Identification of a nursery area for the critically endangered hammerhead shark (Sphyrna lewini) amid intense fisheries in the southern Gulf of Mexico

Since the 1980s, there has been growing concern in the Mexican Atlantic regarding high catches of neonate and juvenile sharks in small-scale fisheries. Fishery-dependent data from 1993 to 1994 and 2007 to 2017 and fishers' ecological knowledge from 2017 were used to identify nursery areas for scalloped hammerhead,Sphyrna lewini, in the southern Gulf of Mexico. Catch records and fishing areas of neonates, YOYs, juveniles and adults ofS. lewini(N= 1885) were obtained from calcareous and terrigenous regions in the western Yucatan Peninsula. The results suggest that a nursery for scalloped hammerhead is found in the terrigenous region, characterized by relatively shallow and turbid waters due to rivers' discharges. Neonates and YOYs (96% and 86% of their total records, respectively) were commonly found there over the years in May-August in multiple fishing areas identified by fishers, although mainly between isobaths 10-30 m. The enforcement of management measures is necessary because the nursery is located in a region with intense fishing effort.