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

Abstract:

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.