# McGuire Nuclear Station

2006-2007 Impingement Study and Assessment of Adverse Environmental Impact

Final Report, 2010

Duke Energy P.O. Box 1006 Charlotte, NC 28201-1006iiiii 

## CITATIONS

This technical report was prepared by

ASA Analysis & Communication, Inc. 5 Fairlawn Drive, Suite 205
P.O. Box 57 Washingtonville, NY 10992

Principal Investigators

W. Dey
J. McLaren ASA Analysis & Communication, Inc.

This Technical Report describes research spons ored by EPRI and Duke Power Corporation.

The Technical Report is a corporate document that should be cited in th e literature in the following manner:

McGuire Nuclear Station: 2006-2007 Impinge ment Study and Assessment of Adverse Environmental Impact , EPRI, Palo Alto, CA, 2010.v 

## REPORT SUMMARY

This report has been prepared for Duke Ener gy’s McGuire Nuclear Station to support Clean Water Act Section 316(b) requirements. It pr esents the results of sampling conducted during 2000-2002 to document current levels of impingement of fish and other aquatic organisms at the facility’s cooling water intake. Sampling results are interpreted in terms of the status of Lake Norman, from which the cooling water is wit hdrawn, and its fish community. Impingement losses are interpreted as to whether they constitu te adverse impact to the fish community of Lake
Norman.

Background

McGuire Nuclear Station (MNS) is located in Huntersville, Mecklenburg County, North Carolina on Lake Norman, an impoundment of th e Catawba River formed by the Cowans Ford Dam. MNS has two nuclear reactor units, each with a net generation capacity of 1,129 MW for a total rating of 2,258 MW. MNS uses once-throug h cooling for its steam condensers. Unit 1 began commercial operation in December 1981 a nd Unit 2 began in March 1984. Both units are operated as base-loaded and toge ther had a capacity utilization of 94.5 pe rcent for 2000 through
2007.

Estimates of numbers of fish impinged were obtained from monito ring the MNS traveling screens from 3 December 2000 through 29 November 2002. On 3 December 2000, all screens were washed of all fish and debr is. Thereafter, the screens were allowed to accumulate impinged fish for one week before the screens were washed again. At the end of e ach week, all debris and fish from each screen were collected in co ated-wire baskets (5-mm x 10-mm mesh openings) placed in the screen-wash sluiceway. These we ekly collections would represent a complete census of impingement as long as there were no losses of impinged fish during the weekly intervals between screen rotations due to decay, predation, or other r easons. Fish losses to such sources would result in an underestim ation of the impingement rate.

To address this concern, a special study was conduc ted to estimate the loss rate of impinged fish during a weekly collection interv al and to adjust impingement numbers to account for these losses. Over a seven-day period (21-27 July 200 5), a total of 1,600 threadfin shad or alewives were fin-clipped and introduced onto all 16 freshl y washed upper level intake screens at periodic intervals. Treatments consisted of the release of four lots of 400 marked fish each at intervals of seven, five, three, and one day prior to screen washing on 27 July. A set of four screens was randomly chosen for each of the f our release dates (100 fish per sc reen), such that all 16 screens were tested once. At the end of this 7-day period, all screens we re washed and all marked fish were collected.vi Impingement Sampling Results

A total of 1,690 fish were impinged and collected in the first year of sampling, December 2000 – November 2001, and 698 fish were impinged and co llected in the second year, December 2001 – November 2002. Over this two-year period, 23 fish species were identifie d in the impingement collections. Threadfin shad numerically domin ated in 2000-2001, comprising 51.5 percent of the total, and alewife dominated in 2001-2002, comp rising 23.8 percent. Other commonly impinged species (in decreasing order fo r both years combined) included white perch, bluegill, striped bass, white bass, channel catfish, and gizzard shad. Impingement wa s highest for all fish species combined in mid-winter (January) for th e 2000-2001 and late summer (August) for the 2001-
2002.

The impingement totals for 2000-2001 and 2001-2002 we re adjusted for fish losses that might have occurred during the 1-week collection peri od, based on the results of the special study conducted in July 2005 using releases of marked fish in front of the traveling screens. A total of 243 of the 1,600 fin-clipped fish released during th e study were recovered at the screen washing on the seventh day. Releases of 400 marked fish on each of the four release dates resulted in 98 being recovered after one day on th e screens, 93 after three days, 36 after five days, and 16 after seven days. These data showed a steady decline in the number of recovered fish through time, indicating a cumulative loss of impinged fish due to decay, predation, or other reasons. Depending on the assumptions made, the adjusted total annual impingement would be 2,726 to 2,996 fish for 2000-2001 and 1,126 to 1,238 fish for 2001-2002. These estimates would be conservative because the special study was conduc ted at warm temperatures conducive to rapid decomposition, the test species were comparativel y fragile clupeids, and the adjustment factors were applied to all species (including durable ones) and all seasons, incl uding cold months when clupeids were primarily impinged.

AEI Assessment Results

The potential for the estimated levels of im pingement at MNS to be considered “adverse environmental impact” under §316(b) of th e Clean Water Act was assessed. Adverse environmental impact was defined as an unacceptable reduction in:



###  biological integrity as meas ured in terms of aquatic community species composition, diversity, and functional organi zation in Lake Norman; or



###  human use of the aquatic resources of Lake Norman, especially fishing opportunity or catch quantity or quality.

The assessment used the U.S. Environmental Pr otection Agency’s well-established Framework for Ecological Risk Assessment. Potential adverse effects were addressed from two perspectives: prospective (predict ed future risks) and retrospe ctive (effects linked to present operation). The results were used in a “weight -of-evidence” approach to determine the overall risk of adverse environmental impact from opera tion of the MNS cooling water intake structure
on Lake Norman.vii There was no evidence that impingement at MN S is causing adverse environmental impact in
Lake Norman. This conclusion is based on a care ful evaluation of all rele vant lines of evidence including the following:

1. Numbers of fish lost as a re sult of impingement are exceedingly small compared to likely sizes of fish populations in Lake Norman. For all but two species, removal rates amounted to less than 1 fish per day. It is ha rd to imagine that such a removal rate would constitute an adverse environmental impact on Lake Norman.

2. Total numbers impinged each year for the two most abundant species, threadfin shad and alewife, amounted to less than 0.01 percent of the population in the lake. Both species are highly prolific spawners with high gr owth rates and short life spans. This high reproductive potential can easily compensate fo r the relatively small losses at MNS with no long-term effects.

3. The aquatic community of Lake Norman has been relatively stable in terms of fish abundance and trophic structure, particularly in recent years. Fish abundance in pelagic areas has stabilized since 1997. There also has been no sustained trend in the size of the littoral zone catch since 1993, while species ri chness has increased w ith the addition of several new species.

4. Intensive recreational fishery management a nd species introductions likely have been responsible for changes in the fish community experienced in the past. However, there is no evidence of changes related to operati on of the MNS cooling water intake and impingement losses.

5. Estimates of total fishery catch that could re sult from the fish impinged at MNS had they survived amount to only 111 to 168 lb (50.5 - 76. 4 kg) per year. That amount translates to one-half pound per day or less. This leve l of harvest is less than what would be expected from a small number of anglers.

6. Estimates of the total production foregone as a result of fish impinged at MNS amounted to just over 111 - 152 lb (50.5 - 69.1 kg) per year of biomass. Almost all of this was a
result of threadfin shad and alewife, both of which are high ly abundant species in Lake
Norman. That biomass translates to less th an 0.2 ounces per surface acre (37 g/ha) across the entire reservoir.

7. The best estimate of the total economic va lue of fish impinged at MNS was $281 - 431 per year. Even considering the uncertainty in these estimates, it is highly unlikely that the economic value exceeds $800 per year. Th ese values must be considered trivial compared to the likely total economic value of the recreational fishery in Lake Norman.

Keywords Clean Water Act §316(b)
Economics Cooling water intake structuresviii Fisheries Environmental impact assessmentix 

## CONTENTS

INTRODUCTION .................................................................................................................. .......... 1-1
Background .................................................................................................................... ............ 1-1
Report Organization ........................................................................................................... ........ 1-2

PLANT AND SOURCE WATERBOD Y DESCRIPTIONS .............................................................. 2-1

McGuire Nuclear Station ....................................................................................................... ..... 2-1
Cooling Water Intake Structure ............................................................................................. 2- 1
Plant Operation and Water Withdrawal ................................................................................. 2-2

Lake Norman ................................................................................................................... ........... 2-2
Geomorphology and Aquatic Habitat ..................................................................................... 2-2
Water Quality ................................................................................................................. ........ 2-3

FISH COMMUNITY DESCRIPTION ............................................................................................... 3-1
Description of Available Information .......................................................................................... . 3-1
Species Composition............................................................................................................ ...... 3-2
Protected Species ............................................................................................................. ......... 3-3
Target Species ................................................................................................................ ........... 3-3

Threadfin Shad ................................................................................................................ ...... 3-4

Alewife ....................................................................................................................... ............ 3-5

White Perch ................................................................................................................... ........ 3-6
Bluegill ...................................................................................................................... ............. 3-7
Striped Bass .................................................................................................................. ........ 3-7

White Bass .................................................................................................................... ........ 3-8

Channel Catfish ............................................................................................................... ...... 3-8

Blue Catfish .................................................................................................................. ......... 3-9

IMPINGEMENT MORTALITY ......................................................................................................... 4-1
Impingement Monitoring Program .............................................................................................. 4 -1

Results ....................................................................................................................... ................ 4-2

Seasonal Patterns ............................................................................................................. .... 4-4

VARIABLES AFFECTING IMPINGEMENT RATES .............................................................. 4-6x Environmental Variables ................................................................................................... 4-6
Species-Specific Abundance and Spatial Distribution ...................................................... 4-8

Annual Losses ................................................................................................................. ........... 4-8
Annual Variability ............................................................................................................ ....... 4-9
Intake Operation .............................................................................................................. . 4-9

Environmental Variables ................................................................................................... 4-9

Fish Abundance ................................................................................................................ 4-10
Comparison of Annual Monitoring Programs .................................................................... 4-10

ASSESSMENT OF ADVERSE ENVI RONMENTAL IMPACT ........................................................ 5-1

Introduction .................................................................................................................. .............. 5-1
Assessment of Ecosystem Effects ............................................................................................. 5 -3
Prospective Approach .......................................................................................................... . 5-3
Retrospective Approach ........................................................................................................ 5-5

Fish Abundance ................................................................................................................ 5-5
Species Richness ............................................................................................................. 5-6
Trophic Structure ............................................................................................................. . 5-7
Retrospective Summary.................................................................................................... 5-7

Effects on Human Uses.......................................................................................................... .... 5-8
Equivalent Loss Measures .................................................................................................... 5 -8

Economic Value ..................................................................................................................... 5-9
Uncertainty in Economic Value .............................................................................................. 5-10

Conclusions ................................................................................................................... ............. 5-11

REFERENCES CITED .............................................................................................................. ...... 6-1

APPENDIX A: METHODS TO ESTIMATE EQUIVALENT LOSS AND ECONOMIC VALUE OF FISH IMPINGED AT MARSHALL ............................................................................... A-1

Introduction .................................................................................................................. .............. A-1
Estimates of Target Species Equivalent Losses ........................................................................ A-1
Assignment of Age Categories for Impinged Individuals ....................................................... A-3

Life Table Information ........................................................................................................ .... A-3
Life Stage Durations .......................................................................................................... .... A-4
Natural Mortality Rates ....................................................................................................... ... A-4
Fishing Mortality Rates ....................................................................................................... ... A-5
Fishing Vulnerability Rates ................................................................................................... . A-6xi Weight at Beginning of Age ................................................................................................... A-7

Economic Valuation Methods .................................................................................................... . A-8

Direct Use Values ............................................................................................................. ..... A-8
Market Values (Commercial Fishing) .................................................................................... A-8
Non-Market Direct Use Values (Recreational Fishing) .......................................................... A-9

Indirect Use Benefits ......................................................................................................... .... A-11

Non-Use Benefits .............................................................................................................. .... A-13
Adjustment for Other Species ................................................................................................ A-13
Uncertainty Analysis .......................................................................................................... ......... A-14
Inputs to Direct and Indirect Use Benefits ............................................................................. A-15
Sensitivity Analysis .......................................................................................................... ...... A-16
Monte Carlo Analysis ............................................................................................................. A-16xii 

## LIST OF FIGURES

Figure 2-1 Location of MNS ................................................................................................... ... 2-5 Figure 2-2 Aerial View of MNS ................................................................................................ .. 2-6 Figure 3-1 Sampling Zones and Locations for Lake Norman ................................................. 3-11 Figure 4-1 Plot of Number of Marked Fish Recovered After One to Seven Days of Traveling Screen Impingement at MNS, 21-27 July 2005 ................................................ 4-11 Figure 4-2 Seasonal Pattern of Impingement Rates for All Species Combined, December 2000 – November 2001 .................................................................................. 4-12 Figure 4-3 Seasonal Pattern of Impingement Rates for All Species Combined, December 2001 – November 2002 .................................................................................. 4-13 Figure 4-4 Seasonal Impingement Pattern and Length Frequency of Impinged Threadfin Shad, December 2000 – November 2001 ........................................................................ 4-14 Figure 4-5 Seasonal Impingement Pattern and Length Frequency of Impinged Alewife, December 2000 – November 2001 .................................................................................. 4-15 Figure 4-6 Seasonal Impingement Pattern and Length Frequency of Impinged Alewife, December 2001 – November 2002 .................................................................................. 4-16 Figure 4-7 Seasonal Impingement Pattern and Length Frequency of Impinged Threadfin Shad, December 2001 – November 2002 ........................................................................ 4-17 Figure 4-8 Seasonal Impingement Pattern and Length Frequency of Impinged White Perch, December 2000 – November 2001 ....................................................................... 4-18 Figure 4-9 Seasonal Impingement Pattern and Length Frequency of Impinged White Perch, December 2001 – November 2002 ....................................................................... 4-19 Figure 4-10 Seasonal Impingement Pattern and Length Frequency of Impinged Striped Bass, December 2000 – November 2001 ........................................................................ 4-20 Figure 4-11 Seasonal Impingement Pattern and Length Frequency of Impinged Striped Bass, December 2001 – November 2002 ........................................................................ 4-21 Figure 4-12 Seasonal Impingement Pattern and Length Frequency of Impinged Bluegill, December 2000 – November 2001 .................................................................................. 4-22 Figure 4-13 Seasonal Impingement Pattern and Length Frequency of Impinged Bluegill, December 2001 – November 2002 .................................................................................. 4-23 Figure 4-14 Seasonal Impingement Pattern and Length Frequency of Impinged White Bass, December 2000 – November 2001 ........................................................................ 4-24 Figure 4-15 Seasonal Impingement Pattern and Length Frequency of Impinged White Bass, December 2001 – November 2002 ........................................................................ 4-25 Figure 4-16 Seasonal Impingement Pattern and Length Frequency of Impinged Channel Catfish, December 2000 – November 2001 ..................................................................... 4-26 Figure 4-17 Seasonal Impingement Pattern and Length Frequency of Impinged Channel Catfish, December 2001 – November 2002 ..................................................................... 4-27 Figure 4-18 Seasonal Impingement Pattern and Length Frequency of Impinged Blue Catfish, December 2000 – November 2001 ..................................................................... 4-28xiii Figure 4-19 Seasonal Impingement Pattern and Length Frequency of Impinged Channel Catfish, December 2001 – November 2002 ..................................................................... 4-29 Figure 4-20 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for All Species Combined, December 2000-November 2001 ................... 4-30 Figure 4-21 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for All Species Combined, December 2001-November 2002 ................... 4-31 Figure 4-22 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad, December 2000-November 2001 .......................................................................... 4-32 Figure 4-23 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad, December 2001-November 2002 .......................................................................... 4-33 Figure 4-24 Plots of Numbers of Impinged Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad Collected vs. Daily Mean Water Temperature at the MNS Intake, December 2000-November 2001 ......................................................................... 4-34 Figure 4-25 Plots of Numbers of Impinged Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad Collected vs. Daily Mean Water Temperature at the MNS Intake, December 2001-November 2002 ......................................................................... 4-35 Figure 4-26 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for Young-of-Year (YOY) and Yearling and Older (YAO) Alewife, December 2000-November 2001 ..................................................................................... 4-36 Figure 4-27 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for Young-of-Year (YOY) and Yearling and Older (YAO) Alewife, December 2001-November 2002 ..................................................................................... 4-37 Figure 4-28 Plots of Numbers of Impinged Young-of-Year (YOY) and Yearling and Older (YAO) Alewife Collected vs. Daily Mean Water Temperature at the MNS Intake, December 2000-November 2001 ..................................................................................... 4-38 Figure 4-29 Plots of Numbers of Impinged Young-of-Year (YOY) and Yearling and Older (YAO) Alewife Collected vs. Daily Mean Water Temperature at the MNS Intake, December 2001-November 2002 ..................................................................................... 4-39 Figure 5-1 Annual Population Estimates of Pelagic Fish in Lake Norman Using Hydroacoustic Sampling, 1993-2006 ............................................................................... 5-13 Figure 5-2 Total Annual Electrofishing Catch for Bluegill, Redbreast Sunfish, Largemouth Bass, and All Species Combined at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-2007 ................................................................................ 5-14 Figure 5-3 Total Annual Electrofishing Catch for Blue Catfish, Alewife, and Threadfin Shad at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-2007 ..................... 5-15 Figure 5-4 Total Annual Electrofishing Catch for Bluegill, Channel Catfish and White Perch at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-2007 .................... 5-16 Figure 5-5 Total Annual Electrofishing Catch for Striped Bass and White Bass at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-2007 ....................................... 5-17 Figure 5-6 Species Composition in the Littoral Zone of Lake Norman as Determined by Electrofishing in 1993-1997 and 1999-2007 (Shading Denotes Species Presence) ........ 5-18 Figure 5-7 Percent Composition of Fish Trophic Guilds in the Littoral Zone of Lake Norman Based on Electrofishing Results of 1993-1997 and 1999-2007 ......................... 5-20xiv Figure 5-8 Estimates of the Range of Effects of Uncertainty in Each Input Parameter on Estimates of Annual Economic Benefit at MNS ............................................................... 5-21 Figure 5-9 Results of Monte Carlo Analysis of Uncertainty in Key Input Parameters on Estimates of Annual Economic Benefits at MNS ............................................................. 5-22xv 

