The three-spined stickleback (Gasterosteus aculeatus) is a species of fish that exhibits a wide range of morphological variation within its subspecies, which typically fit into two categories, anadromous (spawn in freshwater, migrate from saltwater) and freshwater varieties. Saltwater marine varieties of the fish typically have two dorsal spines, along with a pelvic spine. These spines, as studies have shown, act as a defense mechanism against soft-mouthed predators, by increasing the diameter of the fish making it more of a challenge to swallow, thus conferring a fitness advantage. (Hoogland et al., 1956) However, in the environments of the freshwater G. aculeatus, large soft mouthed predators are largely absent, and instead these spines serve
