NUTRITIONAL REQUIREMENTS OF STURGEON BROODSTOCKS Dr. Özgür ALTAN Aquaculture Expert FAO-Sub-Regional Office for Central Asia Tel: +90.312. 307 95 36 Fax: +90.312. 327 17 05 E-mail: Ozgur.Altan@fao.org
Habitat Natural and Feeding Acipenceriformes inhabit rivers, near shore oceanic environments and inland seas. Some Sturgeon species spend their entire life in freshwater. However the majority of them are anadromous; they spend their adult life in the sea; but swim upriver to freshwater spawning grounds in order to reproduce. They spawn in habitats with hard substrates (gravel, cobbles, boulders etc) with varying depths and water currents.
Most sturgeon species are bottom dwellers and feed benthically on insect larvae, small fish, and occasionally on fish related carrion. In rivers that support salmon populations, sturgeon will forage on roe, as well as the decaying salmon remnants.
Sturgeon possess tactile barbels located at the front of a of a thick-lipped, protractile mouth. Sturgeon also dig with their rostrum in search of food. Their eyes are very small relative to fish size and probably do not contribute much to the location and capture of prey. Due to their benthic feeding habits and their late puberty, which increases bioaccumulation in the various tissues (muscles, fat, gonads etc), sturgeon are more sensitive to habitat degradation than most other fish.
Feeding and Feed Quality All sturgeon species develop normally when reared in freshwater only. Depending on the conditions and an species, males can generally spawn every year, while females every 2-4 years.
Protein Development of gonads depends largely on feed quality, mainly on the protein supply of animal origin. The best course of action is to feed the fish with the feed that is specially designed for broodstock. Fish that are starved will not undergo vitellogenesis and will not develop ripe gonads. However it is recommended to stop feeding at very low temperatures during wintering and 1-2 month period prior to spawning. Total crude protein level should be more than 50% and it should be supported first class protein sources such as fish meal, squid meal and shrimp meal.
Proteins Contain carbon, hydrogen, oxygen, nitrogen, and sulfur Serve as structural components of animals Provide energy Serve as control molecules (enzymes) Serve as transport and messenger molecules Basic building block is the amino acid
Protein Sources in fish Feed Fisheries based ingredients; 1. Fish meal, 2. Shrimp meal, 3. Squid meal,
1. Fish Meal Fish meal is the main ingredient with its suitable crude protein rate (65-72%) in fish feeds. Its amino acid content is suitable for fish nutrition. There are some local fish meal sources that are changes according to country by country but; the main exporter is Peru and Chile. Fishmeal can be made from almost any type of seafood but is generally manufactured from wild-caught, small marine fish that contain a high percentage of bones and oil, and is usually deemed not suitable for direct human consumption.
1. Fish Meal (Cont d) The fish caught for fishmeal purposes solely are termed industrial. Other sources of fishmeal is from by-catch of other fisheries and byproducts of trimmings made during processing (fish waste or offal) of various seafood products destined for direct human consumption.
2. Shrimp Meal Shrimp meal can be made from either cull shrimp that are being processed before freezing or from whole shrimp that is not of suitable quality for human consumption. The material to be made into shrimp meal is dried (sun or using a dryer) and then ground. Shrimp meal has been used in trout and salmon diets as a source of pigments to impart the desirable color in the tissues.
3. Squid Meal Squid Meal have a very high content of protein 80% minimum with high levels of amino acids,execelent to blend with other vegetable protein sources, also its hight levels of hydroxiproline estimulate bone formation in fishes. The farm will have a increment for 30% in the larval production incremention. Plus is essential for shrimp weigth gain, recent studies confirm that, squid meal increases weight gain on shrimps and fishes, if compares with normal steam dry fish meals, also improve egg hatching to 30%.
Fat and Fatty Acids The main fat source is the fish oil. It includes high level of unsaturated fatty acids and its profile promotes spawning. The level for W-3 should be 1-1.6% for broodstocks. If the level increases more than 1.6%, a negative effect occurs and spawning rate incraeses rapidly. Total fat percentage should be kept around 12-15% in commercial feeds.
Alfa Tocopherol As a Vitamin E Source Vitamin E-Alfa Tocopherol helps to reduce egg abnormalities The level of Vitamin E should be kept around 200-250 mg/kg in commercial broodstock feeds.
Vitamin C Vitamin C is one of the important parts of the broodstock feeds. The requirement of the fish is about 600-800 mg/kg in the feeds. This amount provides to increase fegundity of the eggs.
Carotenoid Sources Most of the experts know this as a pigment source. Actually carotenoid sources and their commercial forms like Astaxhantine is one of useful sources to promote spawning if it is used at correct amounts/levels. The level should be kept about 400-500 mg/kg in commercial broodstock feeds.