## LIST OF TABLES

Table 2-1 Monthly Mean Cooling Water Flow Rate (MGD) and Percentage of Maximum Flow Rate and Net Capacity Generation at MNS, 2000-2007 ............................................ 2-7 Table 3-1 Fish Species Collected in Lake Norman Fishery Surveys (Siler et al. 1981; Duke 2004a, 2004b, 2006, 2007) ..................................................................................... 3-12 Table 4-1 Number of Impinged Fish Collected by Weekly Sampling at MNS, December 2000-November 2002 (ranked according to abundance) ................................................. 4-40 Table 4-2 Estimated Total Number of Fish Impinged at MNS, December 2000 - November 2001 and December 2001-November 2002 (ranked according to abundance) .................................................................................................................... .. 4-41 Table 4-3 Maximum Total Length (mm) Used to Distinguish Young-of-Year from Yearling Fish by Month .................................................................................................... 4-4 2 Table 4-4 Estimated Annual Impingement of Fish by Age Group at all Units of MNS, December 2000 - November 2001 ................................................................................... 4-43 Table 4-5 Estimated Annual Impingement of Fish by Age Group at all Units of MNS, December 2001 - November 2002 ................................................................................... 4-44 Table 4-6 Adjusted* Monthly Impinged Fish Collections at MNS, December 2000- November 2001 at Actual Flows ...................................................................................... 4-45 Table 4-7 Adjusted* Monthly Impinged Fish Collections at MNS, December 2001- November 2002 at Actual Flows ...................................................................................... 4-46 Table 4-8 Species Composition of the Purse Seine Catch in Lake Norman, 1993-2006 ....... 4-47 Table 4-9 Comparison of Relative Abundance of Fish Species in 2001and 2002 Littoral Zone Electrofishing Surveys and the December 2000- November 2002 MNS Impingement Collections (Unadjusted) ............................................................................ 4-48 Table 4-10 Adjusted* Monthly Impinged Fish Collections at MNS, December 2000- November 2001 at Full Design Flows .............................................................................. 4-49 Table 4-11 Adjusted* Monthly Impinged Fish Collections at MNS, December 2001- November 2002 at Full Design Flows .............................................................................. 4-50 Table 5-1 Trophic Guild Assignments for Fish Species in Lake Norman ................................ 5-23 Table 5-2 Estimates of Potential Total Annual Equivalent Fishery Yield (lb) from Individuals Impinged for Each Target Species at MNS .................................................... 5-24 Table 5-3 Estimates of Potential Total Annual Production Foregone (lb) from Individuals Impinged for Each Target Species at MNS ...................................................................... 5-25 Table 5-4 Estimates of Economic Value (2009$) of Fish Impinged at MNS ........................... 5-26xvi1-1 

# 1

INTRODUCTION

Background

ASA Analysis & Communication, In c. has prepared this repor t for Duke Energy’s McGuire Nuclear Station (MNS) as part of the applic ation process for a National Pollution Discharge Elimination System (NPDES) permit from the No rth Carolina Department of Environment and Natural Resources (NCDENR). Under the Clean Water Act §316(b), an NPDES permit applicant must demonstrate that the location, de sign, construction and cap acity of its cooling water intake structure represents Best Tec hnology Available (BTA) for minimizing adverse environmental impact. The primary impacts of concern under §316(b) are entrainment of smaller aquatic organisms into the cooling wate r system and impingement of larger organisms onto traveling screens in the cooling water intake.

In an effort to establish and enforce consis tent national standards under CWA §316(b), the U.S. Environmental Protection Agency (EPA) publishe d a Phase II Rule [69 Fed. Reg. 41576 (9 July 2004)]. The Rule applied to existing electric generating facilities that operate cooling water intake structures (CWIS) with a minimum de sign capacity of 50 million gallons per day (MGD), withdraw water from waters of the U.S., and us e 25 percent or more of the water withdrawn for cooling purposes. MNS fits this definition for a Phase II facility. Compliance with the Phase II Rule was based on achieving performance standards for reduction of impingement mortality and entrainment set by the EPA on the basis of facilit y location. The Rule required that impingement mortality be reduced by 80 to 95 percent and entrainment be reduced by 60 to 90 percent, compared to a baseline level (i.e., the calcula tion baseline) specifica lly determined for the facility. Adhering to the Phas e II Rule guidelines, MNS would not be subject to entrainment reduction performance standards because it is lo cated on a reservoir that has a retention time exceeding seven days.

In 2006, the Phase II Rule was challenged in the U. S. Court of Appeals for the Second Circuit, which reached a decision on 25 January 2007. The decision remanded several provisions of the Phase II Rule, including BTA determination, perfor mance standards, cost-cost and cost-benefit analysis, compliance according to the Technology In stallation and Opera tion Plan (TIOP), restoration as a compliance alternative, and “inde pendent supplier” provisions. In response to this decision, EPA suspended the Phase II Rule [72 Fed. Reg. 37107 (9 July 2007)] and directed that permit requirements for cooling water intake structures at Phase II fa cilities be established on a case-by-case best professiona l judgment (BPJ) basis. Ho wever, the requirement that permitting agencies develop BPJ controls for cooling water intake structures that reflect BTA for minimizing adverse environmental impact (AEI) was retained. In December 2008, the U.S. Supreme Court agreed to review the Second Circuit C ourt’s decision relative to the remand of the cost-benefit component of th e original Phase II Rule. In April 2009, the U.S. Supreme CourtIntroduction

1-2 overturned the Second Circuit Court’s decision and determined that EPA ha d the authority to use a comparison of costs and benefits in making BTA determinations under §316(b).

To comply with the regulations, Duke Energy in tends to use the result s of an impingement sampling program conducted from December 2 000 through November 2002 as representative of current impingement rates and composition. In this report, the 2000- 2002 study results are presented and interpreted as support for deci sion-making using a BPJ approach. Sampling results are interpreted in terms of the status of the fish community of Lake Norman, the impoundment from which the co oling water is withdrawn.



### Report Organization

Section 2 provides pertinent information on the st ructure and operation of the station’s cooling water intake structure, as well as a brief desc ription of the geomorphol ogy of Lake Norman and the aquatic habitat it provides. Section 3 describes the lake’s fish community composition and structure, particularly as relate d to susceptibility to impingement at the MNS intake. Section 4 presents the results of the 2000-2002 impingement sampling program, describes the seasonality and size distribution of impinged fish, and anal yzes the possible influence of environmental factors and changes in the fish community on impi ngement rates. This information is used to characterize current baseline levels of impingeme nt at MNS. Section 5 discusses the observed level of impingement mortality in terms of whether it constitutes adverse impact on the fish community of Lake Norman, using both a predictiv e approach and a retros pective approach. The predictive approach uses modeling to express impingement losses in terms of equivalent reductions in yield to the Lake Norman fishery a nd to estimate the economic value of the losses. The retrospective approach evalua tes the composition of the current fish community to determine whether there is evidence of trends that coul d indicate impairments or instability related to annual impingement losses.2-1 

# 2

PLANT AND SOURCE WATERBODY DESCRIPTIONS

This section describes the cooling water intake structure of the McGuire Nuclear Station, its operation, and its cooling wate r source, Lake Norman.



### McGuire Nuclear Station

McGuire Nuclear Station (MNS) in located in Huntersville, Meck lenburg County, North Carolina on Lake Norman, an impoundment of th e Catawba River formed by the Cowans Ford Dam (Figure 2-1). MNS has two nuclear reactor units, each with a net ge neration capacity of 1,129 MW for a total rating of 2,258 MW. MNS uses once-through cool ing for its steam condensers. Unit 1 began commercial operati on in December 1981 and Unit 2 began in March
1984.

Cooling Water Intake Structure

MNS has a shoreline intake struct ure and two lower level intakes located near the Cowans Ford Dam at a distance of approximately 550 m from the shoreline intake (Figure 2-2). The lower level intakes are designed to w ithdraw cooler water from a de pth of approximately 30 m when the lake is stratified during summer, in orde r to meet NPDES permit-imposed thermal criteria and to increase generation efficiency. The Unit 2 lower level intake has been retired, and the Unit 1 lower level intake is only used sparingl y (e.g., two weeks per year) due to concern for lowering the lake’s thermocline and depleting the hypolimnion. If the thermocline would be lowered, it would affect the operation of Duke’s Marshall Steam Station (MSS), which draws its cooling water from a depth greater than 18.3 m.

The shoreline intake structure has eight 7.9-m wide bays, four for each unit. Each bay splits to house two trash rack structures with 11.4-cm on- center bar spacing and two conventional vertical traveling water screens. The traveling screens are 30.5 m wide and have 3/8-in. (9.5-mm) square woven-wire, stainless steel mes h. Downstream from the screens the bays converge for a single circulating pump (four per unit, or eight total pumps for the facility). Each of the eight circulating pumps is rated at 254,000 gpm (566 cfs) for a tota l design flow rate of 2,032,000 gpm (4,528 cfs) at 7 m of head. Generally, two circ ulating pumps per unit are operated during late fall to early spring, and three pumps per unit ar e operated during the remainder of the year.

Cooling water withdrawn from the lower level intake near Cowens Ford Dam for Unit 1 is pumped by three 150,000-gpm pumps up to the shor eline intake and mixe s with the shorelinedrawn water in the forebays in front of the travel ing screens. The lower level intakes have trashPlant and Source Waterbody Descriptions

2-2 racks similar to those on the shoreline intake. During late summer and early fall, hypolimnetic water is withdrawn through the lo wer level intake as necessary to maintain lower containment temperatures and discharge temperatures with in permit specifications (Barwick et al. 2003).

The approach velocity in front of the traveling screens is 0.9 ft/s (0.3 m/s), assuming a flow of 283 cfs per screen at low water level (Alden 2004 ). The screens are rotated weekly (or more frequently if necessary) for cleaning by a high-pre ssure (85-psi) spray wash system. Debris and fish are washed into a trough leadin g to trash bins on either side of the intake structure. Heated water is discharged into a 91-m long discharge canal 168 m to the east of the intake (Figure 2-2).

Plant Operation and Water Withdrawal

Total generation and condenser cooling water pu mping data are presented in Table 2-1 for 2000 through 2007. Over this period, the average annual capacity factor, based on Maximum Net Dependable Capacity, was 94.5 percent. The aver age total annual intake flow rate for 2000-2007 was 89.7 percent of the maximum design capaci ty, 2,264cfs or 1,463 MGD for the upper level cooling water pumps (Table 2-1). Annual flow s ranged from 85.8 percent (2005) to 91.2 percent (2004) of the maximum design capacity for the upper level cooling water pumps.



### Lake Norman

Geomorphology and Aquatic Habitat

Lake Norman is an impoundment of the Catawba River formed by the Cowans Ford Dam (Figure 2-1). The Catawba River Basin lies in the south-central por tion of western North Carolina and has its source in th e eastern slopes of the Blue Ridge Mountains in Old Ford, McDowell County, North Carolina. From its sour ce, the Catawba River flows eastward, then southward toward the City of Charlotte. The Catawba River Basin and the Broad River Basin join to form the headwaters of the Santee-Cooper River system.

Lake Norman is located in the portion of th e Catawba River Basin designated as the Middle Catawba River Subbasin 32, which lies within the North Carolina Piedmont physiographic region (Hogan 1981) and the Northern Inner Pied mont and Southern Outer Piedmont ecoregions (NCDENR 2003). The underlying rock in the Pi edmont geologic province predominantly includes the Inner Piedmont and Charlotte be lts. Rocks of the Inner Piedmont belt are metamorphic in origin and consist almost enti rely of mica gneisses a nd schists, with lesser amounts of hornblende gneiss and granite (Hogan 1981). Rocks of the Ch arlotte belt are of plutonic and metamorphic origin a nd consist largely of granites, di orites, and gabbros. Soils are acidic, highly leached, and weathe red clay subsoils, with slow percolation rates (Hogan 1981).

Lake Norman and the Cowans Ford Dam are part of a system known as the Catawba Chain of Lakes formed by seven Duke Energy hydroelectri c dams. The seven lakes consist of Lake James, Rhodkiss Lake, Lake Hickory, Lookout Shoals Lake, Lake Norman, Mountain Island Lake, and Lake Wylie. The lakes were created between 1904 and 1928, except for Lake Norman, which was created in 1963. Lake Norman is the largest reservoir in the Chain of Lakes2-3 and lies between Lookout Shoals Lake upstrea m to the north and Mountain Island Lake downstream to the south.

The surface area of Lake Norman is 13,156 ha, it s mean depth is 10 m, and it drains a 4,636-km 2 watershed (NCDENR 2003). Lake Norman is 54 miles long from the tailrace of Lookout Shoals Lake downstream to Cowans Ford Dam (NCDENR and NCWRC 2001). MNS is at the southern tip of the lake. Major tributaries to Lake Norm an are Lyle Creek and Buffalo Shoals Creek.

Land use in Subbasin 32 is 54 percent forested, 31 percent pasture, 9 percent water, and 3 percent each for urban and cultivated crop land. Th e primary use of Lake Norman is for cooling water at MNS and MSS and for hydroelectric ge neration at the Cowens Ford Dam. The secondary use is public recreation.

Lake Norman provides an important recreational fishery for the region, particularly for striped bass, largemouth bass, and black crappie. Striped bass do not repr oduce naturally in the reservoir and have been stocked annually (Van Horn 2001). The lake is managed for these game species and the forage species upon which they are dependent, such as shad species. Other game species include blue catfish, ch annel catfish, flathead catfish, white bass, white perch, yellow perch, white crappie, spotted bass, and several sunfish species such as bluegill. Several fishing tournaments are held on the lake for striped bass, largemouth bass, and catfish (e.g., blue catfish) by local and national organizations.

Water Quality

Lake Norman is characterized as being oligot rophic with low nutrien t values and low algal production, and is classified as a water s upply, WS-IV (NCDENR 2003, 2008). Based on longterm mean phytoplankton concentration, the lake might be classified as oligo-mesotrophic (Duke 2006). Water quality sampling by the NCDENR Division of Water Quality during MaySeptember 2007 recorded Secchi disc readings of 1.8-2.6 m, low total phosphorus concentrations (usually below detection limits), low to moderate ch lorophyll a concentrati ons, and low ammonia and total organic nitrogen concentrations (N CDENR 2008). However, nitrite plus nitrate concentrations were elevated.

Mean ambient surface water temperatures range from <7 o C (44.6 o F) in January to 30-32 o C (86- 89.6 o F) in August (Duke 2004a). The lake begins to stratify thermally in April or May, and fall turnover occurs by November. In the summer, the thermocline is approximately at 15-20 m depth. Surface DO concentration typically ra nges from 6 to 11 mg/L, but hypolimnetic DO concentrations usually are <5 mg/L from June to November and are near 0 mg/L in August to October (Duke 2004a). Anoxic conditions in the hypolimnion are more prevalent during particularly warm summers.

Water quality monitoring by Duke has shown pH ranging from 6.2 to 7.4, low surface turbidity (1.02-5.05 NTU), low conductivity (69-110 mhos/cm), and heavy metal concentrations that do not exceed state water quality standards, alt hough iron and manganese can be released from bottom sediments during anoxic conditions (Duke 2004a). Surface DO concentrations uplake can exceed 110 percent saturation, as in 2002 (N CDENR 2003). Nutrients and chlorophyll aPlant and Source Waterbody Descriptions

2-4 concentrations in Lake Norman remain low or less than detection limits. The biggest water quality hazard for the lake is the infestation of the exotic macrophytes Hydrilla and Myriophyllum , which can decrease fish habitat an d impact recreation (NCDENR 2003). Macrophyte control using herbicides and triploid grass carp ( Ctenopharyngodon idella ) stocking has been conducted in 2006-2007 through a joint effort by Duke, the Lake Norman Marine Commission, and the N.C. Divison of Water Re sources (NCDENR 2008). There are no fish consumption advisories except for the stat ewide advisory for bowfin due to mercury
contamination.

