White grouper a Mediterranean species, is a new promising candidate for Israeli mariculture. In order to develop feeds that promote the most efficient growth and cause low environmental impact the requirements of grouper for key nutrients have been quantified. Daily requirements for energy and protein were determined as the sum of maintenance and growth and the efficiencies for energy and protein deposition were estimated according to the following approach: Requirement=a×BW (kg)b+c×gain; BW (kg)b=Metabolic body weight; a=maintenance requirement; c=coefficient describing the efficiency of utilization of dietary energy or protein for growth. The daily weight gain as a function of body weight (g) and temperature (°C) was predicted by the equation: y=0.062×BW (g)0.558×exp0.030×Temp. The composition of the gain was measured by analyzing whole fish ranging from 1 to 1600 g. The energy content was dependent upon fish weight and increased from 4.8 to 7.5 kJ g−1 body mass, whereas the protein content remained constant at 169 mg g−1. The efficiencies of utilization of digestible energy (DE) and digestible protein (DP) for maintenance and growth in white grouper were determined by feeding fish of various sizes at increasing levels from zero to maximum voluntary feed intake, as well as three different water temperature regimes. Maintenance requirement for energy and protein increased with increasing temperatures. The relationships between DE intake and energy gain as well as DP intake and protein gain were found to be linear throughout and were both independent of feed intake, body weight and temperature. Daily requirements of white grouper at 24 °C can be thus calculated as follows: Digestible energy need (kJ fish−1 day−1)=40.7×BW (kg)0.80+1.52×energy gain; Digestible protein need (g fish−1 day−1)=0.39×BW (kg)0.70+1.85×protein gain. Based on those results, feeds can be formulated for white grouper with optimal energy to protein ratio during the entire grow-out period to increase retention efficiency and reduce excretion of nutrients.

Soy protein concentrate, wheat gluten, and corn gluten meal were evaluated in combination and as sole dietary protein sources in diets for gilthead seabream. A growth trial and digestibility determinations demonstrated the effectiveness of these plant proteins as alternatives to fish- meal. Digestibility trials indicated superior protein digestibility for soy protein (92%), wheat gluten (96%), and corn gluten (90%) in comparison with fishmeal (86%), while energy digestibility was higher than fishmeal (84%) only in wheat gluten (91%; it was 75% for soy protein and 72% for corn gluten). For the growth trial, eight isonitrogenous and isoenergetic (as-fed basis) diets were formulated with differences in the protein sources. Growth in the range of 40-130 g was superi- or to the fishmeal control with the diet containing wheat gluten but inferior in the diets containing soy protein concentrate or corn gluten meal. Diets that replaced 25-100% of the fishmeal with a mixture containing equal portions of all three plant proteins outperformed the control with a 9- 16% greater weight gain and 4-10% lower feed conversion ratio. The use of soy protein or corn gluten as the sole protein source in diets for seabream is not recommended but their use in com- bination with wheat gluten can provide a partial or complete alternative to fishmeal. However, the cost of supplemental arginine made replacement economic at only the lowest replacement level (25%). An in-depth evaluation of the need for this amino acid in the protein mixture could signif- icantly affect the feasibility of using higher replacement levels.

Energy and protein requirements of growing fish can be quantified as the sum of the amounts of energy and protein retained as growth plus the amounts simultaneously lost from the body. The requirement for dietary gross energy and protein can be calculated using the respective effi- ciencies of utilization. Growth of gilthead seabream as a function of body weight and tempera- ture was predicted by the equation: y = 0.024 x BW0.514 x exp0.060T (where y = daily weight gain in g/fish, BW = body weight in g and T = temperature in °C). The gain was determined in fish ranging 1-470 g. The energy content of the fish depended on fish weight and rose from 4.7 to 11.0 kJ/g body mass as the fish grew whereas the protein content was constant at 176 mg/g regardless of fish weight. The efficiencies of utilization of digestible energy (DE) and digestible protein (DP) for maintenance and growth were determined by feeding the fish at increasing feed- ing levels from zero to the maximum voluntary feed intake. The daily requirement of DE for main- tenance was dependent on temperature and determined as (16.6kJ x exp0.055T)/BW in kg0.82. The maintenance requirement for DP was independent of temperature and equaled 0.62g/ BW in kg0.70. The relationship between DE intake and energy gain was linear, constant at kDEg = 0.67 and independent of feed intake and temperature. Efficiency of protein utilization for growth var- ied between 0.33 and 0.80 depending on the DP/DE ratio in the diet. The optimal protein uti- lization for protein deposition was estimated at kDPg = 0.47. Using these values allows optimiza- tion of feeding for seabream culture.

