Age and growth of the Scalloped Hammerhead shark, Sphyrna lewini (Griffith and Smith, 1834), from the southern Brazilian coast

Abstract

Age and growth studies for the scalloped hammerhead shark, Sphyrna lewini (Griffith and Smith, 1834) caught along the southern Brazilian coast, were based on ring measurements of vertebrae sections of 115 males, 116 females and 14 unknown sexed sharks between 48 and 344 cm total length (TL). The von Bertalanffy growth models were best fit using back-calculated data. The growth parameters obtained for males, were L ∞ = 266 cm; K = 0.05/year; L 0 = 47 cm. For females, L ∞ = 300 cm; K = 0.05/year; L 0 = 51 cm. An adult female reached 217 cm TL and was 31.5 years old. On the other hand, an adult male was 29.5 years old and measured 234 cm TL. Longevity estimate for males and females was 55 years. Therefore, S. lewini is a long-lived fish. Ageing precision, based on the IAPE index, was 5.6%. Marginal Increment analysis based on MIR index from hammerheads smaller than 105 cm, compared with the percentual of opaque and hyaline bands found per month ageing whole vertebrae, showed an annual ring formation, i.e., in winter.Keywords: elasmobranchs, fisheries biology, conservation.Idade e crescimento do tubarão-martelo-entalhado, Sphyrna lewini (Griffith and Smith, 1834), da costa sul do Brasil ResumoO estudo da idade e do crescimento do tubarão-martelo-entalhado, Sphyrna lewini (Griffith and Smith, 1834), na costa sul do Brasil, baseou-se na leitura de anéis em seções de vértebras de 115 machos, 116 fêmeas e de 14 exemplares com sexo indeterminado, com comprimentos totais (CT) entre 48 e 344 cm. Modelos de crescimento de von Bertalanffy foram mais bem ajustados aos dados de idade e comprimento retrocalculados, considerando sexos em separado. Os parâmetros de crescimento obtidos para os machos foram L ∞ = 266 cm; K = 0,05/ano; L 0 = 47 cm. Para as fêmeas L ∞ = 300 cm; K = 0,05/ano; L 0 = 51 cm. Uma fêmea adulta atingiu um CT de 217 cm e uma idade de 31,5 anos. Por sua vez, um macho adulto tinha 29,5 anos e CT de 234 cm. A estimativa de longevidade para machos e fêmeas foi de 55 anos. O índice de erro percentual médio (IAPE), que avalia a precisão na leitura de idades, foi de 5,6%. A análise do incremento marginal baseada no índice MIR e aplicada em tubarões com CT < 105 cm, comparada com o percentual de bandas opacas e hialinas mensais, obtido através de leituras de vértebras inteiras, indicou um padrão anual na formação dos anéis, ou seja, anéis de inverno.Palavras-chave: elasmobrânquios, biologia pesqueira, conservação.

Periodicity of the growth‐band formation in vertebrae of juvenile scalloped hammerhead shark Sphyrna lewini from the Mexican Pacific Ocean

“…Accordingly, the CV value obtained in this study (6.1%) was consistent with a precise age estimation, especially since CV values as low as 6.8% (Drew et al, ) and as high as 17.9% (Harry et al, ) have been reported in studies of S. lewini elsewhere. In addition, the I APE value obtained here (4.3%) was also consistent with those obtained from previous ageing studies of S. lewini (3.2%, Piercy et al, ; 3.7%, Anislado‐Tolentino et al, ; 5.6%, Kotas et al, ), a further indication of a precise age estimation with low bias.…”

“…No significant relationship was found between peaks in 43 Ca profiles and the opaque growth bands but the peaks in 31 P:Ca and 55 Mn:Ca spatially corresponded with the annual banding pattern in most of the samples. 31 P:Ca profiles displayed 1.19 peak per opaque band while 55 Mn:Ca displayed 0.88 peak per opaque band; this closely matched the annual deposition rate in juveniles obtained from the verification analyses of this and previous studies (Branstetter, ; Harry et al, ; Kotas et al, ; Piercy et al, ). However, these interpretations remain tentative because age estimates explained only half of the variability of the elemental patterns, as shown by the low, but significant, correlation coefficients.…”

“…It is well established that in the southeastern Gulf of California, pregnant females of S. lewini give birth during the summer months, between May and July (Torres‐Huerta et al, ), with the formation of the vertebral birthmark deposited at that moment being representative of the transition from an in‐utero to a post‐partum life history (Cailliet & Goldman, ). Considering that the first translucent band is possibly formed during the following winter months (Kotas et al, ; Piercy et al, ), the first vertebral growth band pair of S. lewini would therefore represent less than 1 year (8–11 months of age) once such translucent bands are fully formed. However, for the purposes of this study, it was assumed that the first growth band pair represented a complete year of growth to simplify the age estimates and comparisons with previous studies.…”

“…Knowledge of the age structure and growth rate of a population is required for population models that estimate the productivity of a stock and demonstrate whether a species is harvested at sustainable levels (Cortés, 2000). Studies of age and growth of S. lewini around the world (Branstetter, 1987a;Chen et al, 1990;Drew et al, 2015;Harry et al, 2011;Kotas et al, 2011;Piercy et al, 2007) have included Mexico (Anislado-Tolentino et al, 2008;Anislado-Tolentino & Robinson-Mendoza, 2001) but no consensus has been achieved regarding the growth pattern of the species. Some authors (Branstetter, 1987a;Harry et al, 2011;Kotas et al, 2011;Piercy et al, 2007) have suggested that a single pair of a growth band in the vertebrae whereas others (Anislado-Tolentino et al, 2008;Anislado-Tolentino & Robinson-Mendoza, 2001;Chen et al, 1990) have suggested that two pairs of growth bands are formed each year.…”

Age, growth and maturity of the pelagic thresher Alopias pelagicus and the scalloped hammerhead Sphyrna lewini

“…Numerous age and growth studies have previously been undertaken on S . lewini , although none within Indonesian waters (Chen et al , ; Tolentino & Mendoza, ; de Bruyn et al , ; Piercy et al , ; Tolentino et al , ; Harry et al , ; Kotas et al , ). Few studies have been able to adequately obtain samples from all components of a population, with sex and life‐stage bias commonly occurring within S .…”