Maturation of the pancreatic and intestinal digestive functions in sea bass (Dicentrarchus labrax): effect of weaning with different protein sources

The maturation of the digestive functions in sea bass (Dicentrarchus labrax) larvae was evaluated by the enzymatic profile of pancreas and intestine brush border membranes. Sea bass larvae were weaned at day 25 with three simplified diets different by their protein nature: 100% fish meal (FP), 100% casein mixture (CP) and 50% fish meal-50% casein mixture (CFP). The casein mixture contained 35% of hydrolysate. The control group was fed live preys. The specific activity of amylase decreased with age irrespectively of the diets whereas the specific activity of trypsin was enhanced. The casein mixture reduced pancreatic secretion in amylase and trypsin. The CFP group differed from the other groups fed on compound diets, exhibiting as soon as day 32 high activities of brush border enzymes, similar to controls. This sharp increase between day 25 and 32 appeared to be crucial for larval survival. The addition of a protein hydrolysate in a weaning diet seems to facilitate this maturation process.     

Development and response to a diet change of some digestive enzymes in sea bass (Dicentrarchus labrax) larvae

Variations in some enzyme activities during larval development of sea bass fed live prey were investigated from hatching to day 40. Fluctuations in the enzyme specific activities (except for trypsin) occurred in three phases: initially a sharp increase until day 12, followed by a plateau and subsequently a decrease around day 23. Then activities remained constant until day 40. Trypsin activity kept rising until day 23, then fell. Enzymatic adaptation to a change in diet was studied by feeding larvae with microparticulate diet from day 25. Adaptation to dietary change was observed for amylase, alkaline phosphatase and leucine aminopeptidase, assayed in whole larvae. In larvae fed microparticulate dry diet, the activities of these three enzymes tended to be higher than in those fed natural prey. Although poor growth was observed in larvae fed microparticles, the brush border enzyme activities purified from whole body homogenate, were not impaired.     

Dietary spermine supplementation induces intestinal maturation in sea bass (Dicentrarchus labrax) larvae

Sea bass (Dicentrarchus labrax) larvae were fed microparticulated compound diet containing 0 (FP0), 0.10 (FP10) and 0.33% (FP33) of a polyamine, spermine, from day 20 to day 38. LP group was fed live prey. This group exhibited the highest growth and survival. The addition of spermine did not lead to growth enhancement. A 33% survival improvement was obtained in FP33 group compared to FP0 group. The spermine addition affected the activity of pancreatic enzymes, trypsin, chymotrypsin and amylase, during larvae development. This non specific effect suggested that the action of spermine would be mediated by hormones. In the intestine, the FP33 group exhibited from day 31 higher activities of brush border membrane enzymes (leucine aminopeptidase and alkaline phosphatase) and lower level in a cytosolic enzyme (leucine-alanine peptidase) compared to FP10 and FP0 group. The diet containing the highest spermine level induced an enzymatic profile similar to that obtained in LP group and characteristic of a mature enterocyte. The initiation of enterocyte maturation at a proper development stage was associated to the survival improvement observed in FP33 group.     

Amylase and trypsin responses to intake of dietary carbohydrate and protein depend on the developmental stage in sea bass (Dicentrarchus labrax) larvae

Sea bass (Dicentrarchus labrax) larvae were fed from day 15 to day 35 with 4 isoenergetic formulated diets that varied in protein (30, 40, 50, 60%) and carbohydrate (37, 27, 17, 7%) content. The diets were designated as P30, P40, P50 and P60, respectively. Best growth and survival were noted for P50 larvae. Poor growth and survival were observed for P30 larvae. The specific activity of amylase increased in direct relation to the dietary carbohydrate level from day 18 onwards. This increase was the result of extensive amylase synthesis. Trypsin activity was positively correlated with dietary protein level only at day 35. This study shows that the mechanisms involved in amylase regulation are efficient in very young sea bass larvae, while those related to trypsin appear later in ontogeny and thus suggests an age-dependent regulation of enzyme synthesis.     

