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Article << Previous     |     Next >>   Contents Vol 51(4)

Age and growth of the daggernose shark, Isogomphodon oxyrhynchus, from northern Brazil

Rosangela Lessa, Francisco M. Santana, Vandick Batista and Zafira Almeida

Marine and Freshwater Research 51(4) 339 - 347
Published: 2000

Abstract

Age and growth of the daggernose shark, Isogomphodon oxyrhynchus, from northern Brazil were determined from 105 vertebral sections stained with alizarin red-S representing 46 males, 52 females and 7 specimens of unknown sex (58.4 to 141 cm-TL) and verified with length–frequency analysis of 1135 specimens (632 females and 503 males, 58–160 cm ). Marginal increments did not show significant differences throughout the year, and it was assumed that one band is formed annually. Different tests provided varying results for growth curve comparisons between sexes; the curves were similar, despite biological differences. von Bertalanffy growth parameters estimated from back-calculated mean lengths, observed mean lengths-at-age and length–frequency analysis were of the same magnitude. Parameters generated from observed length-at-age were chosen for describing growth for the species: L• 171.4 cm, k 0.12 year –1 and t0 –2.612 years. The largest female aged from vertebrae was 12 years old, whereas the largest male was aged at 7 years. Neonates, ~42.3 cm, showed one band in the vertebrae, formed at birth, or soon thereafter. Males are mature at 103 cm or 5–6 years and females at 115 cm or 6–7 years.

Resumo. A idade e o crescimento do cação quati, Isogomphodon oxyrhynchus, do norte do Brasil foi determinada usando 105 vértebras seccionadas e coradas com alizarina vermelha-S de 46 machos, 52 fêmeas e 7 exemplares de sexo indeterminado (58,4–141 cm-CT). Análise de distribuição de frequência de comprimentos de 1135 indivíduos (632 femeas e 503 machos, 58–160 cm) foi utilizada como método de verificação. Os incrementos marginais não mostraram diferenças significativas ao longo do ano, assumindo-se que uma banda é formada anualmente. Com diferentes testes, usados para comparar curvas de crescimento entre os sexos, obteve-se resultados conflitantes; o crescimento foi considerado idêntico entre os sexos, apesar das diferenças biológicas entre machos e fêmeas. Os parâmetros de von Bertalanffy estimados do retrocálculo, comprimentos médios observados e da análise de comprimentos foram semelhantes, tendo sido escolhidos para descrever o crescimento da espécie: L• 8171,4 cm; k 0,12 year –1 et 0 –2,612 years. Amaior fêmea cuja idade foi estimada pelas vértebras tinha 12 anos enquanto o maior macho tinha 7 anos. Recém-nascidos de 42,3 cm apresentavam uma banda nas vertebras, formada ao nascer, ou logo depois do nascimento. Machos estão maduros em 103 cm ou 5–6 anos e fêmeas em 115 cm ou 6–7 anos.



Full text doi:10.1071/MF99125

© CSIRO 2000

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