In the study area, the Eightmile River is a second to fourth order river, largely .... Senators Chris Dodd (D-CT) and Joseph Lieberman (D-CT) presented the legislation to ...... aquatic ecosystem health; a novel use of Nei's modified genetic distance (DA) in ...... Mortar (Mill), Stevenson (Housatonic), Kinneytown (Naugatuck), ...
Integrative Assessment of Biological and Physical Attributes of the Eightmile River Phase 1 Final Report Diana L. Walden and Dr. Piotr Parasiewicz Northeast Instream Habitat Program Department of Natural Resources Conservation University of Massachusetts Amherst
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Integrative Assessment of Biological and Physical Attributes of the Eightmile River A Component of the Wild and Scenic River Study Phase 1 Final Report Prepared by: Diana L. Walden and Dr. Piotr Parasiewicz With Appendix L written by Stephen Gephard and Timothy Wildman CTDEP/Inland Fisheries Division Collaborators: Scott Jackson, Dr. Sean Werle, Jennifer Hogue, Hunter Brawley, Lori Johnson, Joe Rogers, Brett Longworth, Jeffrey J. Fountain, Abby Cadman, Anthony Trani, Rich Peccorelli, Jeffrey Legros, Jessica Dodge and Robbette Schmit in conjunction with the Northeast Instream Habitat Program Department of Natural Resources Conservation 331 Holdsworth Hall University of Massachusetts, Amherst, MA 01003 Prepared for: The National Park Service Wild and Scenic River Study for the Eightmile River and the Eightmile River Wild and Scenic Study Committee December 2005
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Table of Contents GENERAL OBSERVATIONS OF THE EXISTING STATUS OF THE WATERSHED ........................6 ACKNOWLEDGEMENTS ...............................................................................................9 1 INTRODUCTION..........................................................................................................10 1.1 HISTORY OF THE PROJECT ..........................................................................................10 1.1.1 Eightmile River Wild & Scenic Committee/Eightmile River Watershed Advisory Committee ...................................................................................................13 1.1.2 Wild and Scenic River Designation Study .......................................................14 1.1.3 General Background of the Northeast Instream Habitat Program ................15 2 PROJECT OVERVIEW AND METHODS ................................................................16 2.1 GENERAL DESCRIPTION OF THE APPROACHES TO THE PROJECT .................................16 2.1.1 Literature and Resources Reviewed for Background Data.............................16 2.1.2 Proposed Physical Habitat Modeling (Theories behind MesoHABSIM).......18 2.1.3 Target Fish Community Concept .....................................................................21 2.2 FIELD DATA COLLECTION ..........................................................................................28 2.2.1 Watershed Delineation and Selection of Representative Sampling Sites .......28 2.2.2 Temperature and flow data...............................................................................30 2.2.3 Fishing Surveys.................................................................................................33 2.2.4 Habitat Surveys .................................................................................................35 2.2.5 Mussel Survey Methods ....................................................................................36 2.3 DATA ANALYSIS ........................................................................................................37 2.3.1 Transfer of Information and Quality Control .................................................37 2.3.2 Calculation ........................................................................................................37 2.3.3 Biodiversity and Evenness Indices ...................................................................39 2.3.4 Unweighted Pair Group Method With Arithmetic Mean (UPGMA) Trees for Site Similarities ..........................................................................................................40 3 RESULTS .......................................................................................................................42 3.1 FINDINGS OF LITERATURE REVIEW ............................................................................42 3.1.1 Physical Characteristics....................................................................................42 3.1.2 Historical Use of the Watershed.......................................................................47 3.1.3 Land Use and Cover Types ...............................................................................48 3.1.4 Natural Ecological Communities .....................................................................49 3.2 TEMPERATURE DATA RESULTS ..................................................................................52 3.2.1 Early Season Records .......................................................................................53 3.2.2 Late Season Records .........................................................................................57 3.3 FLOW DATA ...............................................................................................................61 3.4 RESULTS OF REFERENCE FISH COMMUNITY INVESTIGATION .....................................68 3.4.1 Historical Review of Fish Community .............................................................68 3.4.2 East Branch and Upper Branch Complex .......................................................69 3.4.3 Mainstem Eightmile (Below Confluence)........................................................72 3.5 FISH AND HABITAT OBSERVATIONS ...........................................................................75 3.5.1 Site 1 Upper Branch- Fish and Game Land ....................................................75 3.5.2 Site 2 Mid Upper Branch – Devil’s Hopyard State Park.................................77 3.5.3 Site 3 Lower Upper Branch – Near Kaczynsky Land ......................................79 3
3.5.4 Site 4 East Branch – Upper Reaches................................................................81 3.5.5 Site 5 Mid East Branch- Near Route 11 Overpass ..........................................83 3.5.6 Site 6 Lower East Branch- Along Darling Road .............................................85 3.5.7 Site 7 East Branch and Upper Branch Confluence Area ...............................87 3.5.8 Site 8 Upper Eightmile Mainstem– Pleasant Valley Preserve.........................89 3.5.9 Site 9 Beaver Brook- Tributary to Eightmile Mainstem..................................91 3.5.10 Site 10 Mid Mainstem- Below Mt. Archer Dam ............................................93 3.5.11 Site 11 Lower Mainstem- Near Hamburg Cove.............................................95 3.6 LENGTH FREQUENCY RESULTS ..................................................................................97 3.7 SPECIES RICHNESS, DIVERSITY AND DENDROGRAMS ................................................98 3.8 RESULTS OF MUSSEL SURVEYS ..................................................................................99 3.9 REPTILE AND AMPHIBIAN SPECIES OBSERVED.........................................................100 4.0 DISCUSSION ............................................................................................................101 4.1 PHYSICAL SETTINGS ................................................................................................101 4.2 FISH FAUNA .............................................................................................................106 4.2.1 Reference fish community ..............................................................................106 4.2.2 Fish distribution in sites .................................................................................108 4.2.3 Diversity and Abundance................................................................................113 4.3 MUSSEL FAUNA........................................................................................................115 4.4 RESPONSE TO DEP’S INTERESTS AND ISSUES...........................................................115 4.4.1 Atlantic Salmon...............................................................................................116 4.4.2 American Eel...................................................................................................116 4.4.3 Other Species of Interest.................................................................................117 5 CONCLUSIONS AND IMPLICATIONS .................................................................118 6 REFERENCES.............................................................................................................122
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EXECUTIVE SUMMARY ____________________________________________________________ Walden, D. L. and Parasiewicz, P. 2005. Initial Biological and Physical Attribute Survey of the Eightmile River – A Component of the Wild and Scenic River Study - Phase 1 Final Report. Presented to the National Park Service and the Eightmile River Wild and Scenic Study Committee. Presented by the Northeast Instream Habitat Program, Department of Natural Resources Conservation, University of Massachusetts, Amherst, MA. ______________________________________________________________________
This initial biological and physical survey of the Eightmile River in southeastern Connecticut was performed as a component of the ongoing Wild and Scenic River study being conducted by the National Park Service (NPS). The Wild and Scenic study was authorized during a 2001 session of Congress for the Eightmile and its major tributary, the East Branch. The river was nominated for study due to a concerted effort by local citizens who recognized the importance of the Eightmile Watershed and had a desire to see it further protected. They requested Congressman Rob Simmons and Senator Christopher Dodd lead an effort to have the study authorized by Congress. The study is led by the Eightmile River Study Committee and supported by the National Park Service. The Northeast Instream Habitat Program (NEIHP) at the University of Massachusetts Amherst began work in Spring 2004 on a segment of the study focused on fish and freshwater mussel habitat in the river. NEIHP completed field work and initial analysis for Phase I of our study in late 2004 and those results are presented in this report. The information we collected contributes to the knowledge of the baseline status of the river and associated watershed and assists the development of instream flow and habitat models. This will allow for the protection and enhancement of the aquatic system and the species it supports. The completed portion of the NEIHP Eightmile study serves as a basis for future field work and analysis, as well as provides initial management and planning recommendations to the Committee. NEIHP anticipates completing a further phase of the study in the coming year and revising our recommendations upon the new results.
