Cradles of the sea: a global review of shark nurseries

Conservation requires the management and protection of not only wildlife populations, but the habitats they rely on. The identification and characterization of these essential habitats is a key first step. For many sharks, nurseries increase juvenile survival and recruitment, and in this review, 443 nurseries were identified globally across 62 countries for 94 species of sharks based on an analysis of peer-reviewed literature. Nearly all nurseries were located in nearshore waters (92%), with many in bays, estuaries, and lagoons (61%) or rivers (19%) that are at risk from human actions like fishing and coastal development. Nurseries varied in number, distribution, and characteristics across species and regions, but mangroves were identified to be the most important structural component of these habitats in tropical latitudes (79%). The persistent use of many nurseries (33%) by numerous cohorts of juvenile sharks over decades, and their inherently communal nature (38%) among multiple species indicates that the effective management of these habitats will benefit many populations and contribute to shark conservation. However, based on sensitivity analysis, >35% of nurseries and shark species that use nurseries have yet to be identified, with 14% of identified nurseries having experienced declines or the complete loss of sharks within their waters when assessed for temporal variability in nursery status. Therefore, the continued identification and evaluation of shark nurseries are imperative for their protection, particularly for endangered and endemic species in data-deficient regions that face growing human impacts, like the Western and Northern Indian Ocean, Indo-Pacific, and Western Africa.