Contrasts in the movements and habitat use of juvenile and adult white sharks (Carcharodon carcharias) at Guadalupe Island, Mexico

Abstract

Background: Although the effort in the study of white sharks in Mexico is rapidly elucidating adult biology, almost nothing is known about the juveniles. Current understanding of this life history is based largely on the incidental take of juveniles in nursery grounds in the Pacific coast of Baja California and some individuals tagged in the USA that have migrated to Mexican waters. Also, it is not known how or when they recruit to adult aggregation sites or how they learn to make seasonal migrations offshore. Results: We found that: (1) juvenile white sharks remained close to the island throughout the day between the surface and 50 m depth in warm waters (from 14 to 20 °C), whereas the adults moved offshore into deep waters during the day and stayed close to the island during the night presenting a broader tolerance of colder waters (from 9 to 20 °C); (2) tagged white sharks had a positive correlation between total length and habitat range, and the core areas of adults were related to pinniped colonies; (3) adults patrolled in deep waters in November and December when the northern elephant seals (NESs) returned back to the island for pupping with their mean mass higher than during the winter post-breeding migration; (4) tagged juvenile white sharks remained near the island for 12-14 months before departing; and (5) tagged subadults undertook coastal migrations before starting their offshore migrations. Conclusions:The data collected in our study suggest that white shark juveniles arrive to GI from nursery grounds on the mainland after they have reached at least 180 cm TL; then, they remained around the island for several months, potentially taking advantage of the diversity of prey. In addition, they may start their first offshore migrations, coming back to their nursery grounds and GI before they reach maturity, while at GI juveniles stayed close to the shore and in shallow water to avoid adults, probably feeding on demersal prey and species that perform nocturnal migrations such as squid and mackerel. It is argued that the distribution of the large white sharks in GI is controlled by the availability of NES and that adult white sharks look for this prey in deep waters during the day in the vicinity of the seal colonies, taking advantage of the great visibility of GI waters. It is also possible that white sharks take advantage of NES in GI before they go to their pupping grounds to give birth in California and Baja California or to their offshore migration to the west.

The surface behaviour of white sharks during ecotourism: A baseline for monitoring this threatened species around Guadalupe Island, Mexico

“…Guadalupe Island Biosphere Reserve (29°00′N, 118°26′W) is located 240 km off Baja California's coast, Mexico (Gallo‐Reynoso & Figueroa‐Carranza, ). This oceanic environment is characterized by the abundance of macroalgae, invertebrates, bony fishes, elasmobranchs, cetaceans, and pinnipeds, such as the California sea lion Zalophus californianus , the northern elephant seal Mirounga angustirostris , and the Guadalupe fur seal Arctocephalus townsendi (Gallo‐Reynoso & Figueroa‐Carranza, ; Hoyos‐Padilla et al, ). Abundance of prey has been suggested as one of the main reasons for the seasonal presence of white sharks in this aggregation site during July to January of each year (Domeier & Nasby‐Lucas, ; Hoyos‐Padilla et al, ; Jaime‐Rivera et al, ).…”

“…Knowledge about C. carcharias around Guadalupe Island is derived from a limited number of studies related to migration (Domeier & Nasby‐Lucas, ), ecology (Becerril‐García, ; Bonfil & O'Brien, ; Hoyos‐Padilla, Klimley, Galván‐Magaña, & Antoniou, ; Jaime‐Rivera, Caraveo‐Patiño, Hoyos‐Padilla, & Galván‐Magaña, ), and local movements (Hoyos‐Padilla et al, ; Skomal, Hoyos‐Padilla, Kukulya, & Stokey, ). There is no ethological research describing the surface behaviour of white sharks related to cage‐diving boats in Mexico or in the whole eastern Pacific, despite its importance for the Mexican authorities (Becerril‐García, ; Torres‐Aguilar et al, ).…”

Sexual maturity increases mobility and heterogeneity in individual space use in Atlantic salmon (Salmo salar) parr

“…For instance, Hoyos‐Padilla et al . () found that adult white sharks ( Carcharodon carcharias ) utilized broader home ranges than juveniles. Other examples are available in sea birds, such as Cory's shearwater ( Calonectris diomedia ), in which immature individuals and adults use different migration routes (Péron & Grémillet, ).…”

“…Other examples are available in sea birds, such as Cory's shearwater ( Calonectris diomedia ), in which immature individuals and adults use different migration routes (Péron & Grémillet, ). However, the effects of age may mask the effects of maturity in studies comparing immature and mature individuals by separating individuals based on their age (Hoyos‐Padilla et al ., ; Péron & Grémillet, ). A similar issue arises when all individuals belonging to the same cohort mature at once as age effects mix with maturity effects (Lucifora et al ., ).…”

“…As individuals grow and develop, their focal resources evolve, which changes their spatiotemporal distribution throughout their lifetime. Indeed, individuals may change habitats and ecological niches to maximize their fitness (Hoyos-Padilla et al, 2016;Kimirei et al, 2013;Long et al, 2009;Starking-Szymanski et al, 2018). The space use of individuals may be impacted by their distribution (centroid of their placement), but also by their movements (home range, distances covered).…”