Plankton composition in Milkfish's ( Chanos chanos) stomach cultivated in traditional pond

Milkfish is a brackish-water cultured fish that is widely cultivated in traditional ponds because the business capital is relatively small and the feed provided is only from natural food in the form of plankton. This study aims to determine the type of plankton in the stomach and the frequency of feeding occurence milkfish in order to determine the type of plankton preferred by milkfish. This study used a survey method. The composition of plankton found in milkfish consists of 8 divisions, namely Bacillariophyta, Chlorophyta, Cryptophyta, Cyanophyta, Myozoa, Charophyta, Rotifera, and Arthropoda. However, Charophyta and Arthropoda divisions not found in the stomach of milkfish in the Probolinggo pond. The highest composition of plankton in the milkfish stomach in the Pasuruan pond was the Chlorophyta division (38%), while in the pond of Probolinggo, Bacillariophyta division (52.4%). Feeding occurrence frequency of milkfish is in the second pond 100% for the division of Chlorophyta, Cyanophyta, and Bacillariophyta. The similarity index based on the plankton composition in the milkfish stomach from two ponds was around 66.9%, indicating that the similarity of the plankton types consumed by milkfish was sufficiently high between the two ponds. Based on the results of this study, milkfish can be said to be herbivores because in their stomachs there are 99.8% phytoplankton and 0.2% zooplankton.