Browsing by Author "Correia, A. T."
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- Diversity of anchovy migration patterns in an European temperate estuary and in its adjacent coastal area: implications for fishery managementPublication . Morais, P.; Babaluk, J.; Correia, A. T.; Chicharo, Maria Alexandra; Campbell, J. L.; Chícharo, LuísThis study aims to study the diversity of the migration patterns of the anchovy Engraulis encrasicolus (L.,1758) collected in the Guadiana estuary (SE-Portugal/SW-Spain) and in the adjacent coastal area, by analysing Sr concentration distribution in sagittal otoliths. The distribution of Sr in otoliths of anchovy captured in the estuary allowed us to identify two major patterns: a) fish that do not migrate through estuarine salinity gradients and b) fish that make differential use of the estuary throughout their lives, occupying areas of lower salinity during the early stages of the life cycle followed by migrations to areas of higher salinity later in life. The patterns for fish captured in coastal areas inferred that they probably hatched in an estuarine environment and progressively migrated along an estuary to the coast. There is no massive migration of coastal anchovy to spawn in the estuary, as previously suggested. These results suggest that fishery managers should evaluate the contribution of estuarine populations to coastal stocks and the impact of estuarine recruitment fluctuations on this stock.
- Insights into population structure of Diplodus vulgaris along the SW Portuguese coast from otolith elemental signaturesPublication . Correia, A. T.; Pipa, T.; Gonçalves, J. M. S.; Erzini, Karim; Hamer, P. A.The common two-banded sea bream (Diplodus vulgaris) is an important fish in the marine ecosystems of the NW Atlantic and Mediterranean. In southern Portugal it is a major fishery resource being targeted mainly by the artisanal fleets. Although there is some knowledge of the age, growth and reproductive biology of the species, information about its population structure is scarce and somewhat limited to the Mediterranean Sea. In this study the otolith elemental signatures of 90 specimens of D. vulgaris of the same age group (2+ years) and cohort collected from the important fishery regions of SW Portugal (Sesimbra, Sagres and Faro) have been analysed by inductively coupled plasma mass spectrometry (ICP-MS). Two different methodologies have been applied: solution based analysis of the whole otoliths; representative of the entire life-history prior to capture, and laser ablation analysis of otolith cores; representative of the larval and early post-settlement phase. Whole otolith comparisons utilised Sr/Ca, Ba/Ca, Mn/Ca, Li/Ca and Ni/Ca to demonstrate regional population structure. Classification accuracy rates from linear discriminant function analyses (LDFA) of whole otolith chemistry data were high for each region; Faro - 93%, Sagres - 90% and Sesimbra - 80%. Comparison of the otolith core chemistry utilised Sr/Ca, Ba/Ca, Mn/Ca and Mg/Ca and Zn/Ca. LDFA for the otolith core chemistry also achieved accurate classification for samples from Sesimbra (73%), but there was high overlap of otolith chemistry between samples from Faro and Sagres (47 and 43% classification accuracy respectively). The whole otolith results suggest that D. vulgaris are resident in the regional fishing areas during the juvenile phase. Both the core and whole otolith chemistry data supported separation of the Sesimbra fishery region from the more southern and closely associated Faro and Sagres regions for management purposes. However, while the whole otolith data indicated that the populations at Faro and Sagres likely remained separated in the juvenile stage, the otolith core chemistry data was inconclusive as to whether recruitment to these two areas was derived, or not, from different spawning areas.
