A Stable Isotopic and Fatty Acid Foodweb Comparison of Atlantic Menhaden and Gulf Menhaden

Atlantic menhaden (Brevoortia tyrannus) and Gulf menhaden (Brevoortia patronus) are keystone forage species that can be found along the eastern coast of the US to the Gulf of Mexico. This species serves as an important food source for recreational and commercial fish, such as blue fish and striped bass. Menhaden feed on phytoplankton and zooplankton, giving them a unique lipid content. In this study, we investigated the isotopic signatures and fatty acid composition of bulk plankton and fish found in the Gulf and Atlantic. Through this study we hope to determine the impact climate change has had on the lipid quality and quantity of menhaden found in the sub-tropical region of their range versus the temperate region. Samples of fish, diatoms, copepods, and water were collected during spring and summer from the Chesapeake Bay, MD and Apalachicola Bay, FL. We analyzed and compared samples using δ ¹⁵N and δ ¹³C stable isotopic composition, δ¹⁵N of water sample NO₃^- and the fatty acid content. Differences between stable isotopic signatures were found when comparing Gulf and Atlantic menhaden. The overall aim is to provide a health status of this species.