Christopher Kan, Class of 2013

Blueback herring are anadromous fish that live as adults in the ocean and migrate to spawn, in rivers from Florida to Maine. They are critical ecological link between marine fisheries and inland watersheds. Through their mortality they provide nutrient input. They also are critical prey for economic species of interest such as cod and Atlantic salmon. Bluebacks themselves were exploited to make smoked fish and shipped from New England around the world for over a hundred years. Bluebacks have been threatened for several decades due to habitat destruction due to dams and overfishing. Recent efforts across Maine to remove dams, restore stream habitat and reduce fishing pressure have begun to pay off.

Monitoring this recovery and gathering data to ensure that future policies support the recovery are critical. My project seeks to use microsatellite markers to assess the genetic diversity across the state. This data will be used in several ways. Most directly genetic diversity can be a measure of a population’s ecological health. Genetic diversity can also hint toward past ecological events. Populations that exhibit lower diversity have likely encountered population bottlenecks in the past. The degree to which this effect is observed indicated the level of decline a population has experienced. This is particularly valuable in Maine where dams have existed since the 1800s, before reliable historical records.

Genetic data can further be used to determine migration patterns. Microsatellite data will be analyzed to determine the genetic distance between populations. This data coupled with analysis overlaying physical distance can give a measure of the number of fish that cross watershed boundaries. These boundaries are important for stock management. Managers need to know if any project along a watershed will affect a subpopulation greatly by eliminating their habitat or simply displace them to other parts of their range.

My project will continue well into the year. The field season will end in September. During the year I will begin genetic analysis and data compilation.

Min Lee, Class of 2014

The Gulf of Maine had once supported an economically thriving fishing industry with fish spawning grounds located within near shore sites. However, through human-induced factors such as over-fishing, industrial pollution, and the creation of dams, many of these fishing grounds collapsed and have not been able to recover despite restoration efforts. This study, conducted using Ted Ames’ data on historic fishing grounds of the 1920s when fish populations were still plentiful, hopes to identify environmental characteristics that correspond to higher abundances of groundfish populations to help support and restore these fish species. Through linear regression calculations using relative abundances and substrate data, we computed seasonal landings of multiple fish species. These calculations provide numerical values of historical catches to compare with current fishery levels to help rebuild the fish biomass within the Gulf of Maine to meet the maximum sustainable yield. Statistical questions such as “what makes a fishing ground a fishing ground?” and “why are some fishing grounds better than others?” were considered when evaluating habitat features. Using programs such as ArcGIS, R, and GeoDa, statistical analysis was conducted to isolate variables, ranging from depth to distance from the nearest historical herring run, that correlate with higher fish abundance levels. This information could be used to inform future management on the ecosystem types fish species need to recover.

Jane Carpenter, Class of 2013

River herring, a collective term for the Clupeid fish species alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), have experienced great population declines over the past few centuries. River herring are anadromous, spending most of their lives in the ocean but spawning in freshwater. Dam construction and pollution of Maine’s rivers have blocked the fish from much of their spawning habitat, thereby reducing their population sizes to a tiny fraction of historical levels. River herring represent an essential component of the Kennebec estuary, as a primary prey item for other fish species and a vector of nutrient exchange. Recently, it has been suggested that river herring may have also historically served as an important food source for Atlantic cod, a major commercial groundfish species, and that the decline of river herring forage stocks contributed significantly to the collapse of the Atlantic cod fishery. Evidence supporting this hypothesis include the occurrence of the collapse following the alewife decline despite an abundance of other prey species for cod, as well as the correlation between Atlantic cod movements and the arrival and departure of alewives.

My component of this project is aimed at determining the potential size of the river herring population in the Kennebec estuary under historical conditions and different restoration scenarios. Life-stage population models were constructed to represent separately the Atlantic cod and river herring populations, and matrices were developed to account for the interactions between the different life stages of each species. I will continue to refine these models throughout the academic year, incorporating juvenile productivity and mortality data, and expand on the spatial component by creating maps demonstrating potential population sizes if different historical spawning areas were to be made accessible.

