Similar life history traits in bull (Carcharhinus leucas) and pig-eye (C. amboinensis) sharks

Abstract

Appropriate management strategies for coastal regions require an understanding of how ecological similarities and differences among species shape ecosystem processes. Here, we tested whether morphological similarity equated to similar age and growth patterns in two common coastal sharks in northern Australia. Vertebrae of 199 pig-eye (Carcharhinus amboinensis) and 94 bull (C. leucas) sharks were sourced principally from commercial fisheries operating along the Northern Territory coastline during 2007-2009. We sectioned vertebrae to provide estimates of age of these animals. Model averaging results indicated female pig-eye sharks matured at 13 years and lived .30 years. Theoretical asymptotic length (L N ) (AEs.e.) was estimated to be 2672 (AE11.94) mm with a growth coefficient (k) of 0.145 year À1 . Male pig-eye sharks matured slightly earlier than females (12 years) and survived .26 years. Theoretical asymptotic length for males (L N ) (AEs.e.) was also smaller (2540 AE 13.056) mm and they grew faster (k ¼ 0.161 year À1 ) than females. Bull sharks matured at 9.5 years and reached a maximum theoretical size (L N ) (AEs.e.) of 3119 mm (AE9.803) with a similar growth coefficient (k ¼ 0.158 year À1 ) to pig-eye sharks. Longevity of bull sharks was estimated to be more than 27 years. Our results indicate that these patterns of high longevity and slow growth are indicative of low resilience and high susceptibility to over-exploitation of these coastal sharks.

Sex-based spatial segregation of adult bull sharks,Carcharhinus leucas, in the New Caledonian great lagoon

“…For example, Clua et al (2013) observed adult bull sharks as the shark species responsible for the killing of an exhausted blue whale calf after entering this same area. Fishing efforts in the numerous rivers along the west coast of New Caledonia revealed several small juvenile bull sharks providing evidence that localised pupping occurs which is consistent with other studies showing female's return to rivers or estuaries, probably for pupping (Tillet et al 2011;Werry et al 2011). Females may also remain close to rivers for feeding purposes but display divergent behaviours.…”

“…Adult males may remain offshore, while pregnant females may return to rivers to pup (Werry et al , 2012Tillett et al 2012). Recent studies have also shown a Corresponding author: jwerry@oc-research.com the use of coastal habitats for older and larger bull sharks (Brunnschweiler and Baensch 2011;Tillet et al 2011;Werry et al 2011;Hammerschlag et al 2012), but the literature examining the movement patterns of adult bull sharks is rare, especially regarding their behaviours away from shallow coastal areas. Whether more oceanic habitats should be considered as essential for this species is uncertain due to the paucity of data.…”

Decoding fingerprints: elemental composition of vertebrae correlates to age-related habitat use in two morphologically similar sharks

“…We regarded the change of angle caused by differences in growth rate from intra-uterine to post-natal life history stages as the point of birth, or birth mark and recorded it as year zero (Cailliet & Goldman 2004). Annual growth band deposition has been confirmed for bull sharks (Branstetter & Stiles 1987, Neer et al 2005) and pig-eye sharks (Tillett et al 2011a).…”

“…We regarded the change of angle caused by differences in growth rate from intra-uterine to post-natal life history stages as the point of birth, or birth mark and recorded it as year zero (Cailliet & Goldman 2004). Annual growth band deposition has been confirmed for bull sharks (Branstetter & Stiles 1987, Neer et al 2005) and pig-eye sharks (Tillett et al 2011a).Preliminary study. Initial analyses determined (1) the concentric manner in which the calcareous vertebral matrix was deposited and the corresponding 3-dimensional structure of the sagittal section, and (2) inter-vertebral variation in chemical composition of the matrix.…”

Dietary overlap and partitioning among three sympatric carcharhinid sharks

“…occupying the East Alligator River (n = 5); these were stored frozen. Maturity was determined from previously described age structure and growth dynamic assessments (Tillett et al 2011a). Sex, total weight (TW) total length (TL) and fork length (FL) were collected when possible from dead specimens.…”