Weaning (Feed Transition)

Weaning is the gradual transition of larval fish and crustaceans from live prey (rotifers, Artemia nauplii) onto formulated inert diets, and its timing is dictated by digestive physiology, not convenience: the larval gut must develop sufficient pancreatic and intestinal enzyme capacity, and co-feeding — offering both live and formulated feed together for several days — exploits the live prey as an attractant and gut primer while the animal learns to recognize and accept the new particle. Typical protocols overlap feeds for three to seven days while shrinking live-prey density daily, then judge success by gut-content checks under magnification: the percentage of larvae with formulated feed in the gut, and stable or rising growth through the transition window, are the operational success metrics, since a failed weaning shows as a feeding-response collapse and a growth stall that is costly to reverse. Weaning difficulty varies enormously by species: freshwater species and tilapia accept inert diets within the first week or two of exogenous feeding, while many marine finfish larvae (sea bass, grouper, flatfish) and crustacean zoea have narrow acceptance windows and may need extended Artemia phases or sophisticated microdiets, which is why live feed remains the most expensive and failure-prone link in marine hatcheries. Hatchery nutrition research focuses on earlier, more reliable weaning — every day cut from the live-feed phase reduces cost, biosecurity risk, and operational fragility.