at 15°C, and the development and feeding were observed. All larvae hatched at the 'prezoea stage' with no natatory setae on the exopodite of the pereiopods. Without feeding, 50% of prezoea molted into the megalopa stage, having small buds as the exopodite, within 1 h and all molted within 22 h. The megalopa fed with Artemia nauplii, shrimp meat and pelleted food molted into the first juvenile stage with no exopodite after approximately 17 days. The average carapace lengths of prezoea, megalopa and the first juvenile stage were 3.2, 3.6 and 4.4 mm, respectively. The survival rate from hatching to the first juvenile stage was high (90–100%). This lobster may be the only known nephropid species with no zoeal stage.     

Heat treatment affects protein quality and protease activity in decapsulated cysts of Artemia when used as starter food for larvae of African catfish Clarias gariepinus (Burchell)

Decapsulated cysts of Artemia subjected to different heat treatments (40, 60, 80 and 96 °C) were fed to African catfish Clarias gariepinus larvae. Heated cysts, untreated cysts and live Artemia nauplii as control constituted the experimental diets. Protein denaturation and solubility, total alkaline protease and specific trypsin activities in the cyst diets were evaluated. The growth of catfish larvae and the proteolytic activity of larval samples during development were also determined. Heat treatment of cysts increased protein denaturation and decreased protein solubility. The protease activity in the cyst diets decreased with higher heating temperatures. The growth of catfish larvae differed according to the diet; higher fish growth was achieved with nauplii and cysts heated at 40 °C. The digestive enzyme activity in larval samples remained similar in all dietary treatments during larval development. The quality of food protein and the way this protein is processed might be more important for successful larval growth than exogenous enzyme supply.     

Larval rearing of the shrimps Metapenaeus ensis (de Haan) and Penaeus chinensis (Osbeck) on artificial feed

Abstract. This study explored the feasibility of completely replacing live foods with an artificial diet for rearing the larvae of Metapenaeus ensis (de Haan) and Penaeus chinensis (Osbeck). The artificial diets tested were a microparticulate diet developed at the Centre Océanologique du Pacifique, Tahiti, and Artificial Plankton B.P. (Nippai Shrimp Feed Inc., Japan). Survival and development of shrimp were assessed in 1-l cones stocked with 100 nauplius V-VI or protozoea I larvae. Live feeds of the diatom Chaetoceros gracilis and Artemia nauplii served as controls. Whereas the larvae could be reared to post-larvae with artificial diets alone, the highest survival and development rates were always obtained with live foods. Larvae fed with artificial diets had retarded development and their survival to post-larvae was always lower than those fed live foods. Total replacement of live foods with artificial diets resulted in a reduction in the body length of post-larvae I in P.chinensis . Supplementing Artificial Plankton B.P. with Artemia nauplii enhanced survival and development in this species. It was concluded that the two artificial diets are not satisfactory complete substitutes for live foods in raising the two penaeids but can be used as a convenient supplement when algal diet is limited.     

Diet and Light Intensity Effects on Survival, Growth and Pigmentation of Southern Flounder Paralichthys lethostigma

Interest in the culture of flatfishes has increased globally due to high consumer demand and decreased commercial landings. The Southern flounder Paralichthys lethostigma inhabit South Atlantic and Gulf of Mexico waters and support important commercial and recreational fisheries. In spring, 1996, a two-part larval rearing study was performed with Southern flounder to examine the effects of three larval diets and two light intensities on survival, growth, and pigmentation. The first part of the study consisted of feeding 6 d post-hatch (dph) (3.0 ± 0.1 mm TL) larvae three diets: 1) rotifers Brachionus plicatilis at a rate of 10/mL from day 1–9 and Artemia nauplii (3/mL) from day 7 through metamorphosis; 2) rotifers fed day 1 through metamorphosis and Artemia fed day 7 through metamorphosis; or 3) same diet as treatment 1 plus a commercial larval diet added day 13 through metamorphosis. The second part of the study examined the effects of two light levels: low-light (mean 457 lux) and high-light (mean 1362 lux). At 24 C, metamorphosis began on day 23 (mean fish size 8.2 ± 0.6 mm TL) in all treatments and was completed by day 30. Analysis of survival, size, and pigmentation data indicated there were no significant differences among feed treatments or between light treatments. Overall survival was 33.4% (±15.9) and mean length was 11.5 mm TL ± 1.3. Only 35% of the larvae were normally pigmented. Reexamination of the pigmentation on day 37 indicated fish reared at the low light intensity through metamorphosis (day 30) but exposed to high light intensity for 1 wk post-metamorphosis had become significantly more pigmented.     

