Dynamic ecology of bocachico ( Prochilodus magdalenae ) fingerlings' feeding habits under controlled conditions

Research has provided biological and ecological knowledge about the bocachico ( Prochilodus magdalenae ). Although this species was believed not to accept concentrated feed due to its natural feeding habits, studies have shown that it does in the form of moist cakes. Besides, the postlarvae growth curve can be considered a reference model for management techniques adapted to each stage in a production program. Indeed, bootstrap test results showed a normal distribution, indicating that the rearing conditions (e.g., quality and quantity of feed) and other factors were appropriate. Also, the postlarvae changed their feeding habits, transitioning from consuming zooplankton to organisms in the benthos. When there was no prey at the bottom of the rearing pond, the postlarvae migrated to the surface and adopted the feeding behavior of "gasping for air "; at this moment, they were provided with moist cakes, which they took and then moved to the bottom of the pond to consume them. This model is fairly similar to the bocachico natural way of feeding, where, after taking the zooplankton, they move towards the bottom and feed on organic matter floccules and phytoplankton. This is an important finding for the development of sustainable aquaculture techniques for the bocachico. Additionally, during the zooplankton feeding period, they selectively feed on cladocerans, mainly Moina micrura , due to their size and high reproductive capacity. M. micrura undergoes physical decomposition as it passes through the pharynx and digestive tract, and its protoplasmic fluid is directly absorbed as nutrients, a crucial characteristic of the ideal live food for the postlarvae. When the quantity and quality of zooplankton, particularly M. micrura , are high during the postlarval stage, the individuals grow healthily and rapidly. Finally, the relative intestinal index and the digestive tract content suggested that the change in feeding habits begins when the postlarvae reach a total length of approximately 18 mm and their digestive capacity resembles that of adult fish upon reaching a 25-30 mm length.