The present study was carried out to study the preferred prey in the larval and post-larval stages of
Heterobranchus lonsifilis. Two hundred and forty larvae and fry of H. longifilis aged 2 to 23 days were
stored in aquariums of 8 liters, fasted for 24 hours at the end of which they were fed to satiety with
freshly collected zooplankton from fishponds. The day after feeding, the fish were euthanized and stored
for stomach contents examination. The results showed that the zooplanktonic population density of the
station ponds was 1356.73 individuals / L. This stand is composed of Cladocerans (455.85 individuals /l),
nauplii (289.11 individuals / l), Rotifers (255.47 individuals / l), Copepodites (182.21 individuals / l) and
Copepods adults (174.07 individuals /l). Furthermore, examination of stomach contents showed that adult
Copepods were the most frequent and abundant prey category in stomach contents in terms of frequency
of occurrence (66.7%) and numerical percentage (48.25%). In addition, these preys (adult copepods)
constituted the preferred zooplankton prey in larvae and post-larvae of H. longifilis with an electivity
index (E) equal to +0.5. Apart from the first size classes in which no prey has been observed in the
stomach contents, the food preferences of H. longifilis larvae and fry do not vary with the size of the
individuals. This study showed that adult copepods were the preferred zooplankton prey of H. longifilis
larvae and fry.