This summer, our group also focused on assessing the current ecological conditions in the Kennebec estuary. In order to accomplish this, we evaluated the species composition of the fish communities on the Kennebec and Eastern Rivers by beach seining weekly, and determined the water conditions during each sampling occasion. Length and weight measurements of river herring caught and released at these sites will be used to quantify juvenile productivity. We also mapped submerged aquatic vegetation beds in Merrymeeting Bay using ArcMap in order to compare the extent of vegetation in previous years with current conditions.

Our efforts this summer have been essential for shedding light on the current ecological status of the Kennebec estuary. I hope to prove through further research that past river herring population levels could have supported Atlantic cod in the Gulf of Maine, and thus that efforts to restore historical spawning habitat would bring tremendous economic benefits to Maine by aiding the recovery of the Atlantic cod fishery.

Faculty Mentor: John Lichter
Funded by the Sustainability Solutions Partnership

John Hobbs, Class of 2015

As a research group under the Professor John Lichter lab, our focus was to measure the ecological recovery of the Kennebec estuary and the nearshore environment. To acheive this goal, we quantified the recovery of both the river herring species and submerge aquatic vegetation (SAV). River herring, a term for both the alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) anadromous fish species, are ecological important because they serve as food for both inshore and offshore fish species and distribute nutrients between the two habitats. Submerged aquatic vegetation filters water in a given area and provides habitat for microinvertebrates and macroinvertebrates which are prey to many fish species. To measure river herring recovery we did weekly beach seines at three points along both Abby Point and the Eastern River in order to determine species presence and length over the course of the summer. The recovery of submerge aquatic vegetation was measured by walking around submerged vegetated areas along the Kennebec and Androscoggin River and recording the area using a Trimble Geo XM unit. The data was then placed a map using the Arc Map 10 software, and was compared the previous year’s SAV data coverage.

For my individual summer research, I focused on observing freshwater mussel habitats along several sites of the Kennebec and Androscoggin River to determine if there are any correlations of mussel presence or abundance based on substrate type, host fish availability, and the presence of submerged aquatic vegetation. This information is important because freshwater mussels are currently one the most endangered taxa with only 25% of the 297 species known to have stable populations. Three major contributors to the decline of freshwater mussels are the construction of dams, organic/inorganic river pollution, and overfishing. These human actives resulted in the collapse of aquatic plants, macroinvertebrates, and fish within the Kennebec River, all of which are necessary to maintain healthy mussel populations.

The results showed that habitats consisting of dense mud appear to have a smaller prevalence of mussels compared to areas with silt or sandy substrate types. The sandy substrate habitat appears to have the highest abundance of mussels, although the area mostly consist of the Alewife floater (Anodonta implicata) species.

Another aspect of my research was to determine whether the absence of fossilized freshwater mussel shells is due to historic pollution, which decreased the pH of the Kennebec River years prior. To answer this question I placed mussel shells in historically low pH levels, and observed how they degrade within the solutions. However, my results showed that shell mass did not appear to degrade significantly over time, meaning there is a different variable explaining the lack of a historical mussel presence.

Faculty Mentor: John Lichter
Funded by the Sustainability Solutions Partnership

Eric Chien, Class of 2014

Atlantic cod were historically key ecological and economic components to Gulf of Maine ecosystems and communities. Highly productive nearshore cod stocks that have been depleted since World War II have failed to recover despite decades of zero-fishing pressure. The failure of nearshore cod recovery may be strongly linked to the parallel collapse of anadromous river herring that served as an enormous forage base for cod. Adult river herring entering the river in the spring and juvenile river herring moving offshore in the fall provided a dependable forage source in consistent locations. With an incipient recovery of river herring populations there is potential for the recovery of related nearshore cod fishing grounds, but little is known about the status of cod habitat within these grounds. Biogenic habitat like kelp beds identified as important to various life stages of cod have undergone significant changes in range and composition due to trophic cascade effects brought on by overfishing. The drastic reduction in the abundance of cod allowed cod prey populations like those of the sea urchins to explode, resulting in overgrazing of kelp. Additionally, little is known about the effects bottom trawling has had on benthic habitats in the nearshore Gulf of Maine. Bottom trawling often results in extensive damage to benthic habitats that can take years to recover. Habitat characteristics will be surveyed along several transects using an underwater video camera and fish sounder. Images from the camera will be used to confirm the identity of the sonar signatures on the fish sounder and proved the ability to identify specific taxa. The resulting information will be used to map and analyze the condition of habitat in historical nearshore cod fishing grounds.

