Echinaster (Othilia) guyanensis Clark, 1987 is an endangered starfish distributed throughout the Caribbean and Atlantic Ocean. Even though it has been extensively harvested, little is known about the biology and ecology of this starfish. Here, we examine reproduction seasonality in E. (O.) guyanensis. Individuals were collected monthly for one year, including four complete lunar phases. The gonad index (GI) was calculated to determine annual and monthly reproductive peaks. Gametogenesis stages were also determined. Sex ratio was 1:1.33 (M:F). Gonadosomatic index, body weight, central disc width and arm length were similar for both sexes. Gonads were present in all animals with arm length greater than 36.2 mm. Lunar phase was not associated with E. (O.) guyanensis reproduction. GI and gametogenesis patterns suggest that starfish have an annual reproductive peak with spawning during autumn months (March to May)

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