The IUCN and CITES have recognized the Java eel species, Anguilla bicolor bicolor, and A. marmorata as significant species requiring conservation efforts. Thus, the objective of this study was to document seasonal catches and assess their sustainability in the waters of Cilacap, which is situated in the southern estuary of Java, Indonesia.  This study employed survey methods and collected research data from three eel collectors located in distinct riverine areas. Additionally, annual fisheries bycatch data were obtained from the Fisheries Office of Cilacap District in Central Java. Levene's test was conducted to evaluate variance equality, followed by a T-test to examine mean equality. Several factors, including the number of eels caught, their potential growth, eel fecundity, and risk factors, must be taken into account when releasing eels back into their natural habitat.  The findings revealed the presence of four distinct classes of eel sizes during both the dry and wet seasons. Notably, two sizes of elvers and glass eels were not captured in either season. The highest monthly catch, recorded at CA I (760.6kg), occurred during the wet season in December, while the lowest, with no eels found at CA II (0 kg) was in the dry season of June. The combined catch from three collectors averaged 429.63± 47.95kg/ month during the wet season and 103.57± 40.04kg/ month during the dry season. From yearly catches, 5.1% of the eels should be released back into nature. Therefore, the comparison of eel catches between wet and dry seasons at three riverine locations in the Cilacap estuaries showed significant differences (α< 0.05).  In summary, eels caught in the Cilacap estuary were significantly larger during the wet season compared to the dry season.