In fishes, the parents' presence generally improves embryos' survival through parental care, but it is also associated with some disadvantages such as clutch cannibalism and loss of male physical condition. Captive breeding of the river blenny Salaria fluviatilis might improve if these disadvantages were avoided by artificially replacing parental care benefits in the lab. Before accepting this procedure, it should be studied whether embryo development is dependent or not on any other unknown effect related to the parents' presence. In this study, the ontogenetic sequence and several morphological structures - standard length, head height, jaw length and yolk-sac volume - from embryos reared both in the presence and in the absence of the parents were compared. At day 11 after oviposition, in the parents' absence treatment, well-developed embryos were obtained, but a smaller size of the yolk-sac, a greater head height and a tendency to have a greater jaw length than in the parents' presence treatment were found. These results suggest that the parents' presence might affect embryo development and perhaps offspring sexual determination. Given these differences, the practise of depriving clutches from their parents in captivity breeding programmes should be questioned.