Loading...
Publication
Ageing of swordfish, Xiphias gladius Linnaeus, 1758, from the Azores, using sagittae, anal-fin spines and vertebrae
| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 2.65 MB | Adobe PDF |
Advisor(s)
Abstract(s)
Determinaram-se as idades de espadartes, Xiphias gladius Linnaeus 1758, capturados nos Açores a partir de três estruturas ósseas diferentes (sagittae esquerdos, 2º espinhos da barbatana anal e vértebras; n=155). Comparam-se estas estruturas em termos de: facilidade de amostragem e processamento; leitura e interpretação de marcas de idade e repetibilidade das estimações de idade. Obtiveram-se relações lineares, estatisticamente significativas, entre as dimensões das peças, o número de anéis contados ("idades" estimadas) e o comprimento mandíbula-furca dos indivíduos. Em 94.4% das secções de espinhos, 45% dos otólitos e 27.8% dos corpos vertebrais, concordaram 2 dos 3 replicados das estimações de "idade". O erro das estimações, expresso pelo coeficiente de variação, variou entre um máximo de 22.8% nas vértebras e mínimos de 8.9% e 7.5% nos otólitos e espinhos, respectivamente. Obteve-se uma relação complexa (1:2:3, espinhos, sagittae e vértebras) entre o número de anéis contados ("idades" estimadas) a partir das três estruturas. O crescimento parece variar sazonalmente embora a análise de incrementos marginais não permita estabelecer um "modelo" de deposição de incrementos de crescimento/idade em qualquer das peças. Os resultados obtidos recomendam os espinhos para estudos de avaliação de idade e crescimento de espadarte.
ABSTRACT: Age was estimated from 155 calcified structures (sagittae, anal-fin spines and vertebrae) collected from swordfish, Xiphias gladius, caught in the Azores. The ease of collection and processing, legibility and precision among the structures were compared, to determine the most useful for age determination. Statistically significant linear relationships were obtained between the size of the structures, ring counts and lower jaw fork length. In 94.4% of the spine sections, 45% of the otoliths and 27.8% of the vertebral centra the replicate "age" estimates agreed in 2 out of 3 readings. The error of "age" estimates, as expressed by the coefficient of variation, varied between a maximum of 22.8% in vertebrae and minima of 8.9% and 7.5% in otoliths and spine sections respectively. A complex 1:2:3 ratio was derived for the relationship between the "ages" estimated from spine sections, sagittae and vertebral centra. Although growth seems to vary seasonally, marginal increment analyses could not establish the time of ring formation in any of the structures. We recommend second anal-fin spine sections for age determination of swordfish. Therefore, this structure should continue to be used in routine age and growth assessment programs of swordfish.
ABSTRACT: Age was estimated from 155 calcified structures (sagittae, anal-fin spines and vertebrae) collected from swordfish, Xiphias gladius, caught in the Azores. The ease of collection and processing, legibility and precision among the structures were compared, to determine the most useful for age determination. Statistically significant linear relationships were obtained between the size of the structures, ring counts and lower jaw fork length. In 94.4% of the spine sections, 45% of the otoliths and 27.8% of the vertebral centra the replicate "age" estimates agreed in 2 out of 3 readings. The error of "age" estimates, as expressed by the coefficient of variation, varied between a maximum of 22.8% in vertebrae and minima of 8.9% and 7.5% in otoliths and spine sections respectively. A complex 1:2:3 ratio was derived for the relationship between the "ages" estimated from spine sections, sagittae and vertebral centra. Although growth seems to vary seasonally, marginal increment analyses could not establish the time of ring formation in any of the structures. We recommend second anal-fin spine sections for age determination of swordfish. Therefore, this structure should continue to be used in routine age and growth assessment programs of swordfish.
Description
Keywords
Xiphias gladius Espadarte Swordfish Açores Azores
Citation
"ARQUIPÉLAGO. Ciências Biológicas e Marinhas = Life and Marine Sciences". ISSN 0870-6581. Nº 13A (1995): 39-51.