This study was carried out in order to compare the daily energy needs in three fish species: gilthead sea bream, European sea bass and white grouper. The requirements for maintenance and growth and the efficiencies for protein and lipid deposition were estimated. The energy requirement for maintenance is proportional to the metabolic body weight in the form of a x BW(kg)(b), whereas the requirement for growth is dependent on the amount and the composition of the added tissue. The exponent b of the metabolic body weight was determined by energy loss during starvation using fish ranging from 1 to 400 g. Similar values of 0.82, 0.80 and 0.79 were determined for the three species. The efficiencies of digestible energy for growth were determined by feeding fish at increasing levels, starting at zero and up to close to maximum voluntary feed intake. Digestible energy intake and the subsequent energy gain partitioned into protein and lipid gain were measured by comparative slaughter technique. Plotting the relationships (x = DE intake, y = energy gain) for each fish species, the resulting equations proved to be linear throughout, defining the efficiency of utilization of energy by the value of the slope. As the energy gain consists of protein, as well as lipid energy, a multiple regression was employed to determine the energy coefficients for protein and lipid deposition simultaneously with the maintenance requirement: DE intake (kJ) = DEmaint + 1/k(p) x protein energy (kJ) + 1/k(L) x lipid energy (kJ).The calculated energy cost for protein gain (1/k(p)) ranged from 1.79 to 1.90 kJ per kJ protein energy deposited. Energy cost (1/k(L)) for lipid gain was lower than the energy cost for protein gain and ranged from 1.10 to 1.31 kJ per kJ lipid deposited.Therefore, we conclude that utilization of energy and protein for growth does not appear to be very different across the species examined. Differences were found, however, in the magnitude and the composition of the weight gain, which ultimately determines the amount of energy and protein required. (C) 2003 Elsevier Science B.V. All rights reserved.

Diets formulated with increasing digestible energy (10-22 DE MJ kg(-1)) contents and decreasing digestible crude protein (DCP)/DE ratios (34-15 g MJ(-1)) were fed to triplicate groups of Sparus nul atn in three consecutive trials. Fish were hand-fed to apparent satiation and voluntary feed intake was found to be dependent upon dietary DE content. Daily growth was regulated both by energy and protein intake and reached its maximum at high energy levels. Growth composition showed narrow limits regarding protein gain (157-190 g kg(-1)) and a wider range regarding lipid (55-210 g kg(-1)) deposition reflecting the dietary energy to protein supply. Energy utilization for growth was constant at a value of 0.50 regardless of energy intake. Efficiency of protein utilization for growth varied between 0.33 and 0.60 depending on the DCP/DE ratio in the diet. The optimal protein utilization for protein deposition was found to be at 0.47. These values allow daily energy and protein requirements for growing S. aurata to be quantified. This demonstrates that the optimal dietary DCP/DE supply changes with fish size, growth potential and daily feed intake.

Requirements for dietary energy and protein in growing fish can be quantified using the factorial approach, which assumes that the requirement is the sum of growth and maintenance. Thus dietary intake can be calculated using the respective partial efficiencies of utilization.Growth for Dicentrarchus labrax as a function of body weight and temperature was predicted by the equation: y = 0.64 X BW (kg)(0.587) x exp(0.07 X T) (where y = weight gain in g fish(-1) day(-1), BW = body weight in kg and T = temperature in T). The composition of the gain was measured by analyzing whole fish ranging from 1 to 400 g. The energy content was dependent upon fish weight and increased from 5.4 to 10 MJ kg(-1) body mass, whereas the protein content remained constant at 171 g kg(-1). The comparative slaughter technique was used to determine the loss in the fish during starvation and the values amounted to 33.7 kJ BW (kg)(-0.79) day(-1) and 0.39 BW (kg)(-0.69) day(-1) for energy and protein, respectively. The efficiencies of utilization of digestible energy (DE) and digestible protein (DP) for maintenance and growth in D. labrax were determined by feeding fish of various sizes at increasing feeding levels, from zero to maximum voluntary feed intake. DE intake and the subsequent energy gain were measured. The relationship between DE intake and energy gain was found to be linear and was independent of feed intake and body weight. The requirement for digestible energy for maintenance was calculated to be 43.6 kJ BW (kg)(-0.79) day(-1) and for digestible protein 0.66 g BW (kg)(-0.69) day(-1). The partial efficiency of utilization for growth was 0.68 and 0.52 for digestible energy and digestible protein, respectively.Using these values allows optimization of practical feeding at different growth rates for D. labrax culture. (C) 2001 Elsevier Science B.V. All rights reserved.

