A global review of white shark (Carcharodon carcharias) parturition

Abstract

The white shark (Carcharodon carcharias) is a globally distributed top predator. Due to its ecological importance and historical declining population trends, data contributing to conservation initiatives (e.g. habitat protections and resource management) pertaining to all life stages of this species are essential to facilitate population recovery. Of particular interest, the locations and discrete seasonality of C. carcharias parturition remain uncertain. Understanding C. carcharias parturition in relation to each population is relevant to population recovery since neonate to young-of-the-year (YOY) sharks are more vulnerable to predation and particularly threatened by and susceptible to commercial fishing pressure. Herein, this paper provides a synthesis from published literature across seven well-studied C. carcharias populations to identify common trends associated with parturition location, seasonality, and habitat characteristics. The data reviewed in this study are consistent with previous population-specific hypotheses, that C. carcharias parturition occurs during spring and summer for all populations. Further, this review also indicates that parturition likely occurs in insular shelf waters and water temperatures ranging from15.7 to 23.1 °C. Although discrete parturition sites were not identified, the compiled data are suggestive that C. carcharias parturition may occur over horizontal and vertical spatial scales that exceed the inshore, shallow water environments associated with nursery area habitat to perhaps minimize predation by conspecifics. Due to the vulnerability of C. carcharias, conducting non-lethal technological (e.g., baited remote underwater video systems—BRUVS), morphological (i.e., ontogenetic changes in dorsal fin shape), and reproductive (e.g., blood chemistry and ultrasonography) research that may help identify parturition location and seasonality are thus warranted.