Reproductive Characters of the Ricefield Eel (Monopterus albus Zuieuw) in Babakan Village, Karang Lewas District, Banyumas, Central Java

Abstract

One of the villages in Banyumas Regency which provides a high potential habitat for ricefield eel (Monopterus albus Zuieuw), a protogynous hermaphrodite, is Babakan. However, information concerning their reproduction cycles is lacking. This research aimed to understand the reproductive characters including Gonad Maturity Level (GML), Gonad Maturity Index (GMI), fecundity, egg diameter, and to examine the correlation of body length with both GML and GMI of the fish. We applied the survey method with purposive sampling design. The sampling was done once in a month for four times from November 2017 to March 2018. There were 30 samples for each sampling time (total of 120 eels). The results showed that the ricefield eels underwent intersex phase at a body length of 30.5-30.7 cm. The fish less than 30.5 cm were females, and those more than 30.7 cm was a male. The ricefield eel sex based on stages of gonad development was GML I (there were oocytes equipped with nucleus and cytoplasm), GML II (the presence of cortical alveoli stage), GML III (the stage of vitellogenesis), and GML IV (mature stage). The presence of degenerated oocytes and testicular lobes characterized their intersex stage. A testicular lobe characterized the male stage. The dominant GML during November, December, January, and March were GML I and II, GML I and II, GML III, and GML IV, respectively. Fecundity of the ricefield eels during the research was between 207 and 370 eggs, with an average of 252 eggs. The egg diameter of 0.22-2.5 mm indicated that the ricefield eel was on the batch spawner. The highest GMI of the eels occurred in January between 00017 and 0.0242 during the entire month of sampling. The body length of the fish did not correlate to their GML. On the other hand, their body length correlated to their GMI.