Morphometric differentiation between two juvenile tuna species [Thunnus thynnus (Linnaeus, 1758) and Euthynnus alletteratus (Rafinesque, 1810)] from the Eastern Mediterranean Sea

Abstract

Summary The main objective of this study was to analyse the differences in morphometric characteristics among specimens of Atlantic juvenile bluefin tuna Thunnus thynnus [12.2–46.5 cm fork length (FL)] and juvenile little tuna Euthynnus alletteratus (14.1–26.4 cm FL). A total of 353 bluefin tuna (young of the year) and 288 little tuna (young of the year) were collected from the commercial hand line fisheries in the eastern Mediterranean Sea between July and October of 2011–2013 with three round‐bent hook sizes (numbers 10, 12 and 14; Mustad 2315S). By using univariate and multivariate analysis, 11 morphometric characters were investigated. anova revealed highly significant differences (P < 0.001) for all morphometric parameters among the two species. The principal component analysis showed that the difference between the species resulted mainly from preanal length (LA), caudal fin hight (CC), snout length (SnL), eye diameter (ED) and postorbital length (PO). The stepwise discriminant analysis revealed that juveniles of the two tuna species were correctly classified, with a percentage of 99.2%. Length of pectoral fin (LP) was the strongest predictor in the discriminant functions.

Morphometric variations of Kawakawa (Euthynnus affinis Cantor, 1849) in Malaysian and Yemeni waters

“…Furthermore, a similar study in Tunisian waters revealed that fork length, standard length, and pectoral fin are important characteristics in differentiating between bluefin tuna populations Auxis rochei (Allaya et al 2016). Likewise, a study conducted by Karakulak et al (2016) demonstrated that there is a clear relationship between the length of the head and the length of the pectoral fin, the first predorsal, and the height of the second dorsal fin between Thunnus thynnus and E. alletteratus. Furthermore, Griffiths et al (2017) divulged a highly significant relationship between fork length-total length and length-weight among four Scombridae fish species (E. affinis, T. tonggol, R. kanagurta, and C. elegans).…”

Stock identification of Kawakawa Euthynnus affinis (Cantor, 1849) from Peninsular Malaysia using discriminant analysis

“…Another study in Tunisian waters revealed that the pectoral fin, standard length, and fork length play an important roles to discriminate between the population of bullet tuna, Auxis rochei [22]. Additionally, [23] demonstrated a strong correlation of head length, pectoral fin length, first predorsal length, and second dorsal fin height between Thunnus thynnus and Euthynnus alletteratus. Likewise, the maximum value to separate among five populations of Clupisoma garua in DFA was function 1 as reported by [24] .…”

NEW GEOGRAPHIC OCCURRENCE: DIGENEA Lobatozoum multisacculatum (DIDYMOZOIDAE) ON LITTLE TUNNY, Euthynnus alletteratus (SCOMBRIDAE)

“…Little tunny, Euthynnus alletteratus (Rafinesque, 1810) is a pelagic and highly migratory fish of the family Scombridae that inhabits the tropical and subtropical coastal waters of both sides of the Atlantic Ocean. There are three main populations of E. alletteratus known in the Atlantic Ocean, located in the center-east, in the southeast and in the west of the Atlantic Ocean (Karakulak et al, 2016;Mele et al, 2016). It is considered an abundant fish species in the Brazilian Northeast coast (Lucena et al, 2004) with very little information regarding its parasitic fauna in this region (Alves & Luque, 2006).…”