ARTICLE 64 FEED & ADDITIVE MAGAZINE May 2023 food organism in terms of nutritional requirements of fish/shrimp. The most significant disadvantages of Artemia are significant differences in cost, physical qualities, and nutritional quality among different sources. As a result, the production of very small, rapidly developing, and extremely sensitive larvae continues to be a bottleneck in the commercially viable culture of many marine fish species. EMINENCES Nutritional components such as n-3 fatty acids, essential amino acids (EAA), and protein content in live feeds are vital for larval finfish and crustaceans' survival and growth. As a consequence, the development of copepods becomes increasingly important. Copepods are the most numerous creatures in marine habitats. Their nauplii are the natural food of most wild fish larvae, making copepod nauplii a better diet for rearing fish than rotifers or Artemia nauplii. Copepod nauplii are an appealing prey item for larval fish because their chaotic "zig-zag" motion which stimulates foraging animals. Copepod nauplii are also considered great live food because they do not require enrichment due to the high quantities of fatty acids in their diet. Marine copepods are regarded as "nutritionally superior live feeds" for commercially important cultivable species because they are a valuable source of protein, lipid (especially HUFA, 20:5 n3 and 22:6 n3), carbohydrates, and enzymes (amylase, protease, exonuclease, and esterase), all of which are required for larval survival, growth, digestion, and metamorphosis, and have a relatively high weight specific caloric content. Furthermore, the calanoids' maturation stages from first nauplius to adult present a diverse range of prey sizes (80 to 900 μm in length and 3–5 μg in dry weight) which makes them a suitable prey for a wide variety of developing fish sizes. ENCUMBRANCES The advantages of raising marine fish using copepod nauplii are self-evident. Smaller nauplii, on the other hand, may be unable to maintain larger larvae once they reach a certain size. The appropriate copepod species should be chosen based on these facts. The biggest challenge they will have if they are approved by the mainstream aquaculture business is finding a practical use. A live culture is essential to ensure a consistent supply of nauplii. While captive-bred cultures typically have densities less than two adults or ten nauplii per millilitre, live cultures seldom have densities greater than two adults or ten nauplii per millilitre. Maintaining copepod densities in higher levels of culture, however, does not always result in increased output. Cultures should be kept at or below maximum density to maximise output. Nauplius of cyclopoid copepod (Image: R.Dinesh)
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