Abdel-Fattah M. El-Sayed

Alternative dietary protein sources for farmed tilapia, Oreochromis spp.

Tilapia are widely cultured in the tropical and subtropical regions of the world and constitute the third largest group of farmed finfish, only after carps and salmonids, with an annual growth rate of about 11.5%. Global production of farmed tilapia has increased more than three-fold since 1984, from 186,544 m.t. to 659,000 m.t., representing about 4.48% of total farmed finfish in 1995, with a value of US

Long-term evaluation of cotton seed meal as a protein source for Nile tilapia, Oreochromis niloticus (Linn.).

925 million. Feeding represents over 50% of the operational costs of aquaculture. The shortage in world production of fish meal (the main conventional protein source), coupled with increased demand for fish meal in feeds for livestock and poultry is likely to reduce the dependence on fish meal as a single protein source in aquafeeds. Therefore, fish nutritionists have made several attempts to partially or totally replace fish meal with less expensive, locally available protein sources. The present review presents alternative dietary protein sources for tilapia, with emphasis on fishery by-products, terrestrial animal by-products, oilseed plants, aquatic plants, single cell proteins, grain legumes, plant protein concentrates and cereal by-products. The nutritive values, inclusion levels, constraints and economic evaluation of these sources are discussed.

Carbohydrate-to-lipid ratios in diets for Tilapia zillii fingerlings

Long-term evaluation of different cotton seed meals (CSM) as protein sources for Nile tilapia, Oreochromis niloticus, was conducted. Corticated CSM (CC) and decorticated CSM (DC), with or without crystalline L-lysine supplementation, were incorporated into practical, isocaloric (475 kcal GE100 g) diets containing approximately 30% crude protein. Fish meal (FM)-based diet served as a control. Test diets were fed to triplicate groups of O. niloticus (20 g) at a daily rate of 2–3% of their body weight for 130 days. Fish which received FM diet had significantly better percent gain, specific growth rate (SGR), feed conversion (FC) and protein efficiency ratio (PER) than those fed CSM diets. DC diets produced significantly better growth and FC than CC diets, while PER was not significantly different. The addition of crystalline L-lysine to CSM diets did not significantly affect fish performance. Cost/benefit analyses of the test diets indicated that CC was economically the best, followed by DC, while FM diet showed the least economic potential.

Anthropogenic enhancement of Egypt's Mediterranean fishery

Abstract Four isonitrogenous (30% crude protein), isocaloric (300 kcal ME/100 g), semipurified diets with variable levels of carbohydrates (dextrin) and lipids (cod liver oil-soybean oil mixture) were formulated to determine the ability of Tilapia zillii fingerlings to utilize each as an energy source. The diets were fed to triplicate groups of fish at a daily rate of 3% of their body weights for 6 weeks. No significant differences were observed in the growth and feed conversion of T. zillii fed diets with carbohydrate-to-lipid (CHO:L) ratios ranging from 8.76 to 0.81. A diet containing a CHO:L ratio of 24.11 produced significantly retarded performance, presumably caused by an essential fatty acid deficiency in the diet. These results indicate that T. zillii can efficiently utilize carbohydrates and lipids as energy sources. They can be substituted for one another at a rate of 2.25:1 commensurate with the CHO:L physiological fuel values.

Effects of fermentation methods on the nutritive value of water hyacinth for Nile tilapia Oreochromis niloticus (L.) fingerlings

The highly productive coastal Mediterranean fishery off the Nile River delta collapsed after the completion of the Aswan High Dam in 1965. But the fishery has been recovering dramatically since the mid-1980s, coincident with large increases in fertilizer application and sewage discharge in Egypt. We use stable isotopes of nitrogen (δ15N) to demonstrate that 60%–100% of the current fishery production may be from primary production stimulated by nutrients from fertilizer and sewage runoff. Although the establishment of the dam put Egypt in an ideal position to observe the impact of rapid increases in nutrient loading on coastal productivity in an extremely oligotrophic sea, the Egyptian situation is not unique. Such anthropogenically enhanced fisheries also may occur along the northern rim of the Mediterranean and offshore of some rapidly developing tropical countries, where nutrient concentrations in the coastal waters were previously very low.

