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Body posture, vocalizations or coloration play variable roles in the mating success and social dominance of species. Increasing our knowledge of how these specific features function helps improve our understanding of evolutionary trends and the ecological associations of species with their habitats. Through observations and still photography of the temperate marine tubesnout Aulorhynchus flavidus in display at the Aquarium of the Pacific in Long Beach, California during early May, 2013 we documented male mating behavior, a previously uncharacterized aspect of this species. Males position their body in a declined position from tail to head facing a prospective female, undulating their bright red pelvic fins for courtship display. Although male pelvic fins appear to be red year-round, their vibrancy seems to increase during peak breeding. Male heads are dark blue to black with a prominent iridescent blue patch on the snout and similar patches down the length of the body in contrast to females that are a drab brown throughout. While bright colors are often uncommon in temperate systems, it is present in other temperate gasteriform fishes suggesting red coloration may have developed in a common ancestor and has persisted over time. However, research has shown variable success relative to body coloration in other gasteriform species under interspecific competition for nesting space. These results may suggest variable selective pressures for body coloration under differing habitat conditions and may result in fluctuating prominence over evolutionary time.