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NEIHP developed a Reference Fish Community (RFC) for the Upper Branch and East Branch of the Eightmile River, as well as the Mainstem of the river below the confluence. These reference communities are intended to approximate the assemblage of fish species, which should be expected in a river similar to the Eightmile (based on size, ecoregion, and physical characteristics) with very limited anthropogenic influences (i.e. maintained ecological integrity). The generalized, actual species assemblage (the eXisting Fish Community, or XFC) was compared to the reference community. During Summer 2004 the Eightmile River was surveyed using the grid electrofishing technique at numerous representative locations for fish distribution. Concurrently, physical characteristics were also recorded at fishing locations in an attempt to determine associations between fish species densities and physical habitat. Hourly water temperature readings were documented with 14 thermal recorders through the summer. The hydromorphology, physical attributes, fish density, and temperature data were analyzed in each site to document the present status of the river. To investigate a need for future research on non-fish members of the community, we conducted freshwater mussel surveys in few selected locations. We also performed a detailed literature review to supplement the information presented here. In the study area, the Eightmile River is a second to fourth order river, largely undeveloped in a densely populated area of the country. It is rare for a watershed in coastal Connecticut to remain so highly forested, with few point and nonpoint pollutant discharge sources. Its baseline condition may serve as a target for other rivers in the state. The following list includes a number of basic observations regarding the aquatic community.
General Observations of the Existing Status of the Watershed -
The Eightmile River represents a high quality ecosystem that is unusual in the highest populated area of the country.
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The river system has a diverse community of species overall and relative fish density is similar to the regional average.
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The existing fish community roughly corresponds to the projected reference community.
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The introduced species make up a small proportion of the existing fish community (less than 10%)
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There is a good recruitment for the majority of common fish species.
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Some lead species such as longnose dace, brook trout, Atlantic salmon and American eel are present in abundances lower than expected.
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There is a significant correlation between fish community and habitat settings in the sampling sites. o Species diversity decreases in sites where the river channel has been modified.
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Compared to a historical template, the river lacks large woody debris and associated structure. It is reflected in the fish community as follows: o A lower than expected proportion of longnose dace and brook trout potentially suggests a lack of flow concentration caused by structures (e.g. boulders or large woody debris). o A higher than expected proportion of blacknose dace potentially suggests abundance of shallow margin/higher velocity habitat in the Upper Branch and East Branch.
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Compared to the early 20th century, the magnitude, duration and frequency of low flows have significantly changed, creating more stable flow conditions.
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Water temperature is raised by a high number of shallow impoundments in headwaters as well as and channel modifications. Consequently: . o Compared to the reference, the existing fish community is shifted towards high temperature tolerant species indicated by: A higher than expected proportion of fallfish A lower than expected proportion of longnose dace and brook trout.
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o Water temperatures in the East Branch were warmer than the Upper Branch likely due to lack of canopy shading. -
The sites in or immediately downstream of large alluvial deposits generally had high fish densities and low species diversity.
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These preliminary investigations documented a diverse freshwater mussel community that includes at least two state listed species.
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Hamburg Cove has a high level of boat traffic. The most abundant mollusk species here was the invasive Asian clam.
Potential methods to protect and enhance the high quality status of the river are: -
Develop simulation models of habitat, flow and temperature conditions as a tool to precisely define protection/restoration targets and management options for the watershed.
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More closely investigate and document the abundance and diversity of mussel fauna.
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Lower water temperature by removal of small dams in the headwaters and by increase of canopy cover.
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Applying land use practices and restoration measures that induce additional woody habitat structure.
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Carefully take into account the potential impact of new and planned development on temperature and flow regime, especially in the areas of gravel deposits.
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Study the potential effects of boat traffic on the aquatic fauna in Hamburg Cove.
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Continuously evaluate management and conservation measures by monitoring the status of fish fauna, habitat, flow and water temperature.
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Promoting the Eightmile River Watershed as a model for sustainable development and regional reference.
