Dynamics of the deep-sea teleost black scabbardfish (Aphanopus carbo Lowe, 1839) in the Northeast Atlantic
[eng] Aphanopus carbo (Lowe, 1839), the black scabbardfish, is a benthopelagic teleost with high commercial value in the NE Atlantic, especially in Madeira Archipelago and mainland Portugal. Given its commercial interest and high susceptibility to overfishing, as a consequence of low fecundity and l...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/673480 |
| Acceso en línea: | http://hdl.handle.net/10803/673480 |
| Access Level: | acceso abierto |
| Palabra clave: | Aphanopus carbo black scabbardfish benthopelagic NE Atlantic population dynamics migration fatty acids stable isotopes sex steroids otolith trace elements peix sable negra bentopelàgic NE Atlàntic dinàmica de la població migració àcids grassos isòtops estables esteroids sexuals otòlit elements traça sable negro bentopelágico Atlántico NE dinámica poblacional migración ácidos grasos isotopos estables esteroides sexuales otolito elementos traza Ictiologia i Biologia Pesquera 57 574 |
| Sumario: | [eng] Aphanopus carbo (Lowe, 1839), the black scabbardfish, is a benthopelagic teleost with high commercial value in the NE Atlantic, especially in Madeira Archipelago and mainland Portugal. Given its commercial interest and high susceptibility to overfishing, as a consequence of low fecundity and low growth rate, improving the knowledge on its life cycle and population dynamics is of uttermost importance for improving fisheries management and advice. Although some questions persist, the agreed assumption is that there is a unique stock that undergoes a clockwise migration around the NE Atlantic driven by feeding and reproduction. The available information that supports the hypothetical migratory cycle of A. carbo was reviewed in this Thesis and different methodological approaches were proposed to explore its life history traits and relate them with the migratory cycle, in order to increase information on the species for a sustainable knowledge-based fishery management, and to assess its population dynamics and spatial pattern in the NE Atlantic. Differences in fatty acids and stable isotopes concentrations in the muscle tissue of specimens from different areas supported the species hypothetical migratory cycle. Mature specimens showed a prevalence of polyunsaturated fatty acids (PUFA) which are related with high energetic demands, supporting the hypothesis that the black scabbardfish continues to feed during the spawning period. PUFA associated with a response to stress were high in specimens from the southernmost areas which might be related with the expected long-distance migrations. The analysis of sex steroids in blood serum confirmed their role as intrinsic triggers for gonadal maturation and spawning in black scabbardfish. Based on estradiol (E2) and testosterone (T) concentrations, some developing females from Madeira were clustered with females from mainland Portugal, giving evidence that not all developing females will have the ability to mature and reproduce during the current spawning season. The previous methodologies allowed relating biochemical traits with the species life cycle and compare them between geographical areas in a short and recent time-frame. To understand the species taxonomic and species spatial diversity throughout its life cycle, otoliths were used as chemical markers. In a first study, otolith trace element composition (TEC) was shown to be adequate to separate the two Aphanopus species that are mixed in landings from the Madeiran longline fleet. It was further demonstrated that quantifying Mg, Cr, Sr, and Ba in the otolith increment that corresponds to age-class 9 can be an effective way to identify the species using LA- ICPMS at relatively reduced costs. This technique could be applied to archived collections of otoliths to perceive the historical presence of A. intermedius in landings in Madeira, reconstruct species abundance time-series and infer if the species is moving northwards. Otolith microchemical analysis was also applied to infer the migratory movements of A. carbo along the NE Atlantic by quantifying certain trace elements at selected otolith zones that represent different life history stages, namely the core, age three, age five, and the edge. TEC in the otolith edge could discriminate the locations where specimens were caught, separating the northernmost from the southernmost areas. The longitudinal multivariate analyses of TEC also sustained the separation of the otoliths into two groups, but there is high mixing between them, which agrees with the migratory hypothesis. The existence of two natal sources was suggested from otolith core TEC analysis. The acceptance of both southern and northern spawning grounds and of migratory movements along the NE Atlantic in both northward and southward directions implies changes to the current migratory hypothesis that might translate into changes in A. carbo’s stock assessment. |
|---|