| The mangrove blenny, Omobranchus rotundiceps obliquus is an invasive species found in the sheltered fouling community in South Kaneohe Bay. A diurnal grazing herbivore without strong annual trends in feeding, this fish shows an ontogenetic feeding shift; juveniles consume proportionately more invertebrates, while adults do not selectively feed on most invertebrates in higher proportions than would be encountered while foraging. Juveniles also spend significantly more time foraging than adult males, and are also more submissive than other individuals.; The size of the largest male and the population size of the co-occurring native goby Eviota susannae are significantly correlated with the population size of blennies, as was the percent cover of algal microturf. On a finer scale, actual use of the habitat by blennies is not significantly influenced by any habitat factor except for the amount of bare space, which is negatively correlated with the number of visits by blennies to an area. Laboratory experiments show that blennies have a preference for previously occupied habitats, choose oyster shells as refuges more than an offered alternate, and prefer high-relief habitats.; Omobranchus individuals have overlapping home ranges and a diffuse territorial structure where small, moveable “individual distances” around individual fish are defended. Sharing of refuges by non-nesting fish further supports a diffuse territorial model. Access to refuges is controlled by position in a dominance hierarchy, which is attained through aggressive encounters with other individuals. Large males are usually the alpha individuals in the hierarchy. Prior residency of a refuge also plays a role in influencing access. Residents hold refuges significantly more often than newcomers.; Size asymmetry has a significant influence on aggressive behavior in blennies, although size and sex does not. The proportion of aggressive encounters, the ratio of one-sidedness of the relationship, and the number of fights between pairs in communities of blennies are all significantly influenced by size asymmetry, with similar sized combatants being more likely to behave aggressively to one another. Blennies that are similar in size also spend more time behaving aggressively, have more aggressive interactions, and take longer to achieve a dominance relationship. |
