A review of the biology, fisheries and conservation of the whale shark Rhincodon typus

Abstract

Although the whale shark Rhincodon typus is the largest extant fish, it was not described until 1828 and by 1986 there were only 320 records of this species. Since then, growth in tourism and marine recreation globally has lead to a significant increase in the number of sightings and several areas with annual occurrences have been identified, spurring a surge of research on the species. Simultaneously, there was a great expansion in targeted R. typus fisheries to supply the Asian restaurant trade, as well as a largely un-quantified by-catch of the species in purse-seine tuna fisheries. Currently R. typus is listed by the IUCN as vulnerable, due mainly to the effects of targeted fishing in two areas. Photo-identification has shown that R. typus form seasonal size and sex segregated feeding aggregations and that a large proportion of fish in these aggregations are philopatric in the broadest sense, tending to return to, or remain near, a particular site. Somewhat conversely, satellite tracking studies have shown that fish from these aggregations can migrate at ocean-basin scales and genetic studies have, to date, found little graphic differentiation globally. Conservation approaches are now informed by observational and environmental studies that have provided insight into the feeding habits of the species and its preferred habitats. Notwithstanding these advances, there remain notable gaps in the knowledge of this species particularly with respect to the life history of neonates and adults who are not found in the feeding aggregations.

Diet of whale sharks Rhincodon typus inferred from stomach content and signature fatty acid analyses

“…Results of whale shark stomach content and FA analyses presented here have shown that whale sharks feed on a variety of zooplankton prey, which is also supported by observational evidence (see Rowat & Brooks 2012). The reliance of this large predator on different prey groups means that no single matching prey FA profile exists.…”

Long-Term Photo-Identification Reveals the Population Dynamics and Strong Site Fidelity of Adult Whale Sharks to the Coastal Waters of Donsol, Philippines

“…Researchers used boats and swimmers of known lengths to estimate the size of the animals. Given the longitudinal nature of the dataset and variability in size estimates from multiple researchers, we discarded intra-and inter-seasonal size estimates that differed by >2.5 m for individual whale sharks (n = 44), based on maximum growth estimates (Rowat and Brooks, 2012). To ensure this did not discard larger sharks only, we tested the relationship between visual estimate differences (2-10 m) and mean L T and found it to be not significant (r 2 = 0.038, p > 0.05).…”

“…The largest of the shark species, whale sharks are highly mobile (e.g., Wilson et al, 2006;Sleeman et al, 2010;Berumen et al, 2014;Robinson et al, 2017), but form predictable seasonal aggregations in hotspots around the world, predominantly associated with the presence of food (e.g., Motta et al, 2010;Robinson et al, 2013;Rohner et al, 2015a). Some whale sharks display a degree of site fidelity on an annual and inter-annual basis (Graham and Roberts, 2007;Holmberg et al, 2008;Fox et al, 2013;Araujo et al, 2017), and this predictability makes the whale shark an ideal target species for wildlife tourism (Catlin and Jones, 2010;Rowat and Brooks, 2012).…”

“…The whale shark, Rhincodon typus Smith 1828, a large planktivorous elasmobranch, is found in tropical and warmtemperate waters worldwide (Rowat and Brooks, 2012). The largest of the shark species, whale sharks are highly mobile (e.g., Wilson et al, 2006;Sleeman et al, 2010;Berumen et al, 2014;Robinson et al, 2017), but form predictable seasonal aggregations in hotspots around the world, predominantly associated with the presence of food (e.g., Motta et al, 2010;Robinson et al, 2013;Rohner et al, 2015a).…”

Simple criteria to determine detachment point of towed satellite tags provide first evidence of return migrations of whale sharks (Rhincodon typus) at the Galapagos Islands, Ecuador

“…Whale sharks are known to move large distances [20] and their movements or presence at some sites have been linked with oceanographic features [20,21]. However, true migration, implying the movement away from a location over a long distance and a subsequent return, has not been registered to date [22], although photo identification studies have shown that individuals persist at sites over extended periods [23].…”