Soy and rapeseed protein concentrates (SPC and RPC) were evaluated as fish meal substitutes in gilthead seabream Sparus aurata L. diets. The protein concentrates were used to replace 30%, 60% and 100% fish meal, and effects on feed intake, weight gain and feed gain ratio were determined in a 56-day growth trial. Some groups were then grown beyond 56 days, until all reached an average weight of 50 g. A comparison of body composition at 50 g showed no significant differences in protein and ash content among all fish, while lipid and energy contents were different. The 100% RPC and 60% and 100% SPC replacement diets had lower body lipid and energy contents compared with those of the control diet. Feed intake and weight gains were inversely related to inclusion levels of plant proteins. Feed intake dropped to 52-72% of that of the control treatment and weight gain to 46-61%. Energy retention followed this same trend, decreasing from ERV values of 53 to 44 with an increase in dietary plant protein content. With the exception of 100% SPC substitution (PPV = 35), protein retention among treatments was similar (PPV = 37-39). These results suggest that both SPC and RPC may be promising protein sources for inclusion in seabream diets. The relative palatability of these plant proteins could be a limiting factor in their use.

Live adult brine shrimp, Artemia franciscana (Latreille), were enriched with erythromycin to determine if Artemia could accumulate therapeutic levels for subsequent feeding to young fish. Three trials were conducted to determine the erythromycin incorporation and survival rates of enriched Artemia when fed either liposomes containing erythromycin or various erythromycin suspensions. Erythromycin concentration in Artemia fed a liposome suspension was low (∼ 5 μg mL−1) relative to Artemia fed the direct suspension (> 100 μg mL−1) over the same time period. When enriched with suspensions up to 1 g erythromycin L−1 sea water for 14 h, Artemia survival was not significantly affected (P > 0.05) relative to controls. Using a suspension of 1 g L−1, tissue erythromycin concentrations of 109 ± 16 μg erythromycin mL−1 Artemia homogenate (mean ± SEM) were achieved after 12 h. Concentrations above 170 μg mL−1 were obtained using suspensions of 2–5 g L−1, but Artemia survival significantly (P < 0.05) decreased.

A model to estimate the waste production from sea cage culture was established. Using known feed inputs of nitrogen, phosphorus and organic matter, the model quantifies waste discharge from seabream culture. Daily feed intake and growth in Sparus aurata fed a commercial diet with known composition were measured and found to be dependent on fish weight and water temperature. Digestibility of the commercial feed was measured using chromic oxide as a marker and collection of feces by stripping. The proximate composition of Sparus aurata at different sizes was determined and nitrogen and phosphorus content were on average 28.5 and 7.2 g·kg −1 body mass, respectively. Excretion of ammonia-nitrogen and inorganic phosphorus after metabolic processes was calculated as the difference.

Factorial determinations of energy and protein requirements in growing Sparus aurata were carried out at 23–24°C. The energy content in the whole fish was dependent on fish weight and ranged from 5 to 11 MJ kg−1 body mass for 1–250 g fish, whereas the protein content remained constant at 179 g kg−1. During starvation the fish lost 42.5 kJ body weight (BW) (kg)−0.83 day−1 and 0.42 g protein BW (kg)−0.70 day−1. The maintenance requirement for energy was calculated to be 55.8 kJ BW (kg)−0.83 day−1 and for protein 0.86 g BW (kg)−0.70 day−1. Utilization of digestible energy and digestible crude protein below and at maintenance was determined as 0.72 and 0.51, respectively. Utilization of digestible energy and digestible crude protein for growth above maintenance was determined as 0.46 and 0.28, respectively. These values allow estimation of requirements for growing Sparus aurata.

This study was undertaken to assess the potential for including rapeseed protein concentrate (RPC) as a partial replacement for locally available fish meal (Chilean origin) in diets for gilthead seabream cultured in Israel. Fifteen groups of seabream of 2.6 g mean weight held in 26 degrees C sea water on a natural photoperiod were each fed one of five isonitrogenous (390 g digestible protein/kg) and isoenergetic (16.3 MJ digestible energy/kg) diets twice daily at 3.5% of their biomass for 60 days. Chilean fish meal in the control diet was replaced progressively (30%, 45%, and 60%) by RPC so that the latter protein source replaced 26%, 38.9% and 53.3% of the fish meal protein in diets 2, 3, and 4, respectively. A fifth diet contained a blend of premium quality fish meal, Norse LT-94(R) which replaced the Chilean source of fish meal at the level of diet 3, and RPC. This was done to determine whether the available levels of nutrients (e.g. essential amino acids and minerals) in the premium quality meal were more complementary to those in RPC for performance of seabream relative to the local fish meal source.Weight gains and specific growth rates of seabream after 60 days were noted to be inversely related to the dietary level of RPC when the source of fish meal was Chilean. Fish fed diet 5, however, grew as well as those fed the control diet even though 38.9% of the fish meal protein in diet 5 was replaced by protein from RPC. The trend for feed utilization paralleled that for growth.The results suggest that there is potential for including high levels of RPC in diets for seabream if this protein source is blended with premium quality fish meal. The poorer performance of seabream fed diets based upon combinations of RPC and Chilean fish meal may indicate deficiencies of one or more essential amino acids and minerals that possibly can be corrected through appropriate dietary supplementation.