The Catawba River Basin is the most densely pop ulated river basin in North Carolina, with a population exceeding 1 million persons, inclusive of the City of Ch arlotte (NCDENR and NCWRC 2001). Because the river basin faces unus ually high development pressures, a Catawba River Basin Natural Resources Plan has been prepared by the NCDENR and the North Carolina Wildlife Resources Commission (NCWRC), with input from multiple plan participants including Duke, for the protection and enhancement of the basin’s natural re sources (NCDENR and NCWRC 2001). This Natural Resources Plan complements the Catawba River Basinwide Management Plan and assigns priorities for sp ecific resources or issues. The upper portion of Lake Norman has been assigned the top priority (I) due to its lower level of development and more natural riverine environment and resour ces (e.g., shoreline and wetland habitats). The lower portion of Lake Norman has been assigned medium priority (II), with emphasis on its high recreational demand. Fish and wild life habitat are to be protected and enhanced in both areas.2-5Figure 2-1 Location of MNSPlant and Source Waterbody Descriptions2-6Figure 2-2 Aerial View of MNS2-7Table 2-1 Monthly Mean Cooling Water Flow Rate (MGD) and Percentage of Maximum Flow Rate and Net Capacity Generation at MNS,2000-2007Capacity FactorsYear Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual2000 102.3 96.9 105.5 105.2100.4 102.7 100.8 92.1 52.0 80.4 101.2 105.3 95.42001 94.2 104.4 65.7 73.2104.2 102.8 96.8 101.3 102.0 103.7 104.3 103.8 96.42002 105.1 92.9 50.7 104.7104.0 102.6 101.0 97.3 72.0 83.6 104.4 103.6 93.52003 102.5 105.2 104.4 103.9102.3 102.8 101.4 100.3 58.2 89.6 103.8 104.9 98.32004 105.1 105 60.8 82.7 103.8 102.3101.3 101.2 101.9 79.5 84.4 104.9 94.42005 105.2 105 53.2 67.6 104.1 103.3100.7 101.3 77.7 70.6 101.1 101.7 91.02006 105.5 105.5 105.2 105 103.2 102.8101.5 101.4 76.2 51.6 82.9 105.3 95.52007 105.4 105.3 64.5 52.4 53.1 100101.9 101.4 101.6 102.9 104.5 105.1 91.5Average 103.2 102.5 76.386.8 96.9 102.4 100.7 99.580.2 82.7 98.3 104.3 94.5Actual Plant Flow Rate (MGD)Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual2000 2,500 2,500 2,503 2,6532,900 2,900 2,900 2,900 1,683 2,694 2,857 2,500 2,6352001 2,500 2,500 1,687 2,2732,829 2,900 2,900 2,900 2,900 2,894 2,900 2,771 2,6782002 2,500 2,361 1,800 2,6272,900 2,900 2,900 2,900 2,187 2,858 2,900 2,561 2,6212003 2,500 2,514 2,500 2,5002,845 2,900 2,900 2,900 1,927 2,877 2,900 2,755 2,6602004 2,506 2,500 1,635 2,5002,881 2,900 2,900 2,900 2,900 2,900 2,837 2,500 2,6692005 2,500 2,500 1,326 2,2802,865 2,900 2,900 2,900 2,327 2,326 2,797 2,500 2,5112006 2,500 2,500 2,503 2,7832,900 2,900 2,900 2,900 2,263 2,181 2,700 2,516 2,6392007 2,500 2,500 1,639 1,8372,900 2,900 2,900 2,900 2,900 2,900 2,827 2,500 2,609Average 2,501 2,484 1,949 2,432 2,877 2,900 2,900 2,9002,386 2,704 2,840 2,575 2,621Percentage of Maximum Flow Rate (4,528 CFS or 2,926 MGD)Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual2000 85.4 85.4 85.6 90.799.1 99.1 99.1 99.1 57.5 92.1 97.6 85.4 89.72001 85.4 85.4 57.7 77.796.7 99.1 99.1 99.1 99.1 98.9 99.1 94.7 91.02002 85.4 80.7 61.5 89.899.1 99.1 99.1 99.1 74.7 97.7 99.1 87.5 89.62003 85.4 85.9 85.4 85.497.2 99.1 99.1 99.1 65.8 98.3 99.1 94.2 90.92004 85.7 85.4 55.9 85.498.4 99.1 99.1 99.1 99.1 99.1 96.9 85.4 91.22005 85.4 85.4 45.3 77.997.9 99.1 99.1 99.1 79.5 79.5 95.6 85.4 85.82006 85.4 85.4 85.6 95.199.1 99.1 99.1 99.1 77.4 74.5 92.3 86.0 90.22007 85.4 85.4 56.0 62.899.1 99.1 99.1 99.1 99.1 99.1 96.6 85.4 89.2Average 85.5 84.9 66.683.1 98.3 99.1 99.1 99.181.5 92.4 97.0 88.0 89.73-1 

# 3

FISH COMMUNITY DESCRIPTION

This section describes the fish community in La ke Norman. The sources and types of available historical and recent information on the fish community are described first. The species composition and structure of the fish community then are discussed. Finally, the general life history of fish species comm only found in impingement samp ling at MNS are discussed as background information that might provide insi ghts on annual or seasonal susceptibility to impingement.



### Description of Available Information

Duke conducted extensive ecological investigat ions of Lake Norman during 1973-1980 (Hogan and Adair 1981). These investigations, and pa rticularly the fisherie s studies, provide a description of the aquatic habitat and fish co mmunity of Lake Norman during a portion of its transformation from a riverine to lacustrine e nvironment, which began when the Catawba River was impounded in 1963 to form Lake Norman. Fish eries surveys were conducted by Siler et al. (1981) from August 1973 through December 1980.

Sampling methods included boat electrofishing, 27-m long variable-mesh (2.5 to 5.1-cm mesh) gill nets, rotenone for cove sampling, 2-m by 3-m or 1.5-m by 2-m mid-water Tucker trawls, and a 0.91-m diameter conical ichthyoplankton net (Sile r et al. 1981). Boat electrofishing was quarterly at four to five lo cations in Lake Norman during 1974 through 1979 and monthly during June 1978 through May 1979. Gill netting was quarte rly at three or four locations during 1974 through 1979 and monthly at five locations during June 1978 through May 1979. Rotenone sampling in lake coves was conducted annually in la te June or early August at three locations. Mid-water trawling at four lo cations was conducted monthly from July 1978 through April 1979 and quarterly from April 1979 through Apr il 1980. Ichthyoplankton sampling was either biweekly or weekly at up to five locations . A special study was conducted on 21 February 1975 to investigate the relative abundance of fish sp ecies within the intake cove by using boat electrofishing.

Under an agreement with the NCDENR, D uke has performed annual physicochemical, macroinvertebrate, and fish community monitoring of Lake Norman since 1993 (Duke 2001, 2003, 2004a, 2004c, 2005, 2006, 2007). The fish community is monitored using boat electrofishing and a combination of hydroacousti cs, purse seining, and sometimes gill netting. For these fisheries assessments, Lake Norman is divided into five zones. MNS is located in Zone 1 (Figure 3-1). Special sampling programs also have been conducted to monitor striped bass summer mortalities; age, species and si ze composition of forage fish; and cooperativelyFish Community Description

3-2 with North Carolina Wildlife Resources Commi ssion (NCWRC), age, growth and condition of striped bass by gill net sampling; and age and growth of crappies by trap net sampling.

The spring electrofishing program samples three lo cations in late March and early April: near MSS in Zone 4, a reference area in Zone 3, and near MNS in Zone 1 (Figure 3-1). At each location, ten 300-m shoreline transects are sa mpled. These transects were found to be representative of habitat types found in Lake No rman, and have been sampled consistently since 1993. Electrofishing is conducted du ring daylight when water temperatures are expected to be
15-20 o C.

Hydroacoustics sampling techniqu es and purse seining are used to assess the forage fish populations throughout the entire la ke and its tributaries, and da ta are available for the period 1993-2006 (Duke 2004b, 2007). Sampling is conducted at night during July, September, or November. For the hydroacoustics surveys, all six zones in Figure 3-1 are included. The hydroacoustics gear consists of a multiplexing 200- kHz digital transducer system with side-scan split-beam and down-looking dual-beam transducers. The side-scan transducer samples the top 2 m of the water column, and the down-looking tran sducer samples the remainder of the water
column 1 . The output is integrated to estimate fish densities at 0.25-km intervals along sampling transects, and the estimated zonal densities are summed to estimate total lake standing crops. Species and size composition data are provided by purse seining at night using a 400-ft (121.9- m) by 30-ft (9.1-m) purse seine with 3/16-in. (4.8-mm) mesh.

Duke conducts an electrofishing survey in July in the vicinity of MSS in addition to the lakewide spring electrofishing survey described above. This summer electrofishing program samples five stations located in coves of Lake Norman in July during daylight hours (Duke 2004b). One sampling station is up-lake from the MSS intake in Zone 4 and is used as reference data, two stations are near the MSS discharge in Zone 4, and two are downlake near the middle of Lake Norman in Zones 3 and 4. Shoreline segments that are 100-m in length are sampled on the right and left banks of each cove.



### Species Composition

A composite of records of fish species collected during fisheries surveys of Lake Norman from 1974 to 2006 indicate that 58 species and two hybrid varieties have been found in the reservoir since 1974 (Table 3-1). The total number of re ported species decreased from 48 to 32 during the interval from 1974-1980 to 2004-2007. This decrease in species richne ss could be an artifact of differences in sampling methodology, but more likely is the result of the e volution of the fish community from a riverine community to a l acustrine community following the impoundment of the Catawba River. Examples of typically lotic species (Rohde et al. 1994, Pflieger 1997) that have not appeared recently in survey catches incl ude cyprinids such as whitetail shiner and creek chub; catostomids such as white sucker, silver redhorse, V-lip redhorse, br assy jumprock, striped jumprock, and creek chubsucker; and ictalurids such as snail bullhead. Other species not found

1 Prior to 1996, only the down-looking transducer was used.3-3 since 1980 include the river ca rpsucker, smallmouth buffalo, yellow bullhead, and western mosquitofish.

Recently, electrofishing has indicated that the nu merically dominant shore-zone species in the sampled coves are bluegill and redbreast sunf ish (Duke 2007). In terms of biomass, the dominant species are the spotte d bass, largemouth bass, and common carp. Some species have only recently appeared in survey catches, such as alewife, white perch, goldfish, striped mullet, and spotted bass (Table 3-1). These species have not been st ocked by the NCWRC and probably were introduced accidentally or intentionally by anglers. The spotted bass and white perch, in particular, have become established and support ac tive recreational fisherie s. White perch first appeared in 1998 and spotted bass in 2001. There is concern that spotte d bass and white perch may be competing with largemouth bass and white bass, and could be resp onsible for declining populations of these latter two species (Duke 2007, NCWF 2008).

The introduction of alewife to the lake in 1999 ha s affected the composition of the pelagic forage fish community in the lake in re cent years. Prior to the year 2 000, over 99 percent of the forage fish caught by purse seine duri ng the hydroacoustic surveys were threadfin shad (Duke 2007). The percentage of the forage fish catch cons isting of alewife increa sed to 25 percent in 2002, then began to decline again until it was appr oximately 2-5 percent in 2005 and 2006. Gizzard shad have constituted less than 0.5 per cent of the forage base since 1993.



### Protected Species

No fish species currently listed as federal or st ate endangered or threaten ed species have been
collected in Lake Norman. Ther e are, however, three fish species listed by the North Carolina Natural Heritage Program (NCNHP) for Mecklenbur g County as rare animal species for North Carolina (LeGrand et al. 2008). These are Atlantic highfin carpsucker ( Carpoides sp. cf. velifer ), the Santee chub, ( Cyprinella zanema ), and the Central Piedmont population of the Carolina darter ( Etheostoma collis pop. 1). The Atlantic highfin carpsuc ker is currently listed by NCNHP as a state species of concer n with a state ranking of S1 2 . The Santee chub is listed as a significantly rare species with a state ranking of S3 3 . The Central Piedmont population of the Carolina darter is listed as a species of concern with a state ranking of S 3. It is unlikely that these three species would occur in Lake Norman since they prefer lotic environments (Rohde et al. 1994).



### Target Species

Among all fish species found in Lake Norman, a s ubset of species was selected for a detailed evaluation of impingement mortality presently occurring at the MNS cooling water intake.

2 S1=Critically impaired in North Carolina due to extreme rar ity or some factor(s) making it especially vulnerable to extirpation from the state.

3 S3=Vulnerable to extinction in North Carolina because of rare or uncommon, or found only in a restricted range (even if abundant in some locations), or due to other factors making it vulnerable to extirpation.Fish Community Description

3-4 These species are most frequently observed in impingement collections, or are important because of their economic value or value to the ecosystem. The selected target species include threadfin shad, alewife, white perch, bluegill, striped bass, white bass, channel catfish, and blue catfish.

The threadfin shad dominates the pelagic fish community in Lake Norman as well as impingement collections at the MNS intake (Section 4). Although much less abundant, the alewife, like the threadfin sha d, is an important component of the forage base for the recreationally important fish species in Lake No rman. For these reasons, both threadfin shad and alewife were selected as target species for deta iled evaluation. The two catfish species—channel catfish and blue catfish— are traditionally im portant game species in Lake Norman. White perch, a newcomer to the fish community, has be come abundant in the sportfishing catch in the
lake and ranked third in abundance in the 2000-2002 impingement samples (Section 4). The other two temperate bass species, striped bass and white bass, are among the most popular game fish in the lake. In particul ar, striped bass is the primary ga me species managed in the lake through annual stocking and programs that monito r the health of the st riped bass population and its forage. Bluegill was th e fourth-most frequently impi nged species in 2000-2002 and is a popular panfish species and a forage species fo r some gamefish such as largemouth bass.

This section presents background information on the life history of these eight species.

Threadfin Shad

Historically, the threadfin shad has been the mo st abundant pelagic species in Lake Norman. Threadfin shad is an important forage base for several predator species that provide the recreational fishery of Lake Norm an, including the striped bass, largemouth bass, spotted bass, catfish species, and crappie. Threadfin shad is an excellent forage species because of its size, which seldom will exceed 150 mm, and its great pr oductivity. It is a planktivore, relying on filter feeding through its gill rakers . Threadfin shad were introduced into Lake Norman after its impoundment (Siler et al. 1981).

Threadfin shad spawn when water temperatures reach 65-70 o F (18.3-21.1 o C) and can have multiple spawning peaks through the spring, summe r and early fall (Plfieger 1997, Smith 2002). In the late 1970s, clupeid larvae, which include d threadfin shad and gizzard shad, were caught during ichthyoplankton sampling in Lake Norman from April through August, peaking in May and June (Siler et al. 1981). Spawning primarily occurs from dawn to shortly after sunrise as spawning schools gather along the sh oreline. The adhesive eggs are broadcast over submerged objects and hatch within three days . Young threadfin shad grow very rapidly (up to 25 mm per month), with many reaching maturity and spawning by the end of their first summer at 64 mm in length. Females generally grow larger and live longer than males, with a maximum age of about four years for females and three years for males.

For habitat, threadfin shad prefer open water ove r sand, mud or debris. Threadfin shad tend to be more abundant in the northern port ions of the lake rath er than the southern portions nearer MNS, possibly due to differences in habitat or nutrient levels and productivity among in lake zones (Siler et al. 1981, Duke 2004b). The continued ex istence and relative ab undance of threadfin shad, which is intolerant of water temperatures below 10 o C (Ruelle et al. 1977, Griffith 1978), in3-5 Lake Norman may be dependent upon the therma l input from MNS and MSS, and the thermal refuges they provide during the winter.

Alewife

The alewife is a re lative newcomer to the Lake Norman fi sh community, first appearing in 1999. Its introduction probably originated from angler releases, as it was not stocked by NCWRC. At the time of its appearance, threadfin shad dominated the forage fish base in Lake Norman. Threadfin shad continues to dominate pelagic fo rage species, but at its peak abundance in 2002, alewife may have comprised numerically as much as 25 percent of this pelagic forage fish base. Alewife was the second-most frequently im pinged species at the MNS intake in 2000-2002, behind threadfin shad (Section 4).

The alewife is an anad romous clupeid that is indigenous to the Atlantic Coast from Newfoundland to South Carolina an d spawns in coastal freshwat er or brackish rivers and tributaries (Pardue 1983). Landloc ked populations have long been established in the Great Lakes and several northern inland lakes such as the Finger Lakes of New York. Rarely has this species been introduced to southern lakes or reservoirs but Claytor Lake in Virginia is such an example. Studies at Claytor Lake, a mesothermal lake with temperatures ranging from 2 o C to 27 o C (Kohler and Ney 1981, Nigro and Ne y 1982), may provide insights into the general life history of the alewife in a southern re servoir such as Lake Norman.

Nigro and Ney (1982) found alewives in Claytor La ke to be shorter-lived than alewives in northern landlocked populations, while achieving maturity earlie r and having higher absolute and relative fecundity. They attributed these differe nces to a longer grow ing season in the south, rather than accelerated growth rates. Maturity was reached at approximately the same size as their northern counterparts. Eight y-six percent of age-1 females we re mature at a median length of 160 mm total length (TL) while all age 2 and ag e 3 females were mature. Maximum first year growth was 130-160 mm.

