الفهرس 
PRODUCTION OF MARINE ALGAE
Protein and energy utilizationOnly 14 pages are availabe for public view
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Abstract
Fish culture in Egypt has developed into a major industry. Tilapias, mullets and carp spp. are the main cultured species almost poly-cultured in commercial and governmental fish farms. For both sectors, increasing fish production is a problem of a major priority. Thus scientific research in this field under Egyptian environmental conditions as well are needed as under locally available production facilities.
Mullets (Mugil cephalus and Liza ramada, Family Mugilidae) are considered highly esteemed in Egypt .They are also the most important marine fish, used for culture either in brackish or fresh water ( Eissawy et al., 1974 and Sarig 1981 ). Because of their great productivity for aquaculture, there is a worldwide interest in mullet culture. They are recognized a highly wanted fish for pond culture in Italy, Japan, Philippines and other parts of the world (Yashouv, 1966; Yashouv and Ben-Shachar 1968, Bardach et al.,1972, Oren,1975, Benetti and Fugundo Netto, 1991a,band El-Dahhar, 2000).
Because of the tremendous increase in human population, it is urgently needed to increase fish production at a low-cost and to make it available at low price to the majority of Egyptians.
The poor survival rates of the wild mullet larvae is a limiting factor in mullet production and many investigation were made to determine environmental and nutrition requirements (Brusle, 1981; Alexis and Papaparaskeva- Papoutsoglou, 1986; Benetti and Fagundes Netto, 1991a,b and El-Dahhar, 1999). The poor digestion in their larvae stages according to the primitive digestive system leads to the importance of exogenous additives in the diet to improve survival and growth of mullet larvae (Person Le Ruyet et al., 1993 and El-Dahhar, 1999). Treating the diet by heat and pressure improve the diet quality and make the best nutritional use of the raw materials. It can sterilize the diet and give the opportunity to use raw materials with different quality (Botting, 1991 and De-Silva and Anderson, 1995).
Current procedures for optimising the presentation of dietary polyunsaturated fatty acid (PUFA) to marine fish larvae are reviewed in relation to the advantages and disadvantages of using (a) single-cell eukaryotic organisms or, (b) purified oils, as primary sources of these essential nutrients in larval production systems (Sargent et al., 1998). For the former option (a), autotrophic and heterotrophic organisms can both be used to advantage and current knowledge of the origins and functions of PUFA in marine organisms which help to identify suitable organisms. For the latter option (b), control of PUFA peroxidation by various antioxidant systems. Progress in this field requires definition of the optimal dietary ratio of 22:6(n−3): 20:5(n−3): 20:4(n−6); the significance of phospholipids vs. neutral lipid in larval diets, and larval requirements for antioxidant vitamins.
In the first-feeding of larval, turbot (Scophthalmus maximus) and halibut (Hippoglossus hippoglossus), microalgae are used in the production of rotifers (Brachionus plicatilis) in order to transfer essential nutrients from the algae to the live food. In addition, the algae may be given directly to the larvae along with the live food. In this circumstance, they act as food for both the fish larvae and the live food. Microalgal addition to the first-feeding tanks along with the rotifers improved growth and survival of larvae, whereas short-term enrichment of rotifers with algae did not improve growth and survival of larvae in tanks without algae added. The algae in larval tanks tend to modify and stabilize the nutritional quality of the rotifers in the period before they were consumed by the larvae. The lipid content and fatty acid composition of the rotifers reflected the composition of the algal diets, and the algal species used may be an effective tool to control the fatty acid content (especially DHA, 22:6n−3, docosahexaenoic acid, and EPA, 20:5n−3, eicosapentaenoic acid). The content of n−3 polyunsaturated fatty acids varied between algal species, and to some extent, with the growth limitation of the algal cells. The algae in larval tanks most probably modified the bacterial flora of the water and the rotifers. In addition, the algae in larval tanks may have modified the light milieu for the larvae (kjell lnge Reitan et al., 1998).
Generally, algae can be divided into two categories: microalgae and macroalgae. Microalgae are unicellular algae not visible to the naked eye. They are referred to as phytoplankton and can be found anywhere in the oceans where there is light. Some types of microalgae have flagella to move around in the water. There is a great variety of microalgae. The most common ones include diatoms and dinoflagellates. Microalgae play an important role in the food web in the aquatic environments. Macroalgae refers to multicellular algae found in littoral or infralittoral zones. They have rhizoids to attach themselves to any suitable sub stratum. Their structures are more complex and they appear in a variety of colors and forms. Some algae, such as Macrocystis can grow up to 60 meters in height, making it the largest alga in the world.
Seaweeds are large algae (macro algae) that grow in a saltwater or marine environment (White and Keleshian, 1994). They are plants, although they lack true stems, roots, and leaves. However, they possess a blade that is leaf like, a stipe that is stem like, and a holdfast that resembles a root. Like land plants, seaweeds contain photosynthetic pigments (similar to chlorophyll) and use sunlight to produce food and oxygen from carbon dioxide and water. Certain seaweeds tend to group together in bands or ”stripes” that run roughly parallel to the coast.
Ulva sp. known by the common name sea lettuce, it can be eaten in salads or used in soups. Ulva is a particularly popular food in Scotland. Nutritionally, it is very healthy. U. lactuca is consisting of 20% protein, 50% sugar and starch, less than 1% fat. It is useful as roughage in the human digestive system. Ulva are very high in iron, as well as in protein, iodine, aluminum, manganese and nickel. They also contain vitamin A, vitamin B1, vitamin C, sodium, potassium, magnesium, calcium, soluble nitrogen, phosphorous, chloride, silicon, rubidium, strontium, barium, radium, cobalt, boron and other trace elements. (Anna Kirby, 2001).
The present work aimed at studying the effect of different levels of seaweed Ulva.sp., collected from Alexandria beach and microalgae Nannochloropsis oculata, produced in the marine fish laboratory (MFL), Faculty of Agriculture, Saba- Basha, (Alexandria University) on performance, feed utilization and survival rate of striped mullet (Mugil cephalus and Liza ramada, Family Mugilidae) either separately or together.