Influence of dietary lipid on growth performance and some lipogenesis‐related gene expression of tongue sole (Cynoglossus semilaevis) larvae

A 30‐day feeding trial was conducted to investigate the effects of dietary lipid levels on growth performance, activities of digestive enzymes, fatty acid composition and some lipogenesis‐related gene expression of half‐smooth tongue sole (Cynoglossus semilaevis) larvae. Five isoproteic diets were formulated with graded lipid levels (6.68%, 9.84%, 13.47%, 17.89% and 21.88% dry weight) using fish oil as the main lipid source. Each diet was randomly allocated to triplicate groups of 150 larval tongue sole (35 DAH, 54 ± 1 mg). Fish were fed five times daily to apparent satiation during the feeding experiment. Results showed that, the survival rate (SR) of larvae increased significantly firstly, and thereafter decreased significantly. The specific growth rates (SGR) of larvae fed the diet with 13.47% lipid were significantly higher than other treatments. Larvae fed 9.84% or 13.47% dietary lipid showed higher trypsin, lipase, leucine aminopeptidase and alkaline phosphatase (AP) activities than other treatments, whereas amylase activity nearly showed reverse trend with them. The fatty acid composition of the tongue sole larvae was well correlated with dietary fatty acid profile. Expression of acetyl‐CoA carboxylase alpha (ACC1) was found to be slightly negatively correlated with dietary lipid level, and high dietary lipid level depressed the expressions of acetyl‐CoA carboxylase beta (ACC2) and fatty acid synthase (FAS) mRNA expression significantly, implying that larvae may cope with high dietary lipid mainly through down‐regulating lipogenesis‐related gene expression of FAS and ACC2. Besides, on the basis of SGR, the optimal dietary lipid level for larval tongue sole was estimated to be 13.56% using second‐order polynomial curve.     

Effect of different dietary levels of docosahexaenoic acid (DHA, 22:6w-3) on the DHA composition of lipid classes in sea bass larvae eyes

The effect of different dietary levels of docosahexaenoic acid (DHA, 22:6w-3) on the corresponding composition of lipid classes of the eyes of sea bass, Dicentraxrchus labrax, larvae was studied using Artemia nauplii enriched with different products: oil emulsions, liposomes, a dry microalga and baker's yeast. DHA was found to be a major constituent of phosphatidylserine and phosphatidylethanolamine of visual tissues. The different DHA dietary levels were markedly reflected in the fatty acid composition of the lipid classes of eyes, suggesting a dose-dependent relationship between DHA in the food and in visual tissue lipids of sea bass larvae. The possible implications of this dietary effect are discussed.     

Effects of dietary protein levels on the growth,survival, amylase and trypsin activities in large yellow croaker,Pseudosciaena Crocea R., larvae

A feeding trial was conducted to investigate the effects of dietary graded protein levels on the growth, survival, amylase and trypsin activities of large yellow croaker (Pseudosciaena crocea R.) larvae from 12 to 42 days after hatching (DAH). Five approximately isoenergetic microbound diets (16.65 MJ/kg diet) were formulated to contain different protein (47.1%, 52.0%, 57.1%, 62.2% and 67.5%) levels. Frozen copepods, containing 54.5% crude protein (CP), 6.0% crude lipid, 27.2% ash and 6.7% glycogen, were used as a control. Each diet was randomly fed to triplicate groups of larvae with an initial mean body weight of 1.76 ± 0.09 mg (mean ± SD) in 180 L white plastic tanks, and each tank was stocked initially with 3500 larvae. Both the survival and the specific growth rate (SGR) of large yellow croaker larvae significantly increased with increasing dietary protein level up to 57.1%, and decreased thereafter. Frozen copepods resulted in intermediate survival and low SGR compared with the other diets. Whole‐body moisture and protein of larvae were not significantly affected by the dietary protein level. In contrast, whole‐body lipid of larvae fed diet with 47.1% CP was significantly higher (P<0.05) than those from fish fed the diets containing more than 57.1% CP. Additionally, fish fed the frozen copepods had the lowest whole‐body protein and lipid. The amylase‐specific activity increased with increasing dietary carbohydrate level during the period of this experiment. However, trypsin activity was not significantly affected by the dietary protein content before 42 DAH, indicating a later onset of trypsin than amylase in the regulation of enzymatic synthesis induced by a dietary substrate.     

