Anal-fin ray morphology indicates sexual maturity in Brevimyrus niger (Teleostei, Mormyridae)

This osteological survey of 249 specimens of Brevimyrus niger ranging in size from 44 to 137 mm standard length (LS) demonstrated that developmental changes in anal-fin morphology can serve as a predictor of sexual maturity in this species. Anal-fin ray bases begin to expand when fish reach c. 90 mm LS at which size and above there were roughly equal numbers of individuals observed with expanded and unmodified anal-fin bases, reflecting a 1:1 sex ratio.