Claude Patrick Millet ’14 (Biology and Environmental Studies). Bowdoin College. “Ecological recovery in the Kennebec estuary and nearshore marine environment.” John Lichter, advisor.
Project Summary:
Merrymeeting bay is an inland, freshwater estuary shared by six rivers, the biggest ones being the Kennebec and Androscoggin Rivers. As such, it is a unique and highly productive body of water. In the past, and especially in the 20th century, because of industrial pollution and the building of dams, the riverine and estuarine environments were highly degraded. However, the past few decades have seen substantial recovery. The Sustainability Solutions Initiative, a collaborative project by Bowdoin College, Bates College, and University of Southern Maine, aims at catalyzing this recovery, and its ecology branch seeks to increase scientific knowledge of the Merrymeeting bay ecosystem. This summer, as an SSI fellow I have contributed to this effort by studying the ecology of the American eel (Anguilla rostrata) in the bay under the mentorship of Professor John Lichter.
The American eel (Anguillidae) is a catadromous fish, spending most of its life in freshwater and migrating to the Sargasso Sea in the Atlantic Ocean upon maturity to spawn and die. Juvenile and adult eels occur in various bodies of water (lakes, rivers, estuaries…) and are both predators and scavengers. Historically, and like many other species of fish in the “bay”, A. rostrata occurred in extremely large numbers on the US East coast, but because of environmental degradation and overfishing, their numbers are depleted. Indeed, there is significant demand for live elvers (small juveniles) from Maine, one of only two states to allow elver harvesting. These juveniles are typically sent to China to be farm-grown and sold for food.
I investigated the effect of submersed aquatic vegetation (SAV) on the distribution of adult eels in the bay. To that end, I sampled six locations in Merrymeeting bay: Abbagadassett (Abby) point, Butler’s Cove, Center’s Point, near Lily’s Cove, and the mouths of the Androscoggin and upper Kennebec Rivers. At each location, a 3 foot eel trap baited with either river herring (Alosa sp.) or Atlantic herring (Clupea harengus) was placed in an SAV bed, and another was placed on bare substrate, away from vegetation. The next day, traps were checked and the caught eels were measured and released. Abby point and Butler’s cove were sampled weekly for 7 weeks, and the other locations were sampled three or four times. My teammates helped me collect each of the data.
The rationale for this study was that aquatic vegetation provides shelter from large predators which eels, and especially the smaller ones, may encounter in the bay (including aerial predators-birds). Furthermore, SAV is expected to harbor small fish and invertebrates which eels may forage on. The data will be analyzed and the research compiled into a document as an independent study during the 2013-2014 academic year. Preliminary statistical tests have shown however that eels indeed showed a significant preference for vegetated areas overall. However, this was not the case when the Butler’s Cove data were considered separately, which suggests that factors other than vegetation may influence eel distribution in Merrymeeting Bay.
I am indebted to the SSI for funding my summer project, to John Lichter for his mentorship, to Eileen Johnson, Nate Niles, Elizabeth Brown and Teresa Withee for their help, as well as to the Maine Department of Marine Resource who provided the fish used as bait and to Paul Joyce for his boat training.