Gasterosteiformes, an order of fish that include pipefish and sticklebacks, consist of both elongated and non-elongated body forms. This makes it an excellent group for comparing the effects of elongation on paired fin reduction. Evolutionary elongation patterns within tetrapods have been widely studied in which highly elongate tetrapods tend to have reduced limbs Measurements for species examined were collected of the American Museum of Natural History. My hypothesis is that there will be significant fin reduction correlated with body elongation found in Gasterosteiformes. Similar to tetrapods, I have also speculated a more simplified morphological anatomy within the pectoral fins. In agreement with the hypothesis, body elongation within Gasterosteiformes correlates with significant pectoral and pelvic fin reduction, as well as retaining its basic pectoral fin musculature. I was able to quantify pectoral fin reduction correlated with body elongation as well as provide pectoral fin musculature descriptions in elongate and non-elongate forms.