Honors College

Document Type

Honors Thesis

Publication Date



Although vital to the protection and conservation of species listed under the U.S. Endangered Species Act, critical habitat of shortnose sturgeon and Atlantic sturgeon in the Penobscot River, Maine have not yet been described. Critical habitat includes food availability as well as the physical characteristics of foraging habitat. To characterize seasonal availability of benthic prey, a ponar grab was used to collect over 125 benthic samples between 21 May and 8 October 2012. Samples were stratified throughout the river and broadly categorized by sediment type. All organisms within samples were identified to the family level. To characterize diet, stomach contents were collected from eight Atlantic sturgeon and sixteen shortnose sturgeon using gastric lavage. Fifty-six percent of shortnose sturgeon and 33% of Atlantic sturgeon had empty stomachs. In the upper river, characterized by a freshwater environment, all of the lavaged sturgeon had empty stomachs. No successful ponar grabs were taken in the upper river because of compacted sediment and cobbles obstructing the grab. In the middle river there were no sturgeon caught and the benthic community had more freshwater benthic organisms than marine organisms. In the lower river, characterized by a brackish water environment and brackish water benthic community, only 7% of the lavaged sturgeon had empty stomachs. In the lower river 81% of ponar grabs were successful and no seasonal differences in species diversity were apparent. Spionid polychaetes were not only the most available prey in substrate samples (over 75% by abundance) but also in the diet (over 75% for both species). The distribution and abundance of spionid worms may provide an indication of critical foraging habitat for these species.