Gape : Body Size Relationship in Smallmouth Bass

To understand the potential top-down influences on prey fish populations by piscivorous predators such as Smallmouth Bass Micropterus dolomieu, it is important to understand the limitations of that predator’s gape.  Although Smallmouth Bass diets and predatory impacts have been previously evaluated, relationships between horizontal gape width (GW) and total length (TL) have not been defined; previous studies have used published relationships for ecomorphologically similar Butterfly Peacock Bass Cichla ocellaris.  Thus, the objectives of this study were to quantify the relationship between GW and TL for Smallmouth Bass and to compare estimated GW between the relationship defined for Smallmouth Bass and the relationship defined for Butterfly Peacock Bass.  As expected, GW increased linearly with increasing TL, and approximately 97% (P < 0.001) of the variation in GW was explained by TL.  Additionally, GW estimated using the equation defined herein was significantly greater than GW estimated using the equation for Butterfly Peacock Bass (t = -9.48; P < 0.001).  Results ultimately provide the basis for further evaluation of gape limitation and the threat of predation that Smallmouth Bass may impose on other species in systems where they are present or may be introduced.