Feeding guides for salmonid fishes have been available from various sources for many years. These feeding guides have originated in one way or another from earlier feeding charts of the 1950-60s when meal-meat mixture diets were widely used. Few of the feeding guides available today are based on actual bioenergetics data at different water temperatures and are adapted to high energy diets. New feeding standards have been developed based on principles of nutritional energetics in which the digestible energy content of diet, digestible protein and energy ratio and the amount of digestible energy required per unit of live weight gain are taken into account. The gain expressed as retained energy in carcass and maintenance energy at different water temperatures is the main criteria for energy and feed allocations. Series of bioenergetic models were developed based on these principles and a stand-alone multimedia program was written to facilitate computation of the models. This program predicts growth and energy, nitrogen and phosphorus retention, requirements and excretions to determine feeding standards, waste outputs and effluent water quality based on a biological method. The models require initial and final body weights, water temperature, growth coefficient, carcass energy content and waste coefficients to estimate input and output. Accurate determinations of the thermal-unit growth coefficient, apparent digestibility coefficients and retention efficiencies are essential and these coefficients are determined by biological experiments in the laboratory and field. Oxygen requirement is included to aid environmental control in fish culture system. The Fish-PrFEQ program also contains modules for production records, performance calculations and data base management for input and output data which may be exported for further data and graphic manipulations.

The general principles behind the bioenergetic approach for predicting growth, as well as for decreasing feed and nutrient losses, have been set forth for salmonids. Given the diversification of fish farming activities around the world and the ever increasing concern for water quality management, it becomes essential to verify whether an approach developed for salmonids is applicable to other species. Given this general background, an attempt is made here to check the theoretical assumptions and technical considerations behind the bioenergetic principles developed for rainbow trout with other freshwater or marine species. From a conceptual point of view, recent literature data do indicate that as far as nitrogen or energy balance is concerned, the general scheme is as valid for marine species as it is for salmonids, even in quantitative terms. Given the methodological tools available today, it should not be difficult to reduce feed and nutrient losses and to estimate the potential environmental loadings using the same principles for non-salmonids.

The incorporation of various bulk agents by substitution of an equivalent amount of the basal mixture was studied in terms of protein digestibility, growth performance and body composition in European seabass (Dicentrarchus labrax) juveniles. During the growth trial, triplicate groups of 40 seabass (mean initial weight: 7.0 g) were grown in seawater (salinity: 35; temperature: 18 °C) over 60 days. Fish were hand-fed, three times a day, one of seven experimental diets. Bulk agents tested at 10 or 20 % level of incorporation were silica, cellulose and a natural zeolite (chabamin). Feeding rates were adjusted in proportion to the percent dilution of the control diet without bulk incorporation. The incorporation of the bulk agents, at a 10 and 20 % level, did not affect protein digestibility or growth performance. Dietary bulk incorporation reduced feed efficiency values, particularly at the 20 % incorporation level. However, this reduction was mostly caused by the dietary nutrient dilution of the bulk-incorporated diets, rather than by a negative effect of the bulk agents as dietary ingredients. In comparison to the control treatment, bulk incorporation at 10 and 20 % level did not affect protein retention values. When compared with the control diet, 20 % bulk agent incorporation changed the evacuation profile of faeces and increased faecal egestion time.

A study was carried out to determine the effect of feeding level and water temperature on growth and feed efficiency, nutrient and energy utilization and waste outputs of rainbow trout. A practical diet was fed to near-satiation to groups of fish reared at 6, 9, 12 and 15 °C. At each temperature, the feed intake of other groups of fish was restricted to about 85 % or 70 % of the amount of feed consumed in the previous week by the fish fed to near-satiation. Total feed intakes over 12 weeks were, on average, 76 % and 65 % of total feed intake of the near-satiety group for R1 and R2, respectively. Reducing the feed allocation resulted in significantly (P < 0.05) lower weight gains compared to feeding to near-satiation regardless of the rearing temperature. Feeding level and water temperature had no significant (P < 0.05) effect on feed efficiency, carcass composition or efficiencies of digestible nitrogen and digestible energy retention. Increasing temperature resulted in an increase in the apparent digestibility of dietary dry matter, nitrogen and energy (P < 0.05). The increase in digestibility of dry matter and nitrogen with increasing temperature resulted in higher estimated total solid and solid nitrogen waste outputs per kg fish produced (P < 0.05) at lower water temperatures. Estimated dissolved nitrogen and phosphorus waste outputs (g/kg fish produced) were not affected by the feeding level or water temperature. A highly significant (P < 0.01) linear relationship was observed between metabolizable energy (ME) intake above basal metabolism and recovered energy. The efficiency of ME utilization for growth (Kpf) was 0.61 and this coefficient was not affected by feed intake or water temperature. Protein and lipid were deposited in a constant ratio (1 kJ protein gain: 1.4 kJ lipid gain) regardless of ME intake or water temperature.