In Claytor Lake, as may happen in Lake Norman, alewives move inshore in large concentrations to spawn in the spring and early summer. Ripe ma les were first seen in the littoral zone when water temperatures were 13 o C, and spawning was first obs erved in early May at 16-18 o C (Nigro and Ney 1982). Peak egg densities occurr ed in the third week of May at 21-23 o C, then declined during June through July. This extended spawni ng season was interpreted as possibly indicating fractional spawning, i.e., repeated egg deposition by individual females.

Alewife eggs initially are demers al and adhesive, but when water-hardened they become pelagic and lose their adhesive propert ies (Pardue 1983). Egg incubation lasts from 36 hours to 6 days, depending on water temperature (Carlander 1969, Au er 1982). The yolk sac is absorbed in 2-5 days at a length of 5.1 mm (Pardue 1983) and larv ae transform to the juvenile stage at 20 mm. Early life stages are positively phototaxic and pe lagic. The principal food items are diatoms, copepods, and ostracods (Carland er 1969). Adults are size-sel ective planktivores feeding on cyclopoid copepods, and occasionally are pisc ivorous (Kohler and Ney 1981, Nigro and Ney 1982).Fish Community Description

3-6 White Perch

White perch was the third-most frequently impinged fish species at MNS during 2000-2002 (Section 4). Like severa l other species, it is not native to La ke Norman. It likely was introduced to Lake Norman by anglers, and first appeared in 1998. Since then, it s population has grown rapidly, and it now supports a recr eational fishery in Lake Norman. There is, however, the fear that its establishment has affected or will affect the fishery for other species, such as white bass, crappie, largemouth bass, and striped bass. While the white perch popul ation has expanded, the white bass population has become decimated, possibl y due to predation on the eggs or fry of white bass ( http://www.ncwildlifederation.or g/home/lakenormanfishery.htm ) or through competition for food. There is also the fear that eventually white perch will become overpopulated and stunted. Most adult white perch in Lake Norman are 150-305 mm long and <0.5 lb (227 g).

White perch is distributed ge ographically along the Atlantic Coast from Canada to South Carolina. In coastal areas, it is semi-anadromous, leaving brackish water to spawn in freshwater. It has become established in inland lakes, in cluding the Great Lakes, and through stocking in several states in the eastern and central US (Rohde et al. 1994). It also recently has invaded the Mississippi River system (Irons et al. 2002) and the Arkansas Rive r system as far as Oklahoma (Harris 2006). In the southeast, white perch has established popul ations in the Kerr Reservoir in Virginia and North Carolina, and the B. Evere tt Jordan Reservoir in North Carolina (Harris 2006).

There is little or no information on the life hist ory of white perch in Lake Norman. Based on studies elsewhere, spawning in freshwater lake s occurs in April and May (Stanley and Danie 1983). In the Hudson River, peak spawning occurred at water temperatures of 16-20 o C (Klauda et al. 1988). Eggs are broadcast at depths of <12 ft (3.7 m). The demersal and adhesive eggs attach to vegetation and other firm substrates, an d no parental care is given to the eggs or young. The eggs hatch in 30 hours at water temperatures of 20 o C, or may take as long as 96-108 hours at
15 o C. The yolk-sac life stage lasts 3-5 days until a length of 3.5-4 mm is reached (Klauda et al. 1988). Juveniles tend to be demersal in depths of 8-12 ft (2.4-2.7 m) (Stanley and Danie 1983).

In daylight, white perch school in open water, of ten over shoals or brush piles, and at night go inshore. Young white perch feed on zooplankton such as copepods, cladocerans, and ostracods (Prout et al. 1990). Adults cons ume benthic invertebrates and fish eggs, and when larger than 80-150 mm are primarily pisciv orous (Harris 2006).

Males mature slightly earlier than females, beginning at age 2 when males are 100-110 mm TL and females are 110-120 mm TL (Klauda et al. 19 88, Rohde et al. 1994). Most are mature by age 3-4. Maximum age is approximately 17 year s but few are older than age 7. Fecundity ranges from approximately 5,000 to 300,000 eggs de pending on female size (Stanley and Danie 1983). In Kerr Reservoir, North Carolina, whit e perch reach a mean length of 104 mm at age 1, 175 mm at age 3, 239 mm at age 5, 264 mm at ag e 7, and 303 mm at age 9 (Harris 2006). Angler exploitation of white perch on Kerr Re servoir begins at lengths of 150-200 mm TL.3-7 Bluegill

The bluegill, along with redbreast sunfish, is numerically the most abundant species in the Lake Norman fish community. While it may be too sma ll to attract most fishermen in Lake Norman (Siler et al. 1981), it is an important prey species, particularly largemouth bass. The bluegill is native to much of the eastern and central U.S. a nd occurs in warm, slow or still water, usually associated with aquatic vegetation and woody debr is (Rohde et al. 1994). Individual movements tend to be highly localized. Its diet consists mo stly of invertebrates, but larger bluegills may become piscivorous.

In the Middle Atlantic region, bluegill spawn during May and June when water temperatures reach 70 o F (21 o C) (Rohde et al. 1994). The spawning season can be protracted over several months. Bluegill are col onial breeders in the sense that spawni ng fish build nests that are usually in close proximity to each other. Males constr uct nests that are about 0.3 m in diameter in shallow water (depths of 0.3-0.9 m). The eggs from several females can be fertilized and deposited in the nest, which is then defended by the male until the eggs have hatched. Because the nests are located in shallow depths, water le vel fluctuations can severely impact successful reproduction. Nests and young can be stranded by a lowering water level or disrupted by severe wave action (Heman et al. 1969), or surviv al of the young may be reduced by increased ultraviolet light radiation in highly tr ansparent water (Ols on et al. 2008).

Bluegill in the southeastern U.S. commonly be gin to mature by at age 1 or 75-125 mm for both sexes (Spotte 2007) and can live up to 11 years. Most adults do not exceed 0.5-0.75 lb (227-340 g) (Rohde et al 1994).

Striped Bass

The striped bass fishery in Lake Norman is a “put-grow-and-take” fishery maintained by annual stocking of 162,500 fingerling fish in late spring. Striped bass were first introduced into the lake in the late 1960s or early 1970s with annual stockings of approximate ly 100,000 fingerling fish (Van Horn et al. 1999). While this has crea ted a very popular recreational fishery, there are indications that growth and conditi on of the fish are limited by the forage base in the lake (Van Horn et al. 1999, Van Horn 2001, Thompson et al. 2005, Davias 2006), as well as summer water temperatures and dissolved oxygen depletion (Lewis 1983, Van Horn et al. 1996, Thompson et al. 2005, Davias 2006). As a result , growth rates for striped bass in Lake Norman are slower than for several other North Carolina reservoi rs (Davias 2006). The NCWRC very actively manages the lake’s striped bass fishery thr ough size and creel limits, forage fish density monitoring, and experimentation with stocking rates to increa se the growth, condition, and standing crop of striped bass in the lake. Striped bass is largel y a pelagic species, feeding on pelagic clupeids including threadfi n shad, alewife, and blueback herring and gizzard shad when present.

Thompson et al. (2005) observed st riped bass in Lake Norman to average 269 mm TL at age 1, 424 mm TL at age 2, 499 mm at age 3, 535 mm at age 4, 553 mm at age 5, 561 mm at age 6, 566 mm at age 7, and 568 mm at age 8. Earlier, Van Horn et al. (1999) had reported age-specificFish Community Description

3-8 mean lengths at time of capture during 1994-1998 to be 413-533 mm TL at age 2, 487-569 mm at age 3, 533-588 at age 4, 541-641 mm at age 5, and 604-690 mm at age 6.

White Bass

The white bass is rated by anglers as a fair to good food fish and an excellent sport fish. In the mid-Atlantic region, white bass is most successful in large reservoirs in the piedmont and mountains (Rohde et al. 1994). It is a schooling species that pr efers open, deeper areas in streams, rivers, and lakes (Rohde et al. 1994, Pfli eger 1997). The primary prey species for white bass is gizzard shad or thread fin shad (Rohde et al. 1994, Guy et al. 2002). The abundance of white bass in Lake Norman recently has been d eclining, possibly as the result of interspecific competition with or predation by introduced spec ies such as the white perch. However, it remains a popular sport fish in Lake Norman.

White bass begin to spawn in April or May when water temperatures reach 60 o F (15.6 o C) and they migrate from open waters into tributarie s streams (Rohde et al. 1994). Spawning occurs over rocky or gravelly areas (Pflieger 1997). Whit e bass broadcast their eggs, which then adhere to rocks or debris. They provide no parental care. The free-swimming fry and young begin to school and gradually add small fish to their diet. For the first 2 months post-hatch, growth rates can average 0.08 mm/day, then increase to 0.56 mm/ day thereafter (Kindschi 1979, in Quist et al. 2002a). In Glen Elder Reservoir, Kansas the gr owth rates for larvae 3 to 35 days old were 0.32 mm/day (Quist et al. 2002). Annual survival ra tes and recruitment have been observed to be highly variable (Schultz and R obinson 2002, Lovell and Maceina 2002).

As adults, white bass typically are fast growi ng and short-lived, often experiencing relatively high fishery exploitation rate s (Guy et al. 2002, Lovell and Maceina 2002, Colvin 2002, Schulz and Robinson 2002). In Missouri reservoirs, most age-0 white bass were 150-230 mm long by the fall. Colvin (2002) found similar age structure for white bass in four large Missouri reservoirs, where the oldest fish were age 7, but there was a sharp decline in abundance and growth after age 4 when they reach 370-400 mm in le ngth. They mature at ages 2-3 at a length of approximately 8-10 in. (203- 254 mm) (Sallee et al. 2004). White bass in the Upper Mississippi River system can reach a maximu m length of 18 in. ( 457 mm) and a maximum weight of 3 lb (1.4 kg). Females produce more ova than they shed during spawning, leading Ruelle (1977) to conclude that the averag e calculated “effective fecundity” is 124,000-134,000 eggs per 300-mm female and 429,000- 608,000 eggs per 390-mm female.

Channel Catfish

A total of 73 channel catfish were collected during impingeme nt sampling at MNS in 2000-2002, making it the seventh-most frequently impinged sp ecies (Section 4). Cha nnel catfish is a longterm resident of Lake Norman and historically has supported commercial or recreational fisheries on the lake (Siler et al. 1981).

The channel catfish is a very important and hi ghly desirable commercia l and recreational fish species throughout its geographic dist ribution and in North Carolina. It is native to the central3-9 part of North America (Smith 1985), but it has b een stocked in rivers and reservoirs throughout the southeast region. It occurs in a variety of habitats and is esp ecially characteri stic of large, turbid streams and rivers that have a low or mode rate gradient. In Lake Moultrie, South Carolina channel catfish can reach up to 58 lb (26 kg) in size (Rohde et al. 1994).

Channel catfish spawn in late spring and ear ly summer when water temperatures reach 65 o F (18.3 o C) or more (McMahon and Terrell 1982, Pitlo et al. 2004). Spawning generally occurs over a range from 21 o C to 29 o C, with an optimal temperature of 27 o C (Hubert 1999). Sustained temperatures in this range (21 o C to 29 o C) in Lake Norman would correspond to June and July.

Several weeks prior to spawning, males select and clear suitable nest sites, usually consisting of secluded, dark areas such as hollow logs, drift pi les, undercut banks, muskrat or beaver burrows, or rip rap. A single male often will spawn with several females (Rohde et al. 1994). Eggs are deposited in a gelatinous mass. Inc ubation lasts for 5.5 to 10 days at 75-82 o F (23.9-27.8 o C) (Holland-Bartels and Duval 1988). The male tends the nest while eggs hatch and stays there for about one week after hatching to guard the fry. Early growth is variable among year classes and apparently is dependent upon existi ng conditions (Pitlo et al. 2004).

Adults may be found in many habitats including cha nnels and large open ar eas, but prefer habitat with woody debris, bank cavities and moderate curre nts (Koel et al. 1998). In daylight they seek depths with cover and current. At night or in rising water levels they feed near or on the bottom in shallower depths. Young feed largely on aquatic insects and other bent hic arthropods, but at 100 mm length become omnivorous with fish maki ng up a large part of their diet (Smith 1985).

Channel catfish begin to mature at age 4 a nd 305 mm in length, and 75 percent of females are mature by age 6 (Pitlo et al. 2004). The averag e fecundity is 6,088 eggs per lb of body weight.

Blue Catfish

The blue catfish is native to the Mississippi, Miss ouri, and Ohio river basins and is considered a big river species (Graham 1999). It is the largest catfish in the United States. The largest recorded blue catfish weighed 315 lb (142.9 kg) and was caught in the Missouri River just below Portland, Missouri in 1866 (Graham 1999). Duri ng the mid-1800s, it was common to catch blue catfish weighing 125-200 lb (45.4-90.7 kg). The North Carolina record was caught in Lake Norman; the record fish was 51.25 in. (1,302 mm ) in length and weighed 85 lb (38.6 kg). Maximum age is 18 years.

The blue catfish is an introduced species in Lake Norman, apparently being stocked by the NCWRC when Lake Norman was impounded. It was not detected until 1983, but its population has been growing rapidly ever si nce (Grist 2002). During this peri od, there has been a decline in the white catfish and snail bullhead populations. An active fishery has developed for blue catfish in Lake Norman, including tournaments specifically for this and other ca tfish species. Blue catfish dominate the catch and harvest of catfish species in Lake Norman, with 70 percent of the numbers caught and 77 percent of the biomass harv ested (Grist 2002). Nort h Carolina treats the blue catfish as a non-game species for which ther e is no catch limit, and the catch can be sold commercially.Fish Community Description

3-10 Blue catfish prefer open waters of large reservoirs and main channels, backwaters, and embayments of large flowing rivers where water is normally turbid and substrate varies from gravel-sand to silt-mud (Graham 1999). In Lake Norman, they are found at greater depths (e.g., >5 m) than channel catfish and prefer more open water (Grist 2002) . Clupeids such as threadfin shad and alewife are their primary food, but they also feed on mollusks such as the Asiatic clam Corbicula and on stonewort Chara (Grist 2002). They likely compete with the stocked striped bass in Lake Norman for clupeids.

Adult blue catfish in the lower reaches of Lake Norman have been shown to move up to 34 km or more to the upper, more riverine portion of the lake in the spring, possibly to spawn, then return in the fall and winter to the lower lake (Grist 2002). Mi gratory movements in rivers can span several hundred kilometers with movement upstream in the spring and downstream in the fall in response to water temperature (Lagler 1961, Pflieger 1997). Spaw ning in the Ohio River has been reported to occur at water temperatures ranging from 68 o F to 86 o F (20-30 o C), with optimum temperatures of 72-82 o F (22.2-27.8 o C) (Simon and Wallus 2003). In Lake Norman, water temperatures of 72-82 o F would occur in June and July.

Their spawning habits are believed to be simila r to channel catfish (Pflieger 1997, Hubert 1999). Blue catfish are cavity nesters and deposit eggs in protected ar eas behind rocks, root-wads, depressions, undercut streambanks, or other areas with minimal cu rrents. The male guards the eggs and fry. Egg diameters are between 3.0 and 3.3 mm, and fecundity ranges from 900 to 1350 eggs/kg of body weight (Graham 1999). Egg incubation lasts 168 to 240 hours at 75 to
79 o F (23.9-26.1 o C) in the Ohio River (Simon and Wallus 2003). Eggs hatch in 7-8 days at temperatures between 21 to 24 o C (Graham 1999; Pflieger 1997). Bl ue catfish yolk-sac larvae are 4.1 to 8.9 mm long when they hatch (Simon an d Wallus 2003), and youn g may grow slower during their first year than channel catfish (T idwell and Mims 1990). In Lake Norman, early growth rates and body condition are lower than in other impoundments (G rist 2002) but improve as the fish grow older and become more piscivorous.