The effect of dietary ribonucleic acid incorporation in performance of European sea bass (Dicentrarchus labrax) juveniles

The aim of this study was to evaluate the effect of dietary ribonucleic acid (RNA) on the performance of European sea bass juveniles. Two diets containing fish meal as the only nitrogen source were formulated with 39% or 50% of crude protein (LP and HP diet, respectively). Two other diets were formulated similarly to LP diet, but included yeast-RNA extract at 6.2% and 12.4% levels (LP6 and LP12 diets, respectively) by replacing dextrin. Total nitrogen content of the LP12 diet was equivalent to that of the HP diet. The four experimental diets were isoenergetic (22 kJ GE g⁻¹ DM). Triplicate groups of 25 fish (IBW=13 g) were fed the test diets for 10 weeks. The reduction of dietary protein level did not significantly affect growth rate but significantly increased feed intake and decreased feed efficiency. However, nitrogen retention (%N intake) was significantly improved with the decrease in dietary protein level. Dietary RNA incorporation did not affect feed intake or feed efficiency, although it reduced growth rate of fish fed the highest dietary RNA level. Nitrogen retention (%N intake) significantly decreased with the dietary supplementation of RNA. Dry matter, nitrogen and energy digestibilities were not significantly affected by dietary treatments. Final whole-body composition was also unaffected by dietary treatments, except for ash content which was significantly higher in the LP12 group. Hepatosomatic index was significantly increased by the dietary incorporation of RNA. The dietary supplementation of RNA had no protein sparing effect and significantly reduced energy retention. It may be concluded that dietary RNA supplementation had no nutritive value for European sea bass.     

Importance of dietary arachidonic acid for the growth,survival and stress resistance of larval European sea bass (Dicentrarchus labrax) fed high dietary docosahexaenoic and eicosapentaenoic acids

Together with docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), arachidonic acid (ARA) is being considered to be an essential fatty acid in marine fish larval diets. The objective of the present study was to determine the importance of dietary ARA levels for larval European sea bass performance, when EPA and DHA are also present in the diet. Eighteen‐day‐old larvae were fed, for 14 days, gelatine‐based microdiets containing the following ARA levels: 0.3%, 0.6% or 1.2%. Elevation of dietary ARA up to 1.2% showed a positive correlation with larval survival and a significant improvement in the specific growth rates, body weight and total length. Arachidonic acid was efficiently incorporated into larval lipids, even at a higher proportion than that in the diets. Increased accumulation of ARA did not affect the incorporation of DHA or EPA from the diet into larval total lipids. A significant positive correlation was found between dietary ARA levels and survival after handling stress, indicating the importance of this fatty acid in sea bass larvae response to acute stressors. The results show the importance of ARA for sea bass larvae, but higher dietary levels should be tested to determine whether there is a negative effect of ARA in sea bass as reported for other species.     

Growth and feed utilization of gilthead sea bream (<Emphasis Type="Italic">Sparus aurata</Emphasis>, L.) fed to satiation and restrictively at increasing dietary energy levels

Three isoproteic (47% protein) diets were formulated to contain graded levels of crude fat (diet D16:16%, diet D24: 24% and diet D32: 32%). Each diet was fed to satiation in three and to 80% satiation in two replicate groups of gilthead sea bream (Sparus aurata), having an initial body weight of 72–74 g. The trial lasted 81 days. Groups fed to satiation showed higher final body weight (FBW; 238.8–252.3 g vs. 218.0–229.3 g) and daily growth index (DGI; 2.49–2.65%/day vs. 2.27–2.34%/day) than those fed to 80% satiation. Feed intake was significantly different both for feeding level and for diet composition. Fish fed to satiation had higher feed conversion rate (FCR) compared to the 80% satiation groups (1.33–1.44 vs. 1.13–1.17; P ≤ 0.001). Within satiation groups, FCR was significantly lower in fish fed D16 compared to fish fed D32 (1.33 vs. 1.44, P ≤ 0.05), whereas no statistical differences were found within the 80% satiation groups. The increase in dietary lipid level did not improve growth performance, feed efficiency and protein utilization but decreased gross lipid efficiency. Conversely, a reduction in ration from satiation to 80% satiation decreased DGI, thus improving FCR. Feed costs were influenced by dietary energy level and feeding ratio, the lowest energy diet at 80% satiation being the most profitable combination among the variables.     

