Geometric quantification of lordosis effects on body shape in European sea bass, Dicentrarchus labrax (Linnaeus, 1758)

Lordosis is one of the most severe deformities developing in reared fish; evaluating its effects on fish and aquaculture industry has been difficult to establish since there is no objective way of quantifying its severity and impact on the final product's image, fish shape. The effect of lordosis on body shape was analysed by geometric morphometrics on 791 sea bass juveniles. Morphometric analysis revealed that lordosis angle is a useful measure of the degree of severity, since it significantly affected fish body shape (p < 0.05). The area of the body mostly affected by the presence of lordosis was the posterior abdominal region, framed by the anterior and middle base of the dorsal fin, the base of pelvic fins, the anterior base of anal fin and the dorsal base of caudal fin. The analysis of distance ratios between these landmarks demonstrated that lordosis severity can be quantified with the use of external, and thus easily applicable, indices. The results are discussed in respect to their value in the precise quality assessment of reared sea bass.