The evolution and subsequent maintenance of sex has been debated for many years, and there are numerous aspects which remain poorly understood. When comparing sexual to asexual reproduction there are many more apparent benefits to being asexual than sexual. The Frozen Niche-Variation (FNV) Model describes how asexual clones can arise from a sexual population, and how the two reproductive types can coexist. Herein we compared three sympatric populations of sexual and asexual fish (one sexual population, Poeciliopsis monacha, and two clonal populations, P. 2-monacha-lucida) to test the assumption of the FNV model that sexual populations have a broader dietary niche (as measured by gut contents analysis) than clonal populations. Individual sexuals had similar dietary breadth when compared with clonal individuals. However, dietary breadth for sexual populations as a whole was broader than for either clonal population, indicating differences in between-individual dietary choice. Our results support the primary assumption of the FNV Model, and thereby provide a possible explanation for the maintenance of sexual reproduction in this clonal/sexual complex.