Scientia Marina, Vol 76, No 3 (2012)

Species identification of Ommastrephes bartramii, Dosidicus gigas, Sthenoteuthis oualaniensis and Illex argentinus (Ommastrephidae) using beak morphological variables

Xinjun Chen
College of Marine Sciences, Shanghai Ocean University - The Key Laboratory of the Shanghai Education Commission for Oceanic Fisheries Resources Exploitation - The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources (Shanghai Ocean University), Ministry of Education , China

Huajie Lu
College of Marine Sciences, Shanghai Ocean University , China

Bilin Liu
College of Marine Sciences, Shanghai Ocean University - The Key Laboratory of the Shanghai Education Commission for Oceanic Fisheries Resources Exploitation - The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources (Shanghai Ocean University), Ministry of Education , China

Yong Chen
School of Marine Sciences, University of Maine - The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources (Shanghai Ocean University), Ministry of Education , United States

Siliang Li
College of Marine Sciences, Shanghai Ocean University , China

Ma Jin
College of Marine Sciences, Shanghai Ocean University , China


Four oceanic squid species, Ommastrephes bartramii, Dosidicus gigas, Sthenoteuthis oualaniensis and Illex argentinus, not only support important commercial fisheries, but also play a vital role in their marine ecosystems. It is therefore important to identify them in the analyses of their predators’ stomach contents as this can yield critical information on the trophic dynamics of ecosystems. Hard beaks of the four species frequently found in their predators’ stomachs can be used to identify them. In this study, to remove the effect of size differences among individuals, measurements of upper and lower beaks were standardized with an allometric model. A discriminant analysis was carried out to compare morphological differences among the four species and between the sexes for each species. The upper rostral width and upper rostral length showed the greatest interspecific variation in the beak morphological variables of the four Ommastrephidae. The linear discriminant
functions of beak morphological variables were developed for the four Ommastraphidae, which resulted in a rate of correct species classification of over 97%. Sexual dimorphism was also found in the beak morphology of O. bartramii and I. argentinus. This study suggests that morphological variables can be used to reliably classify Ommastrephidae at genus level, which can help identify the specie in the stomachs of cephalopod predators. This helps to improve the understanding of the role cephalopods play in their marine ecosystems.


beak morphological variable; species classification; Ommastrephes bartramii; Dosidicus gigas; Sthenoteuthis oualaniensis; Illex argentinus

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