- Population structure and connectivity of the European conger eel (Conger conger) across the north-eastern Atlantic and western Mediterranean: Integrating molecular and otolith elemental approachesPublication . Correia, A. T.; Ramos, Ana; Barros, F.; Silva, Goncalo; Hamer, P.; Morais, P.; Cunha, R. L.; Castilho, RitaGenetic variation (mtDNA) of the European conger eel, Conger conger, was compared across five locations in the north-eastern Atlantic (Madeira, Azores, South Portugal, North Portugal and Ireland) and one location in the western Mediterranean (Mallorca). Genetic diversity of conger eel was high, and differentiation among regions was not significant. Additionally, comparisons of element:Ca ratios (Sr:Ca, Ba:Ca, Mn:Ca and Mg:Ca) in otolith cores (larval phase) and edges (3 months prior to capture) among the Azores, North Portugal, Madeira and Mallorca regions for 2 years indicated that variation among regions were greater for edges than cores. Therefore, while benthic conger may display residency at regional scales, recruitment may not necessarily be derived from local spawning and larval retention. Furthermore, data from otoliths suggest a separated replenishment source for western Mediterranean and NE Atlantic stocks. The combination of genetics and otolith chemistry suggests a population model for conger eel involving a broad-scale dispersal of larvae, with limited connectivity for benthic juvenile life stages at large spatial scales, although the existence of one or multiple spawning grounds for the species remains uncertain.
- Population structure and dynamics of the Atlantic mackerel (Scomber scombrus) in the North Atlantic inferred from otolith chemical and shape signaturesPublication . Moura, A.; Muniz, A. A.; Mullis, E.; Wilson, J. M.; Vieira, R. P.; Almeida, A. A.; Pinto, E.; Brummer, G. J. A.; Gaever, P., V; Goncalves, J. M. S.; Correia, A. T.The Atlantic mackerel, Scomber scombrus, is an economically important and widely distributed fish species in the North Atlantic, currently considered to comprise two stocks: the North-West Atlantic (NWA) and the North-East Atlantic (NEA). Each stock is composed of different spawning components which involve temporal and spatial movements driven by the environment. Thus, resolving the species population structure and dynamics presents a challenge to scientists. In this study, the stock structure of S. scombrus was evaluated using otolith shape and chemical signatures. One hundred and eighty individuals of the same cohort (age 3), caught between January and February of 2018 from six key locations in the North Atlantic, were used. Individuals were collected from the two spawning components in the NWA stock, the Canadian Northern component (NWA-N) and the US Southern component (NWA-S); and from the three spawning components in the NEA stock, the North Sea (NEA-NS), the Western (NEA-W) and the Southern components (NEA-S), plus, an overlapping area of these last two components, the Bay of Biscay (NEA-BB). Combined otolith signatures fully discriminated the NEA and NWA stocks (100% of reclassification success, indicates distinct population-units) and discriminated the components within each stock with high reclassification percentages (100% and 68% for the overall reclassification of the NWA and NEA components, respectively). These data suggest that NWA stock should be regard as two distinct populationunits for fisheries management purposes, confirms the complex metapopulational structure of the NEA stock, and calls for the need of continuous evaluation of these complex stocks in order to achieve a sustainable exploitation.
- Population structure of the black seabream Spondyliosoma cantharus along the south-west Portuguese coast inferred from otolith chemistryPublication . Correia, A. T.; Gomes, P.; Gonçalves, J. M. S.; Erzini, Karim; Hamer, P. A.The chemistry of black seabream Spondyliosoma cantharus otoliths from three main fishery grounds (Olhao, Sagres and Sesimbra) located along c. 400 km of the Portuguese south and west coasts was examined. Element:Ca ratios were determined in whole otoliths and otolith cores of young adult specimens of 23 years of age. Using the data from whole otoliths, it was possible to discriminate among S. cantharus from the three fishing grounds with an average accuracy of 91%. Differences among fishing grounds were significant for all element:Ca ratios, and otoliths from Sagres had significantly higher levels of all ratios compared to the other fishing grounds. In contrast, the chemical composition of the otolith core, representative of the larval stage, showed limited variation among the fishing grounds, with an average discrimination accuracy of only 44%, although the Mg:Ca ratio of the otolith cores was also significantly higher for the Sagres samples. The data suggest that larval stages experienced a homogenous environment consistent with an offshore oceanic spawning. Juveniles appeared to display local residency on the inshore fishing grounds, areas probably characterized by greater environmental heterogeneity. Spondyliosoma cantharus population structure is consistent with distinct local population units that share a spawning ground providing recruits to different coastal fishery areas.