Dietary Protein Requirements of Juvenile Black Sea Bass,Centropristis striata

A feeding trial was conducted in a recirculating system to determine the dietary protein requirement for juvenile black sea bass. Six isocaloric diets were formulated to contain varying levels of crude protein (CP) ranging from 36 to 56% (36, 40, 44, 48, 52, and 56%) by substituting a mixture of carbohydrates and lipid for fish meal. The feeding experiment was carried out in 18‐75 L aquaria stocked at a density of 15 juveniles (initial average weight 6.7 g) per tank. Fish were fed test diets in triplicate tanks to apparent satiation twice a day for 8 wk. Whole‐body proximate composition was analyzed after the feeding trial. After the feeding trial, weight gain and specific growth rate of fish fed the 44% CP diet were not significantly different from those fed the 48, 52, and 56% CP diets, but were significantly higher (P < 0.05) than those fed the 36 and 40% CP diets. Feed conversion efficiency and protein efficiency ratio were significantly affected by dietary protein level. The dietary requirement of protein for maximum growth of black sea bass juveniles, estimated using broken‐line regression analysis on weight gain, was 45.3% and maximum weight gain occurred at 52.6% based on polynomial regression analysis.     

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.     

Effects of dietary lipid levels on the growth, digestive enzyme, feed utilization and fatty acid composition of Japanese sea bass (Lateolabrax japonicus L.) reared in freshwater

Triplicate groups of 40 Japanese sea bass Lateolabrax japonicus reared in freshwater (average weight, 9.52±0.47 g) were fed with six isonitrogenous (∼46% crude protein) diets containing 6%, 8%, 10%, 12%, 14% or 16% lipid for 10 weeks respectively. The results showed that the maximum weight gain (WG), specific growth rate (SGR), feed intake (FI) and protein efficiency ratio (PER) all occurred at the 10% lipid level ( P <0.05) and growth depression occurred when the dietary lipid level was over 12%. Whole body and liver lipid concentrations were enhanced with the increase in the dietary lipid levels, but the muscle lipid content did not significantly change with the increase in the dietary lipid levels. Both liver pepsin and trypsin activities increased with dietary lipid levels ranging from 6% to 10%, and then decreased with a further increase in the dietary lipid content. Liver lipase activities showed a positive correlation with dietary lipid levels, but amylase activities were not markedly influenced by dietary lipid levels. High proportions of 18:1n-9, 20:1n-9, eicosapentaenoic acid (20:5n-3; EPA), 22:1n-11 and docosahexaenoic acid (22:6n-3; DHA), and low concentrations of n-6 fatty acids, particularly 18:2n-6 occurring in the liver and muscle, to some extent, reflected the fatty acid composition in experimental diets.     

Optimization of Artemia Metanauplii on Growth and Survival of Gilthead Sea Bream Larvae Sparus aurata

–Growth, feed efficiency and survival of gilthead sea bream Sparus aurata larvae fed exclusively various levels of enriched Artemia during the period 25 DPH-34 DPH were investigated. Larvae had an average initial fresh body weight (BW) of 4.99 mg and were fed on Artemia at rates of 20, 35, 50, 65, and 80% of their body weight per day, in two equal meals. Each ration was administered to duplicate groups of 1,000 larvae, with ration readjusted every second day. Feeding rate had a significant effect on larval survival, which was lower in larvae fed the 20 and 35% BS/d rations. The specific growth rate (SGR) showed a curvilinear significant increase when the feeding rate was increased from 20 to 65% BW/d, but there was no improvement when the feeding rate was increased from 65 to 80% BW/d. Percent feed efficiency (FE) decreased significantly from a maximum value at 20% ration to 80% BW/d but at 65% and 80% rations the values of FE were not significantly different. Optimum ration (minimum quantity of Artemia concomitant with maximum larval growth) was estimated close to 65% BW/d. The significance of the results is discussed in relation to potential economics of Artemia cysts use in commercial hatcheries.     

