Bassas da India is an important area for undefined aggregations of one shark species.

A visual survey in July 2010 identified 34 Galapagos Sharks, of which 32 were seen inside the Bassas da India lagoon (Clarke et al. 2012). They formed loose aggregations, with a maximum of 20 seen in a group. Almost all were visually estimated to be < 150 cm total length (TL), but no further size details were recorded. Based on additional visual observations, several juvenile specimens of 140 cm TL were seen at night outside the reef (van der Elst et al. 2021). At this size class, juvenile Galapagos Sharks tend to leave the shallow protected inshore waters and start to occupy deeper waters (Gausmann, submitted). A photographic expedition to Bassas da India recorded aggregations of Galapagos Sharks in the lagoon during the day (up to three in a frame) and at night when they estimated 30 individuals in an aggregation (up to six in a frame; SOSF 2014). Clarke et al. (2012) termed the site a ‘nursery area’, also based on an earlier study which recorded 54 Galapagos Sharks, including aggregations of up to six individuals, during a survey in October 2003 (Hammerschlag & Fallows 2005). One of these was estimated to be 120 cm TL and 15 others were < 200 cm TL (Hammerschlag & Fallows 2005). The size-at-birth of the species is 57–80 cm TL (Compagno 1984), so without more detailed length estimates, it is unclear whether any of the sharks reported in 2010 were neonates or young-of-the-year, and if this area is important for the reproduction of this species. Further information is required to determine the function of these aggregations.