The Biology and Ecology of the White Shark, Carcharodon Carcharias

Abstract

White sharks (Carcharodon carcharias) occur worldwide, primarily in coastal temperate and subtropical regions, but are occasional visitors to tropical regions. They are known to make open ocean excursions, and some exchange across ocean basins has been documented by tagging and is supported by genetics data. However, global stock structure is still poorly known, and accurate population assessments are not yet possible for any region. Estimates of some biological parameters are available, but most are based on limited data that pool both sexes. White sharks are 120-150 cm total length (TL) at birth. Lengths and estimated ages at maturity are 4.5-5.0 m and 12-17 years for females and 3.6-3.8 m and 7-9 years for males. Females reach larger sizes than males. Maximum length for females is estimated to be at least 6.0 m and longevity estimates range up to 60 years, although the latter is unverifi ed and estimates of 40-50 years may be more reasonable. Estimated growth is 20-30 cm/year in sharks less than 3.0 m, but is poorly documented after maturity. Reported von Bertalanffy growth coeffi cients (0.058-0.071) are within the range of other lamnids and indicative of slow growth. The gestation period may be up to 18 months with a 3-year reproductive cycle. Reported litter sizes range from 2 to 17 with an embryonic sex ratio of 1:1. White sharks are naturally low in abundance, have low reproductive potential, are believed to have low natural mortality, and presumably have a low capacity for density-dependent compensation to rapid declines in population size. It is therefore reasonable to conclude that populations are vulnerable to recruitment overfi shing and all forms of nonnatural mortality.

Population genetics of Australian white sharks reveals fine-scale spatial structure, transoceanic dispersal events and low effective population sizes

“…Waples & Do (2010) provision-ally suggest that the CN e producing a generation is loosely estimated if the generation length of a species is equivalent to the number of cohorts sampled. White sharks have an estimated generation time of 22 yr (Bruce 2008, Dulvy et al 2008, and the present study has samples spanning 21 yr, which theoretically approximates this requirement. In reality, the high proportion of juveniles makes it unlikely that so many discrete cohorts could have been sampled here, making the impact of overlapping generations impossible to quantify.…”

“…Sharks below these sizes were considered juveniles. Sampled shark TL ranged from 138 to 510 cm (2 x = 287 cm) as compared with the known TL range of the species of 130 to 600 or 700 cm (Bruce 2008). Juvenile sharks made up 71% (n = 69) of the total.…”

“…We defined mature sharks by the total length (TL; all lengths are TL unless otherwise specified) at which each gender is considered by Bruce (2008) as sexually mature (> 360 cm [males]; > 450 cm [females]). Sharks below these sizes were considered juveniles.…”

“…In addition, localized depletion rates may be increased by fidelity to favoured sites . White sharks exemplify these traits (Smith et al 1998, Bruce 2008, Dulvy et al 2008, the species is slow to mature (7 to 9 yr [males]; 12 to 17 yr [females]), has low fecundity (litter size: 2 to 12), has infrequent reproduction (every 2 to 3 yr), a long life-span (up to 60 yr) and shows indications of site-fidelity (Pardini et al 2001, Domeier & Nasby-Lucas 2007, Jorgensen et al 2010, Anderson et al 2011. Several abundance estimates suggest their numbers have declined during the 20th century, alongside the rise of industrialized fishing and ma rine recreation (Pepperell 1992, Reid & Krogh 1992, Baum et al 2003.…”

Residency and Local Connectivity of White Sharks at Liguanea Island: A Second Aggregation Site in South Australia?

“…We therefore surmise that this location may also be an important aggregation site. The reasons for white sharks utilizing LI may lay both in its location and local fauna: it is found along the 60-120 m depth contour, which appears to be an important migration depth corridor for travelling adult [17] and juvenile [16,35] white sharks in Australian waters. This depth range has also been demonstrated as the preferred range for patrolling white sharks at the Farallon Islands [13].…”