Graham and DeiSanti (1999) aged 2,389 blue ca tfish collected from 1988-1995 at the Truman Dam Tailwater, Osage River, Missouri. The m ean back-calculated total lengths at annulus formation for the first eight years of life were as follows: 105 mm at age 1, 178 mm at age 2, 243 mm at age 3, 309 mm at age 4, 371 mm at age 5, 371 mm at age 6, 426 mm at age 7, and 484 mm at age 8. Blue catfish become sexually mature at about 381 mm in the Mississippi river near St. Louis (Graham 1999) and between 420-480 mm (a bout 6-7 years) in Lake of the Ozarks, Missouri (Graham and DeiSanti 1999).3-11 Figure 3-1 Sampling Zones and Locations for Lake Norman

.Fish Community Description3-12Table 3-1 Fish Species Collected in Lake Norman Fishery Surveys (Siler et al. 1981; Duke 2004a, 2004b, 2006, 2007)Family Scientific Name Common Name 1974-1980 1993-1999 2000-2003 2004-2007LepistosteidaeLepistosteus osseusLongnose gar X X XAmiidaeAmia calvaBowfin XClupeidaeDorosoma cepedianumGizzard shad X X X XDorosoma petenseThreadin shad X X X XAlosa pseudoharengusAlewife X XAlosa aestivalisBlueback herring* XSalmonidaeOncorhynchus mykissRainbow trout XCyprinidaeCyprinus carpioCommon carp X X X XCarassius auratusGoldfish XHypognathus regiusEastern silvery minnow X XNocomis leptocephalusBluehead chub X XNotemigonus crysoleucasGolden shiner X X XCyprinella analostanaSatinfin shiner ?Cyprinella chloristiaGreenfin shiner X X X XCyprinella galacturaWhitetail shiner XNotropis hudsoniusSpottail shiner X X X XCyprinella niveaWhitefin shiner X X X XSemotilus atromaculatusCreek chub XNotropis procneSwallowtail shiner X XPimephales promelasFathead minnow XCatostomidaeCarpoides carpioRiver carpsucker XCarpoides cyprinusQuillback X X X XCatostomus commersoniWhite sucker XErimyzon oblongusCreek chubsucker XIctiobus bubalusSmallmouth buffalo XMoxostoma anisurumSilver redhorse XMoxostoma macrolepidotumShorthead redhorse X X X XMoxostoma pappilosumV-lip redhorse XScartomyzonsp.Brassy jumprock XScartomyzon rupiscartesStriped jumprock X3-13Table 3-1 continuedFamily Scientific Name Common Name 1974-1980 1993-1999 2000-2003 2004-2007IctaluridaeAmeirus brunneusSnail bullhead XAmeirus catusWhite catfish X XIctalurus furcatusBlue catfish X X XAmeirus melasBlack bullhead XAmeirus natalisYellow bullhead XAmeirus nebulosusBrown bullhead XAmeirus platycephalusFlathead bullhead XPylodictis olivarisFlathead catfish X X X XIctalurus punctatusChannel catfish X X X XMugilidaeMugil cephalusStriped mullet XPoecilidaeGambusia affinisWestern mosquitofish XMoronidaeMorone chrysopsWhite bass X X XMorone saxatilisStriped bass X X X XMorone americanaWhite perch X X XCentrarchidaeLepomis auritusRedbreast sunfish X X X XLepomis gibbosusPumpkinseed X XLepomis gulosusWarmouth X X X XLepomis macrochirusBluegill X X X XLepomis microlophusRedear sunfish X X X XLepomis cyanellusGreen sunfish XMicropterus salmoidesLargemouth bass X X X XPomoxis annularisWhite crappie X X XPomoxis nigromaculatusBlack crappie X X X XLepomishybridSunfish hybrid X X XMicropterus punctulatusSpotted bass X XMicropoterushybridBlack bass hybrid XPercidaeEtheostoma fusiformeSwamp darter X XEtheostoma nigrumJohnny darter ?Etheostoma olmstediTessellated darter X X X XPerca flavescensYellow perch X X X XTotal species 48 26 29 32Total hybrids 0 1 1 24-1 

# 4

IMPINGEMENT MORTALITY

This section presents the results of a two-year impingement monitoring program conducted at MNS during 2000-2002. The results of this program are used to estimate annual impingement rates at the station and are applied in an evalation of the potential for adverse environmental impact, presented in Section 5.



### Impingement Monitoring Program

Weekly numbers impinged were obtained fr om impingement monitoring conducted by Duke from 3 December 2000 through 29 Novemb er 2002 (Barwick et al. 2003). On 3 December 2000, all screens were washed of all fish and debris. Thereafter, the screens were allowed to accumulate impinged fish for one week before the screens were washed again. At the end of each week, all debris a nd fish from each screen were collected in coated-wire baskets (5-mm x 10-mm mesh openings) placed in the screen-wash sluiceway. Fish were sorted from the debris and identified to the lowest practical taxon. Fish identified to species were measured fo r total length (mm). In addition, surface water temperatures near the intake structure we re recorded during each sampling period.

The numbers of fish impinged weekly on each screen were summed for all screens and reported in Barwick et al. ( 2003) as monthly totals. On occasion, mechanical problems regarding rotation and washing of screens we re encountered, and fish impingement could
not be determined for the affected screen dur ing a particular time period. In such cases, fish impingement for the missed sample was estimated to be that observed during the same period from the other paired screen for the specific circulating pump or from a similar time period immediately before the mi ssed sample (in the event that it was not possible to wash both paired screens). Duri ng plant outages and at other times when the pumps were not operational dur ing the weekly sampling period, the screens associated with those pumps were not washed and no fish impingement was assumed to have
occurred.

The weekly impingement collections dur ing 2000-2002 would represent a complete census of impingement, rather than a samp ling, as long as there were no losses of impinged fish during the weekly intervals be tween screen rotations. These losses could be caused by predators or scavengers taking im pinged fish off the screens, decay, or fish bypassing the screens or being tra pped in locations where they are not recoverable. Fish losses to such sources would result in an underestimation of the impingement rate at
MNS.Impingement Mortality

4-2 To address this concern, Duke conducted a sp ecial study to estimate the loss rate of impinged fish due to decay or other reasons during a weekly collection interval and to adjust impingement numbers to account for th ese losses (Barwick et al. 2005). Over a seven-day period (21-27 July 2005), a total of 1,600 fish were fin-clipped and introduced onto all 16 freshly washed upper level intake screens at MNS at periodic intervals.
Treatments consisted of the release of four lo ts of 400 marked fish each at intervals of seven, five, three, and one day prior to screen washing on 27 July. A set of four screens was randomly chosen for each of the four release dates (100 fish per screen), such that all 16 screens were tested once. At the end of this seven-day period, all screens were washed and all marked fish were collected.

The test fish (threadfin shad and a few alew ives) were collected from Lake Norman using a boat-mounted electrofisher during the morning on the day of introduction. Once sufficient numbers of fish were collected by electrofishing, they were transported to the Environmental Center fishery lab near MNS. In the lab, 400 fish were selected for use in each treatment and a subsample of 100 fish wa s randomly selected and measured for total length (mean 92-95 mm TL, range 77-116 mm TL). All fish were fin-clipped (complete removal of caudal fin) and bagged in groups of 100 and placed on ice.

The marked fish were introduced betw een 1030 and 1130 h onto individual intake screens by placing them in paper bags, att aching the bags to a weighted rope, and lowering the bags to the center of the trash rack associated with indivi dual intake screens. After a 3-minute waiting period, a sharp tug on the rope ruptured th e wet paper bags and released the fish directly in to the flow entering the intake bay. Condenser cooling water pump flows transported a portion of these fish onto the intake screens where they were impinged.



### Results

A total of 1,690 fish were collected in the first year of sampling, December 2000 – November 2001, and 698 fish in the sec ond year, December 2001 – November 2002 (Table 4-1). Over this two-year period, 23 fish species were identified in the impingement collections. Threadfin shad dominated the 2000-2001 collections, comprising 51.5 percent of the total, and alewife dominated th e 2001-2002 collections, comprising 23.8 percent (Table 4-1). Othe r commonly impinged species (in decreasing order for both years combined) included white perch (7.0 percent), bl uegill (6.6 percent), striped bass (3.9 percent), white bass (3.2 pe rcent), channel catfish (3.1 percent), and gizzard shad (2.6 percent). Ninety-four fish could not be identified to species, or approximately 4 percent of all fish collect ed during the two-year monitoring program.

The special study to assess impinged fish lo sses during a collection week was conducted at mid-summer surface water temperatures ranging from 31.7 °C to 32.5 °C near the intake. Therefore, adjustments to impingeme nt estimates to account for these losses would be conservative (overestimate losses) relative to months of cooler water temperatures and thus slower decay rates. Also, the test fish were threadfin shad or alewife, two species known to be fr agile and susceptible to rapid decay.4-3 Of the 1,600 fin-clipped fish released during the study, a total of 243 were recovered at the screen washing on the seventh day. Releas es of 400 marked fish on each of the four release dates resulted in 98 being recovered after one day on the sc reens, 93 after three days, 36 after five days, and 16 after seven da ys. These data showed a steady decline in the number of recovered fish through time, indicating a cumulative loss of impinged fish due to decay, predation, or other reasons. Barwick et al. (2005) presented photographic evidence of the effects of decay on the inte grity of the impinged fish, where fish impinged for three days exhibited some decay (e.g., belly missing), fish impinged for five days were badly decayed (e.g., head and belly missing), and fish impinged for seven days were “decayed sufficiently that marked fish were not readily apparent and species identification was at times difficult.”

Barwick et al. (2005) derived an adjustment factor for impingement estimates made during the 200-2002 monitoring program. They considered the proportion of released fish that became impinged to be the “intr oduction efficiency.” Introduction efficiency (%) was calculated as the number of marked fi sh released one day prior to the screen washing and recovered divided by the number introduced, multiplied by 100, i.e, 98/400 or 24.5 percent. The overall recovery rate (%) for the entire seven-day test period was
calculated as the number of marked fish rec overed from all screen s (243 fish) divided by the number of fish estimated to have been originally impinged on the screens (98 x 4, or 392 fish) and multiplied by 100, yielding a recove ry rate of 62 percent. This method assumed that (1) the introducti on efficiency (24.5 percent) was the same for all four releases, (2) impingement rates were constant during the seven-day interval, and (3) no fish were lost during the firs t 24-h interval of impingement.

An alternative method for estimating fish loss over the seven-day test would be to apply regression analysis on the numbe r of recovered fish over time . When plotted, these data showed a clear linear relationship (Figure 4-1), which was statistically significant (R 2 =0.910, 3 d.f., P=0.046) and de scribed by the formula:

N r = 121.35-15.1(T)

Where

N r = number of fish recovered

T = number of days prior to screen washing

The intercept value of 121.35 w ould represent the average nu mber of impinged fish at time 0 for each release. This method theref ore would produce an alternative estimate of the initial number impinged out of 400 fish released, i.e., 121 fish or an introduction efficiency of 30.0 percent, and remove the a ssumption that no fish were lost during the first 24 hours. Using this method and applyi ng a constant of 121 fish initially impinged for each release, an overall rec overy rate of 50.2 percent (243 /484 fish) would result. The mean recovery over the entire seven-day test period (equivalent to 3.5 days at large) using the linear relationship would be 56.4 percent. This method assumes impingementImpingement Mortality

4-4 rates were constant during the seven-day in terval, but relies upon the empirical linear relationship to estimate the initial number of released fish impinged.

The number of impinged fish collected weekly at MNS during the 2000-2001 and 2001- 2002 monitoring programs can be adjusted by ei ther the 60 percent recovery rate or the 56.4 percent recovery rate, depending on the assumptions found to be acceptable. The results of these adjustments do not differ greatly from one anot her (Table 4-2). Using the 60 percent recovery rate, the total annual impingement would be 2,726 fish for 2000- 2001 and 1,126 fish for 2001-2002. Using the 56.4 pe rcent recovery rate , the total annual impingement would be 2,996 fish for 2000-2001 and 1,238 fish for 2001-2002.

Since these adjustment factors were applied equally for all species , there was no change in the relative abundance of species from th e original, unadjusted collections shown in Table 4-1. Either set of estimates would be conservative because the special study was conducted at warm temperatures conducive to rapid decomposition, the test species were comparatively fragile clupeids, and the adjust ment factors were applied to all species (including durable ones) and all seasons, incl uding cold months when clupeids were primarily impinged.

The most conservative adjustment to impinge ment numbers simply would be to use the
ratio of the number of marked fish rele ased to the number recovered, i.e., 243/1600 or 15.2 percent mark recovery. Non-recovered fi sh would include those lost to decay or predation, as well as those that were not transported to the screens by the current or those otherwise not found in the intake structure. If this most conservative approach is used, the estimated annual total impingement would be 11,118 fish in 2000-2001 and 4,592 fish in 2001-2002. This approach may be too conservative. Nevertheless, the estimated impingement totals remain relatively low.

Seasonal Patterns

Impingement was lowest for all fish species combined during the spring, March – June for both years, and highest in mid-winter (January) for the 2000-2001 period and late summer (August) for the 2001-2002 period (Figures 4-2 and 4-3). There were two peaks in number of fish impinged for all fish species combined from December 2000 to November 2001 (Figure 4-2); the highest peak occurred in January 2001 due to a large number of threadfin shad (Figure 4-4). A s econdary, smaller peak occurred in July 2001 and was comprised mainly of alewife (Figure 4-5). During the December 2001 to November 2002 sampling period, there was a la rge peak in impingement during August mainly due to alewife (Figure 4-6).

Threadfin shad impingement clearly was a winter phenomenon, as illustrated by the increased impingement counts in both 2000-2001 (Figure 4-4) and 2001-2002 (Figure 4- 7), particularly in late December and Janua ry. Impinged threadfin shad ranged from 40 to 109 mmTL and consisted of young-of-the-year (YOY) as well as yearling and older fish during this winter impingement peri od (Figures 4-4 and 4-7). Based on their observed length frequency distribution and lite rature values on age-length relationships4-5 for threadfin shad (Table 4-3), approximatel y 45 percent of the threadfin shad were YOY (Tables 4-4 and 4-5) . Impingement counts were an order of magnitude higher in the winter of 2000-2001 than in the winter of 2001-2002.

Alewife impingement was greatest during su mmer and fall (July – October) (Figures 4-5 and 4-6). Impinged alewives ranged from 27 to 157 mmTL. Yearling and older alewives were more prevalent in the 2001-2002 collec tions than in 2000- 2001 (Tables 4-4 and 4- 5), probably reflecting the aging of the popul ation following its in itial appearance in
1999.

The majority of white perch were impinge d during the summer and fall, July-November (Figures 4-8 and 4-9). Most were yearling or older fish (Tables 4-4 and 4-5), based on their observed length frequency distributi on and literature values on age-length relationships (Table 4-3). Their lengths ranged from 51 to 307 mm TL.

Striped bass are stocked as fingerlings each spring. However, fe w newly stocked fish were impinged at MNS. Almost all of the impinged striped bass were 300 mmTL or larger, and most were impinged during the su mmer and fall (Figures 4-10 and 4-11). The largest fish was 612 mm long.

Bluegill were impinged throughout the year, with no obvious seasonality (Figures 4-12 and 4-13). YOY and yearling or older fish were impi nged, based on their observed length and region-specific literature values on length at age (Table 4-3). Lengths of impinged bluegill ranged from 37 to 254 mmTL, but most fish were less than 100 mm long.

White bass were impinged throughout the year in relatively low numbers (Figures 4-14 and 4-15). Impinged white bass were yearling or older fish (Tables 4-4 and 4-5), based on their lengths (Table 4-3) ; the smallest was 153 mmTL in August and the largest was
373 mm.

Channel catfish impingement was more common in 2000-2001 than in 2001-2002 (Figures 4-16 and 4-17), but it occurred thr oughout the year during both annual surveys. Most impinged channel catfish were yearli ng or older fish (Tables 4-4 and 4-5). Impinged channel catfish ranged in length from 44 to 550 mmTL.

Only 14 impinged blue catfish were co llected in 2000-2001 and only 11 in 2001-2002. They ranged in length from 79 to 418 mmTL (Figures 4-18 and 4-19). Impingement was restricted to the months of August and N ovember in 2002, but occurred in all four seasons in 2000-2001.

The seasonality of impingement for species ot her than the four species discussed above can be summarized as follows (Tables 4-6 and 4-7):

Gizzard shad—year-round Eastern silvery minnow—year-roundImpingement Mortality

4-6 Golden shiner—year-round Flathead catfish—primarily May-August Rainbow trout—no clea r seasonal pattern Black crappie—no clear seasonal pattern Largemouth bass—primarily April-August Redbreast sunfish—year-round Redear sunfish—year-round Spotted bass—August Warmouth—primarily April-May White crappie—December-July Yellow perch—June-August

VARIABLES AFFECTING IMPINGEMENT RATES

Three categories of variables potentially affecting impingement rates are discussed: environmental variables, species-speci fic abundance, and spatial distribution.

Environmental Variables

Two potentially important environmental vari ables that could affect impingement rates are water temperature and lake level or eleva tion. Mean daily water temperature records from the MNS intake and daily lake level data 4 were available for the sampling period from December 2000 through November 2002.

During the two-year study peri od, the mean daily intake te mperature varied seasonally from a low of 46.0 o F (7.8 o C) on 12 January 2001 (Figure 4-20) to a high of 90.2 o F (32.2 o C) on 7 August 2002 (Figure 4-21). Water temperatures generally were warmer during the second year of study (2001-2002; Figu re 4-21) than in th e first year (2000- 2001; Figure 4-20). This was particularly true in the winter months (DecemberFebruary) when mean monthly temp eratures in 2001-2002 were to 2.3 o F (February) to
8.0 o F (December) warmer than in the winter of 2000-2001, and during August when the mean monthly temperature in 2002 was to 2.4 o F warmer than in 2001.

The lake level varied 9.9 ft (3.0 m) du ring the 24-month sampli ng interval from 1 December 2000 to 30 November 2002 (Figures 4- 20 and 4-21). Lake levels were highest in April-May of each year, and lower lake le vels occurred from N ovember-March. On 22 September 2002, the lake level was abruptly lo wered to its minimum values for the twoyear study period, approximately 749 ft. above mean sea level, where it remained until the conclusion of the study.