Evaluation of Streptocephalus dichotomus nauplii as a larval diet for freshwater prawn Macrobrachium rosenbergii

This study was performed to assess the nutritional value of Streptocephalus dichotomus nauplii and compared with standard larval diet and parthenogenetic strain of Artemia nauplii. The effectiveness of live feed was determined by feeding freshwater prawn Macrobrachium rosenbergii postlarvae. Results on the growth rate, weight gain, survival, fatty acid and amino acid composition show a significant variation between the dietary treatments. Mean larval growth was significantly different ( P  < 0.001) between control diet (13.5 ± 0.5 mm) and live feeds ( Streptocephalus nauplii; 18.4 ± 0.5 mm and Artemia nauplii 18.7 ± 0.2 mm). The weight of larvae-fed Streptocephalus (41.1 ± 1.44 mg) and Artemia nauplii (41.7 ± 0.2 mg) was not significantly different; however, treatment with live feeds was significantly higher than the control (16.3 ± 0.5 mg) ( P  < 0.001). Proximate composition on the fairy shrimp reveals that they are rich in protein, lipid, essential amino acids (EAA) and essential fatty acids (EFA). The polyenoic unsaturated fatty acid (18 : 2 n-6 and 18 : 3 n-3) and highly unsaturated fatty acid (20 : 4 n-3 and 20 : 5 n-3) show a dramatic increase in larval tissue relative to its proportional composition in the live diets. Amino acid composition in the live feeds, Streptocephalus and Artemia nauplii, perfectly reflects on the amino acid proportions in the larvae-fed diets which confirm its utilization.     

Phototrophic Bacteria as Feed Supplement for Rearing Penaeus monodon Larvae

Larvae of the giant tiger prawn Penaeus monodon were reared from the naupliar to pos-tlarval stage, based on a diet of waste-grown phototrophic bacterium Rhodovulum sulfido-philum , the marine diatom Skeletonema costatum , and brine shrimp Artemia The experimental design consisted of feeding the protozoea with diatoms and varying proportions of bacterial biomass as diet D0 (0%), D1 (1%), D2 (2%), D3 (3%), and D5 (5%), while mysis and postlarvae were fed the above diet supplemented with Artemia nauplii. Controls were not fed with bacteria biomass (diet D0). The addition of R. sulfidophilum biomass in the diet had significant effects on the growth and survival of P. monodon larvae. In the first experiment, the larvae fed with diet D1 ( Skeletonema + 1% R. sulfidophilum ) reached the first postlarval stage (PL1) on the ninth day of feeding and had a mean total length (TL) of 6.13 ± 0.05 mm, which was significantly higher ( P < 0.001) than TL of larvae fed with the other three diets. In another experiment, prawn larvae fed with diet D2 had the highest overall survival of 46% and a significantly larger mean TL of 6.88 ± 0.18 mm at PL1 compared to larvae fed with diet D0 and D3 ( P > 0.05). However, in both experiments prawn larvae fed with the various diets showed significant differences in their length-at-stage ( P > 0.05), and the lowest growth and survival were obtained from diets comprising 3% and 5% bacterial biomass, which also gave the highest levels of ammonia-nitrogen in the culture water. Addition of more than 2% R. sulfidophilum biomass apparently deteriorates the quality of the culture water.     

Vertical distribution of jack mackerel Trachurus japonicus larvae in the southern part of the East China Sea

ABSTRACT:   The vertical distribution of jack mackerel Trachurus japonicus larvae was described based on discrete depth sampling using a MTD net system from the surface down to 100 m depth at 13 stations in the southern East China Sea between 27 February and 10 March 2002. Of the 20 782 fish larvae collected, T. japonicus larvae were most abundant, accounting for 37.0% of the total catch. The average abundance of the larvae was 419.0 individuals/10 m², with the average (± standard deviation [SD]) body length of 2.6 ± 0.3 mm (range 1.8–7.5 mm). The larvae were concentrated in the mixed layer, with peak densities in the 10–30 m layer. The average (±SD) weighted mean depth was 21.5 ± 7.8 m. There was no evidence of either diel or ontogenetic vertical migration for the early larvae of <5 mm. More than 90% of the T. japonicus larvae were collected in the water temperature ranging from 21 to 23°C. Vertical profiles of the larval densities and chlorophyll a coincided with each other, which might reflect the abundance of their main prey organisms, copepod nauplii and copepodites, since copepod production is known to be closely related with the chlorophyll a concentration.     

