Adult sicydiine gobies visually communicate via a spectacular array of signals, ornaments, and behaviours

Arguably, the most striking aspect of rock-climbing gobies of the subfamily Sicydiinae is their display of colour. Conversely, the taxonomy, biogeography, and migratory aspects of sicydiine biology have progressed much more than has the science of their visual communication and behaviour. Here, we form a virtual team to consolidate and offer our collective experiences in observing sicydiines across many islands, countries, and continental margins, primarily focusing on intraspecific interactions. We provide a framework of visible morphological features of male and female fish, along with natural history commentary, and make preliminary interpretations of the behaviours, their functions, and the circumstances that appear to underlie different types of visual communication by these gobies. We also make use of learning from both (a) studies of sicydiine evolution and ecology where it relates to in-stream migration and predation, and (b) visual communication science which has been derived from studies of other taxa including coral reef fishes (e.g., wrasses, goatfishes) and model freshwater fish groups such as cichlids, darters, guppies and sticklebacks to interpret some of what we have observed sicydiines doing in streams. We then identify priorities for research and management, contending that this group of fishes represents a very promising model animal group for enhancing understanding of animal visual communication. Whilst tropical streams face a range of threatening processes, sicydiine gobies specifically, are additionally vulnerable to overharvest for the aquarium trade as a function of their attractiveness and spectacular visual displays. The latter is a matter of global conservation relevance.