Reproductive biology of the scalloped hammerhead (Sphyrna lewini) in the central-eastern Pacific Ocean

There are limited data regarding the reproductive biology of the scalloped hammerhead (Sphyrna lewini) in Ecuadorian waters, which limits the development of appropriate management measures of its populations. A total of 1664 S. lewini specimens were recorded in Manta, Ecuador in 2003-2009. Specimens were caught by local commercial fisheries and measured between 50-310 cm total length (TL). Females were more frequently caught, with a sex ratio of 1M:1.8F. The median size at maturity was 178.1 cm TL for males and 219.4 cm TL for females, which was larger compared with other localities. Gravid females, which measured 246-298 cm TL, contained 16-22 embryos. Embryos, which were observed from October-July, measured between 11.1-54.6 cm TL and the available data agreed with a gestation period of 10-11 months that starts in September and ends in June/July. Size at birth was 47-55 cm TL. Sampling data indicated that most fishing activity occurred in nearshore and around seamounts in the central-eastern Pacific Ocean, with much of the landed catch comprising immature individuals. This study documents the reproductive biology of S. lewini in the central-eastern Pacific Ocean and provides additional information to improve management and conservation measures for this species.