4 The data presented were recorded at MNS and have since been calibrated to correspond to lake levels recorded at the Cowans Ford Dam. While the absolu te values have changed, the range and incremental daily changes in lake level have not changed.4-7 Peak impingement collections for all species combined for 2000-2001 occurred on 12 January 2001, when the lake’s surface eleva tion and the mean daily water temperature (46.0 o F) were at or near their minimum level for the year (Figure 4-20). Impingement on this date consisted primarily of threadfin sh ad (448 of 459 fish collected or 97.6 percent). The peak impingement collection for all sp ecies combined was much lower in 2001-2002 than in 2000-2001 (53 fish vs. 459 fish) a nd occurred on 16 August 2002. On this date, the lake’s surface elevation was declining but the daily mean water temperature (84.7 o F) was near maximum for the year (Figure 4- 21). Thirty-three of the 50 impinged fish collected (66 percent) were alewives.

The peak impingement event for threadfi n shad on 12 January 2001 consisted of both YOY and yearling or older fish (Figure 4-22). YOY and yearling or older threadfin shad also experienced peak impingement events in January and February of 2002, but to a much lesser degree (Figure 4-23).

The greater impingement levels for threadfi n shad in the winter of 2000-2001 may have
been related to the colder temperatures then, compared to the winter of 2001-2002. The two largest impingement collections for threadfin shad in 2000-2001 occurred on 12 January and 5 January 2001 when water temperatures were 46 o F and 49 o F, respectively (Figure 4-24). Threadfin shad have been s hown to be stressed at water temperatures less than 10 o C (50 o F) and can suffer complete mortality at 4 o C (Griffith 1978). Although there were two other sampling dates in the winter of 2000-2001 when water temperatures were less 50 o F (Figure 4-24), they occurred in late January or early February, possibly after the threadfin shad popul ation had been reduced by the low temperatures (<50 o F) of late December 2000 and January 2001. In the winter of 2001-2002, there were no sampling events when water temperatures were <50 o F, and threadfin shad collections were lower, although there did appear to be a slight increase in the number of impinged yearling or older threadfin as temperatures approached 50 o F (Figure 4-25).

In contrast, impingement of alewife peaked at warmer water temperatures. The peak impingement event for alewife on 27 July 2001 consisted exclusively of YOY fish (Figure 4-26). The peak impingement events on 9 and 16 August 2002 consisted of YOY alewives, although the 16 August event had near ly as many yearling or older fish (Figure 4-27). The daily mean water temperatures on 27 July 2001, 9 August 2002, and 16 August 2002 were 82 o F, 87 o F, and 85 o F, respectively (Figures 4-28 and 4-29). These temperatures should not have been stressf ul to alewives, being well below the upper incipient lethal temperature (89.8 o F) for fish acclimated to 75.2-78.8 o F (Wismer and Christie 1987). Dissolved oxygen (DO) con centrations near the intake also were adequate; DO measurements on 9 July and 4 August 2001, and on 5 August 2002, were 6-7 mg/L (Duke 2003, 2004a). The observed peak impingement events, while not severe, may have been related to the relative abunda nce of alewife schools near the MNS intake
on these dates.Impingement Mortality

4-8 Species-Specific Abundance and Spatial Distribution

Data on the relative abundan ce of individual species and their distribution in Lake Norman are available from recent annual electro fishing surveys of the littoral zone and hydroacoustic/purse seine survey s of the pelagic zone (Section 3). A comparison of the results of these surveys and the species composition of the 2000-2002 impingement collections provides insight into the role of species-specific abundance and spatial distribution on the susceptibility of species to impingement at MNS.

As is typical for many deep reservoirs, th e fish community of Lake Norman may be partitioned into at least two components: the near-shore, littoral zone community and the open water, pelagic community. The annual fi sheries surveys target these two sometimes distinct communities, but relating the relative abundance of individual littoral vs. pelagic species becomes difficult because of the differe nces in sampling gear efficiencies in the

two zones.

Four clupeids have been identified in Lake Norman and are associated with the pelagic zone: threadfin shad, alewife, gizzard shad, and blueback herring. In 2000-2002, threadfin shad appeared to be the domina nt species in the pelagic zone, comprising approximately 75 to 87 percent of the purse se ine catch (Table 4-8) . Alewife comprised approximately 12 to 25 percent. Gizzar d shad, once more common than now, were relatively rare in the purse seine catch. Blueback herring were not reported until 2004 (Duke 2004c).

Threadfin shad and alewife, the principal com ponents of the pelagic fish community, also dominated the 2000-2002 impingement collectio ns at MNS, comprising 42.1 percent and 16.0 percent of the combined December 2000-November 2002 impingement collections (Table 4-9). Their numerical dominance of the impingement collections suggested that pelagic species are more vulnerable to impinge ment than littoral species. White perch, striped bass, and white bass also may be consid ered to be a pelagic species. They were relatively uncommon in the elec trofishing catches from the littoral zone during the 2001- 2002 annual electrofishing surveys, but were th e third, fifth, and sixt h-most frequently impinged species (Table 4-9).

Several abundant littoral zone species either did not appear in the impingement collections or were relatively minor compone nts (Table 4-9). Examples included shiners (whitefin, spottail, and greenfin) and severa l centrachids (e.g., redbrea st sunfish, redear sunfish, hybrid sunfish, largemouth bass). Thei r distribution, and possi bly their size in terms of the shiners, appears to have ma de them less vulnerable to impingement.



### Annual Losses

Impingement sampling during 2000-2001 a nd 2001-2002 has provided two years of estimated seasonal and annual impingement ra tes occurring at the MNS intake, and the best available estimate of current impingement for several reasons. Data collected by the 2000-2002 monitoring programs are representati ve of the recent relative abundance of4-9 fish species in the vicinity of the intake and their susceptibility to impingement. In 2000- 2002, station operation was consistent with its use as a baseload facility, with cooling water flow rates of approximately 90 percen t capacity (Table 2-1). The monitoring program design encompassed complete diel a nd seasonal cycles of impingement, and the program was conducted with strict adhere nce to Standard Op erating Procedures.

Two alternative approaches to estimating th e current levels of impingement are: (1) “Normal Operations” representing recent hi storical and projected operation of the facility, and (2) “Full Oper ations” representing the full design capacity for water withdrawals by the facility. Normal Opera tions would be estimated adjusted annual totals of 2,996 impinged fish in 2000-2001 and 1,238 fish in 2001-2002 (Table 4-2). An adjusted estimate for Full Operations can be derived by substituting the design capacity for cooling water flow rates (2,926 MGD) rath er than actual mean daily flow rates recorded during the 12-month sampling in terval. Impingement losses under full operation are estimated to total 3,639 fish in 2000-2001 (Table 4-10) and 1,395 fish in 2001-2002 (Table 4-11). These totals repres ent a 21 percent and 13 percent increase, respectively, in the numbers and biomass of impinged fish over Normal Operations

.

Annual Variability

Data collected by the 2000-2002 monitoring prog rams are representative of relatively current conditions, especially the abundance of fish species and their susceptibility to impingement. The data must be interpreted in the context of th e existing conditions. Seasonal and annual variability in impingement mortality could occur if cooling water intake operation, lake level, wa ter temperatures, or fish abun dance varied to a significant degree.

Intake Operation

MNS is operated as a baseload facility, with an average annual capacity factor of 94.5 percent during 2000-2007 (Section 2). The aver age annual intake flow rate for this period (2000-2007) was 89.7 percent of the ma ximum design capacity. MNS is expected to continue to operate as a baseload facilit y, so the influence of c ooling water flow rates on the variability of annual impingement rates should be minimal.

Environmental Variables

Impingement rates for threadfin shad during 2000-2002 appeared to be influenced by low water temperatures. Peak impingement of threadfin shad occurred when daily mean water temperatures were <50 o F. The incidence of stressful water temperatures <50 o F might influence impingement rates for thre adfin shad at MNS in future years.Impingement Mortality

4-10 Fish Abundance

The abundance, species composition, and size composition of fishes in Lake Norman could vary annually as the result of ch anging habitat suitability, trophic dynamics, reproductive success, interspecific competition, or several other factors. These changes also could affect impingement rates at the in take. Some annual vari ability would appear random while some may reflect long-term trends in the abundance of individual species.

Future changes in annual impingement totals might be expected if impingement is a
function of fish abundance. If the results of annual hydroacous tic and electrofishing surveys are indicative of the annual abundance of fish in Lake Norman, up to a two or three-fold variation in total impingement r easonably might be expected annually based on
fish abundance alone. Whole lake populations of threadfi n shad and alewife, which contribute the greatest number of fish to impingement counts at MNS, combined have varied from a low of 41 to 91 million fish since 1997 (see Section 5), an approximately two-fold difference. While not contributing as greatly to impingement totals as pelagic populations, the total electrofishing catch for l ittoral zone fish varied approximately two to three-fold since 2000, from 2,753 fi sh in 2006 to 8,266 fish in 2003.

Threadfin shad and alewife dominate impinge ment collections, so annual variations in their relative abundance would have the greate st influence on annual impingement totals. Other species such as Morone spp. also appear to be susceptible to impingement at MNS because of relatively pelagic distribution. White perch is a newcomer to the fish community of Lake Norman (Section 3) a nd has the potential to expand its population rapidly in the reservoir, as it has in the Kerr Reservoir, Virginia/North Carolina and other southeastern reservoi rs (Harris 2006).

Comparison of Annual Monitoring Programs

The results of two or more annual monitoring programs can be compared to evaluate inter-annual variability impi ngement at MNS. Impingement sampling during two consecutive years revealed an over two-fold variation in the total numbers of fish impinged and collected (1,690 in 2000-2001 vs. 698 in 2001-2002). Species composition also varied between the two years, with threadfin shad dominating impingement collections in 2000-2001, the year of greater impingement, and alewife dominating the collections in 2001-2002. This shift in dominant species appeared to be related to the unusual abundance of alewives during 2001- 2002, when they comprised approximately 25 percent of the forage species (alewife, threadfin shad, and gizzard shad) caught in purse seines. Alewives first appeared in purse seine catches in 1999 and their abundance relative to the other two clupeid species peaked in 2001 and 2002 (Table 4-9).4-11 0 20 40 60 80 100 120

012345678
Days since release# recovered

Figure 4-1 Plot of Number of Marked Fish Recovered After One to Seven Days of Traveling Screen Impingement at MNS, 21-27 July 2005Impingement Mortality

4-12 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 0 100 200 300 400 500 Impingement Numbers for All Species Combined

2000 - 2001Impingement Numbers

Figure 4-2 Seasonal Pattern of Impingement Rates for All Species Combined, December 2000 – November 20014-13 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 0 20 40 60 80 100 Impingement Numbers for All Species Combined

2001 - 2002Impingement Numbers

Figure 4-3 Seasonal Pattern of Impingement Rates for All Species Combined, December 2001 – November 2002Impingement Mortality

4-14 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 5 10 15 20 25 30 35 40 45 50 55 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0 20 40 60 80 100 120 140 160 180 200

Young-of-Year Yearling & Older
Undetermined 

### Threadfin Shad

2000 - 2001Impingement Numbers by Age

Length FrequencyPercent in Length Interval

Midpoint of Length Interval (cm)

Figure 4-4 Seasonal Impingement Pattern and Length Frequency of Impinged Threadfin Shad, December 2000 – November 20014-15 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 10 20 30 40 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0 5 10 15 20 25 30 35 40 45

Young-of-Year Yearling & Older 

### Alewife

2000 - 2001Impingement Numbers by Age

Length FrequencyPercent in Length Interval

Midpoint of Length Interval (cm)

Figure 4-5 Seasonal Impingement Pattern and Length Frequency of Impinged Alewife, December 2000 – November 2001Impingement Mortality

4-16 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 10 20 30 40 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0 5 10 15 20 25

Young-of-Year Yearling & Older 

### Alewife

2001 - 2002Impingement Numbers by Age

Length FrequencyPercent in Length Interval

Midpoint of Length Interval (cm)

Figure 4-6 Seasonal Impingement Pattern and Length Frequency of Impinged Alewife, December 2001 – November 20024-17 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 5 10 15 20 25 30 35 40 45 50 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0 2 4 6 8 10 12 14

Young-of-Year Yearling & Older
Undetermined 

### Threadfin Shad

2001 - 2002Impingement Numbers by Age

Length FrequencyPercent in Length Interval

Midpoint of Leng th Interval (cm)

Figure 4-7 Seasonal Impingement Pattern and Length Frequency of Impinged Threadfin Shad, December 2001 – November 2002Impingement Mortality

4-18 

### 0 10 20 30 40 50 60 70 0 5 10 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0 2 4 6 8 10

Young-of-Year Yearling & Older
Undetermined 

### White perch

2000 - 2001Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Le ngth Interval (cm)

Figure 4-8 Seasonal Impingement Pattern and Length Frequency of Impinged White Perch, December 2000 – November 20014-19 

### 0 10 20 30 40 50 60 70 0 5 10 15 20 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0 2 4 6 8 10 12 14 16 18 20

Young-of-Year Yearling & Older
Undetermined 

### White perch

2001 - 2002Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Le ngth Interval (cm)

Figure 4-9 Seasonal Impingement Pattern and Length Frequency of Impinged White Perch, December 2001 – November 2002Impingement Mortality

4-20 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 2 4 6 8 10 12 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 0 1 2 3 4 5 Young-of-Year Yearling & Older
Undetermined 

### Striped bass

2000 - 2001Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Length Interval (cm)

Figure 4-10 Seasonal Impingement Pattern and Length Frequency of Impinged Striped Bass, December 2000 – November 20014-21 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 2 4 6 8 10 12 14 16 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 0 1 2 3 4 5 Young-of-Year Yearling & Older
Undetermined 

### Striped bass

2001 - 2002Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Length Interval (cm)

Figure 4-11 Seasonal Impingement Pattern and Length Frequency of Impinged Striped Bass, December 2001 – November 2002Impingement Mortality

4-22 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 5 10 15 20 25 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0 1 2 3 4 5 6 7 Young-of-Year Yearling & Older
Undetermined 

### Bluegill

2000 - 2001Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Leng th Interval (cm)

Figure 4-12 Seasonal Impingement Pattern and Length Frequency of Impinged Bluegill, December 2000 – November 20014-23 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 5 10 15 20 25 30 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0 1 2 3 4 5 6 7

Young-of-Year Yearling & Older
Undetermined 

### Bluegill

2001 - 2002Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Leng th Interval (cm)

Figure 4-13 Seasonal Impingement Pattern and Length Frequency of Impinged Bluegill, December 2001 – November 2002Impingement Mortality

4-24 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 2 4 6 8 10 12 14 16 18 20 22 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 0 1 2 3 4 5 6 7 Young-of-Year Yearling & Older
Undetermined 

### White bass

2000 - 2001Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Length Interval (cm)

Figure 4-14 Seasonal Impingement Pattern and Length Frequency of Impinged White Bass, December 2000 – November 20014-25 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 2 4 6 8 10 12 14 16 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 0 1 2 3 4 5 6 7 Young-of-Year Yearling & Older
Undetermined 

### White bass

2001 - 2002Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Length Interval (cm)

Figure 4-15 Seasonal Impingement Pattern and Length Frequency of Impinged White Bass, December 2001 – November 2002Impingement Mortality

4-26 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 5 10 15 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

0 1 2 3 4 5 6 7

Young-of-Year Yearling & Older
Undetermined 

### Channel catfish

2000 - 2001Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Leng th Interval (cm)

Figure 4-16 Seasonal Impingement Pattern and Length Frequency of Impinged Channel Catfish, December 2000 – November 20014-27 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 2 4 6 8 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 0 1 2 3 4 5 6

Young-of-Year Yearling & Older
Undetermined 

## Channel catfish

2001 - 2002Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Length Interval (cm)

Figure 4-17 Seasonal Impingement Pattern and Length Frequency of Impinged Channel Catfish, December 2001 – November 2002Impingement Mortality

4-28 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 5 10 15 20 25 30 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Young-of-Year Yearling & Older
Undetermined 

### Blue catfish

2000 - 2001Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Length Interval (cm)

Figure 4-18 Seasonal Impingement Pattern and Length Frequency of Impinged Blue Catfish, December 2000 – November 20014-29 

### 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 0 5 10 15 20 25 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Young-of-Year Yearling & Older
Undetermined 

### Blue catfish

2001 - 2002Impingement Numbers by Age



### Length FrequencyPercent in Length Interval



### Midpoint of Length Interval (cm)

Figure 4-19 Seasonal Impingement Pattern and Length Frequency of Impinged Channel Catfish, December 2001 – November 2002Impingement Mortality

4-30 744 746 748 750 752 754 756 758 760

12/1/2000 2/1/2001 4/1/2001 6/1/2001 8/1/2001 10/1/2001 

### 0 20 40 60 80 100 120 400 440 480

DateAll Taxa #'s Impinged 2000-2001 

### 40 50 60 70 80 90

Intake Temp.Mean Intake Temp. (F)

ElevationElevation (ft)

Figure 4-20 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for All Species Combined, December 2000-November 20014-31 744 746 748 750 752 754 756 758 760

12/1/2001 2/1/2002 4/1/2002 6/1/2002 8/1/2002 10/1/2002



### 0 20 40 60

DateAll Taxa #'s Impinged 2001-2002 

### 40 50 60 70 80 90

Intake Temp.Mean Intake Temp. (F)

