Darters in the sub-genus Catonotus are small benthic fish that adopt a reproductive strategy in which a male establishes a cavity and recruits multiple females to lay eggs within his shelter. These nest guarding males have been shown to be vocal and acoustic communication is thought to be critical in allowing these males to recruit females (courtship vocalizations) and also ward off other males (aggressive vocalizations). One such species, Ethesotoma crossopterum is known to produce, three types of vocalizations including knocks and purrs which consist of pulses as well as a harmonic component previously termed a ‘drum’. Although these vocalizations have been previously studied, little is known about individual differences between males and how these differences are related to the size of the male, or the physiological effect of these vocalizations on other conspecifics. We examined the behaviours of the fish associated with each of these vocalizations and examined the inter-individual differences in call components. Recordings were conducted in the laboratory, using nest guarding males which were exposed to both gravid females, and intruder males. This poster will examine the specific use of each of these vocalizations as well as associated behaviours, in both aggressive and courtship contexts. Future planned research includes an investigation of possible hormone modulation in response to playbacks of conspecific vocalizations.