Using oxytetracycline validation for confirmation of changes in vertebral band-pair deposition rates with ontogeny in sandbar sharks (Carcharhinus plumbeus) in the western North Atlantic Ocean

Abstract

Age underestimation of many shark species, such as the sandbar shark (Carcharhinus plumbeus), has been proven with age validation methods including bomb radiocarbon dating, oxytetracycline (OTC) injection, and tagrecapture data. Validation studies indicate that band-pair deposition in vertebral centra may not be directly related to time, especially in older individuals of a species. In this study, vertebrae from tagged, OTCinjected, and recaptured sandbar sharks were examined to determine if band-pair deposition past the OTC mark matched time at liberty. In 6 of 8 OTC-injected sharks at liberty for >1 year, band-pair count past the OTC mark underestimated time at liberty by 24-58%. Additionally, growth rates derived from tag-recapture data were slower than those described by previously published vertebral band-pair growth curves but were similar to those predicted by previous bomb radiocarbon dating and OTC results from this study. Together, the results from these studies indicate that modeling tag-recapture data may be more accurate for age determination in elasmobranchs given that band-pair counts on vertebral centra do not coincide with age throughout life. Analyses indicate that sandbar sharks may be less productive than previously understood.Research has shown that the rate of vertebral band-pair deposition in elasmobranchs is variable and not necessarily related to time (Harry, 2018;Natanson et al., 2018). At least 30% of studies attempting to validate the periodicity of vertebral band-pair deposition in elasmobranchs in relation to age have shown that ages were underestimated (Harry, 2018).

Growth rates of bonnetheads (Sphyrna tiburo) estimated from tag-recapture data

“…Significant differences in growth characteristics of bonnetheads have been found between populations in the GOM and the Atlantic region (Frazier et al, 2014). For the population in the Atlantic region, estimated maximum age (males: 12.0 years; females: 17.9 years) and age at 50% maturity (males: 3.9 years; females: 6.7 years) are more than twice the estimates for the population in the GOM (males: 5.5+ years for maximum age, 1.7 years for age at 50% maturity; females: 7.5+ years for maximum age, 2.9 years for age at 50% maturity) (Lombardi-Carlson et al, 2003;Frazier et al, 2014). Previous age and growth studies of bonnetheads in the eastern GOM (Parsons, 1993;Carlson and Parsons, 1997;Lombardi-Carlson et al, 2003) found significant latitudinal variation in life history traits; however, latitudinal variation has not been detected in the population off the Atlantic coast (Frazier et al, 2014).…”

“…For the population in the Atlantic region, estimated maximum age (males: 12.0 years; females: 17.9 years) and age at 50% maturity (males: 3.9 years; females: 6.7 years) are more than twice the estimates for the population in the GOM (males: 5.5+ years for maximum age, 1.7 years for age at 50% maturity; females: 7.5+ years for maximum age, 2.9 years for age at 50% maturity) (Lombardi-Carlson et al, 2003;Frazier et al, 2014). Previous age and growth studies of bonnetheads in the eastern GOM (Parsons, 1993;Carlson and Parsons, 1997;Lombardi-Carlson et al, 2003) found significant latitudinal variation in life history traits; however, latitudinal variation has not been detected in the population off the Atlantic coast (Frazier et al, 2014). High degrees of site fidelity have been documented for this species (Heupel et al, 2006;Driggers et al, 2014), and tagging data indicate that there is no mixing between populations in the GOM and Atlantic region (Kohler and Turner, 2019).…”

“…Data for all recaptured sharks (excluding data as previously mentioned for sharks recaptured multiple times) were used in the model regardless of time at liberty, negative growth, or potential outliers because the GROTAG model can use these data to inform several calculated parameters. Growth has been found to be significantly different between sexes in previous growth studies (Parsons, 1993;Carlson and Parsons, 1997;Lombardi-Carlson et al, 2003;Frazier et al, 2014); therefore, sex-specific growth was modeled for both regions.…”

“…To allow direct comparison of growth estimates based on age data and those based on tag-recapture data, region-specific length-at-age data from Lombardi-Carlson et al (2003) and Frazier et al (2014) were remodeled (the authors of both publications used the Beverton and Holt, 1957, method of modeling VBGF parameters) by using an alternative parameterization of the VBGF recommended by Francis (1988a), in which mean length (L) of fish of age t is determined with this equation: 5where where Χ = (Φ + Ψ)/2; l Φ = mean length at age Φ; l Χ = mean length at age Χ; and l Ψ = mean length at age Ψ.…”

Articulated remains of the extinct shark Ptychodus (Elasmobranchii, Ptychodontidae) from the Upper Cretaceous of Spain provide insights into gigantism, growth rate and life history of ptychodontid sharks

“…[63][64][65][66][67][68][69][70][71]. However, this is questioned by recent studies [72][73][74] and especially in old individuals of long living species the age determination seems to be highly underestimated as the growth rate decreases with age resulting in a band width decline at the centrum edges that can become unresolvable in older individuals [56,72,[75][76][77][78][79]. The section of EMRG-Chond-SK-1b revealed 31 band pairs (birth mark + 30 band pairs), suggesting, under the assumption of an annual growth band deposition, that EMRG-Chond-SK-1 was around 30 years old.…”