ElevationElevation (ft)

Figure 4-21 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for All Species Combined, December 2001-November 2002Impingement Mortality

4-32 744 746 748 750 752 754 756 758 760

12/1/2000 2/1/2001 4/1/2001 6/1/2001 8/1/2001 10/1/2001 

### 0 20 40 60 80 100 120

DateYOY #'s Impinged 2000-2001 

### 0 10 20 30 140 160 180YAO #'s Impinged 2000-2001 

### 40 50 60 70 80 90

Intake Temp.Mean Intake Temp. (F)

ElevationElevation (ft)

Figure 4-22 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad, December 2000-November 20014-33 744 746 748 750 752 754 756 758 760

12/1/2001 2/1/2002 4/1/2002 6/1/2002 8/1/2002 10/1/2002



### 0 2 4 6 8 10

DateYOY #'s Impinged 2001-2002 

### 0

2 4 6 8 10 12 14YAO #'s Impinged 2001-2002 

### 40 50 60 70 80 90

Intake Temp.Mean Intake Temp. (F)

ElevationElevation (ft)

Figure 4-23 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad, December 2001-November 2002Impingement Mortality

4-34 0 20 40 60 80 100 120

40.00 50.00 60.00 70.00 80.00 90.00

Average Intake Temperature (°F)Total Numbers Impinged Threadfin Shad YOY (2000-2001)

0 20 40 60 80 100 120 140 160 180

40.00 50.00 60.00 70.00 80.00 90.00

Average Intake Temperature (°F)Total Numbers Impinged Threadfin Shad YAO (2000-2001)

Figure 4-24 Plots of Numbers of Impinged Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad Collected vs. Daily Mean Water Temperature at the MNS Intake, December 2000-November 20014-35 0 1 2 3 4 5 6 7 8 9

40.00 50.00 60.00 70.00 80.00 90.00

Average Intake Temperature (°F)Total Numbers Impinged Threadfin Shad YOY (2001-2002)

0 2 4 6 8 10 12

40.00 50.00 60.00 70.00 80.00 90.00

Average Intake Temperature (°F)Total Numbers Impinged Threadfin Shad YAO (2001-2002)

Figure 4-25 Plots of Numbers of Impinged Young-of-Year (YOY) and Yearling and Older (YAO) Threadfin Shad Collected vs. Daily Mean Water Temperature at the MNS Intake, December 2001-November 2002Impingement Mortality

4-36 744 746 748 750 752 754 756 758 760

12/1/2000 2/1/2001 4/1/2001 6/1/2001 8/1/2001 10/1/2001 

### 0 10 20 30 40 50

DateYOY #'s Impinged 2000-2001 

### 0 2 4 6 8 10YAO #'s Impinged 2000-2001 

### 40

50 60 70 80 90

Intake Temp.Mean Intake Temp. (F)

ElevationElevation (ft)

Figure 4-26 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for Young-of-Year (YOY) and Yearling and Older (YAO) Alewife, December 2000-November 20014-37 744 746 748 750 752 754 756 758 760

12/1/2001 2/1/2002 4/1/2002 6/1/2002 8/1/2002 10/1/2002



### 0 5 10 15 20

DateYOY #'s Impinged 2001-2002 

### 0

5 10 15 20YAO #'s Impinged 2001-2002 

### 40 50 60 70 80 90

Intake Temp.Mean Intake Temp. (F)

ElevationElevation (ft)

Figure 4-27 Daily Lake Level and Intake Water Temperature vs. Number of Impinged Fish Collected for Young-of-Year (YOY) and Yearling and Older (YAO) Alewife, December 2001-November 2002Impingement Mortality

4-38 0 5 10 15 20 25 30 35 40 45

40.00 50.00 60.00 70.00 80.00 90.00

Average Intake Temperature (°F)Total Numbers Impinged Alewife YOY (2000-2001)

0 1 2 3 4 5 6 7 8

40.00 50.00 60.00 70.00 80.00 90.00

Average Intake Temperature (°F)Total Numbers Impinged Alewife YAO (2000-2001)

Figure 4-28 Plots of Numbers of Impinged Young-of-Year (YOY) and Yearling and Older (YAO) Alewife Collected vs. Daily Mean Water Temperature at the MNS Intake, December 2000-November 20014-39 0 2 4 6 8 10 12 14 16 18 20

40.00 50.00 60.00 70.00 80.00 90.00

Average Intake Temperature (°F)Total Numbers Impinged Alewife YOY (2001-2002)

0 2 4 6 8 10 12 14 16

40.00 50.00 60.00 70.00 80.00 90.00

Average Intake Temperature (°F)Total Numbers Impinged Alewife YAO (2001-2002)

Figure 4-29 Plots of Numbers of Impinged Young-of-Year (YOY) and Yearling and Older (YAO) Alewife Collected vs. Daily Mean Water Temperature at the MNS Intake, December 2001-November 2002Impingement Mortality

4-40 Table 4-1 Number of Impinged Fish Coll ected by Weekly Sampling at MNS, December 2000-November 2002 (ranked according to abundance)

Species 12/00-11/01 % of Total 12/01-11/02 % of Total
Threadfin shad 871 51.54 134 19.20
Alewife 215 12.72 166 23.78 Bluegill 97 5.74 60 8.60 White perch 61 3.61 107 15.33
Channel catfish 54 3.20 19 2.72
White bass 47 2.78 29 4.15
Golden shiner 44 2.60 1 0.14 Striped bass 44 2.60 50 7.16
Gizzard shad 37 2.19 24 3.44
Unidentified 31 1.83 29 4.15
Flathead catfish 30 1.78 13 1.86
Redbreast sunfish 29 1.72 14 2.01 Yellow perch 23 1.36 2 0.29
Warmouth 19 1.12 1 0.14
Blue catfish 14 0.83 11 1.58 Largemouth bass 13 0.77 6 0.86 White crappie 12 0.71 0 0.00 Unidentified catfish sp. 9 0.53 7 1.00
Redear sunfish 9 0.53 12 1.72 Black crappie 8 0.47 0 0.00 Unidentified herring sp. 7 0.41 0 0.00 Unidentified sunfish sp. 5 0.30 2 0.29 Unidentified temperate bass 4 0.24 0 0.00 Sunfish hybrid 3 0.18 0 0.00
Rainbow trout 2 0.12 0 0.00 Eastern silvery minnow 1 0.06 0 0.00 Spotted bass 1 0.06 8 1.15 Common carp 0 0.00 2 0.29 Quillback 0 0.00 1 0.14
Total 1690 100.00 698 100.004-41Table 4-2 Estimated Total Number of Fish Impinged at MNS, December 2000 - November 2001 and December 2001-November 2002(ranked according to abundance)2000-2001 2001-2002Species Unadjusted Adjusted A1Adjusted B2Unadjusted Adjusted A1Adjusted B2Threadfin shad 871 1405 1544 134 216 238Alewife 215 347 381 166 268 294Bluegill 97 156 172 60 97 106White perch 61 98 108 107 173 190Channel catfish 54 87 96 19 31 34White bass 47 76 83 29 47 51Golden shiner 44 71 78 1 2 2Striped bass 44 71 78 50 81 89Gizzard shad 37 60 66 24 39 43Unidentified 31 50 55 29 47 51Flathead catfish 30 48 53 13 21 23Redbreast sunfish 29 47 51 14 23 25Yellow perch 23 37 41 2 3 4Warmouth 19 31 34 1 2 2Blue catfish 14 23 25 11 18 20Largemouth bass 13 21 23 6 10 11White crappie 12 19 21 0 0 0Unidentified catfish 9 15 16 7 11 12Redear sunfish 9 15 16 12 19 21Black crappie 8 13 14 0 0 0Unidentified herring 7 11 12 0 0 0Unidentified sunfish 5 8 9 2 3 4Unidentified temperate bass 4 6 7 0 0 0Sunfish hybrid 3 5 5 0 0 0Rainbow trout 2 3 4 0 0 0Eastern silvery minnow 1 2 2 0 0 0Spotted bass 1 2 2 8 13 14Common carp 0 0 0 2 3 4Quillback 0 0 0 1 2 2Total 1690 2726 2996 698 1126 1238162 % recovery rate (Barwick et al. 2005)256.4% recovery rate based on linear relationship of test fish recoveriesImpingement Mortality4-42Table 4-3 Maximum Total Length (mm) Used to Distinguish Young-of-Year from Yearling Fish by MonthSpecies Age Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecThreadfin shad 0 65 68 72 75 7845 50 55 60 65 65 651 89 89 90 94 9980 82 84 86 87 88 88Alewife 0 130 130 130 140 15050 70 90 115 130 130 1301 200 200 200 205 210160 175 190 200 200 200 200Blue catfish 0 100 100 100 110 120 13050 60 80 100 100 1001 180 180 180 185 190 195145 160 175 180 180 180White perch 0110 110 110 115 12035 65 85 95 110 110 1101155 155 155 160 165130 140 150 155 155 155 155Bluegill 070 70 70 75 80 8530 45 60 70 70 701125 125 125 130 135 14595 110 120 125 125 125Striped bass 0190 190 195 215 240 270100 130 160 190 190 1901385 385 390 405 430 460300 330 360 385 385 385White bass 0145 145 150 160 170 19080 100 120 140 145 1451240 240 245 255 265 280210 220 230 240 240 240Channel catfish 0 80 80 80 90 100 11050 60 70 80 80 801 180 180 180 185 190 195125 145 165 180 180 180Note: shaded month indicated appearance of new year classSources: Grist (2002), Nigro and Ney (1982), Pierce etal. (2003), van Horn et al. (1999), Carlander (1997),Hales and Belk (1992)4-43 Table 4-4 Estimated Annual Impingement of Fish by Age Group at all Units of MNS, December 2000 - November 2001

Young-of-Year Yearling & Older Undetermined Species Count Percent Count Percent Count Percent
Alewife 198 93.40 14 6.60 0 0.00
Gizzard shad 0 0.00 0 0.00 32 100.00
Threadfin shad 313 45.43 376 54.57 0 0.00 Unidentified clupeid 0 0.00 0 0.00 3 100.00 Eastern silvery minnow 0 0.00 0 0.00 1 100.00
Golden shiner 0 0.00 0 0.00 43 100.00
Blue catfish 0 0.00 17 100.00 0 0.00
Channel catfish 4 8.00 46 92.00 0 0.00
Flathead catfish 0 0.00 0 0.00 33 100.00
Unidentified catfish 0 0.00 0 0.00 8 100.00
Rainbow trout 0 0.00 0 0.00 1 100.00 Striped bass 0 0.00 41 95.35 2 4.65
White bass 0 0.00 45 100.00 0 0.00 White perch 12 19.35 50 80.65 0 0.00 Hybrid sunfish 0 0.00 0 0.00 3 100.00 Lepomis spp. 0 0.00 0 0.00 1 100.00
Redbreast sunfish 0 0.00 0 0.00 32 100.00 Bluegill 44 41.51 62 58.49 0 0.00
Redear sunfish 0 0.00 0 0.00 9 100.00
Unidentified sunfish 0 0.00 0 0.00 3 100.00
Warmouth 0 0.00 0 0.00 18 100.00 Largemouth bass 0 0.00 0 0.00 13 100.00 Spotted bass 0 0.00 0 0.00 2 100.00 Black crappie 0 0.00 0 0.00 8 100.00 White crappie 0 0.00 0 0.00 12 100.00 Yellow perch 0 0.00 0 0.00 23 100.00
Unidentified remains 0 0.00 0 0.00 13 100.00
Total 571 38.53 651 43.93 260 17.54Impingement Mortality

4-44 Table 4-5 Estimated Annual Impingement of Fish by Age Group at all Units of MNS, December 2001 - November 2002

Young-of-Year Yearling & Older Undetermined Species Count Percent Count Percent Count Percent
Alewife 126 75.45 41 24.55 0 0.00
Gizzard shad 0 0.00 0 0.00 21 100.00
Threadfin shad 59 44.03 75 55.97 0 0.00
Unidentified shad 0 0.00 0 0.00 1 100.00 Common carp 0 0.00 0 0.00 2 100.00
Golden shiner 0 0.00 0 0.00 1 100.00 Quillback 0 0.00 0 0.00 1 100.00
Blue catfish 0 0.00 10 100.00 0 0.00
Channel catfish 3 16.67 15 83.33 0 0.00
Flathead catfish 0 0.00 0 0.00 15 100.00
Unidentified catfish 0 0.00 0 0.00 5 100.00 Striped bass 1 2.08 45 93.75 2 4.17
White bass 0 0.00 28 100.00 0 0.00 White perch 31 30.10 71 68.93 1 0.97 Largemouth bass 0 0.00 0 0.00 6 100.00
Redbreast sunfish 0 0.00 0 0.00 15 100.00 Bluegill 21 35.00 39 65.00 0 0.00
Redear sunfish 0 0.00 0 0.00 12 100.00
Unidentified sunfish 0 0.00 0 0.00 2 100.00
Warmouth 0 0.00 0 0.00 1 100.00 Yellow perch 0 0.00 0 0.00 2 100.00
Unidentified 0 0.00 0 0.00 7 100.00
Total 241 36.57 324 49.17 94 14.264-45Table 4-6 Adjusted* Monthly Impinged Fish Collectionsat MNS, December 2000-November 2001 at Actual FlowsTaxonDec00Jan-01Feb-01Mar-01Apr-01May-01Jun-01Jul-01Aug-01Sep-01Oct-01Nov-01 TotalAlewife 9 5 4 0 4 0 30 94 46 43 92 55 381Gizzard shad 2 7 4 4 4 4 2 18 4 7 7 5 66Threadfin shad 183 1188 41 27 4 4 4 12 2 4 16 62 1544Unidentified herring 0 0 0 0 0 0 2 0 0 7 4 0 12Eastern silvery minnow 2 0 0 0 0 0 0 0 0 0 0 0 2Golden shiner 0 7 9 2 4 2 35 12 2 0 2 4 78Blue catfish 2 0 7 2 0 2 0 5 4 2 2 0 25Channel catfish 2 4 9 2 12 7 2 28 7 7 5 11 96Flathead catfish 0 0 2 0 0 4 21 14 11 2 0 0 53Unidentified catfish 0 0 0 0 0 0 2 9 4 0 0 2 16Rainbow trout 0 0 4 0 0 0 0 0 0 0 0 0 4Striped bass 2 2 0 0 4 5 5 16 11 20 9 5 78Unidentified temperate bass 0 0 0 0 0 0 4 4 0 0 0 0 7White bass 11 2 0 0 2 20 20 7 11 4 4 5 83White perch 4 0 0 4 0 0 4 18 12 21 27 20 108Hybrid sunfish 0 0 0 0 0 2 2 2 0 0 0 0 5Redbreast sunfish 4 0 4 4 0 5 12 12 4 5 0 2 51Bluegill 12 4 20 16 32 11 9 14 18 11 16 11 172Redear sunfish 0 2 0 2 2 2 0 0 2 2 2 4 16Unidentified sunfish 0 0 0 0 0 0 5 0 4 0 0 0 9Largemouth bass 0 2 0 0 2 4 11 4 2 0 0 0 23Spotted bass 0 0 0 0 0 0 0 0 2 0 0 0 2Warmouth 0 0 2 2 16 11 0 2 0 0 0 2 34Black crappie 0 0 2 4 0 0 5 0 0 0 0 4 14White crappie 2 2 5 5 0 4 2 2 0 0 0 0 21Yellow perch 0 0 0 0 0 0 7 28 5 0 0 0 41Unidentified fish 0 0 0 4 0 7 12 7 11 9 0 5 55TOTAL 232 1223 110 74 83 90 195 309 158 142 184 195 2996*Based on 56.4 percent recovery rate of released marked fish in July2005 special studyImpingement Mortality4-46Table 4-7 Adjusted* Monthly Impinged Fish Collectionsat MNS, December 2001-November 2002 at Actual FlowsTaxonDec01Jan-02Feb-02Mar-02Apr-02May-02Jun-02Jul-02Aug-02Sep-02Oct-02Nov-02 TotalAlewife 11 5 0 7 0 2 16 25 156 25 25 23 294Gizzard shad 4 5 0 2 2 2 4 5 0 7 7 5 43Threadfin shad 32 67 60 11 4 2 4 5 5 7 12 28 238Common carp 0 0 0 0 0 2 0 0 2 0 0 0 4Golden shiner 0 0 0 0 0 0 0 0 0 0 0 2 2Quillback 0 0 0 0 2 0 0 0 0 0 0 0 2Blue catfish 2 0 0 0 0 0 0 0 12 0 0 5 20Channel catfish 0 7 2 0 2 5 0 0 4 4 9 2 34Flathead catfish 0 0 0 0 0 2 5 11 2 0 4 0 23Unidentified catfish 0 0 0 0 0 0 4 4 4 0 2 0 12Striped bass 11 4 2 0 0 2 4 4 20 12 12 20 89White perch 5 2 7 0 2 7 0 27 55 14 35 35 190White bass 16 9 0 2 2 11 4 0 5 2 0 2 51Redbreast sunfish 0 2 4 4 0 4 0 4 5 2 0 2 25Bluegill 9 12 11 7 4 20 5 2 21 0 12 4 106Redear sunfish 0 4 5 4 4 2 0 0 0 4 0 0 21Unidentified sunfish 2 0 0 0 0 0 0 2 0 0 0 0 4Largemouth bass 0 0 2 0 0 4 4 0 0 2 0 0 11Spotted bass 0 0 0 0 0 2 7 2 0 2 2 0 14Warmouth 0 0 0 2 0 0 0 0 0 0 0 0 2Yellow perch 0 0 0 0 0 0 4 0 0 0 0 0 4Unidentified fish 2 0 0 0 2 2 0 12 27 5 0 2 51TOTAL 92 117 92 37 21 66 59 101 317 85 121 129 1238*Based on 56.4 percent recovery rate of released marked fish in July2005 special study4-47Table 4-8 Species Composition of the Purse Seine Catch in Lake Norman, 1993-2006Species Composition (%)Species19931994199519961997199819992000200120022003200420052006Threadfin shad 100 99.94 99.95 100 99.99 99.95 99.26 87.4 76.47 74.96 82.59 86.55 98.1 94.87Gizzard shad 0 0.06 0.05 0 0.01 0.05 0.26 0.22 0.01 0 0.14 0.24 0 0Alewife 0 0 0 0 0 0 0.48 12.37 23.52 25.04 17.27 13.2 1.9 5.13Impingement Mortality