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ACKNOWLEDGEMENTS
The National Park Service and the Eightmile River Wild and Scenic Study Committee provided support for this study. We thank the project management of the study, which has been provided by Mr. Kevin M. Case and Mr. Jamie Fosburgh of the National Park Service. We would like to thank the entire Eightmile River Wild and Scenic Study Committee for their interest in and support of the survey, and their time and continuing assistance in providing information essential to our success during the field season. Special thanks are due to Dr. David Bingham of the Committee and Salem Land Trust for significant time spent arranging access to survey sites, assisting us in data collection, and his willingness to share his vast knowledge of the watershed. We are grateful to Mr. Richard Jacobson, Mr. Neal Hagstrom, Mr. Steve Gephard, Mr. Bob Jacobs, and others from the Inland Fisheries Division of the Connecticut Department of Environmental Protection for providing us with reference survey data and invaluable advice. Thanks to all of the private landowners who graciously granted us access to the river through their properties. Our gratitude also goes to Salem Farms Campground for providing our lodging and taking an interest in our wellbeing during the field season and to all of the citizens of the towns in the study area for recognizing the value of this resource area and supporting its protection. We would like to thank Lauren Todd and Dr. Ethan Carr at the University of Massachusetts Amherst for providing us with their work on the cultural landscape study, as well as Jim MacBroom and his students at the Yale School of Forestry and Environmental Studies for providing us with their report on the geomorphology of the area. Special thanks to all those who helped in data collection and analysis: Jennifer Hogue, Hunter Brawley, Dr. Sean Werle, Dr. Betsy Dumont, Jeffrey J. Fountain, Lori Johnson, Joe Rogers, Brett Longworth, Abby Cadman, Anthony Trani, Richard Pecorelli, and Robbette Schmit. It is especially important to note the outstanding contributions of Jenniffer Hogue, Lori Johnson, Brett Longworth, Joe Rogers, Jeffrey Legros, Jessica Dodge and Sean Werle to the content and production of this report, and Hunter Brawley to the data collection. Their significance to this study cannot be sufficiently acknowledged. 9
1 INTRODUCTION
The Wild and Scenic River study is a multidisciplinary effort to gather information on the outstanding natural, cultural and recreational resources within the Eightmile River Watershed. The contribution of the Northeast Instream Habitat Program (NEIHP) establishes a necessary benchmark for further study of the Eightmile watershed, which will also be useful for future watershed studies in Connecticut. The following report presents the data collected during the initial biological and physical survey performed by NEIHP for the Eightmile River. The Phase I survey was completed as part of the overall data collection for the Wild and Scenic River Study sponsored by the National Park Service. The purpose of this phase is to gain a general overview of the ecological composition of the river, building upon literature review and preliminary fish and mussel data collection. The outcome of Phase I helps to specify further steps in the development of a management plan. Phase II of this project will include more detailed analysis of fish and mussel habitat which will be used to run a simulation model of the instream habitat. This model should be used for evaluation of various watershed management scenarios with respect to their impact on available aquatic habitat. Our report includes the history of the project, a literature review of the existing information on the area, a description of the theory behind the NEIHP work, a detailed protocol for the field methodology, a summary of the existing conditions in the watershed, and finally, a discussion of recommended measures and areas of the watershed may require additional attention with regard to either protection or restoration.
1.1 History of the Project and location
The Eightmile River watershed is located in southeastern central Connecticut and covers approximately 62 square miles. It is one of the southernmost tributaries to the Connecticut River and was named for the fact it is located eight miles north of the river’s mouth at Long Island Sound. The total length of the Eightmile Mainstem and the East 10
Branch of the river is approximately 17.3 miles (28 km). The entire watershed is encompassed within the five towns of East Haddam, Lyme, Salem, East Lyme, and Colchester. The confluence of the Eightmile with the Connecticut River is found at Hamburg Cove, which is approximately 0.5 miles (0.8 km) wide at the mouth and three miles long. The cove has been a popular spot for hundreds of years and is now one of the most densely populated areas in the watershed. There are 37 dams in this watershed, 32 of which are in headwaters (Figure 1). Although the area has been settled for hundreds of years, a widespread, agricultural lifestyle has been largely abandoned and the forest has been allowed to return and grow for decades. This is unusual in that abandoned farmland in many other areas in New England was subdivided and developed. This is especially true in coastal Connecticut and in areas near the mouths of major rivers. With a low population density, large parcels of private land, and an increased awareness of the potential degradation caused by sprawl, the towns that comprise the Eightmile’s watershed were largely able to avoid this fate. In recent years, the governments and citizens of these towns have made important decisions to protect the river and control the way the watershed is developed in the future.
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Beaver Brook
Figure 1. Site Map of Eightmile River Watershed with locations of dams, wetlands and major roads.
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1.1.1 Eightmile River Wild & Scenic Committee/Eightmile River Watershed Advisory Committee
In 1995, the Nonpoint Education for Municipal Officials (NEMO), part of the University of Connecticut (UConn), helped to develop the Eightmile River Watershed Project. NEMO worked with the UConn Cooperative Extension Forestry Program and the Connecticut Chapter of The Nature Conservancy (TNC) to educate the citizens of East Haddam, Lyme, and Salem about the value of the watershed (Gianotti, NEMO). Local officials and representatives of non-profit organizations formed an Advisory Committee. In 1997, the three towns voluntarily signed the Eightmile River Watershed Conservation Compact in which they recognized the importance of the natural resources the river provides and agreed to plan future growth in their towns in a sustainable way (Compact 1997). The towns also worked to revise their Conservation and Development Plans, and Lyme and East Haddam created open space committees and funds. In Salem, the residents started the Salem Land Trust and began purchasing conservation land whenever feasible (Gianotti, NEMO). The Nature Conservancy has preserved significant tracts of land totaling 1800 acres in the watershed in collaboration with these committees. The Connecticut Department of Environmental Protection (DEP) has worked with TNC as well as independently to obtain parcels for preservation. A recent example was the acquisition of a 331-acre property in Salem in 2002. The DEP is also responsible for the care and management of the state parks and forests throughout Connecticut including Devil’s Hopyard State Park in the Eightmile watershed. The towns have worked on improving GIS coverage of the watershed and local schools are using the river as an educational tool. A project to create fishways over the few existing impediments to the river was completed and the UConn Cooperative Extension Forestry Program worked on outreach to private landowners in an effort to protect the forest cover (Gianotti, NEMO).
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1.1.2 Wild and Scenic River Designation Study
In the next major step, the town officials, the Advisory Committee, and the citizens worked to make legislators at a national level aware of the unique values of the Eightmile River. In a 2001 session of Congress, U.S. Representative Rob Simmons (RConnecticut) presented a bill that would authorize the National Park Service to study the Eightmile River for possible inclusion in the National Wild and Scenic Rivers System. The bill had the support of the remainder of the Connecticut Representatives, and Senators Chris Dodd (D-CT) and Joseph Lieberman (D-CT) presented the legislation to the Senate (Gendreau, 2001). Despite the large backlog of existing studies leading to some reluctance from the Department of the Interior, the legislation was passed through Congress and President Bush signed the bill later that year. To be eligible for inclusion in the National Wild and Scenic Rivers System, a river must be “free-flowing” and demonstrate outstanding scenic, recreational, geologic, ecologic, historic, or cultural values. The watershed community must also demonstrate wide support for the protection of the river and willingness to develop and abide by a conservation/management plan. If the study finds significant values and the Study Committee recommends the river be designated as Wild and Scenic, the river is then eligible for additional federal funding and protection. The funding would be used locally to reach the goals and objectives set forth in the conservation/management plan. The National Park Service would comment on any federally funded project proposed in the watershed to ensure it will not impact the values of the river. The river would also be protected from potentially damaging federal hydro and water resource development projects.
