Matthew Best

Age Structure and Genetic Markers of Semelparous vs. Iteroparous American Shad (Alosa sapidissima) in the Delaware River  

A study of American Shad (Alosa sapidissima) has been initiated in the Delaware River focused on life-history and population structure of adult fish returning from the ocean to spawn. To do this, I am collecting data from the fishes otoliths (structure used to age fish) and spawning condition to determine age structure, growth rates, and probability of surviving to reproduce again. I also hope to relate these life-history traits to underlying genetic variability and determine the extent to which iteroparous (repeated spawning) and semelparous (die after spawning) life-histories are each expressed in this population. In the 2020 field season, 147 shad were collected from the upper portion of the Delaware River between Hancock, NY and Milford, PA. Another 198 shad were collected from Smithfield Beach, PA, further south on the Delaware River by the Pennsylvania Fish and Boat Commission (PAFBC). The next steps for this project will be to determine the age and growth rates of American shad and to conduct genetic analysis on 4 potential markers related to iteroparity in fishes.