Vasconcelos et al.: Population identification of Trachurus picturatus in the Northeast Atlantic 
83 
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Figure 2 
Map showing the 3 locations where blue jack mackerel (Trachurus pictura¬ 
tus) were sampled in 2015 for this study: off Peniche, a city on mainland 
Portugal (open circle), the Madeira archipelago (black circle), and the Ca¬ 
nary Islands (black triangle). Source: Direfao de Servifos de Investigafao 
da Direfao Regional de Pescas. The dashed lines indicate the exclusive eco¬ 
nomic zones (EEZs). 
the blue jack mackerel, no other work has focused 
on the possible population structure over the distri¬ 
butional range of this fish (ICES 3 ; Vasconcelos et ah, 
2017a). Interestingly, some studies on reproduction and 
growth from Madeira (Jesus 4 ; Vasconcelos et al., 2006; 
Vasconcelos et al., 2017b), Azores (Isidro, 1990; Gar¬ 
cia et al., 2015) and the Canary Islands (Shaboneyev 
and Ryazantseva, 1977; Riviero 5 ; Jurado-Ruzafa and 
Santamarfa, 2013) have reported a similar reproduc¬ 
tive season, but differences in growth and age at first 
maturity were observed between individuals from the 
Azores and those from Madeira (Jesus 4 ; Vasconcelos et 
3 ICES. 2016. Report of the working group on southern 
horse mackerel, anchovy and sardine (WGHANSA), 24-29 
June 2016, Lorient, France. ICES CM 2016/ACOM:17, 588 
p. [Available from website.] 
4 Jesus, G. T. 1992. Study of the growth and reproduction 
of Trachurus picturatus (Bowdich, 1825) in Madeira. Doc. 
XIV/C/1-1991/03 (DG XIV/CE), 66 p. Dire ? ao Regional de 
Pescas da Regiao Autonoma da Madeira, Funchal, Madeira, 
Portugal. 
5 Riviero, I. 2006. Biometrics of pelagic fish in Gran Ca¬ 
naria Island waters (Canary Islands), 17 p. Univ. Palmas- 
Gran Canaria, Las Palmas de Gran Canaria, Canary Islands, 
Spain. [Available from website.] 
al., 2006) and the Canaries (Jurado-Ruzafa and San- 
tamarla, 2013). A number of studies have successfully 
used parasites of T. picturatus as biological tags (Gae- 
vskaya and Kovaleva, 1985; Costa et al., 2013; Vascon¬ 
celos et al., 2017a) and it may be that variation in the 
occurrence and infection levels of parasites may reflect 
the existence of different populations of T. picturatus 
in the northeast Atlantic. The goal for this study was 
to provide a first step toward the identification of geo¬ 
graphical variation in blue jack mackerel body and oto¬ 
lith shape by using landmark-based geometric morpho¬ 
metries and elliptic Fourier analysis, respectively, to 
determine whether variation in these parameters may 
have implications for fishery management. 
Materials and methods 
A total of 438 specimens of T. picturatus (135 from wa¬ 
ters off Peniche, mainland Portugal, 155 from the Ma¬ 
deira archipelago and 148 from the Canary archipela¬ 
go) (Fig. 2) were randomly sampled from commercial 
catches, per sampling period (quarter), between Janu¬ 
ary and December 2015. The methods and fishing gear 
used to catch T. picturatus varied among locations: 
