Mystus nigriceps is present in the Tapung Kiri River. A study aims to understand the reproductive biologi of M. nigriceps has been conducted from April to May 2018. Fish sampling were conducted once/ week. Parameters measured were sex ratio, gonad maturnity level, gonad somatic index (GSI), fecundity and egg diameter. Results shown that there were 37 males and 63 females (sex ratio 1:2). There …