Apparent digestibility of crude protein, amino acids, lipid, carbohydrate and energy was measured for a range of feed ingredients fed to gilthead seabream, Sparus aurata L. - fish meal, poultry meal, meat meal, blood meal, squid meal, extracted soyabean and wheat flour. Chromic oxide was used as a non-absorbed reference substance and faeces were collected by stripping. Diets compounded from mixtures of these ingredients were then used to examine the possibility of predicting the digestibility of formulated diets.Apparent digestibility of crude protein ranged from 79% to 90%, lipids from 83% to 95% and energy from 72% to 88% in the different ingredients. Apparent digestibility of carbohydrates was lower and ranged from 49% to 77%. Apparent digestibility of amino acids was higher than that of crude protein and differences were found among digestibilities of individual amino acids.Tests conducted using five compound diets indicated that ingredient digestibility was additive for protein, amino acids, lipids and energy, whereas the digestibility of carbohydrates in the compound feeds was slightly lower than predicted.Diets for Sparus aurata may thus be formulated on the basis of digestibility of individual ingredients.

Food preferences were studied in 11 fish species in order to find out their potential as epiphyte and copepod controllers in Gracilaria cultures, The fish were exposed to mixtures of Gracilaria and Ulva with other epiphytes included, in the presence of copepods, and the intestinal content of the fish was determined. Aphanius dispar and Tilapia zillii (acclimated to seawater) emerged as potentially useful epiphyte controllers, and Aphanius dispar and Diplodus annularis were potential copepod controllers in Gracilaria cultures.

The interaction between essential dietary components and changes in tissue nutrient reserves, egg quality and egg composition, were studied from 60 d before and during the spawning of Sparus aurata broodstock. Fish were given isonitrogenous (550 g/kg dry weight) and isolipidic (100 g/kg dry weight) diets, based on protein and lipid extracts of squid meal. Diets differed in the levels of n-6 (10-30 mg/g dry weight) and n-3 (0-10 mg/g dry weight) essential fatty acids. The effects of these diets on biochemical and fatty acid composition of body tissues, and the subsequent effects on egg composition and egg viability were measured. Dietary essential fatty acids were mostly incorporated into the liver, ovaries, digestive tract and associated adipose tissues. The lipid composition of these tissues reached an equilibrium with dietary lipid composition within 15 d of feeding on any given diet. Muscle and gill cartilage tissues did not show any significant changes in their biochemical and fatty acid composition, even after 60 d feeding. Egg viability decreased significantly within 10 d of feeding the broodstock with a diet deficient in n-3 highly unsaturated fatty acids (n-3 HUFA). The levels of n-3 HUFA in both polar and neutral fractions of egg lipid were directly correlated with their levels in the broodstock diet. When the total amount of egg n-3 HUFA dropped below 17 mg/g dry weight, egg viability and larvae hatching rate decreased by 53 % and 47 % respectively. These results suggest that the biochemical composition of organs involved in S. aurata reproduction are highly sensitive to the nutritional value of the diet, which affects egg and larval quality rapidly.

The success of microdiets commonly used in the cultivation of marine fish larvae is limited to serving as partial replacements for live food. This limited success is thought to be associated with a reduced digestive ability due to an incompletely developed digestive system. The enhanced growth obtained from live food has been partially attributed to the digestive enzyme activity of the food organism. The present study was designed to test the effect of an exogenous digestive enzyme incorporated. into a microdiet on the growth of Sparus aurata.