1.1.2.1 Eightmile Watershed Wild and Scenic Characteristics
The Eightmile River proves to be an excellent candidate for study. In addition to the widespread public interest and concern for the resource, the watershed is considered 14
to have several of the outstanding values the Act states as necessary for designation. The Eightmile River Wild and Scenic Study Committee has endorsed six outstanding resource values for the watershed including; the cultural landscape; geology; water quality; hydrology; unique species and natural communities; and the watershed ecosystem. The river is largely free flowing with several small dams that have been modified with fishways. The specific values identified in the Eightmile River will be discussed in further detail later in this report.
1.1.3 General Background of the Northeast Instream Habitat Program
As previously stated, the NEIHP is one of the selected programs contributing to the evaluation of the existing resources in the Eightmile. NEIHP is part of the Department of Natural Resources Conservation at the University of Massachusetts Amherst and has worked to develop a science-based approach to assess physical habitat attributes and aquatic communities at a watershed level. NEIHP uses modeling to predict effects of increased flows or water withdrawals on the biotic community as well as to recommend restorative measures to the physical characteristics of the river. Using these techniques, NEIHP could model a river and predict what would happen to the existing assemblage of species if a dam was removed or a set amount of industrial water withdrawal was allowed to occur. This knowledge is very useful to agencies in charge of instream flow regulation and river conservation as well as local officials trying to develop and execute a future development plan. Regarding the Eightmile project, NEIHP has been contracted to determine the status of the existing aquatic community, identify any deficiencies, predict the optimal water flow, and provide recommendations to the local officials and committees which will eventually help them develop the watershed management plan.
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2 PROJECT OVERVIEW AND METHODS
2.1 General Description of the Approaches to the Project
As mentioned previously, this project is a preliminary analysis of the Eightmile River Watershed that sets the stage for the simulation model of physical habitat conditions. The analysis and results will serve as a decision support system for future management. The design of this first phase was developed in a way that obtains necessary data, while preparing the foundation for the work that will be necessary in Phase II of the project. Therefore, it is important for the readers to become familiar with the methodology utilized in Phase I and planned for Phase II and to remember that this report only analyzes the data directly gathered in this Phase. The following section provides details regarding the general theories behind the major components of the project and our methods for gathering information in response to the established tasks.
2.1.1 Literature and Resources Reviewed for Background Data
As part of our tasks, the NEIHP performed a review of the existing literature and identified ongoing studies regarding the Eightmile River Watershed. We researched articles in journals, published books and surveys, unpublished work from groups examining the other values of the river, and data from the internet. The information we were most interested in was the historical data regarding the original assemblage of aquatic species in the river as well as the patterns of development and any changes in the alignment or structure of the channel. This included identifying the cultural landscape and forming an understanding of the history of the area. We also identified the general ecological community of plants and wildlife found in the watershed. Basic information on the unique geology and geomorphology was also collected.
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It was difficult to find published sources, which dealt solely with the resources of the Eightmile. Much of the literature we reviewed concentrated on general information on the State of Connecticut, the Connecticut River and Southern New England. The unpublished reports such as Albietz’s and Pokhrel’s “Eightmile River Geomorphic Assessment” from the Yale School of Forestry and Environmental Studies, and Todd’s “The Eightmile River Watershed A Cultural Landscape Study” from the University of Massachusetts Amherst, proved to be the most informative. The Connecticut DEP provided information on state listed species and the typical flora and fauna of the region. Even more difficult to locate was concrete information of the historical assemblage of fish and aquatic species of the Eightmile. It may be almost impossible to determine what the community had been prior to many years of human influence, even in a system in the process of recovery. The Geological and Natural History Survey of Connecticut was available for a wide range of years but the oldest specific data was from the 1968 survey. This indicated whether a species was present in the Eightmile (through interpretation of the catch location maps), but not the potential density or abundance. The DEP Inland Fisheries Division presented catch data from their statewide survey of Connecticut streams and rivers (beginning in 1988), including a number of sites from the Eightmile and the East Branch. This provided valuable background and reference data, but it only covered the status of the fish community within the last few decades. Surveys were performed by Drs Belding and Stillman in the 1920s and 1930s and included stocking recommendations, the number of miles for fishing, and ownership records in the watershed but did not identify the species present. The DEP also performed a statewide lake and pond electrofishing survey (1988-1995), which included Hamburg Cove and gave general numbers of species caught. We also reviewed a number of DEP’s annual Fish Distribution Reports, which presented data on the number of brown trout (Salmo trutta), brook trout (Salvelinus fontinalis) and rainbow trout (Oncorhynchus mykiss) stocked in the Eightmile. The annual report also discussed the catchable trout program and the Atlantic salmon (Salmo salar) restoration program. The 2001-2004 “Rapid Bioassessment in Wadeable Streams and Rivers by Volunteer Monitors” summary reports provided information on general categories of macroinvertebrates identified at 17
several sites in the Eightmile. NEIHP did not have official data on freshwater mussel observations prior to our survey but we did have “A Field Guide to the Freshwater Mussels of Connecticut” for general habitat range. NEIHP also utilized the growing compilation of available GIS data being developed for the Eightmile Watershed for recent information on land cover, geology and other mapping. The Connecticut River Coastal Conservation District is working on the database and the Eightmile Committee has access to this. NEIHP developed several data layers as a result of their survey that can be utilized with the existing information.
2.1.2 Proposed Physical Habitat Modeling (Theories behind MesoHABSIM)
It has been noted that organisms respond to and are affected by changes in the physical environment (Parasiewicz 2003). It goes to reason that models can be created which predict the specific biological reaction to certain variations in the environment and determine what attributes would create more optimal habitat for a species or community. This is also true for aquatic organisms, which react to different patterns in the stream flow or changes in physical attributes (Heede and Rinne 1990, Wright et al., 1993, Statzner et al. 1988). In order to create this physical habitat model, a survey or model of both the physical characteristics and the biological attributes of an area must be performed. Physical habitat models can be used to help regulate and manage instream flow and make recommendations for restoration. In the early 1970s, US Fish and Wildlife developed PHABSIM, which was the first physical habitat model. It was created to make recommendations for regulating water withdrawals and other stream channel modifications. It was widely recognized and applied across the country (Bovee et al 1998). The MesoHABSIM model used by the NEIHP builds upon the concept of PHABSIM, providing further improvement to the method (Parasiewicz 2003). PHABSIM had been developed for habitat modeling at the micro scale and is therefore very work intensive when used correctly for surveying an entire river. It has commonly been extrapolated erroneously to make predictions for 18
entire river systems without doing the work required to get sufficient results. MesoHABSIM involves mapping larger areas of the river and getting information at a meso scale. NEIHP maps large portions of the study river into segments known as Hydromorphologic Units (HMUs) and then remaps the river under various flows to see how the areas change. Various attributes and cover types are also recorded. This information serves as the physical component of the model. The suitability of the physical characteristics is analyzed with the biological information through statistical comparisons, and the areas of good habitat are determined. Developing the model for different flows helps to determine when the amount of suitable habitat is at an optimal or critical level. The major benefit of the MesoHABSIM model is that it can provide information that allows us to make recommendations for restoration and regulation at a watershed level (Parasiewicz 2003). The major mapping effort of the Eightmile River did not occur as part of the Phase I work. This is planned for the second phase where we will map the entire river and then select representative sites to re-map at three different flow conditions. The content of this report describes our current tasks, which focused on the existing biological community in representative areas throughout the watershed. However, observations were made regarding the physical characteristics of the areas where we performed our fish surveys. These observations included dividing the immediate survey areas into HMUs as well as recording important attributes.
