Meeting Abstract
In the Pacific Northwest United States, multiple salmon species exist, each with different feeding habits and ecological niches. Learning how the anatomical differences between these species equate to their discrete environmental roles is of paramount importance to both functional morphologists and fisheries researchers alike. Here, we compare several aspects of muscular and skeletal morphology in the feeding apparatus of the primarily piscivorous King Salmon (Oncorhynchus tshawytscha), omnivorous Chum Salmon (Oncorhynchus keta), and planktivorous Pink Salmon (Oncorhynchus gorbuscha). We quantified mandible architecture, jaw muscle architecture (specifically of the adductor mandibulae), compared tooth morphology, and modeled muscle contractions for all three species to understand how each utilizes different prey resources. Overall, significant differences were found in every facet of adductor mandibulae analysis, especially concerning muscle fiber lengths. King Salmon tend to have shorter fiber lengths while Pink Salmon have the longest fibers. Our models suggest that King Salmon have the largest maximum gape and absolute percent muscle length change, while Pink Salmon have the smallest. The fact that the Pink Salmon have this small absolute gape and muscle length change combined with long fiber lengths means that individuals can produce a large amount of force across nearly all possible gapes. This is opposite to the shorter fiber lengths and larger gapes present in King Salmon, which indicate that individuals can produce an optimal force only for a specific range of gapes. This study demonstrates how closely related species can functionally specialize muscle anatomy to allow for vast differences in feeding habits.