High energy extruded diets were formulated to contain the same level of protein supplied either by soy protein concentrate (SPC) or fish meal. Three experiments were performed in order to measure voluntary feed intake and feed waste, faecal losses and soluble losses of nitrogen and phosphorus in rainbow trout (average body weight: 100 g). Voluntary feed intake and growth performance of fish fed with demand feeders were not different when diets contained 0, 50 or 75 % SPC instead of fish meal. Total replacement of fish meal by SPC led to a significant decrease in feed intake and resulted in poor growth. This was partly due to methionine deficiency in the SPC based diet. With the addition of crystalline DL-methionine in the diets, an improvement of feed intake and growth performance was apparent. Protein digestibility was high, regardless of the protein source. Excretion of ammonia and urea increased with the level of SPC in the diet. Nitrogen losses decreased when methionine was added to the diet containing only SPC as a protein source. Availability of phosphorus increased with the level of SPC in the diets. Daily soluble losses were not affected by the dietary treatments but the pattern of phosphorus excretion after feed intake was modified. The rise in soluble phosphorus in water occurred later when fish were fed diets with soy protein whatever the dietary level of soy protein concentrate.

A study on nitrogenous and phosphorous waste production in European seabass (Dicentrarchus labrax) was carried out in a flow-through land-based farm. The main objectives were (i) to calculate nitrogenous (N) and phosphorous (P) waste production (particulate and dissolved) from in situ measurements for different rearing ponds with specific fish biomasses, fish sizes and flow rates, (ii) to establish nitrogenous and phosphorous waste production budgets, ratios and equations, and (iii) to compare, for the whole farm, in situ measurements to estimate N and P waste production from waste equations. Waste production was manifest by an increase in concentrations of total ammonia nitrogen, total Kjeldhal nitrogen, particulate nitrogen, dissolved phosphorus and total phosphorus concentrations in the outlet water compared to the inlet water for both batches and whole farm. However, no production of nitrite or nitrate was observed. In our budgets, the N and P amounts from biomass gains and wastes were explained by the N and P derived from feed over the range 83.9−105.2 % and 66.5−104.6 % respectively, depending on the fish batch. Values were respectively 103.4 and 87.5 % for the same calculations in the farm. When the whole-farm waste production was calculated from previous equations derived from batches, and then compared with the measured data, the percentages of recovery (estimated by the ratio predicted data/measured data) were 88 and 94 % for total-N and total-P respectively.

A trial was carried out to compare the growth performance, body composition and apparent digestibility coefficients (ADC) of diets by seabass, with an initial weight of 13.5 g, fed diets including fish meal (68.6 % of the dietary protein) or soybean meal (65.6 % of the dietary protein) as the main protein sources. Microbial phytase was added to the soybean meal based diet (1 000 and 2 000 IU·kg−1) and to the fish meal based diet (2 000 IU·kg−1) in order to study its effect on phosphorus utilisation. Results of this trial showed that growth rate, feed conversion and nitrogen retention were significantly better in fish fed the fish meal based diet. Energy retention was similar in both groups. ADC of protein were similar among groups. ADC of phosphorus was significantly higher in the fish meal based diet (63 %) than in the soybean meal based diet (25 %). Supplementation of the fish meal based diet with microbial phytase did not improve the ADC of phosphorus, while in the soybean meal based diet the inclusion of 1 000 and 2 000 IU·kg−1 of microbial phytase significantly increased the ADC of phosphorus to 71.5 % and 79.8 %, respectively. It is concluded that for practical purposes supplementation of diets with microbial phytase may prove valuable in diets including high levels of plant feedstuffs.