2.1.2.1 Types of Hydromorphologic Units (HMUs) and Physical Attributes
Hydromorphologic Units are essentially areas of the river that can be characterized by the gradient, flow pattern and shape of the stream bed. The designations are not quantitative and mapping these unit types is based on visual estimation. However, the NEIHP has performed some tests of the method by having different technicians map the same section of the river. The following definitions are used by NEIHP to designate HMU types. The definitions are taken from Parasiewicz (2001) and are modification of classifications of Bisson and Montgomery (1996) and from Dolloff et al. (1993). 19
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Riffle- Shallow stream reaches with moderate current velocity, some surface turbulence and higher gradient. Convex streambed shape.
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Rapid- Higher gradient reaches with faster current velocity, coarser substrate, and more surface turbulence. Convex streambed shape.
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Ruffle – A transition between a riffle and run. Also similar to dewatered rapids.
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Cascade- Stepped rapids with very small pools behind boulders and small waterfalls.
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Glide- Moderately shallow stream channels with laminar flow, lacking pronounced turbulence. Flat streambed shape.
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Run- Monotone stream channels with well determined thalweg (deeper area along the centerline of the stream). Streambed is longitudinally flat and laterally concave shaped.
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Fast run- Uniform fast flowing stream channels.
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Pool- Deep water impounded by a channel blockage or partial channel obstruction. Slow flow. Concave streambed shape.
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Plunge pool- Where main flow passes over a complete channel obstruction and drops vertically to scour the streambed.
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Backwater- Slack areas along channel margins, caused by eddies behind obstructions.
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Side arm- Channels around the islands, smaller than half river width, frequently at different elevation than main channel.
The other attributes that are determined to be important for sufficient habitat for fish include canopy cover, undercut banks, woody debris, overhanging vegetation, submerged vegetation, boulders, riprapped banks, and shallow margin. These are recorded as absent, present, or abundant within each HMU as well as each fishing grid. Random measurements of depth and velocity are also taken throughout the HMU. The 20
dominant substrate or choriotop of the HMU is determined to be pelal (silt, clay, loam, sludge), psamal (sand), akal (fine gravel < 2cm), micro-lithal (egg to fist size cobbles, 26cm), meso-lithal (fist to hand size cobbles, 6-20cm), macro-lithal (hand-head size boulders, 20-40cm), mega-lithal (large boulders, >40cm), giga-lithal (bedrock), sapropel (organic sludge), detritus (organic matter), debris (snail and mussel shells), phytal (submerged plants, floating mats), or xylal (submerged branches, roots) (Austrian Standard ÖNORM 6232 (1995)). We use this classification system because it has been developed to better reflect the habitat use of benthic fauna. Other systems are based more on geotechnical methods. The status of the adjacent stream banks is also recorded. It is documented whether invasive plant species are present, if the bank is stabilized/armored, eroded, or comprised of clay. It is noted whether each of the banks is forested, field, pasture, roadway, residential, or urbanized. These data will primarily accommodate Phase II of the project in which the relationship between the physical habitat and its suitability will be established. It will only be discussed in this report where it is relevant for the assessment of the fish community.
2.1.3 Target Fish Community Concept
The Target Fish Community (TFC) approach developed by Bain & Meixler (2000) evaluates the status of a river based on a comparison between the current fish community and a regional model of the desired fish community. The TFC is formed using historical fish data from several high quality rivers with characteristics similar to the one being investigated. Its computational framework, accounts for spatial and temporal variations of the native community and creates a robust, interannual representation of the expected native fauna composition at the watershed scale. The Bain and Meixler paper (2000) provides the guidelines and calculations required to create a representation of what the desired species assemblage in a river should resemble. The concept is based on identifying the types of fish species and their 21
expected proportions within the community that is as close as possible to what may have been in the ecosystem with limited human alteration and therefore a goal of natural resources management. Bain and Meixler (2000) acknowledge that finding or restoring a river community to pristine, untouched status would be impossible, especially due to widespread introduction of non-native and desired game species and the highly developed condition of some watersheds. Instead, they state that the use of reference rivers in a mostly natural or desired state will provide a baseline community that can be used to determine where the actual community deviates from management targets (Bain and Meixler 2000). In order to develop the target fish community, typically a comprehensive list of species is assembled based on historical records and previous surveys provided by the Inland Fisheries Division of Connecticut DEP. The reference rivers are chosen, the species caught in previous surveys are identified, the relative abundances of the fish are calculated (excluding the young of year), and calculated into proportions. The proportions from all the reference rivers are summed and ranked (Bain and Meixler 2000). All of the fish species that were observed or recorded previously are placed on the comprehensive list and any that do not make sense for the study river, as far as extirpation, estuarine or coastal habitat etc., are eliminated. Introduced species are also removed from the rankings. The reciprocals of the proportions are calculated to determine what the expected abundance of the species would be in the reference community. This provides a list of species as well as expected proportions that can be compared to what is actually surveyed by using a similarity measurement method such as a percent affinity model (Novak and Bode 1992). The community can also be analyzed using pollution tolerance indices (i.e. intolerant, moderately tolerant and tolerant) and classifications of the habitats required by the species (i.e. fluvial dependent, fluvial specialists, or macrohabitat generalists) (Bain and Meixler 2000). It is useful to look at the target and existing fish species in terms of these macrohabitat guilds. Fluvial specialists are species that rely entirely on rivers and flowing water throughout their life cycle. Fluvial dependents are species that require stream habitat for at least one portion of their life cycle such as spawning, migration etc. Generalists are species that can utilize multiple types of habitat and are often associated 22
with ponded areas (Parker et al 2004). Generalists are becoming more common in rivers as dams or low flows create higher number of ponded areas. In terms of target fish communities, the general objective for rivers is to have of the fish population comprised in a large part of native, fluvial specialists and fluvial dependent species (Parker et al 2004). The actual fish community surveyed in 2004 is shown in Appendix H and displayed by macrohabitat guilds. Within the MesoHABSIM framework (Parasiewicz, 2001) we propose to use a model such as the TFC as a biological template to provide guidelines for the identification of habitat types necessary to support target fauna. This serves to develop a model of river habitat, which is expected to be functional in creating sustainable populations as it did historically. Such models work to fill a gap in the knowledge of channel complexity that was created by centuries of human-induced alteration, and allows for assessing and restoring the baseline conditions. However, in order to develop a model that reflects all the conditions that exist in functioning habitat, we need to consider that some of the naturally occurring species may be under-represented or not occur in the TFC. To account for this, we propose to estimate the expected proportions of these species by using regional averages and ranking their abundance with the help of experts and using this data instead of fish collection. This gross approximation of Reference Fish Community (RFC) provides a starting point to estimate the proportions of various habitat that would occur in natural system. It also allows for further analysis of the extent to which the present fauna departs from the optimal setting and where to set the improvements goals.
