Gut content analysis of tilapia (Oreochromis niloticus) from Jagir River, Surabaya City, East java

Tilapia (Oreochromis niloticus) belongs to omnivorous fish and its natural feed includes phytoplankton, zooplankton, insects and aquatic plants. Tilapia can be found in rivers, reservoirs and other natural waters. This study was aimed to determine the type of feed consumed by tilapia from Jagir River Surabaya, East Java and it employed survey method. Tilapia fish was taken from local fishermen in 3 stations, each station provided 10 tilapia fish in a size ranging from 14-22 cm. The first station was located in the area close to the ceramic industry in the upstream part of the river. The second station was located in a residential area (in the middle) and the third station was located in the area near the rice field in the downstream part of the river. The fish was then dissected at the research site in order to remove its gut. Then, the gut was put into a bottle containing 10 ml Nafis and preserved with 4% formalin. In the laboratory, the content of the gut was removed and put into 25 ml beaker glass and then it was added with aquadest up to 20 ml for observation purpose. The tilapia’s gut from Jagir River contained 3 phytoplankton divisions namely Chlorophyta, Chrysophyta and Cyanophyta, and one type of zooplankton namely Rotifer. The ratio of feed types (Chlorophyta, Chrysophyta, Cyanophyta, and Rotifer) in tilapia’s gut from station 1 was 1.2:1:0.16:0.03. Meanwhile, the ratio from station II was 1.1:1:1:0.03 and from station III was 1.3:1:0.7:0.03, respectively. Based on these results, it could be indicated that tilapia prefer to consume phytoplankton specifically Chlorophyta.