Ingestion Rate and Feeding Behavior of the Peppermint Shrimp Lysmata wurdemanni on Artemia Nauplii

A laboratory study was conducted to examine the effects of food level and water temperature on the ingestion rate in the larvae of the peppermint shrimp Lysmata wurdemanni , a popular aquarium spe cies. Artemia nauplii were used as the food item. Number of newly hatched Artemia nauplii consumed by the larvae (from zoea II to zoea VII, zoea I can metamorphose to zoea II without exogenous nutrition in about one day) was measured daily at four food concentrations (2, 5, 10 and 20 Artemia nauplii/mL) and two temperature levels (25 C and 28 C). The experiment was conducted in 500-mL beakers with three replicates for each treatment. The results show that the shrimp consumed significantly more food at 28 C than at 25 C (P < 0.01). Ingestion rate increased with increasing food concentration in all larval stages and with larval development except for the lowest food level ( 2 Artemia nauplii/mL) where insufficient food supply limited the ingestion rate to around 35 Artemia nauplii/ larva per d after zoea IV stage. The larval development rate was significantly lower (P < 0.05) in the shrimp subjected to the two lowest food concentrations (2 and 5 Artemia nauplii/mL) in the 500-mL beakers. But in a separate experiment conducted in the 1,400-mL beakers, the results were reversed: both survivorship and development rate were significantly lower at the two higher food levels (6 and 12 nauplii/mL) than those at 3 nauplii/mL level. During molting period, ingestion rate decreased significantly, followed by a sharp rise to the normal rate the following day.     

Performance of Larval and Postlarval Pacific White Shrimp,Litopenaeus vannamei (Boone), Fed Two Commercial Liquid Diet Supplements

Abstract

Two commercial liquid diet supplements were evaluated as a partial replacement for live foods fed to larval and postlarval Pacific white shrimp, Litopenaeus vannamei. Larvae were stocked in 20-L buckets at a density of 113 shrimp/L and fed one of four diets (5 replicate buckets per diet): (1) a control diet consisting of the diatom, Chaetoceros neogracile, and live Artemia; (2) the control diet plus Treflan (a fungicide); (3) LiquaLife liquid larval diet supplements with reduced concentrations of C. neogracile and Artemia; and (4) Epifeed liquid larval diet supplements with reduced concentrations of Artemia. Diets were evaluated by comparing shrimp rostro-caudal length and survival to PL-8, survival to osmotic and pH stress, as well as shrimp gut fullness, gut lipid content, and fouling. Rostro-caudal length and survival to PL-8 were not significantly different among the four treatments. However, mean survival to PL-8 was 12-34% greater in the Epifeed treatment than in the other three treatments. Shrimp fed Epifeed exhibited greater survival (P < 0.05) when exposed to 7 ppt water for two hours than shrimp in the control treatments. In contrast, there was no significant difference in survival (P > 0.05) among the four treatments when shrimp were exposed to apH of 3.35 for two hours. Although shrimp fed liquid diet supplements had more fouling (P < 0.05) than shrimp in either of the control treatments, commercial liquid diet supplements can be used in penaeid shrimp hatcheries to partially replace Artemia without compromising shrimp growth or survival.     

Qualitative and quantitative changes of F<Subscript>o</Subscript>F<Subscript>1</Subscript>-ATPase in Japanese flounder and red sea bream associated with rearing temperatures

ABSTRACT:   Fast skeletal muscles of Japanese flounder Paralichthys olivaceus and red sea bream Pagrus major were examined for quantitative and qualitative changes of mitochondrial ATP synthase (F_oF₁-ATPase) in association with rearing temperatures. The specific activities of F_oF₁-ATPase from Japanese flounder reared at 10°C, 15°C and 25°C for 4 weeks were determined to be 81 ± 11, 74 ± 13 and 83 ± 11 nmol/min·mg mitochondrial protein, respectively. The corresponding activity from red sea bream reared at 8°C for 5 weeks was determined to be 65 ± 9 nmol/min·mg mitochondrial protein, which was higher than 33 ± 9 nmol/min·mg mitochondrial protein in fish reared at 23°C. The contents of α- and β-F₁-ATPase in total mitochondrial proteins were not significantly different between fish reared at different temperatures for the two fish species. However, the contents of β-F₁-ATPase in the total fast skeletal muscle extracts, prepared from Japanese flounder reared at 10°C, were 2.1- and 2.9-fold higher than those for fish reared at 15°C and 25°C, respectively. The corresponding content from red seabream reared at 8°C was 2.2-fold higher than that for fish reared at 23°C. Therefore, the changes in F_oF₁-ATPase depending on rearing temperatures were species-specific.     