Dietary lipid requirements of larval genetically improved farmed tilapia,Oreochromis niloticus (L.), and effects on growth performance,expression of digestive enzyme genes,and immune response

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

Studies on the Nutrition of Spotted Sand Bass Paralabrax maculatofasciatus: Effect of the Dietary Protein Level on Growth and Protein Utilization in Juveniles Fed Semipurified Diets

Two feeding trials were conducted to determine the digestibility of a casein-based semi-purified diet and the effects of different protein levels on growth and protein use of spotted sand bass Paralabrax maculatofasciatus juveniles. For trial I, a semipurified diet with vitamin-free casein as the sole source of protein was fed three times a day to apparent satiation, for a period of 20 d. Feces were collected by siphoning each tank. The digestibility of the experimental diet was high: 97% for protein, 89% for lipids, and 84% for gross energy, whereas that of organic matter was 78%. For trial II, seven diets were formulated using vitamin-free casein at graded levels (25, 30, 35, 40, 45, 50, and 55% protein). Triplicate tanks for each dietary treatment were stocked with fish and fed by hand three times a day to apparent satiation for 6 wk. Perfomance of fish fed the different diets was evaluated for survival, percent weight gain, specific growth rate, feed conversion ratio, and protein efficiency ratio. Survival was 100% for all treatments. Growth of spotted sand bass juveniles increased as the dietary protein increased, but no evidence of reaching a plateau was found. The daily feed intake values showed an inverse relation to the protein content of the diets. The feed conversion ratio did not differ among diets containing 40% protein or greater. The results indicate that spotted sand bass juveniles with 2.5-g mean weight need at least 55% dietary protein for best growth when casein is the sole protein source. However, in terms of feed conversion ratio, the requirement apparently could be lower.     

Effect of predigested protein on growth and survival of Atlantic halibut larvae (Hippoglossus hippoglossus L.)

In this study Atlantic halibut (Hippoglossus hippoglossus L.) larvae (0.12 ± 0.04 g) were, from day 40 post first feeding, offered six diets in which 10% or 30% of the dietary protein was hydrolysed with (a) pepsin (P), (b) pepsin + trypsin (PT) or (c) pepsin + trypsin + chymotrypsin (PTC). In addition, a diet without hydrolysed protein was offered, and enriched Artemia was fed as control. The amount of soluble protein increased progressively with the enzyme treatments P, PT and PTC and with higher inclusion levels of hydrolysed protein. Survival was highest among the larvae offered Artemia (83 ± 0%) or the diet 10P (10% pepsin hydrolysed protein; 67 ± 4%). The diet 10P supported survival significantly better than the more hydrolysed diets 10PTC, 30P, 30PT and 30PTC, but not significantly better than the non‐hydrolysed diet and 10PT. Specific growth rate (SGR) was 1.76 ± 0.20 in average for all groups of larvae and was not significantly affected by the diets. Still, the larvae offered pepsin hydrolysed diets tended to have better growth (2.10 ± 0.05 SGR; P < 0.06) than the larvae offered the other hydrolysed diets. The larvae offered the formulated diets did not differ in chemical composition.     

