Evidence of a nursery area for bull shark, Carcharhinus leucas (Müller y Henle, 1839) in the Mesoamerican Reef System region

Nursery areas are essential habitats for sharks, offering protection and increasing the survival of newborns. We conducted interviews with local fishers and collected data from artisanal fishery landings between January 2013 and December 2019 to investigate Chetumal Bay as a nursery area for the bull shark ( Carcharhinus leucas ) in the Mesoamerican Reef region. The bull shark is a coastal euryhaline shark that inhabits temperate and tropical waters worldwide. In the Mexican Caribbean, bull sharks are caught mainly as bycatch in a multi-specific artisanal fishery using nylon bottomset gillnets, longlines, and hand lines. We record 63 bull sharks in the catches ranging from 67 to 125 cm TL corresponding to immature individuals, 23 neonates with either open or healing umbilical scars (67 and 78 cm TL), and 40 YOY with present but healed umbilical scars (79 to 125 cm TL), with a notable absence of large size juveniles and adults in the catches. Bull sharks were present in landings between May and November; the highest abundance was during July. Our data provide evidence to recognize Chetumal Bay as a nursery area for bull sharks, meeting all the criteria proposed to identify nursery areas. These findings constitute the first documented evidence of a bull shark nursery area in an estuary within the Mexican Caribbean as well as within the entire region of the Mesoamerican Reef System. Moreover, we discuss the importance of this nursery in light of a newly described distinct lineage of bull sharks in Chetumal Bay.