Use of digital colour analysis to assess variation within individual adult American lobsters (Homarus americanus) and the process of addition of colour in white lobsters

A relatively low-cost method using digital macro-photography was developed to assess in vivo colour of American lobsters (Homarus americanus). Both R*G*B and Commission Internationale de l'Eclairage (CIE) L*a*b systems of colour analysis were used to investigate animal coloration over 11 body locations within each animal. Assuming that lightness (CIE-L) is biologically important for American lobsters, this species was counter shaded and paired comparisons showed that different colour parameters were all highly correlated among all body locations with the exception of the ventral claw. Using a multiple forward stepwise regression of the five hues on CIE-L, the hue Green was the most significant parameter accounting for 97% of the variation of CIE-L. This methodology was then used to assess how dietary white American lobsters add colour to their shell when switched to a diet containing carotenoid. The rate of colour addition was proportional to the amount of carotenoid in the diet, and to the body location. This digital photographic method of colour analysis was useful in that a wide size range of samples could be assessed. All body areas were suitable for colour analysis although relatively flat and smooth locations were most practical.