2.1.3.1 Choosing Sample Rivers as Representatives Bain and Meixler (2000) suggest gathering a list of rivers recommended from the state agency for natural resources or fish and wildlife protection. These rivers should be from the same or similar major river basin as the study river and be as free from anthropogenic impact or influence as possible. The agency will be able to identify rivers considered most natural or in a preferred condition. NEIHP acquired the list of 23
comparable reference rivers from Neal Hagstrom at the Connecticut DEP Fisheries Division. At the recommendation of Mr. Hagstrom, all sites to the west of the Connecticut River were eliminated from the list due to the difference between native fauna in the eastern and western portions of the state. Similar rivers were then selected using a modified version of the method developed by Kearns et. al. (2003). Stream order, drainage area at the sampling locations, the percent of calcareous geologic formations, gradient, and level III ecoregion (as determined by the Environmental Protection Agency (EPA)) was researched for all rivers in New England. These data came from draft Stream and Lake Classification GIS layers generated by The Nature Conservancy (TNC). Next, acceptable ranges for each of these parameters were specified and all rivers that did not fall into the acceptable ranges were eliminated. To further narrow it down, we included parameters such as mean width and dominant substrate in the sorting process. From the remaining selection any rivers that were identified by DEP as significantly impacted by human development, had poor data, or had unique geology or fauna were eliminated from the list.
2.1.3.2 Dividing the Eightmile Watershed into Communities
The observations of longitudinal zoning of fish communities along the stream corridor have been widely documented in the literature (e.g. Vanotte 1980, Ward and Stanford 1983). In 1961, Illies published a general concept of seven longitudinal fish zones for central Europe, identifying species that would dominate each zone. As documented by Schmutz in 1997 the change in community structure is related to the stream order. Therefore, when we establish target or reference fish community models, we need to consider this longitudinal stratification of fauna. Due to the difference in relief and stream orders (Figures 2 and 3) between the Eightmile River above and below its confluence with the East Branch, two separate sets of reference rivers were identified and a reference fish community was developed for each one. A stream order indicates the size of a river based on the level of tributaries and 24
the confluences it flows from. A first order stream is typically a headwater stream. Where two first order streams meet in a confluence, a second order stream is created, where two second order streams meet in a confluence, a third order stream is created and so on.
Figure 2. Relief map of the Eightmile River watershed depicting general topography and elevation, which presents a good correlation with the stream order.
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Figure 3. Map of the Eightmile River watershed with all stream orders labeled. The information was taken from Stream and Lake Classification GIS layers generated by The Nature Conservancy.
The differences between the ecological communities of lower order streams and higher order streams can be substantial. For this reason, NEIHP divided the watershed into two communities. The first reference fish community was created for the East Branch, the Upper Branch of the Eightmile, and the tributary Beaver Brook, which ranged in stream order from second to third. The second reference community was developed for the Eightmile Mainstem below its confluence with the East Branch where it becomes a fourth order stream. The study site was delineated into two communities due 26
to the occurring habitat conditions related to gradient and river size, which would therefore result into two separate expected fish assemblages. We determined that the difference between a fourth order and lower stream would warrant the development of two reference fish communities.
2.1.3.3 Analysis and Calculations
In terms of creating a comprehensive species list, NEIHP used the list developed for the Quinebaug River as a starting point since we determined that it would be similar to the list for the Eightmile. After consultation with the staff of the Inland Fisheries Division of Connecticut DEP, we modified the list and removed species that would be outside of their geographic range. For each species, we indicated whether they are native, what their pollution tolerance is and their basic habitat usage referring to classification by Kinsolving and Bain (1993). Following the methods of Bain and Meixler (2000), the total numbers of adult fish at each of the reference rivers for the Eightmile study sites were summed. The total of each species was divided by this sum, yielding a proportion of the total catch and these proportions were summed for all sites. The sums of the proportions were then ranked, with that species having the greatest sum ranked as “1”. At this point, all non-native or introduced species were removed from the calculation. Although these species were removed, all of the species remaining on the list maintained the same numerical rank. The reciprocal of each species’ rank was taken, and these reciprocals were summed. The reciprocal rank of any given species divided by the sum of the reciprocal ranks yielded that species’ expected proportion in the Eightmile community. All of these calculations were done on a Microsoft Excel spreadsheet, which was originally designed by Bain and Meixler (2000). In order to refine the RFC, we sought the additional expertise of the Inland Fisheries Division, primarily to estimate the more accurate rankings for American eel (Anguilla rostrata), Atlantic salmon and brook trout. Using extensive fish data, (347 and 891 sample sites for salmon and eel respectively), from the department’s database, Steve Gephard and Neal Hagstrom computed average densities for these species in third and 27
fourth order rivers in the state (Appendix L). To determine the proportion of these species in the fish samples in reference rivers, we replaced the actual eel and salmon numbers with the proportion of the provided means relative to the total fish abundance in the sample. Subsequently, we calculated the rank and expected proportions of these species in the RFC. To compute the proportion of the brook trout, we asked these experts to estimate the rank of this species in the community. The Eightmile River was sampled through electrofishing surveys in order to get a picture of the actual community. Since the survey results of the actual community are considered to be a “snapshot” of the river in time, while the expected proportions in the RFC are calculated as a multi-year, power law-based, projection, in order to have a viable comparison we altered Bain and Meixler’s original methods slightly and determined that the survey results must also be displayed as a power law-based projection. Therefore, the same calculations were applied to the survey results as to the reference data, transferring the observed relative abundances to projected proportions. In contrast to the RFC, the existing fish community (XFC) also includes introduced species. The reference and actual community were then compared using the percent affinity measure. For further detailed instruction on these indices and models, refer to Bain and Meixler (2000).