Larval Rearing and Weaning Techniques for White Bass Morone chrysops

The effects of culture parameters of tank color and feeding regimes were examined on larval white bass Morone chrysops during 1994–1995. Under high surface illumination (998 lux), dark tank walls were essential for effective prey capture. Larvae reared in clear glass aquaria did not grow and had died by day 6 of the study. In contrast, 48.7% of the larvae reared in black-walled tanks were alive on day 24 and had grown to 17.2 mm total length (TL). In another study, larvae were fed rotifers Brachionus plicatilis and Artemia nauplii in different feeding protocols. In one treatment only rotifers (10/mL) were fed day 1 (4 d post-hatch), rotifers and Artemia (3/mL) were fed days 2–4, and Artemia fed days 5–15. This protocol produced similar growth (mean size 11.7 mm TL) and survival (mean 30.3%) as slower weaning times from rotifers to Artemia . Juveniles (27-day-old, 17.2 mm TL) were converted to a dry crumble diet over a 14-d period by slow transfer from a combination diet consisting of live Artemia nauplii, frozen adult Artemia , plankton flakes and dry crumbles. Survival offish weaned to the dry diet was 64.5%. Most of the mortalities during the weaning period were fish with uninflated swim bladders which were cannibalized by larger fish. Using the above tank culture techniques, white bass were reared to a mean size of 73.2 mm TL (mean weight 5.8 g) over a 73-d period. This essentially closes the life cycle of white bass.     

Lipid Nutrition and Feeding of Cobia Rachycentron canadum Larvae

This study examined the fatty acid composition of cobia Rachycentron canadum eggs and yolksac larvae, as well as the ovaries of wild caught females as an initial guide to lipid nutritional requirements. A 2-wk feeding study also was conducted to investigate the effectiveness of four dietary treatments on the growth and survival of cobia larvae. Cobia eggs in the tailbud stage contained 31.4 ± 1.3 μg lipid/egg. After hatching, the amount of lipid decreased significantly (P < 0.05) from 28.3 ± 0.3 to 23.2 ± 0.1 μg lipid/larvae during the yolksac larval stage (days 1 to 3 after hatching). Ovaries from wild caught adults and captive spawned eggs and yolksac larvae contained high levels of PUFAs with docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA) accounting for approximately 80% of the total suggesting that cobia larvae may have a high dietary requirement for these fatty acids. For the feeding study, larvae were fed: 1) Artemia only; 2) enriched rotifers for 1 d only + microparticulate diet (day 313); 3) enriched rotifers for 3 d (day 3–5) + Artemia (day 3–13); and 4) enriched rotifers for 6 d (day 3–8) + Artemia (day 3–13). Cobia larvae began feeding on rotifers 3 d after hatching and on newly hatched Artemia nauplii by the fifth day following the onset of exogenous feeding (day 7). On day 7, no differences in larval growth were found among larvae fed rotifers for 3 versus 6 d, whereas larvae fed only Artemia or rotifers for I d followed by microparticulate diet were significantly smaller (P < 0.05) and did not survive beyond day 9 and 13, respectively. The results of the feeding study indicate that cobia larvae require rotifers for a minimum of 4 d following the onset of exogenous feeding.     

Acceptance and Consumption of Food by Striped Bass and Hybrid Larvae

Food acceptance, consumption and weaning times were investigated for striped bass ( Morone saxatilis ) and hybrid striped bass ( M. saxatilis × M. chrysops ) larvae. Experimental treatments consisted of: control groups of striped bass (SC) and hybrids (HC) fed Artemia nauplii; hybrids fed formula food (HF); and hybrids weaned from Artemia nauplii to formula food at 11–15 days (HF₁), and 18–22 days (HF₂) posthatch. The formula diet did not support growth and resulted in total mortality of the HF hybrids by the third week posthatch. HF₁ fish had significantly slower growth and lower survival than HF₂ of HC. The HF₂, HC and SC groups had similar growth and survival, which indicated no heterosis in hybrids. There were no differences in Artemia nauplii consumption by the SC and HC groups. Daily consumption increased exponentially for both groups (0.8 to 50–60 cal/day/larva between 7 and 30 days posthatch). Weight specific consumption (WSC) decreased initially and then increased for both groups. A mean WSC of 58% (range of 24–83%) was found for the combined SC and HC groups. Food conversion ratio, growth efficiency, caloric efficiency, and productive protein values were similar for striped bass and hybrid larvae.