The present study tested the effect of dietary lecithin and exogenous lipase on the incorporation of oleic acid in the tissue lipids of gilthead seabream larvae (Sparus aurata). Two of four microdiets were prepared by the addition of [14C]oleic acid as free fatty acid (FFA) to diets containing either 5% cuttlefish liver oil (CLO) or 5% soybean lecithin. Glycerol tri[1-14C]oleate was similarly incorporated in two other diets identical in lipid (4% cuttlefish liver oil, 1% soybean lecithin) and non-lipid composition but differed in that one contained a supplement of 0.05% porcine lipase. The effect of these diets was tested by following the incorporation of the label (dpm/mg larvae DBW) in the neutral and phospholipid fractions of seabream larvae at four different ages (21, 27, 32 and 45 days after hatching).

Tissue fractions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of 5–36-day-old Sparus aurata larvae, fed various levels of (n−3) highly unsaturated fatty acids (HUFA), were examined. Regression analyses were performed separately on eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels in these different phospholipids with larval growth as a means of evaluating their possible physiological value. PC and PE were the major phospholipid groups in larvae from this study. Their levels in fish were independent of diet although their composition was markedly influenced by the (n−3) HUFA content in the food they consumed. Larval phosphatidylcholine EPA/DHA ratios generally reflected those of the diet, suggesting that levels of assimilation of these essential fatty acids were similar. In contrast, the PE fraction, although a lesser constituent than PC, demonstrated the highest level (% of phospholipid) of (n−3) HUFA, mainly due to its selective incorporation of DHA. As a result there appears to be a relationship, independent of age, between the suggested patterns of EPA and DHA assimilation and growth. In the PC fraction, EPA and DHA were similarly incorporated and demonstrated high regression values (r2 > 0.73). In contrast, DHA was preferentially assimilated into the PE fraction and was highly correlated with growth in 5–36-day-old larvae (0.77 and 0.80, respectively) while the EPA of PE was poorly associated with this parameter (0.24 and 0.27, respectively). The comparable or higher assimilation of DHA over EPA into the main larval phospholipids accompanied by good correlations with growth implies that DHA may have higher biological value in S. aurata larvae. In addition, the PE fraction may be particularly relevant in growth since there appears to be a higher assimilation of DHA into this phospholipid.

The effect of feeding Artemia nauplii containing different levels of n-3 HUFA on growth, survival and size distribution was tested in 22-36-day Sparus aurata larvae. Five treatments were prepared by feeding 24-h-old nauplii various percent ratios (0:100, 10:90, 25:75, 50:50, 75:25) of a commercial emulsion (high in n-3 HUFA) and a soybean oil-egg yolk emulsion (3:1 preparation, deficient in n-3 HUFA). Each treatment had five replicates and provided the following n-3 HUFA levels in Artemia: 2.6, 7.4, 12.3, 18.8, 29.8 mg/g DBW nauplii.Dietary n-3 HUFA showed a linear correlation (P < 0.01) with larval relative growth rate (RGR), length and final tank biomass. Fish fed the highest level of n-3 HUFA demonstrated an RGR (86.4%) and final tank biomass (30.9 g wet wt) that was more than double the values exhibited by fish fed the lowest n-3 HUFA diet (39.9%, 14.0 g wet wt, respectively). Survival, in contrast, was not linearly correlated with dietary n-3 HUFA although there was a significant survival (P < 0.05) effect between the n-3 HUFA poorest diet and the majority of remaining treatments.The lesser n-3 HUFA diets (2.6, 7.4 and 12.3 mg/g DBW) nauplii produced larval populations consisting mainly of small fish (6.9 mg +/- 1.9) while n-3 HUFA rich diets (18.8 and 29.8 mg n-3 HUFA/g DBW nauplii) increased the fraction of larger larvae (23.0 +/- 6 mg). The level of n-3 HUFA (mg/g DBW) in larval phospholipid was highly influenced by the content of these fatty acids in the diet. However, the phospholipid n-3 HUFA levels (mg/g DBW) in larvae fed the same diet were similar regardless of fish size. Finally, by examining different size larvae in groups under the various n-3 HUFA treatments, this study found that the inverse relationship between larval lipid and moisture was a function of growth rate and not dietary n-3 HUFA.

The use of enrichment emulsions to increase the (n−3) HUFA content of rotifers before feeding to marine culture organisms has been shown to increase growth and survival. These emulsions require (n−3) HUFA-rich oils which are not always available. A technique for the low temperature separation of unsaturated from saturated fatty acids is described, which can be used to enrich oils otherwise poor in (n−3) HUFA. Capelin fish oil that underwent low temperature crystallization separation at −70°C for 8 h produced an enriched fraction containing 50% less saturated fatty acids and 50% more polyunsaturates (2–6 double bonds). Emulsions containing this enriched fraction were fed to rotifers and resulted in a three-fold increase in the polyunsaturates of the rotifers.