2.2 Field Data Collection
The following section will provide specific technical details regarding the protocol we followed to complete the field work. We will also discuss the various methods used to analyze the data.
2.2.1 Watershed Delineation and Selection of Representative Sampling Sites
Prior to beginning the fishing surveys or placing the thermometers, NEIHP examined a map of the Eightmile watershed with Dr. David Bingham in order to determine sites of importance to the study committee, as well as areas for potential 28
access. The main goal was to provide coverage that was as complete as possible of the temperatures in the watershed and the distribution of the fish fauna in the river. We divided the river into sections identified as the Eightmile River Mainstem Upper Branch (Upper Branch), the Eightmile River Mainstem (Mainstem), the Eightmile River East Branch (East Branch), Hamburg Cove and tributaries (Figure 1). The locations of temperature probes were selected to represent various types of existing conditions in the watershed. Consequently, some probes were placed above or below confluences of tributaries to the main stem and others were below dams and ponds on the river. With help of Dr. Bingham and other local volunteers who were very familiar with the watershed, we identified twenty-two locations that represented varying physical circumstances. They were widely distributed along the Upper Branch, the East Branch, the Mainstem, and some of the named tributaries. After the fish data had been collected, the locations were lumped into 11 sites of specific character (Figure 4). Three were located on the Upper Branch, three along the East Branch, one was within the Beaver Brook tributary, and four were located at or below the confluence on the Mainstem of the Eightmile. One of these sites was located directly upstream from the confluence of the river and Hamburg Cove. Hamburg Cove was not included in the electrofishing. The sites on tributaries were selected to represent various settings in the watershed. For example, locations in Site 1 represent the low order, upgradient streams in the headwaters of the Mainstem and Site 4 was located in the headwaters of the East Branch. Site 9 represents Beaver Brook, a second order tributary of the Mainstem, located in a downstream section of the watershed. The sites on the main channels represent various geographical settings (e.g. high gradient, forested areas at Site 2, or the confluence section at Site 7).
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Figure 4. Map of the Eightmile River watershed with an overlay of the eleven sites surveyed for fish during summer 2004. The clusters of pink dots represent the individual fishing grids
2.2.2 Temperature and flow data
Following the initial delineation of the Eightmile watershed, we placed HOBO® temperature probes from Onset Computer Corporation into the river in the predetermined locations (Figure 5). The probe stores hourly temperature data in its memory and is 30
recovered and downloaded to a computer using the BoxCar software from MicroDAQ, approximately 65-70 days after it was set. The probes were initially placed on April 22, 2004 and they were left submerged to record hourly temperatures. Fourteen probes were placed throughout the watershed and we took GPS points of their locations with a Trimble ProXR backpack unit in order to create a GIS datalayer. The following paragraphs describe the basic locations of the probes, which were recovered. All distances were measured in river kilometers from the confluence with Hamburg Cove.
Figure 5. Map of the Eightmile River watershed depicting the locations of the temperature probes which were placed to record hourly water temperatures during the 2004 surveys.
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Three temperature probes were deployed in the lower Mainstem. Starting with the southernmost point, Probe 9 was placed at the Eightmile’s entry into Hamburg cove near the Joshua Town Road bridge. Probe 6 was placed 1.7 km upstream of Probe 9 at the downstream end below the Mt. Archer impoundment; and Probe 2 was placed 2.9 km upstream near Macintosh Road. Three temperature probes were also deployed in the Upper Branch. Probe 1 was placed in Devil’s Hopyard, 11.1 km upstream of Hamburg Cove. Probe 8 was placed 15.0 km upstream on Early Brook just off the Eightmile near Haywardville Road; and Probe 7 was placed 15.0 km upstream on the Eightmile also near Haywardville Road. Four temperature probes were deployed on the East Branch. Probe 14 was placed 9.1 km upstream of Hamburg cove, near the Darling Road bridge. Probe 11 was placed 12.2 km upstream, near the confluence of Harris Brook and the East Branch. Probe 10 was placed 15.8 km upstream, by Morgan Road; and Probe 5 was placed 17.5 km upstream, just below Major Kenny’s Pond by Witch Meadow Road. Three additional temperature probes were deployed on tributaries to both the Eightmile and the East Branch. Probe 13 was placed 16.0 km upstream of Hamburg Cove on Harris Brook (a tributary of the East Branch). Probe 3 was placed 18.2 km upstream, just above Hales Pond on a small tributary to the East Branch named Little Brook near Rattlesnake Ledge Road. Probe 12 was placed 16.5 km upstream, below a large impoundment (Lake Hayward) on the tributary identified as Lake Hayward Brook. All but one of the probes (Probe 4, which was placed just downstream of the confluence of the East Branch and Eightmile) were recovered and downloaded throughout early July during the beginning of the fishing survey season. The probes were reset and continued to collect data until September 21, 2004 when the remaining thirteen were recovered, downloaded and removed from the watershed. The daily flow data recorded between 1938-1981 at the USGS gauge #01194500, located in the lower portion of East Branch, have been downloaded and analyzed using The Nature Conservancy’s Indicators of Hydrological Alteration (IHA) software (Richter et al 1996). This package provides comprehensive statistics consisting of numerous
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parameters that describe magnitude, duration, frequency and rate of change of flows. Only selected parameters are discussed is this report. Because of anecdotal reports that the magnitude and duration of low flows has changed in the last decades, we also performed simplified continuous-under-threshold curve (CUT curve) analysis as presented in a paper by Capra et al. (1995) to determine if these characteristics have indeed changed. The curves essentially represent the durations of the low flow pulses by comparing continuous durations in days when flow is under any selected threshold against the duration of the study period (in per-cent). A set of such curves for a series of thresholds between 0.05 cfsm and 0.5 cfsm was developed using USGS data. We computed two separate series for the time periods 1938-1957 and 19641981 and 2001-2003, (as there is no available data for the period of 1982-2000) . These curves are shown in Figures 19 and 20 We also obtained flow records for summer 2004 to determine if the flow conditions during our fishing survey deviated from a typical season.
2.2.3 Fishing Surveys
Fishing surveys were conducted between July 7, 2004 and August 4, 2004 at the eleven sites mentioned in section 2.2.1. To begin, we collected data on the composition of the existing fish community using an electrofishing grid technique developed by Bain et al. (1985). The fish sampling is done by placing grids in various locations throughout the survey area in an attempt to represent the different habitat types present and the extent to which they exist in the river. In each of selected sample sites, we placed between 12 and 44 grids depending on habitat diversity, with the goal to capture all HMUs occurring in the site in the proportion of their abundance. Within each HMU, the grid locations were also selected to represent the widest variety of circumstances.