Assessment of the effect of plant inhibitors on digestive proteases of nile tilapia using in vitro assays

This study was conducted to evaluate the effects of different fermentation methods on the nutritive value of water hyacinth (WH) for Nile tilapia fingerlings. Fresh dry hyacinth (FH), molasse-fermented hyacinth (MF), cow rumen content-fermented hyacinth (RF) and yeast-fermented hyacinth (YF) were incorporated into nine isonitrogenous (35% CP), isocaloric (450 kcal GE/100 g) test diets, as a replacement of dietary wheat bran at 10% and 20% substitution levels. The test diets were fed to triplicate groups of fish fingerlings (1.1 g average body weight) stocked in 20-l fiberglass tanks, in a closed, recirculating indoor system, twice a day, at 5% body weight/day, for 50 days. The control diet (WH-free) produced significantly better weight gain, specific growth rate (percent SGR) and feed utilization efficiency than WH-based diets. Growth rates and feed utilization efficiency of fish fed WH at 10% inclusion level were not significantly affected (P>0.05) by WH fermentation methods. At 20% inclusion level, fish performance was further reduced (P<0.05); however, fermented WH produced better performance (P<0.05) than fresh WH. Molasse-fermented WH was utilized more efficiently than yeast-fermented and cow rumen-fermented WH, respectively. These results indicate that fermentation of WH may only be necessary when incorporated into Nile tilapia diets at ≥20% inclusion levels.

The scientific strategy needed to promote a regional ecosystem-based approach to fisheries in the Mediterranean and Black Seas

This study was conducted to evaluate the effect that feeding on differently treated soybean meals may have on digestive protease activity of the Nile tilapia (Oreochromis niloticus). Untreated full fat soybean (USB), heated fullfat soybean (HSB), soaked fullfat soybean (SSB) and commercial defatted soybean meal (DSB) totally replaced fish meal (FM) in test diets (30% crude protein) fed to fish juveniles (mixed sexes) for 30 days. After this period, total activity of digestive proteases was determined in each group and the ability of such proteases to hydrolyse the different protein sources and formulated feeds was tested in vitro. Significant differences were observed between treatments, with lower values obtained for fish fed on USB, suggesting a modification in the composition of secreted proteases. In addition, an inhibitory effect produced by wheat bran included in the test diets on protease activity of fish was also shown. The usefulness of using in vitro assays for a preliminary assessment of the nutritive value of aquafeed ingredients is discussed.

Evaluation of marine psychrophile, Psychrobacter namhaensis SO89, as a probiotic in Nile tilapia (Oreochromis niloticus) diets

This manuscript is an outcome of the workshop entitled “Scientific Strategy for a Global Approach to Promote Regional Ecosystem-based Approach to Fisheries (EAF) in the Mediterranean and Black Seas” held in Sète (France) in July 2012. The workshop was organized by Work-Package 6 of the coordination action “Coordinating Research in Support to Application of Ecosystem Approach to Fisheries and Management Advice in the Mediterranean and Black Seas” (CREAM), funded by the EU Seventh Framework Programme. The main aim of the workshop was to discuss what is needed to advance on a robust scientific strategy to promote EAF in the Mediterranean and Black Seas. Participants discussed a series of scientific recommendations for promoting the coordination of initiatives with the aim of contributing to an operational EAF. Discussion was carried out on (i) what can be learnt from case studies that promote EAF worldwide, (ii) how a scientific strategy for EAF can be built, and (iii) which are the future scientific networking activities to promote EAF. Here we summarize the discussions and conclusions of the workshop, and we present the recommendations and future initiatives proposed to advance EAF in the Mediterranean and Black Seas region. Participants to the workshop agreed that the achievement of a common vision regarding the Mediterranean and Black Seas region should be one of the first and most important elements towards a successful EAF. A common vision should recognise the need to promote the reconciliation of conservation and exploitation, and to aim for a good socioeconomic and ecological status. The vision should also promote the recovery of ecosystems and rebuilding of marine commercial stocks and predator species. EAF initiatives, carried out worldwide, illustrated that whilst the development of relevant science is essential to render the EAF process operational, the involvement of stakeholders is the key factor that characterises successful initiatives. This is especially important in the Mediterranean and Black Sea context, where many stakeholders show conflicting interests and associated trade-offs. During the workshop, it became clear that numerous overlapping and poorly coordinated initiatives for EAF exist in the region. The group discussed the integration of the existing initiatives in a coordinated manner and arrived to the conclusion that a scientific network to promote coordinated and operational EAF initiatives created by the scientific community is needed. Ultimately, the discussion was focused on how to build such a scientific network and how to proceed to consolidate the regional scientific vision, with a clear scientific strategy and roadmap, including a diversified toolbox. In the short term, the proposed EAF scientific network should (i) document and coordinate scientific initiatives, (ii) promote the sharing of scientific information and capabilities, (iii) promote data availability, integration, harmonization, and interoperability, (iv) promote training capabilities and capacity building of the scientific community and stakeholders, (v) establish mechanisms to disseminate knowledge, and communicate EAF benefits, and (vi) promote concrete regional scientific initiatives. In the long run, the network should promote scientific advice on EAF to inform adaptive management, and promote EAF implementation at different geographical scales (from local to regional) using a transversal approach. The ultimate goal of the network should be to link management advice to good scientific information providing useful advice to address management objectives (i.e. present the trade-offs), and creating a knowledge-based management approach.