Dietary nitrogen and phosphorus utilisation were evaluated in rainbow trout, Oncorhynchus mykiss, fed fish meal and soy protein concentrate-based diets. Two short term trials were conducted with rainbow trout having initial mean weights of 24 and 156 g maintained at a water temperature of 17 ± 1 °C, during which triplicate groups of trout were fed the respective diets two times a day to apparent satiety by hand. In both trials, fish fed fish meal-based diet exhibited significantly higher growth. In small trout, feed/gain ratio and protein utilisation were slightly higher in groups fed the fish meal-based diet; however, in larger fish, there was no significant difference between treatments. Nitrogen retention and loss were not affected by dietary treatments, while phosphorus retention was higher in fish fed diet containing fish meal (30 and 17 %) than in fish fed diet containing soy protein concentrate (25 and 15 %) and greatly reduced in larger fish. Phosphorus losses were 10 and 13 g·kg gain−1 of fish fed the fish meal-based diet, while those for fish fed the diet without fish meal were 14 and 17 g.

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.

Apparent digestibility coefficients (ADCs) of macro- and micronutrients and energy of two diets were measured with common carp Cyprinus carpio reared at two water temperatures (18 and 25 °C). Two diets containing either soy protein concentrate (SPC) or Norwegian herring meal (FM) as a major protein source were formulated. Dicalcium phosphate was incorporated at a level of 4 % of the former diet. Duplicate groups of 20 fish (body weight: 55 g) were fed by hand twice a day to apparent satiety. After a 7-day conditioning period, faecal collection was made over 10 days using an automatic faeces collector. ADC of dry matter was not different (P > 0.05) between fish fed the two diets at 18 °C, but at 25 °C, we observed a higher ADC value in fish fed the FM diet than in those fed the SPC diet. ADC of protein was higher in fish fed the SPC diet than in the FM groups at either temperature. ADC of lipids was not different between the two groups at 25 °C but was found to be higher in fish fed the SPC diet than in the FM group at 18 °C. ADCs of energy and ash of the two fish groups remained constant at both water temperatures. Availability of phosphorus was significantly higher (P < 0.05) from fish meal based diets than from SPC based diets at both temperatures. A more striking effect of dietary protein source was found in the availability of calcium, which was lower in carp fed SCP based diets.

In the framework of echinoid cultivation, whose objective is to succeed in continuously producing large amounts of edible sea urchins (Paracentrotus lividus) under controlled conditions (aquaculture), gonadal growth is to be optimized. Among the various parameters influencing the production of roe, the quantity of food distributed was tested for optimization. After a 1-month fast, echinoids were fed artificial food pellets (enriched in soybean and fish proteins) for different periods of time over 48 h, the food thus being available ad libitum for 8, 16, 24, 32, 40, and 48 h; the cycles were repeated for a month. The results show that the quantity of food intake and the gonad index peak after about 35 h of food availability. This suggests food should be distributed discontinuously for optimal gonad production and minimal waste.

This paper describes both an experimental and a commercial-scale system for sludge dewatering and stabilisation. In the experimental system, back-wash water from rotating disk microsieves was settled in a conical sedimentation tank. This tank functioned well, commonly removing more than 75−80 % of the solids, at an overflow rate of 1.0−2.7 m·h−1. The hydraulic load was maintained low, so treatment efficiency was significantly positively influenced by inlet concentration and not inflow rate. Lime was added to the settled sludge. More than 99.9 % of the pathogenic viruses and bacteria studied were killed within 7 days at pH 12. In the commercial system, a newly developed combined effluent treatment and sludge processing system, was located in a large Norwegian salmon (Salmo salar) smolt farm. Four drum microsieves were used to separate particles from the primary effluent flow. The back-wash water, amounting to a maximum of 0.3 % of the 30−35 m3·min−1 primary flow, was dewatered using another drum microsieve. Dewatered back-wash water from this sieve was pumped to a sedimentation tank with a top surface area of 3.3 m2 and a volume of 5.5 m3. This system produced on average 0.7 L settled sludge containing ca. 10 % dry matter per kg of feed supplied. Sludge tapped from the bottom of the sedimentation tank was stabilised by mixing with lime. This system produced on average 0.7 L settled sludge containing ca. 10 % dry matter per kg of feed supplied. After stabilisation, the stored sludge was diluted with cattle manure and spread on agricultural land. The primary treated effluent was discharged into the receiving marine water body. The running costs of effluent and sludge treatment, including sieving, settling and stabilisation, amounted to US$ 0.056 per smolt produced, or about 5 % of the total production costs. In the recipient, no settled solids were detected on the seabed at the outlet point of the treated effluent.

