Simple morphometrics for predicting lordosis-induced deviations of body-shape in reared Gilthead seabream (Sparus aurata L.)

Haemal lordosis, V-shape bending of the haemal vertebrae, is a frequent abnormality of reared fish. Lordosis severity ranges from light deformations of vertebral axis, with insignificant effects on external morphology, to severe axis deformations with significant impact on body-shape. In the present study, we developed a simple morphometric index (PrAn) that links lordosis severity at the juvenile stage with fish body-shape at harvesting, without requiring to radiograph or sacrifice the samples. Examined seabream specimens were part of our previous study (Fragkoulis et al. 2019, Sci. Rep. 9, 9832), which monitored the effects of lordosis on the external morphology of pit-tagged seabream juveniles during their growth, up to harvest size. At both juvenile and adult stages, PrAn was effective in discriminating the normal fish from ca the 70% of lordotic fish. Our results suggest the PrAn as a valuable scale of quality, which quantifies the lordosis effects on fish external morphology, both at the juvenile stage and at harvest. Depending on the lordosis rates, and the hatchery strategy on the maximum allowed abnormality rates, this scale can cull out different rates of lordotic fish, without affecting the fish with normal phenotype or the lordotic fish with high recovery potential.