`Ocean triads' in the Mediterranean Sea: physical mechanisms potentially structuring reproductive habitat suitability (with example application to European anchovy, Engraulis encrasicolus )

2002 ◽  
Vol 11 (3) ◽  
pp. 129-142 ◽  
Author(s):  
Vers N. Agostini ◽  
Andrew Bakun
2014 ◽  
Vol 71 (9) ◽  
pp. 2429-2435 ◽  
Author(s):  
Mahmoud Bacha ◽  
Sherif Jemaa ◽  
Azzedine Hamitouche ◽  
Khalef Rabhi ◽  
Rachid Amara

Abstract Understanding the influence of oceanographic features on the structure of fish population is of basic importance to population dynamics studies and fisheries management. The European anchovy (Engraulis encrasicolus) exhibits a complex population structure which has produced conflicting results in previous genetic studies. This study examines the variability in the shape of the anchovy's otolith as a tool for identifying different stocks, and investigates the effects of oceanographic features on population structure. Anchovies were analysed from seven locations in the SW Mediterranean Sea and Atlantic Ocean along the northwestern African (Morocco) and Portuguese (Bay of Cadiz) coasts. A combination of otolith shape indices and elliptic Fourier descriptors were investigated by multivariate statistical procedures. Within the studied area, three distinct anchovy stocks were identified: the Algero-Provençal Basin, the southern Alboran Sea, and the Atlantic Ocean (Morocco and Gulf of Cadiz). The separation of the stocks was based on non-parametric discriminant analysis returning a classification percentage. Over 81% of the separation of the stocks could be explained by oceanographic features. Shape variability of anchovy otoliths was associated with the presence of the Almeria-Oran front, and the strait of Gibraltar. The Alboran stock was distinct from the Algero-Provençal Basin and from the closest Atlantic stocks (Gulf of Cadiz or Atlantic coast of Morocco). Results are discussed and compared with those previously obtained by genetic studies. This study supports the efficiency of otolith shape analysis for the stock identification of anchovy, and highlights the role of oceanographic features in stock separation.


2012 ◽  
Vol 69 (8) ◽  
pp. 1357-1371 ◽  
Author(s):  
Yaisel J. Borrell ◽  
Jorge A. Piñera ◽  
José A. Sánchez Prado ◽  
Gloria Blanco

Abstract Borrell, Y. J., Piñera, J. A., Sanchez Prado, J. A., and Blanco, G. 2012. Mitochondrial DNA and microsatellite genetic differentiation in the European anchovy Engraulis encrasicolus L. – ICES Journal of Marine Science, 69: . The European anchovy Engraulisencrasicolus is currently one of the principal target species for commercial fisheries in Europe, and most stocks are overfished at present. In this work, specimens were sampled in the Bay of Biscay (Cantabrian, Basque Country, and French coasts) in 2009 and also in the Mediterranean (Adriatic Sea). Mitochondrial DNA (mtDNA; cytochrome b and 16S) was sequenced, and 14 nuclear microsatellites showing high and low levels of polymorphism were arranged in three multiplex polymerase chain reaction (PCR) systems and genotyped. Two main ancient mitochondrial clades were found. These clades are separated by 15 mutational steps and 1.7% sequence divergence, corresponding to a separation time of ∼0.5 million years ago. Our results using both mtDNA and microsatellites suggest the presence of at least three genetically differentiated groups: the west Cantabrian Sea, the rest of the populations in the Bay of Biscay, and the Mediterranean. Although it is known that western Iberian Atlantic populations of E. encrasicolus may be genetically different from those of the Bay of Biscay, the results suggest that the transition between these groups may be as close as a 100 km and that a recent genetic homogenization process in the eastward area of the Bay of Biscay has probably occurred.


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