A re-examination of the age and growth of sand tiger sharks, Carcharias taurus, in the western North Atlantic: the importance of ageing protocols and use of multiple back-calculation techniques

Abstract

Age and growth estimates for sand tiger sharks, Carcharias taurus, in the western North Atlantic were derived from 96 vertebral centra collected from sharks ranging from 94 to 277 cm total length (TL), and compared to previously published age and growth data. The oldest female and male sand tiger sharks aged in this study were 17 and 15 years of age, respectively. von Bertalanffy growth parameters derived from vertebral length-at-age data are L ¥ = 295.8 cm TL, k = 0.11 year -1 , and t 0 = -4.2 years for females, and L ¥ = 249.5 cm TL, k = 0.16 year -1 , and t 0 = -3.4 years for males. Sexual maturity is estimated to be 9-10 years for females and 6-7 years for males. Weight-to-length relationships determined for female and male sand tiger sharks in the western North Atlantic are; W = 1.3 · 10 -4 · L 2.4 (r 2 = 0.84, n = 55) and W = 9.0 · 10 -5 · L 2.5 (r 2 = 0.84, n = 47), respectively, and 7.9 · 10 -5 · L 2.5 (r 2 = 0.84) for the sexes combined. Our results show sand tigers possess a slower rate of growth than previously thought. This information is crucial for accurately assessing this population's ability to recover, and further justifies the need for this species to be fully protected.

Seasonal residency, habitat use, and site fidelity of juvenile sand tiger sharks Carcharias taurus in a Massachusetts estuary

“…Examination of data accrued during the monitoring of the juvenile sand tiger population within PKD Bay from 2008 to 2011 suggests that this region meets these 3 criteria and is worthy of classification as a nursery area. Extrapolation of observed sand tiger sizes to length-at-age data presented by Goldman et al (2006) suggests that approximately 71% (n = 84) of all individuals captured within the embayment over the course of the study were young of the year (YOY; 79 to 96 cm FL), 24% were Age 1 (97 to 109 cm; n = 29), and 5% were Age 2 (110 to 130 cm; n = 6). Collectively, these data suggest that PKD Bay is of particular importance as a seasonal nursery area for YOY sharks but also plays an important role for juveniles up to Age 2.…”

“…sandbar shark; NMFS 2006) and evidence of the importance of juvenile survival to shark population growth and, hence, recovery rates (e.g. Cortés 2002, Goldman 2002, Beerkircher et al 2003, Carlson et al 2003, Aires-da-Silva & Gallucci 2007. Given the potential benefits of nursery areas to the maintenance of popu-lations, a thorough spatial and temporal understanding of how shark populations use nursery habitats should improve conservation and management efforts (NMFS 2006), particularly for highly exploited species (Conrath & Musick 2010).…”

“…For example, Carlson et al (2009) were unable to provide a definitive update on the population status of sand tigers in the WNA, despite the inclusion of updated life history information (e.g. Goldman et al 2006) and catch data. The lack of a viable population assessment for this species is particularly problematic given the results of the demographic analysis conducted by Goldman (2002), which suggested that the sand tiger population in the WNA may be more sensitive to fishing mortality than previously thought and may still be decreasing slightly.…”

“…Goldman et al 2006) and catch data. The lack of a viable population assessment for this species is particularly problematic given the results of the demographic analysis conducted by Goldman (2002), which suggested that the sand tiger population in the WNA may be more sensitive to fishing mortality than previously thought and may still be decreasing slightly. Collectively, these findings highlight the need for a better general understanding of the sand tiger population in the WNA, particularly for factors that will contribute to the growth and recovery of the population.…”

“…Although no specific pupping areas have been identified, parturition is thought to occur from December to March off Florida (Gilmore et al 1983, Gilmore 1993, in February and March off North Caro lina/Virginia (Branstetter & Musick 1994, Goldman et al 2006, or throughout its WNA range from March to April (Compagno 2001). After parturition, neonate and juvenile sand tiger sharks are thought to migrate north to summer nursery habitats from North Carolina to Cape Cod, returning to southern latitudes during winter months (Bigelow & Schroeder 1953, Gilmore et al 1983, Gilmore 1993.…”