Behavioural Overlap in Six Caribbean Labrid Species: Intra- and Interspecific Similarities

This study investigates behavioural similarities in six ecologically and morphologically similar labrid species. Ontogenetic shifts in behaviour within species are also considered. There have been many studies on ontogenetic differences in fishes with respect to diet, microhabitat use, and visual acuity and how it pertains to foraging ability; however, fewer studies have been specifically directed towards the ontogeny of behaviours. In this study, detailed behavioural observations were recorded of randomly chosen juveniles, initial phase, and terminal phase adults from each of the following species: Halichoeres bivittatus, H. garnoti, H. maculipinna, H. poeyi, and Thalassoma bifasciatum. Only juvenile H. radiatus were observed. The observation periods lasted 10min, and four periods per individual were pooled for analysis. There were many similarities and few striking differences in the behavioural profiles of the six species [discriminant function analysis (DFA) of behaviours correctly classified 60% of the individuals]. In some cases, life intervals within a species separated more strongly than heterospecifics of the same life interval. For example, H. bivittatus juveniles were more similar to H. maculipinna juveniles than to conspecific initial phase and terminal phase adults. From DFA, species were separated in the first discriminant function by an inverse relationship between the frequency of hiding (= out of view) and eating, and life intervals were separated in the second discriminant function by an inverse relationship between the frequency of swimming alone and eye flickering (= remaining motionless and twitching their eyes). Eye flickering is assumed to be a behaviour that increases an individual's awareness of predators or environmental threats. Notable differences among species included the greater frequencies of hiding by juvenile H. radiatus, and all life intervals of H. garnoti. As these labrids grow, they increase their frequencies of swimming alone, and decrease their frequencies of hovering and searching for food. There was a remarkable similarity in ontogenetic changes in these behaviours for all of the species studied.