Nursery habitat use patterns of the scalloped hammerhead shark, Sphyrna lewini, in coastal areas of the central Mexican Pacific.

This work aimed to characterize the nursery habitat use patterns of the scalloped hammerhead shark, Sphyrna lewini (SPL), in coastal areas of Jalisco and Colima, through the birth pattern, space-time distribution and relationship with environmental conditions. Information was combined from three sources: monitoring bycatch from the artisanal fishery, fishery-independent samplings, and acoustic tracking and monitoring. From September 2013 to May 2017, 408 juvenile SPL (41.6-100.1 cm total length) were recorded. Births occurred between May and December (rainy-warmer season), within a radius of 2 km from river mouths in Marabasco, Navidad Bay, Rebalsito-Tecuan and Cuitzmala mainly in shallow (<20 m), turbid and soft-bottom areas. Some tagged SPL moved from Marabasco and Rebalsito to Navidad Bay. The peak of catch and births occurred in June-August. Tagged SPL remained near the river mouth in Rebalsito for up to 27 days, showing a mean residency index of 0.29, a home range of 5.55 km2 with a core area of 1.23 km2 located within a 1.5 km radius from the river mouth. In December-January SPL left the river mouth areas and the catch was scarce until the following May-June, except in January 2016, when the catch was high due to El Niño 2015. SPL bycatch was significantly associated with temperature, precipitation and the Oceanic Niño Index.