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Summary The lateral line of aquaculture fishes has rarely been studied although it is a very important anatomical organ that could serve as an inexpensive and easy tool to distinguish farmed from wild individuals. In the present study, lateral line deformities were examined in both wild and farmed sea bass (Dicentrarchus labrax) and sea bream (Sparus aurata) specimens to try to detail all possible differences between them. In order to do so, the morphology of the trunk lateral line in wild and farmed adults was examined whereby two major deformities were observed in both species: the ‘scale pocket’ deformity (14–40% incidence in all groups) where the specialized scales are missing but the canal underneath is present and the scale print is obvious, and the ‘somatic scales’ deformity (14–56% incidence in farmed individuals only) where the missing lateral line is covered with normal somatic scales. Histological examination confirmed the macroscopic observations in that the lateral line mechanism was present – although damaged – beneath the scale pocket deformity and completely absent beneath the somatic scales deformity. It is argued that the scale pocket deformity is a result of an accident during the life of the fish whereas the somatic scales deformity is an actual deformity in development.

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Red porgies (Pagrus pagrus) of 20.6 AE 1.5 g mean weight were reared in tanks under four delayed selffeeding conditions (0 5 control, 7, 30 and 90 s) after rod activation. The time intervals were chosen to simulate the time taken for a commercial pelleted feed to transit the tube linking a surface-mounted feed hopper and the depth at which a cage might be submerged. Daily feeding rate, growth, food conversion index and condition factor were quite similar but ¢sh behaviour di¡ered among conditions. Fish remained close to the feeding point in the ¢rst two treatments (0 and 7 s delay) but foraged more widely in the remaining treatments (30 and 90 s delay), only reconsolidating around the feeding point a few seconds before feed was released. Results are discussed in relation to learning capacity and adaptation of ¢sh to feeding behaviour £exibility, in order to develop reliable self-feeding systems suitable for submerged cages.

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