Validated age and growth estimates for the shortfin mako, Isurus oxyrinchus, in the North Atlantic Ocean

Abstract

Age and growth estimates for the shortfin mako, Isurus oxyrinchus, derived from vertebral centra of 258 specimens (118 males, 140 females), ranging in size from 64 to 340 cm fork length (FL) were compared with data from 22 tagrecaptured individuals (74-193 cm FL) and length-frequency data from 1822 individuals (1035 males, 787 females; 65-215 cm FL). Annual bandpair deposition, confirmed by a concurrent bomb radiocarbon validation study, was used as the basis for band interpretation. Validation was further confirmed with a tetracycline-injected male shortfin mako recaptured after being at liberty off South Africa for 1 year and aged at 18 years. Growth rates from tag-recapture analysis (GROTAG) were higher than those derived from vertebral annuli and were only available from sharks up to 193 cm FL at recapture. Modal length-frequency data were used to verify the first four age classes.Growth curves were fit using both von Bertalanffy and Gompertz models. The 3-parameter version of the von Bertalanffy growth function produced the most biologically reasonable values for males, based on observed data (L ¥ = 253 cm FL, K = 0.125 year -1 (estimated longevity = 21 year), and L 0 = 72 cm). The 3-parameter version of the Gompertz growth function produced the most biologically reasonable estimates, for females (L ¥ = 366 cm FL, K = 0.087 year -1 (estimated longevity = 38 year) and L 0 = 88 cm. Males and females were aged to 29 (260 cm FL) and 32 years (335 cm FL), respectively. Both sexes grew similarly to age 11 (207 cm FL, 212 cm FL for males and females, respectively) when the curve leveled in males and continued to rise in females. Age at 50% maturity was estimated at 8 years for males (185 cm FL) and 18 years for females (275 cm FL). The species grows slower, matures later and has a longer life span than previously reported in North Atlantic waters.

Age and growth of Schizopygopsis younghusbandi younghusbandi in the Yarlung Zangbo River in Tibet, China

“…The growth inflexion point signifies the age the growth rate, as a function of body weight is the greatest (Chung et al 1999), while considering the growth potential of fish. The growth inflexion point is usually considered as the catching standard for the fishery management (Ma et al 1999). In this study, the growth inflexion points were 10.2 years for males and 12.0 years for females of S. y. younghusbandi, and the corresponding average standard lengths were approximately 286 and 340 mm, respectively.…”

Comparative rates of growth of the Port Jackson shark throughout its southern Australian range

“…This discrepancy between these two growth models has been observed in other species of elasmobranchs, e.g. Chiloscyllium plagiosum (Chen et al 2007), Carcharhinus plumbeus (Romine et al 2006) and Isurus oxyrinchus (Natanson et al 2006). The Gompertz models fit the data well for both sexes, but provided a biologically unreasonable underestimate of maximum asymptotic length, subsequently overestimating the rate at which the asymptotic length of the species is attained (Romine et al 2006).…”

Size, Age, and Spatial–Temporal Distribution of Shortfin Mako in the Mexican Pacific Ocean

“…Our results agree with Chang and Liu (2009) for the estimated longevity of this species in the Pacific Ocean at 56 years. Natanson et al (2006) used data from RibotCarballal et al (2005) and six other studies to confirm their calculations. Those investigators estimated the longevity of the Shortfin Mako in the Mexican Pacific at 55 years, which is very close to our findings and supports an estimated age range for this species in this specific study area.…”

“…The difference in ring deposition (i.e., periodicity), and consequently dissimilar growth patterns in sharks between nearby study areas (northern Mexican Pacific versus California waters), could be a consequence of the low sample size of the OTC-marked vertebrae analyzed (n = 29) and the maturity stages that were dominated by juveniles in the study of Wells et al (2013). Juvenile Shortfin Makos appear to have higher growth rates during the first years of life (Natanson et al 2006;Barreto et al 2016). This rapid growth in the early stages of life could explain the high growth rate (k = 0.17-0.19 cm/year) reported by Wells et al (2013), which contrasts with that (k = 0.05 cm/year) reported by Ribot-Carballal et al (2005).…”

“…One of the biological variables that has the most influence on population analysis of any species is age, since this is the basis for calculating mortality and productivity rates (Campana 2001). Most studies have reported deposition of one age ring per year for Shortfin Makos (Cailliet and Bedford 1983;Ribot-Carballal et al 2005;Bishop et al 2006;Natanson et al 2006;Semba et al 2009). We chose the growth parameters reported by Ribot-Carballal et al (2005) to estimate the age structure of the Shortfin Mako individuals, because those authors conducted their work in the same study area.…”