Korespondensi_THE COMPOSITION AND ABUNDANCE OF PLANKTON AS NATURAL FISH FOOD IN THE BARITO RIVER OF MARABAHAN DISTRICT, BARITO KUALA REGENCY, INDONESIA

Abstract

The purpose of this study is to determine the level of fertility of the waters in the Barito River so that it can be used sustainably and the quality of the Barito River's water ecosystem is maintained. The research was conducted in the Barito River, Marabahan District, Barito Kuala Regency. Sampling was carried out 3 times in May – June 2021. Sampling was carried out at two stations, namely upstream and downstream of the Barito River. Nutrient conditions in Barito River waters show differences between stations and between sampling times.Overall, station 2 which is located downstream of the river has a higher content than station 1, both for nitrate and phosphate parameters. The opposite result is shown in the abundance of plankton in the waters where station 1 has a higher abundance than station 2 at all sampling times. The relationship between the two variables was then carried out by a simple regression test which showed that the nitrate parameter had a linear relationship to the abundance of plankton with a low-medium relationship. Different results are shown by the phosphate parameters where there is an opposite, namely if the phosphate decreases, the abundance of plankton will increase with a moderate-strong relationship. In addition, the results of the analysis of the fish choice index (E) show that fish have a preference for their food. This is evidenced by the presence of some fish eating organisms that are not found in their environment but are found in their stomachs.