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Each grid is 1m x 6m in dimension and consists of two cables running upstream and parallel to each other for a distance of 6m, and attached to a PVC pipe placed at each end to maintain a distance of 1m between the cables at all times. The grids were prepositioned parallel with the stream channel in groups of 5 to 8, and allowed to settle for at least 15 to 20 minutes prior to sampling (Figure 6). The grids were fished individually and were attached to a Honda EX1000 generator and 15 Amp Coffelt VVP-2C transformer. We tended to use 300 volts of alternate current, however, conductivity is
Figure 6. The photograph presents a view of the electroshock grids that were utilized during the fishing survey in the Eightmile River. This grid was placed in the Mainstem of the river below Mt. Archer Dam.
different for each site and we often lowered the voltage accordingly if mortality appeared to be high. One person pulsed the current in several second increments until all fish within the grid were stunned while two others approached the grid from downstream and gathered the stunned fish. The fish were identified by species and measured prior to their release. The species and length data are recorded on pre-printed data sheets along with the grid number, general location in the stream channel, and time and date of sampling. Young-of –the-year fish were separately noted but were not included in the analysis if they could not be positively identified. As the fish data from DEP did not include any fish 34
smaller than 30mm, we attempted to make our data as similar as possible since our reference and existing communities required comparison. Occasionally, slightly larger individuals could not be identified to species and were labeled as juvenile cyprinids or salmonids and were also excluded from the analysis. Additional data on general habitat characteristics such as stream location, cover, gradient, substrate, and choriotop were collected for each grid location. We also took measurements of stream depth, mean column velocity and substrate at each of the four corners of the grid.
2.2.4 Habitat Surveys
At the same time we performed fish sampling, we gathered general information about the HMUs in the immediate sampling locations where the grids are placed. We used Hewlett-Packard iPAQ h1945 palmtop computers with ArcPAD 6.0.3 software, preloaded with orthophotos of the Eightmile river basin and ArcView templates for data entry. The computers were also equipped with GPS receivers as a navigation system that provided us with a more detailed depiction of our location in the river. When the fishing grids were laid out at a survey site, we delineated the surrounding areas of the river into HMUs by drawing them as geo-referenced polygons overlain on the digital orthophotos. We also drew the fishing grids on the orthophotos in their geo-referenced (+/- 5m) locations. Within each HMU, we completed the GIS data entry form associated with the polygon by identifying the type of HMU and the physical attributes listed in section 2.1.2.1. Seven randomly located measurements for depth, mean column velocity and estimated substrate are taken with a Dipping Bar (Jens 1968).
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2.2.5 Mussel Survey Methods
Four sites in the Mainstem and the East Branch were chosen as locations to do SCUBA surveys for freshwater mussels. The site locations are described in the text and are numbered in increasing order in the downstream direction (M1-M4). These site numbers are independent of the fishing sites. Site M1 was located in the East Branch near Mitchell Pond. The site surveyed extends about 40 meters upstream and 10 meters downstream of an abandoned stone bridge that crosses the river (Bingham's bridge), corresponding with portions of Site 5 of the fishing survey. This is an area that is fed by a cold groundwater spring and has a maximum depth of about 4 meters. Site M2 is a broad, fairly shallow (1-2 meters) impoundment in the Eightmile Mainstem near Macintosh Road, corresponding with Site 8 of the fishing survey. About a 100 meter length upstream of the impoundment was surveyed. Site M3 is in Moulson's Pond, a moderately large impoundment on the Mainstem of the Eightmile River. This impoundment is about 5-6 meters deep and the bottom is primarily mud and coarse organic material. Visibility was limited at this site, and it was surveyed by making several transects across the middle and then concentrating the search effort near the dam, where mud was less of a problem. Site M4 is in Hamburg Cove at the mouth of the Eightmile River, nearing Site 11 of the fishing survey. The divers used a motorized boat and surveyed in a number of spots in the cove that were free from boat traffic. About 8 diver-hours of surveying were done in the cove. This was a preliminary survey, and thus the sites were chosen based upon our expectation of good mussel habitat and water depth (since shallower sites would not require SCUBA). Two expert mussel surveyors were employed: Dr. Sean F. Werle from the University of Massachusetts, and Mr. Ethan Nedeau from the environmental consulting company BioDrawversity.
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2.3 Data Analysis
2.3.1 Transfer of Information and Quality Control
Each evening on a day of field survey, the NEIHP technicians download the daily data file from the iPAQ palmtop to a computer. The general mapping of the HMUs and grids were edited where necessary to correct field error. Each data entry form was checked for errors or omissions and corrected.
2.3.2 Calculation
Length Frequency To gain insight into last year’s recruitment and to determine any potential limitations, length-frequency histograms for six species (longnose dace, blacknose dace, white sucker, brook trout, fallfish and tessellated darter) were developed. This analysis has been conducted at the river scale, but because we suspected potential differences in nursery habitat between the East Branch and the Eightmile Mainstem, two histograms were created for each species. One histogram was created using all of the fish data and the second with data separated for the East Branch and for the entire Eightmile Mainstem (including the Upper Branch). The length-frequency diagrams were used to separate young-of-the-year (YoY) fish by the maximum length. The length cut-off values were compared for plausibility with those observed in other surveys performed by NEIHP. Further calculations were conducted using only those individuals determined to be in life stages of one year and older. The terms juvenile fish or young of the year are somewhat coarse and used interchangeably for the purpose of our investigation, as some species take longer than one year to reach maturity. Reproductive maturity in fish is usually attributed to size rather than age.
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Estimated Density To estimate the density or abundance of each species of adult fish at each site the total number of observations of each fish species was summed and divided by the fished area (the number of grids times six square meters). This was charted for each species separately, as well as for a sum of all fish. The proportions of species in the community were related back to expected proportions in reference fish community.
Physical Attributes The distribution of physical attributes such as canopy cover, boulders, woody debris, HMU type, substrate type, and depth and mean column velocity was also analyzed at the site scale. The total proportions of the areas where each attribute occurred were used to characterize the site. The resulting pie charts showed whether an entire site had a particularly common occurrence or noticeable absence of one of these attributes (for Figures see Appendices A-E)
Depth and Velocity For depth and velocity, we took seven random measurements from each HMU. The measurements were categorized into six different classes ranging from 0 to 125cm in 25 cm increments. The velocities were divided into eight classes of 15cm/s increments ranging from 0 to 105 cm/s and greater. The proportion of measurements that fell into the various ranges was weighted by the area of each HMU. In other words, if three readings fell into the
