Diel cycle size-dependent trophic structure of neotropical fishes: a three year case analysis from 35 floodplain lakes in Colombia

Investigated were whether fish assemblages in 35 neotropical floodplain lakes along the Magdalena River, Colombia (ranging from 4 to 2333 ha) have a trophic structure that is dependent on fish body size within the diel cycle (24 h), and whether any changes to the trophic structure of fish assemblages occur during the diel cycle. Sampling was done during diel cycles in the rainy seasons between 2008 and 2011 (ten lakes in 2008, 20 in 2010, and five in 2011). Small fish (27–87 mm) were most active from 06:01 to 18:00, while larger predatory fish (>87 mm) were inactive during this time. In addition to fish body size, trophic group composition also varied throughout the diel cycle: insectivores, piscivores, and omnivore-insectivores were the dominant groups from 06:01 to 18:00; carnivores, carnivore-insectivores, and detritivores dominated from 18:01 to 06:00. This study highlights the importance of fish size in predicting predator-prey interactions during different periods of the diel cycle.