Heritability of shape in common sole, Solea solea, estimated from image analysis data

In fish, selection on production traits may alter traits such as shape through genetically correlated response to selection. In species which are sold un-filleted, it may be desired to maintain “natural” shape while selecting for increased growth. Several methods have been proposed to describe shape of fish, but most of these are either sensitive to observer perception or time consuming. Digital image analysis is objective, relatively free of bias, rapid and widely used to describe shape in e.g. crops and fruits. To our knowledge there are no reports on its use in selection programs for fish. In this study we compare estimated genetic parameters of shape and body measurements obtained with digital image analysis (DIA) and manual measurements in a captive commercial population of common sole, Solea solea  , with 1222 pedigreed animals. Results show that estimated genetic parameters were similar across methods and that DIA resulted in significantly lower standard errors (se¯DIA = 0.0772, se¯Manual = 0.0880, P = 0.01244). Heritability for shape using DIA was 0.34 ± 0.11. The genetic correlation between shape and body weight was −0.44. Consequently, selecting for increased body weight at harvest yields more circular shaped fish. However, by using a selection index for shape and body weight, it is possible to maintain shape while improving body weight at harvest. This study shows that digital image analysis is an accurate and time efficient method to estimate genetic parameters for shape traits in fish.