Differentiation of Spatial Units of Genus <i>Euthynnus</i> from the Eastern Atlantic and the Mediterranean Using Otolith Shape Analysis
Rubén Muñoz-Lechuga,
Fambaye Ngom Sow,
Diaha N’Guessan Constance,
Davy Angueko,
David Macías,
Alexia Massa-Gallucci,
Guelson Batista da Silva,
Jorge M. S. Gonçalves,
Pedro G. Lino
Affiliations
Rubén Muñoz-Lechuga
Portuguese Institute for the Ocean and Atmosphere (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal
Fambaye Ngom Sow
Oceanographic Research Center of Dakar Thiaroye—CRODT/ISRA, LNERV—Route du Front de Terre, Dakar BP 2241, Senegal
Diaha N’Guessan Constance
Center of Oceanology Research, 29 Rue des Pêcheurs—BP V-18, Abidjan 01, Côte d’Ivoire
Davy Angueko
General Directorate of Fisheries and Aquaculture, Libreville BP 9498, Estuaire, Gabon
David Macías
Spanish Institute of Oceanography, Oceanographic Center of Málaga, Puerto Pesquero s/n, 29460 Fuengirola, Málaga, Spain
Alexia Massa-Gallucci
AquaBioTech Group Central Complex, Naggar Street, Targa Gap, MST 1761 Mosta, Malta
Guelson Batista da Silva
Animal Science Department, University Federal Rural of Semiárido, Av. Francisco Mota, 572—Bairro Pres. Costa e Silva, Mossoró CEP 59.625-900, RN, Brazil
Jorge M. S. Gonçalves
CCMAR—Centre of Marine Sciences, Campus de Gambelas, University of Algarve, 8005-139 Faro, Portugal
Pedro G. Lino
Portuguese Institute for the Ocean and Atmosphere (IPMA), Avenida 5 de Outubro s/n, 8700-305 Olhão, Portugal
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.
