Variations in body shape of European seabass larvae (<i>Dicentrarchus labrax</i>) reared under xenic and axenic conditions

Abstract

High rates of body deformities is one of the most challenging problems in fish culture and is a common source of downgrading the product value of commercially raised fish. The aims of this study are explore the effects of xenic and axenic rearing conditions on the seabass larvae and check whether the rearing condition has a different effect as larvae grow older. The larvae of seabass larvae, Dicentrarchus labrax L. (Teleostea, Moronidae), were reared under xenic and axenic rearing conditions up to fourteenth day after hatching (DAH). The size and shape were analyses for specimens of three age groups: DAH zero, four and 12. The growth comparison was done based on length measurements. For specimens of DAH zero and four, the total length, gut length, predorsal fin length, yolk sac length and height were measured. For specimens of DAH 12 the total length, standard length, gut length, dorsal fin fold length and height, anal fin fold length and height,  preanal fin fold length, predorsal fin fold length, eye diameter, head height, hind gut length and notochord diameter were measured. The average measurements for these metric variables were lower in axenic specimens than xenic ones suggesting better performance in xenic treatment. The variations in body shape were studied and quantified using geometric morphometrics. The results showed significant differences in shape between the xenic and axenic specimens at all age groups. Thus, the importance of larval rearing conditions in determining seabass shape and quality is evident.

Key words/phrases: seabass, aquaculture, body deformity, geometric morphometrics