Data was gathered for several other multi-year projects throughout the summer. Information on the abundance, size, and composition of fish species was gathered on a weekly basis at two locations (Abby Point on Merrymeeting Bay and the Eastern River) using a beach seine. Three tows of the beach seine were conducted at each site and a variety of water parameters were measured during each sampling day. The presence and size of juvenile river herring as the summer progressed was of particular interest because it may shed light on the growth and movements of juveniles in the river-estuary system.

The location and size of submerged aquatic vegetation beds in Merrymeeting Bay were mapped for the finalization of a project begun last summer. Since the introduction of clean water legislation, submerged aquatic plants have begun to recover and recolonize large extents of Merrymeeting Bay. This recovery is significant because aquatic vegetation is key habitat for nearly all fish and macro-invertebrates in Merrymeeting Bay. Initial qualitative observations from the beach seine suggest significantly higher abundances of fish of all species from tows through vegetated transects than bare bottom transects. Bed size and location were mapped on foot during low tide using sub-meter accuracy GPS. Large submerged aquatic vegetation beds were present in the Eastern half of the bay leading up the Androscoggin River, but no substantial beds were found in the Androscoggin beyond the river mouth.

Faculty Mentor: Professor John Lichter
Funded by the Sustainability Solutions Partnership

Claude Patrick Millet, Class of 2014

Alewives (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), which are collectively called river herring, constitute an important part of coastal Maine’s aquatic ecosystem, both inshore and offshore. As anadromous fish, they constitute an ecological link between rivers and the ocean and were once greatly abundant in Maine waters. Stocks have been historically depleted due to pollution, habitat destruction and overfishing, and are currently rebounding. The Sustainability Solutions Initiative (SSI), a collaborative project uniting Bowdoin College, Bates College and University of Southern Maine, aims at studying the fish populations and their environment in order to improve recovery efforts, especially in Merrymeeting Bay (MMB). MMB is a unique estuarine system in which 6 rivers (including the Androscoggin and Kennebec rivers) converge. As a member of Professor John Lichter’s lab, and an SSI fellow, I took part in this effort by helping to conduct censuses of fish populations in MMB and to map vegetation in the estuary. The purpose of the censuses was to track the presence of river herring juveniles in Merrymeeting bay, as well as to determine what other fishes occur in the system and potentially interact with the former. To this end, our team collected fish from 3 plots each at Abbagadasset point and on the Eastern River on a weekly basis using a seine net. Various water parameters such as pH and temperature were also collected on location.

Submerged aquatic vegetation (SAV) is of concern in restoration efforts because vegetation provides habitat for fish and their prey, as well as water oxygenation and improved water clarity. SAV had also been historically depleted in the estuary, and our mapping efforts were aimed at determining where patches of SAV occurred in MMB. We completed the enterprise, which had been started two summers ago. Mapping was conducted using the Trimble GeoExplorer 2008 GPS device which collects data that can be projected unto a map of the region in ArcMap, a GIS software. Data was collected by circling the patches on foot at low tide.

In addition to taking part in these projects, I assisted another student in collecting Alosid fish for his genetic studies, and initiated a research project of my own, which stems from the group project. I decided to investigate the effects of vegetation (its presence and diversity) on fish and benthic macroinvertebrate populations in MMB. Studies have shown that different species of plants harbor different invertebrates, which affects the biodiversity of the area (Strayer et al, 2003). I hypothesized that invertebrate diversity would increase with plant diversity, and that the distribution of fish would differ as vegetation characteristics varied within the system. I collected data on fish species by beach seining at various vegetated and unvegetated locations in the estuary, and data on invertebrates by using an invertebrate net, as well as by collecting plant samples. The invertebrate net samples were inspected to isolate all macroinvertebrates, which were then classified. I have yet to go through the plant samples, which I intend to do during the school year. In addition, I will perform the statistical analyses that will allow me to test my hypothesis.