The use of squid protein hydrolysate as a protein source in microdiets for gilthead seabream Sparus aurata larvae

In the present study, the use of predigested proteins as an ingredient of microdiets offered to gilthead seabream larvae was tested. The protein source (freeze-dried squid powder) was hydrolysed with protease (trypsin and pancreatin). Different levels of raw squid protein and hydrolysate (100% protein, 50% protein/50% hydrolysate, 100% hydrolysate) were added to the microdiets to produce a dietary protein level of 65%. For comparison, cofeeding of Artemia nauplii and microdiet as well as microdiet supplemented with pancreatin were also offered to the larvae. The final average dry weights of 32-day-old larvae were 1.65 ± 0.04 mg, 1.38 ± 0.06 mg and 1.13 ± 0.1 mg, respectively, for larvae cofed 0%, 50% and 100% hydrolysate microdiets and Artemia nauplii. Survival of larvae was not affected by protein source. The survival of larvae cofed Artemia nauplii and microdiet was significantly higher than that of larvae fed exclusively on microdiet (68% and 80%, respectively). These results suggest that the use of hydrolysate (at 50% greater) as a protein source in diets for seabream larvae is not to be recommended.     

Feeding Larval Red Drum on Microparticulate Diets in a Closed Recirculating Water System1

A feeding protocol was developed for red drum larvae based on combining a commercial microparticulate diet (Kyowa Fry Feed) with live prey (rotifers) in a closed, water reuse system. In five trials, growth and survival were measured on larvae reared on a combination of live and microdiet for 1–5 d and then microdiet alone. Results in each trial were compared to control larvae reared on live rotifers Brachionus plicatilis and brine shrimp nauplii Artemia salinas. The most satisfactory combination was feeding live food and microdiet together for the first five days and then completely discontinuing live prey, eliminating the need to feed brine shrimp to the larvae. Growth rates of larvae fed progressively larger sizes of the microdiet were as good as larvae reared on live prey. Both groups metamorphosed to the juvenile stage at less than one month. Survival rates on the five day live food and microdiet combination were a remarkable 60% from egg to the juvenile stage. The successful weaning of red drum to microdiets paves the way to produce a semipurified diet to test nutrient requirements of larval fish.     

Effect of diet and light regime on growth and survival of African catfish (Clarias gariepinus) larvae and early juveniles

Growth of larval sharptooth catfish Clarias gariepinus fed live Artemia nauplii , a specially prepared dry feed (MN-3), a commercial dry salmon starter feed (Silver Cup 3600), or a combination of 50% live Artemia and 50% MN-3, under conditions of either light or dark for 21 days was studied. For all diets, fish reared in darkened tanks were significantly larger than those in illuminated tanks from day 8 onwards. Fish fed a combination of live Artemia plus MN-3 grew significantly more quickly than those fed either live Artemia or MN-3 only. On day 21 of the experiment, average weight of fish fed the combined diet was 649 ± 30 mg (mean ± SEM ) in darkened tanks and 445 ± 16 mg in illuminated tanks, while those fed Artemia alone were 242 ± 9 and 198 ± 13 mg (dark and light, respectively) and fish fed MN-3 only were intermediate at 377 ± 20 and 267 ± 16 mg (dark and light, respectively). Catfish fed the salmon starter initially grew slowly, but after day 11 grew more quickly than the other groups. Mortalities were highest for fish fed salmon feed.
Permanent darkness enhances the growth of C. gariepinus larvae during and after metamorphosis. While dry diets promoted higher growth rate than live Artemia nauplii alone, a combination of the two resulted in the fastest growth.     

Acceptability of various microparticulate diets to first-feeding walleye Stizostedion vitreum larvae

The acceptability of eight diets made by a wide variety of microparticulate manufacturing processes was studied using first-feeding walleye Stizostedion vitreum larvae. Diets were formulated using a common dietary mix but differed in manufacture technique. The microparticulate diets fed were (1) carrageenan bound, (2) alginate bound, (3) starch/konjack bound, (4) microextruded/maurmurized (MEM), (5) zein bound, (6) carboxymethyl cellulose bound (CMC), (7) particle-assisted rotationally agglomerated (PARA) and (8) a commercial microparticulate diet (Fry Feed Kyowa B-700, FFK). Controls were groups fed live Artemia nauplii and unfed. Gut fullness was measured as the cross-sectional optical area of the bolus visible through the transparent body of the larvae using computer-aided image analysis. Feeding incidence on MEM particles (71 ± 8%, mean ± standard error), zein-bound particles (69 ± 7%), alginate-bound particles (68 ± 2%) and PARA particles (65 ± 6%) were not significantly different ( P   0.05) from the feeding incidence for Artemia (71 ± 6%). FFK (49 ± 14%) and particles bound with carboxymethyl cellulose (27 ± 0.07%), starch (21 ± 10%) or carrageenan (20 ± 0.8%) had significantly ( P  < 0.05) lower feeding incidence. Larvae that did initiate feeding did not differ significantly ( P  > 0.05) in the amount of each microparticulate diet or Artemia consumed. This data indicates that once first-feeding walleye start on a diet, they will consume that diet to a similar fixed level of satiation. Given the differences in the amounts of water and nutrients in the various diets, more nutrients were delivered to the gut of walleye larvae feeding on microparticulate diets than on the Artemia control.