An experimental small scale partial recirculating system for rainbow trout was assembled. The system components were two 1.3-m3 fish tanks with sloping bottoms, each connected to a sedimentation column and containing 50 kg rainbow trout biomass, an anaerobic up-flow digester (total volume 0.424 m3, available volume 0.382 m3) connected to the funnel shaped bottom of the sedimentation column by means of a peristaltic pump, an aerobic submerged plug-flow filter (total volume 1 m3; filled with 0.83 m3 plastic rings with a specific surface of 194 m2·m−3) and a submerged pump. Aeration was provided through porous stones. The anaerobic digester was filled with 35 mm cubes of expanded polyurethane foam (25 pores·cm−2, specific surface 1.375 m2·m−3, filtering volume 0.291 m3) and kept at a temperature of 24−25 °C using an electric heater. The gas chamber at the top of the anaerobic digester was connected to a gas meter and to an infrared continuous gas analyser. Measures on system performance with a recirculation rate of 60 % were done following three feeding levels (1, 1.5 and 2 % live weight). At the highest feeding rate, 2.8 L of faecal sludge collected from the trout tanks were pumped every four hours in the anaerobic digester. Slurry characteristic were: total N 0.197 g·L−1, TAN 0.014 g·L−1, volatile solids (VS) 16.91 g·L−1, suspended solids (SS) 21.39 g·L−1 and pH 6.9. Biogas production was 144 L·d−1 (mean value) with a methane content higher than 80 %. Methane volumetric production was 0.3 m3·m−3·d−1 and methane daily yield was 0.4 and 0.32 m3·kg−1 VS and SS respectively. After passing through the anaerobic digester, effluents were characterized by a total N content of 0.243 g·L−1, TAN 0.222 g·L−1, VS 1.1 g·L−1, SS 1.32 g·L−1 and pH 6.8. The anaerobic digester was able to significantly reduce VS and SS content of wastewater and the zeolite ion-exchange column significantly improved water quality of effluent produced by the digester. The aerobic biofilter significantly reduced the ammonia content of the water leaving the fish tanks.

Marine land-based fish farms located in coastal wetlands (salt-pond zones, lagoon banks, etc.), whether extensive or intensive, send farm effluents directly to the sea or after short periods of stocking in retention reservoirs. The aims of our investigation have been to compare the efficiency of current and potential water treatment procedures in open-air. Wastewater retention ponds in commercial farms (Atlantic coasts of France) are efficient in removing up to 1 metric ton of particulate material (dry weight) per hectare and per day (faeces and unconsumed feed), but are inefficient in reducing dissolved wastes, both organic (urea, amino acids, protein) and inorganic (total ammonia nitrogen, phosphates). Forthcoming outdoor technology to treat these forms of waste were examined by trials at different sites: treatment by foam fractionation in extensive systems (Italian fish pond culture), treatment by microalgae production (Skeletonema costatum) and oyster filtration (Crassostrea gigas) in intensive systems (sea bass farm, Dicentrarchus labrax). It can be concluded that foam fractionation coupled with aeration and water circulation is a good way to treat and recirculate wastewaters in extensive systems, but that a multiple treatment combining a retention pond, foam fractionation and microalgae-bivalve filtration, is the best solution to treat all these forms of wastes from intensive systems.