Patterns of agonistic behaviour, shelter occupation and habitat preference in juvenile Lipophrys pholis, Coryphoblennius galerita and Gobius cobitis

The patterns of agonistic behaviour and substratum preferences were investigated in captive groups of juveniles of Lipophrys pholis (Blenniidae), Coryphoblennius galerita (Blenniidae) and Gobius cobitis (Gobiidae). In monospecific groups, size was an excellent predictor of the rank attained by each individual. In heterospecific groups, both C. galerita and L. pholis were dominant over G. cobitis of similar size, and C. galerita dominated L. pholis . Although G. cobitis showed higher rates of activity and of attacks per minute, and a higher ratio of attacks over threats, all these measures were depressed in the presence of either blenniid. In both blennies, in monospecific groups, the dominance rank of each fish was a good predictor of the time spent inside shelters. G. cobitis occupied preferentially the sandy substratum both in mono- and heterospecific groups. Both blennies, when in monospecific groups, occupied preferentially the rocky substratum, with C. galerita showing the highest level of selectivity. In nature, C. galerita also showed a marked preference for rocky substrata, while G. cobitis was especially abundant in mixed bottoms. L. pholis occupied an intermediate position. In the blenniids studied, competition for access to shelter may be one major functional consequence of agonistic behaviour in non-reproductive contexts.