Critical Foraging Habitat of Atlantic Sturgeon Based on Feeding Habits, Prey Distribution, and Movement Patterns in the Saco River Estuary, Maine

Abstract

An overall lack of information prompted the recent listing of Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus under the Endangered Species Act. Key to the restoration of the species and of particular importance is the need to characterize the use of critical habitat across the region, specifically in the Gulf of Maine, where the population was listed as threatened. Much of the research to date has focused on large river systems able to support remnant spawning populations; however, the role of small coastal river systems for Atlantic Sturgeon is not well documented. Several of these systems are being reinhabited, and to facilitate new knowledge about the Gulf of Maine population, a long-term (2009–2014) acoustic telemetry study for 51 Atlantic Sturgeon tagged in the Saco River was evaluated. Results suggested that the majority of fish were aggregating near the natural mouth of the estuary across the 6 years. Gastric lavage samples from 163 (91 juvenile and 72 adult) fish (65.0–171.5 cm fork length) during 2013 and 2014 demonstrated that American Sand Lance Ammodytes americanus was the most common prey (the index of relative importance for 2013 and 2014 was 93.5% and 85.4%, respectively), a finding unique to this river system. In addition, benthic sediment grabs, beam trawls, otter trawls, and beach seines conducted in 2013 and 2014 indicated that the distribution of American Sand Lances was comparable to the aggregation area observed for Atlantic Sturgeon. The combined results suggest that the Saco River estuary provides critical foraging habitat imperative for the future recovery of the Gulf of Maine Atlantic Sturgeon population.

Received May 24, 2016; accepted November 17, 2016 Published online February 15, 2017

ACKNOWLEDGMENTS

We thank the many graduate and undergraduate students of the Sulikowski Laboratory at the University of New England. We also thank Drs. Gayle Zydlewski and Michael Kinnison and two anonymous reviewers whose comments greatly improved the manuscript. This project was supported by the National Oceanic and Atmospheric Administration section 6 grant NA10NMF4720023 and was approved by University of New England’s Animal Care and Use Committee (Institutional Animal Care and Use Committee protocol number UNE-20140401SULIJ and 20101221SUL). This manuscript represents Marine Science Center contribution number 95.