Browsing by Author "Sow, Fambaye Ngom"
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- Differentiation of spatial units of Genus Euthynnus from the Eastern Atlantic and the Mediterranean using Otolith Shape AnalysisPublication . Muñoz-Lechuga, Rubén; Sow, Fambaye Ngom; Constance, Diaha N’Guessan; Angueko, Davy; Macías, David; Massa-Gallucci, Alexia; da Silva, Guelson Batista; Gonçalves, Jorge Manuel Santos; Lino, Pedro G.The shape of sagitta otoliths was used to compare individuals of little tunny (Euthynnus alleteratus) harvested on board commercial fishing vessels from the coastal areas along the Eastern Atlantic, including the Mediterranean Sea. Fish sampling and selection was designed to cover possible seasonal changes and tuna size. The research encompassed both morphometric and shape analyses of left sagittal otoliths extracted of 504 fish specimens. Four shape indices (Circularity, Roundness, Rectangularity, and Form-Factor) were significantly different between two groups, showing a statistical differentiation between two clear spatial units. The degree of divergence was even more pronounced along the rostrum, postrostrum, and excisura of the generated otolith outlines between these two groups. One group corresponds to the samples from the coastal areas in the Northeast Temperate Atlantic and Mediterranean Sea (NETAM Area) and a second group from the coastal areas off the Eastern Tropical Atlantic coast of Africa (ETA Area). This study is the first to use otolith shape to differentiate tunas from separate spatial units. These results could be used to re-classify previously collected samples and to correct time series of data collected.
- Global phylogeography of sailfish: deep evolutionary lineages with implications for fisheries managementPublication . da Silva Ferrette, Bruno Lopes; Mourato, Bruno; Vieira Hazin, Fabio Hissa; Arocha, Freddy; Williams, Samuel Mackey; Rodrigues Junior, Carlos Egberto; Porto-Foresti, Fabio; de Amorim, Alberto Ferreira; Rotundo, Matheus Marcos; Coelho, Rui; Hoolihan, John P.; Sow, Fambaye Ngom; Diaha, N'guessan Constance; Romanov, Evgeny, V; Domingues, Rodrigo Rodrigues; Oliveira, Claudio; Foresti, Fausto; Mendonca, Fernando FernandesSince the Miocene profound climatic changes have influenced the biology and ecology of species worldwide, such as their connectivity, genetic population structure, and biogeography. The goal herein is to evaluate the phylogeography of sailfish Istiophorus platypterus between the Atlantic, Indian, and Pacific oceans. Our results evidenced a high genetic diversity and three distinct populations among the ocean basins with limited gene flow among them. In addition, the species is characterized by two deep evolutionary lineages that diverged during the Miocene/Pliocene transition, one of them is circumtropical while the other is restricted to the Atlantic Ocean. These lineages evolved along the successive glacial-interglacial cycles from the Pleistocene and remained isolated from each other in glacial refugium until deglaciation. Assessments of sailfish suggest it may be subject to overfishing and the results herein imply the need to re-evaluate the current stock delimitations and management measures adopted by the Regional Fisheries Management Organizations, especially in the Atlantic and the Indo-Western Pacific oceans to effectively manage the species. In addition, this work highlights that both lineages should at least be treated as two distinct management units in the Atlantic Ocean until their taxonomic status is fully resolved, given their high genetic divergence.
- Two fish in a pod. Mislabelling on board threatens sustainability in mixed fisheriesPublication . Blanco-Fernandez, Carmen; Erzini, Karim; Rodriguez-Diego, Sara; Alba-Gonzalez, Pablo; Thiam, Ndiaga; Sow, Fambaye Ngom; Diallo, Mamadou; Viðarsson, Jónas R.; Fernández-Vidal, Duarte; Gonçalves, Jorge Manuel Santos; Rangel, Mafalda; Stobberup, Kim; Garcia-Vazquez, Eva; Machado-Schiaffino, GonzaloAccuracy in reporting captures is a key element to achieve fisheries sustainability. However, identification of the catches might be a challenge when two or more species are morphologically similar and caught jointly, like the mixed fisheries of black hakes in East Atlantic African waters. Black hakes (Merluccius senegalensis and M. polli) are tough to differentiate without previous training due to their high morphological resemblance. The two species are managed as a single stock, although the biological differences between them suggest the need of a separate management. In this study, a total of 806 black hakes were visually identified by fishers on deck of fishing vessels operating in Mauritania and Senegal waters, then assigned to a species by sequencing 450bp of the Mitochondrial Control Region. Comparing the results with visual identification we found 31.4% of the total catch were incorrectly labelled on board by the fishermen. The accuracy of the fishers' identification depended on the depth of capture and on fish size, larger individuals caught from deeper waters being more correctly assigned to M. polli. Mislabelling biased to M. polli suggests that M. senegalensis, already catalogued as endangered, is being underreported, which could endanger the conservation of this species and threaten the sustainability of black hake fisheries. Our results highlight the need for separate evaluation of the stocks in mixed fisheries for morphologically similar fish. Thus, monitoring through DNA barcoding in the very first step of the seafood chain surveys would improve accurate species delimitation and reduce its impact on the correct assessment of the stocks.