Effects of food sources on growth rates and survival of Nile tilapia (Oreochromis niloticus) fry

Abstract Marine environment represents a promising source of new, unconventional bioactive compounds with health‐promoting abilities, which can be used as food supplements. The present study was carried out to evaluate the efficacy of marine Psychrobacter namhaensis SO89 on growth performance and immune response of Nile tilapia (Oreochromis niloticus). P. namhaensis were isolated from marine environments and phylogenetically identified by 16S rRNA gene sequences. The bacterial isolate was incorporated in Nile tilapia diets (30% crude protein) at three concentrations (0.0, 0.5 and 1.0%; w/w) (designated as T0, T0.5 and T1, respectively), which were equivalent to 0.0, 2.8 × 107 and 5.6 × 107 CFU g−1 diet, respectively. The diets were fed to Nile tilapia fingerlings (4.58 ± 0.14 g average weight) at a daily rate of 3% of their live body weights (BW), 3 times a day for 50 days. The best growth rates and feed utilization efficiency were obtained at 0.5% P. namhaensis SO89 concentration. Hematocrit (Ht%), hemoglobin (Hb%), erythrocytes (RBC) and total leukocyte (WBCs) values were significantly higher in P. namhaensis SO89‐ fed groups than in the control group. Similarly, immunoglobulin M (IgM), alternative complement hemolysis (ACH50), phagocytic and lysozyme activities significantly increased following dietary P. namhaensis SO89 supplementation at 0.5% concentration compared to the control group. The expression of IL‐4 and IL‐12 genes was also significantly up‐regulated in P. namhaensis SO89‐treated groups up to 0.5% concentration. Increasing bacterial concentration to 1% resulted in a significant decrease in fish performance and immune response. The present results suggest that marine psychrotolerant (Psychrobacter namhaensis) can be considered as a novel feed additive in Nile tilapia feeds. HighlightsWe studied the effect of marine Psychrobacter namhaensis on growth performance and immune response of Nile tilapia.Fish were fed test diets supplemented with three concentrations of bacterial isolate (0.0, 0.5 and 1.0%).Supplemental P. namhaensis improved growth rates, feed utilization efficiency and immune response.The best performance was obtained at 0.5% bacterial concentration.

Evaluation of Periphyton as a Food Source for Nile Tilapia (Oreochromis niloticus) Juveniles Fed Reduced Protein Levels in Cages

The present study was conducted to investigate the effects of live food (Chlorella vulgaris, Artemia fransciscana), artificial feed and combinations of both types (Chlorella + Artemia nauplii; Chlorella + Artificial feed; Artemia nauplii + Artificial feed; and Chlorella + Artemia nauplii + Artificial feed) on the growth, feed utilization efficiency and survival of Nile tilapia (Oreochromis niloticus) fry. Triplicate groups of swim-up fry (0.012 g average body weight) were stocked in 20 l fibreglass tanks, with 6 l of water, in a closed rectangular indoor system, at a density of 24 fry per tank (4 fry l−1). The foods were offered to the fish 3 times a day, for 35 days. The results indicated that the maximum body weight gain and survival were achieved in fry fed on Artemia nauplii and on the combination of the three food types, followed by those fed on Artemia nauplii + Artificial. The lowest growth and survival rates were observed in fry fed on Chlorella suspension alone. The fry fed only with artificial feed showed moderate growth and good survival. In conclusion, Artemia nauplii was the best live food, followed by Artemia nauplii combined with artificial feed, to accelerate the growth rate of the fry.