4-48 Table 4-9 Comparison of Relative Abundance of Fish Species in 2001and 2002 Littoral Zone Electrofishing Surveys and the December 2000- November 2002 MNS Impingement Collections (Unadjusted)

2001-2002 Electrofishing 2001-2002 Impingement Species Total No. % Rank Total No. % Rank Bluegill 2949 31.41 1 157 6.57 4
Whitefin shiner 2263 24.10 2 - - NA
Redbreast sunfish 1080 11.50 3 43 1.80 10 tie
Redear sunfish 773 8.23 4 21 0.88 14 Spottail shiner 705 7.51 5 - - NA Largemouth bass 515 5.49 6 19 0.80 16
Blue catfish 275 2.93 7 25 1.05 12 tie Hybrid sunfish 189 2.01 8 3 0.13 20 Threadfin shad 128 1.36 9 1,005 42.09 1
Greenfin shiner 97 1.03 10 - - NA Common carp 85 0.91 11 2 0.08 21 tie
Gizzard shad 81 0.86 12 tie 61 2.55 8
Warmouth 81 0.86 12 tie 20 0.84 15
Alewife 48 0.51 14 381 15.95 2
Channel catfish 30 0.32 15 tie 73 3.06 7 Spotted bass 30 0.32 15 tie 9 0.38 18 Black crappie 12 0.13 17 8 0.34 19
Flathead catfish 9 0.10 18 43 1.80 10 tie
Green sunfish 7 0.07 19 - - NA Yellow perch 6 0.06 20 25 1.05 12 tie Pumpkinseed 4 0.04 21 - - NA Longnose gar 3 0.03 22 tie - - NA Quillback 3 0.03 22 tie 1 0.04 23 tie
Shorthead redhorse 3 0.03 22 tie - - NA
Tessellated darter 3 0.03 22 tie - - NA
White bass 3 0.03 22 tie 76 3.18 6 White perch 3 0.03 22 tie 168 7.04 3
Bowfin 1 0.01 28 tie - - NA
Rainbow trout 1 0.01 28 tie 2 0.08 21 tie Striped bass 1 0.01 28 tie 94 3.94 5 Walleye 1 0.01 28 tie 0 - NA
Golden shiner 0 0 NA 45 1.88 9 White crappie 0 0 NA 12 0.50 17 Eastern silvery minnow 0 0 NA 1 0.04 23 tie Total 9389 100.00 2,294 96.074-49Table 4-10 Adjusted* Monthly Impinged Fish Collectionsat MNS, December 2000-November 2001 at Full Design FlowsTaxonDec00Jan-01Feb-01Mar-01Apr-01May-01Jun-01Jul-01Aug-01Sep-01Oct-01Nov-01 TotalAlewife 12 7 5 0 5 0 30 94 46 43 92 57 391Gizzard shad 2 9 5 7 5 4 2 18 4 7 7 5 75Threadfin shad 243 1584 55 51 5 4 4 12 2 4 16 64 2044Unidentified herring 0 0 0 0 0 0 2 0 0 7 4 0 12Eastern silvery minnow 2 0 0 0 0 0 0 0 0 0 0 0 2Golden shiner 0 9 12 3 5 2 35 12 2 0 2 4 87Blue catfish 2 0 10 3 0 2 0 5 4 2 2 0 30Channel catfish 2 5 12 3 18 7 2 28 7 7 5 11 109Flathead catfish 0 0 2 0 0 4 21 14 11 2 0 0 54Unidentified catfish 0 0 0 0 0 0 2 9 4 0 0 2 16Rainbow trout 0 0 5 0 0 0 0 0 0 0 0 0 5Striped bass 2 2 0 0 5 6 5 16 11 20 9 5 81Unidentified temperate bass 0 0 0 0 0 0 4 4 0 0 0 0 7White bass 14 2 0 0 3 20 20 7 11 4 4 5 89White perch 5 0 0 7 0 0 4 18 12 21 27 20 113Hybrid sunfish 0 0 0 0 0 2 2 2 0 0 0 0 5Redbreast sunfish 5 0 5 7 0 6 12 12 4 5 0 2 57Bluegill 17 5 26 31 47 11 9 14 18 11 16 11 215Redear sunfish 0 2 0 3 3 2 0 0 2 2 2 4 19Unidentified sunfish 0 0 0 0 0 0 5 0 4 0 0 0 9Warmouth 0 0 2 3 23 11 0 2 0 0 0 2 44Largemouth bass 0 2 0 0 3 4 11 4 2 0 0 0 25Spotted bass 0 0 0 0 0 0 0 0 2 0 0 0 2Black crappie 0 0 2 7 0 0 5 0 0 0 0 4 18White crappie 2 2 7 10 0 4 2 2 0 0 0 0 29Yellow perch 0 0 0 0 0 0 7 28 5 0 0 0 41Unidentified fish 0 0 0 7 0 7 12 7 11 9 0 5 59TOTAL 310 1631 148 144 122 95 195 309 158 142 184 201 3639*Based on 56.4 percent recovery rate of released marked fish in July 2005 special studyImpingement Mortality4-50Table 4-11 Adjusted* Monthly Impinged Fish Collectionsat MNS, December 2001-November 2002 at Full Design FlowsTaxonDec01Jan-02Feb-02Mar-02Apr-02May-02Jun-02Jul-02Aug-02Sep-02Oct-02Nov-02 TotalAlewife 12 7 0 13 0 2 16 25 156 33 25 24 313Gizzard shad 4 7 0 3 2 2 4 5 0 10 7 6 49Threadfin shad 35 90 85 20 4 2 4 5 5 10 13 29 301Common carp 0 0 0 0 0 2 0 0 2 0 0 0 4Golden shiner 0 0 0 0 0 0 0 0 0 0 0 2 2Quillback 0 0 0 0 2 0 0 0 0 0 0 0 2Blue catfish 2 0 0 0 0 0 0 0 12 0 0 6 20Channel catfish 0 9 2 0 2 5 0 0 4 5 9 2 39Flathead catfish 0 0 0 0 0 2 5 11 2 0 4 0 23Unidentified catfish 0 0 0 0 0 0 4 4 4 0 2 0 12Striped bass 12 5 2 0 0 2 4 4 20 17 13 20 97White perch 6 2 10 0 2 7 0 27 55 19 36 37 201White bass 17 12 0 3 2 11 4 0 5 2 0 2 58Redbreast sunfish 0 2 5 7 0 4 0 4 5 2 0 2 31Bluegill 10 17 15 13 4 20 5 2 21 0 13 4 123Redear sunfish 0 5 7 7 4 2 0 0 0 5 0 0 30Unidentified sunfish 2 0 0 0 0 0 0 2 0 0 0 0 4Largemouth bass 0 0 2 0 0 4 4 0 0 2 0 0 12Spotted bass 0 0 0 0 0 2 7 2 0 2 2 0 15Warmouth 0 0 0 3 0 0 0 0 0 0 0 0 3Yellow perch 0 0 0 0 0 0 4 0 0 0 0 0 4Unidentified fish 2 0 0 0 2 2 0 12 27 7 0 2 54TOTAL 100 156 130 69 26 66 59 101 317 115 123 134 1395*Based on 56.4 percent recovery rate of released marked fish in July 2005 special study5-1 

# 5

ASSESSMENT OF ADVERSE ENVIRONMENTAL IMPACT

Introduction

Section 316(b) of the Clean Wa ter Act calls for use of the “...best technology available to minimize adverse environmental impact.” In 2004, EPA issued the Phase II Rule which addressed implementation of §316(b) for existi ng cooling water intake structures that have a design flow of more than 50 MGD. As a result of challenges to this Rule by several groups, the U.S. Court of Appeals fo r the Second Circuit reviewed the Rule and remanded several key provisions on 25 January 2 007 (see Section 1). As a result of this remand, EPA issued a suspension of the Phase II Rule on 9 July 2007 and directed that “Permit requirements for cooling water intake structures at Phase II facilities should be established on a case-by-case best pr ofessional judgment (BPJ) basis”.

Prior to the Phase II Rule, BPJ compliance w ith §316(b) was based on a determination of whether or not the cooling water intake stru cture was resulting in adverse environmental impact (AEI). With the remand of the Phas e II Rule, this approach continues to be appropriate in BPJ determinations. Unfo rtunately, neither the Act nor subsequent guidance provided by the EPA provides any definition of the term “adverse environmental impact” for use by permit writers in making their BPJ determinations. Consequently, it is left up to the permitti ng authority to determine what constitutes adverse environmental impact to be minimized under §316(b).

In this analysis, Duke Energy will evaluate the potential for an a dverse impact of the MNS cooling water intake structure as a result of an unacceptable reduction in:

 biological integrity as meas ured in terms of aquatic community species composition, diversity, and functiona l organization; or

 human use of the aquatic resources in the source waterbody, especially fishing opportunity or catch quantity or quality.

These two evaluation criteria are consiste nt with the EPA’s original draft §316(b) guidance (EPA 1977) as well as histor ical practice (Dey et al. 2000).

Duke proposes to use multiple lines of i nvestigation to determine the potential for unacceptable adverse impacts by evaluating:Assessment of Adverse Environmental Impact

5-2  potential ecosystem impacts by:

o conducting a prospective evaluation ba sed on losses to impinged species

o conducting a retrospective evaluation based on analysis of a long-term data base, and

 impacts to human use by:

o estimating economic losses from impingement.

How do we go about assessing the risk of a dverse environmental impact for MNS? Recognizing the need for a consistent and technically sound approach to assessing the potential effects of a wide variety of an thropogenic stresses on ecosystems, the EPA began an intensive effort to develop an a pproach for ecological risk assessment during the late 1980s. The intent of this effort wa s to develop an approach that would parallel
that used for human health risk assessme nt but focus on the non-human ecosystem. These efforts, which were independent of those to re-promulgate §316(b) regulations, resulted in the publication of a “Framework for Ecological Risk Assessment” (ERA) in 1992 (EPA 1992). Following considerable public review, input and debate, “Guidelines for Ecological Risk Assessment” (ERA Guide lines) were finalized in October 1998 (EPA 1998).

These Guidelines replace the earlier framework, describe general principles, and give examples of how ecological risk assessment can be applied to a wide variety of systems, stressors, and spatial and temporal scales. The general principles reflect an effort to promote consistency in assessing ecological risk among EPA’s offices and regions, while at the same time permitting development of site-specific methods to meet local needs. EPA’s ERA approach has been used to a ddress a variety of chemical, physical, and biological stressors, as well as the combined effects of multiple stressors, across many agencies throughout the United States.

EPA defines ecological risk assessment as “... a process that evaluates the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors” (EPA 1992). Since entrainm ent and impingement result in the exposure of aquatic organisms to physical and chemical st resses, it seems that a logical approach to assessing the risk of adverse environmenta l impact of cooling water withdrawals as required by §316(b) would be through the use of an ecological risk assessment framework, such as th at provided by EPA.

As noted above, the risk of adverse envir onmental impact from the continued operation of the MNS cooling water intake system need s to be addressed from two perspectives: ecosystem (i.e., biological in tegrity) and human (i.e., fishing opportunity). Potential adverse effects from these two perspectives were addressed within the framework of an ecological risk assessment as described in EPRI (2002). The results of these two assessments are then used together as part of a “weight-of-evidence” approach to5-3 determine the overall risk of adverse envir onmental impact from MNS’s cooling water
intake structure on Lake Norman.



### Assessment of Ecosystem Effects

EPA recognized that it is unlikely that risk can be accurately determined through use of a single measure. Therefore, the ecological risk assessment framework calls for careful review of all information relevant to th e issue under a “multiple lines of evidence” approach to risk assessment. These line s are independently as sessed using two broad categories of methods: prospective and retr ospective methods. Prospective methods attempt to predict the effects of a stressor, such as cooling water withdrawal, on the ecological endpoints selected for the assessm ent. Retrospective methods, on the other hand, evaluate the potential effects of an exis ting stressor, such as a cooling water intake structure, by measuring the actual effects on th e ecological endpoints. In this assessment, we use a combination of prospective and retr ospective methods to determine the potential ecosystem effects of cooling water withdrawals at MNS.

Prospective Approach

EPA defines use of prospective methods for ecological risk assessment as “an evaluation
of the future risks of a stre ssor not yet released into th e environment or of future conditions resulting from an existing stre ssor” (EPA 1998). For this assessment, prospective methods entail pred icting the potential consequen ces of impingement at MNS on the fish community composition and func tion and on recreational fishing in Lake
Norman.

As described in Section 4, impingement m onitoring studies were conducted at MNS over the two-year period December 2000 – November 2002. The results of these studies were used to estimate the expected annual im pingement at MNS for each year under normal operations:

Taxon Dec 00 - Nov 01 Dec 01 - Nov 02 Combined

Threadfin shad 1,544 238 1,782

Alewife 381 294 675
White perch 108 190 298
Bluegill 172 106 278
Striped bass 78 89 167

White bass 83 51 134

Channel catfish 96 34 130

Gizzard shad 66 43 109

Unidentified fish 55 51 106

Golden shiner 78 2 80

Flathead catfish 53 23 76Assessment of Adverse Environmental Impact

5-4 Redbreast sunfish 51 25 76

Blue catfish 25 20 45
Yellow perch 41 4 45

Redear sunfish 16 21 37

Warmouth 34 2 36
Largemouth bass 23 11 34

Unidentified catfish 16 12 28
White crappie 21 21
Spotted bass 2 14 16
Black crappie 14 14

Unidentified sunfish 9 4 13
Unidentified herring 12 12
Unidentified temperate bass 7 7
Hybrid sunfish 5 5
Common carp 4 4

Rainbow trout 4 4
Eastern silvery minnow 2 2

Quillback 2 2
TOTAL 2,996 1,240 4,236

Length frequency distributions of the most abundance species collected presented in Section 4 demonstrate most were small and most likely either age 0 or age 1 individuals. Two pelagic forage species, threadfin shad a nd alewife, accounted for 43 to 64 percent of the fish impinged annually based on the results of this study.

All but two of the species collected had esti mates of annual impingement that averaged less than one fish per day in each year. Gi ven that all of these species are common to Lake Norman, it is hard to image that the removal of individuals of each species daily, most likely juveniles, could be considered an adverse environmental impact from Lake Norman, a lake of more than 13,000 ha.

The two most abundant species impinged, th readfin shad and alewife, are abundant throughout the pelagic areas of Lake Norma n. Together, estimated annual impingement of these two species amounted to less than 2,000 individuals. Both species are pelagic and serve as important forage for a variety of gamefish in Lake Norman. Owing to their importance as forage, pelagic species (predom inantly threadfin shad and alewife) have been the subject of annual hydroacoustic studi es designed to determine overall abundance in Lake Norman (Section 3). Based on the resu lts of these studies, th e number of pelagic fish throughout the lake since 1997 has ra nged from 47 million fish in 2004 to 91 million fish in 1998.. At these levels , the removal of these species by impingement at McGuire amounts to < 0.01 percent of the population each year. Given the rapid growth, short life span, and high reproductive potential of both sp ecies, it is hard to imagine that such5-5 removal rates can have any detectable effect s on either population persistence for either species or on the amount of food availa ble to support higher trophic levels.

Retrospective Approach

Within the ecological risk assessment framework, a retrospective assessment of risk is an evaluation of the causal linkages between observed ecological effects and stressors present in the environment (EPA 1998). For this assessment, the stressor would be the loss of fish from the Lake Norman community caused by impingement at the MNS intake. The retrospective approach evalua ted whether effects on individual species populations or the community as a whole are ap parent by examining trends in the species richness and relative abunda nce of individual species dur ing the time that MNS has operated. Community metrics involving species richness and abundance would be appropriate because impingement is equiva lent to harvesting fish, without adding pollutants or altering the physic al habitat of the lake, for which other community metrics might be appropriate.

Fortunately, there exists a database on the occurrence of fish species and their relative abundance in Lake Norman, which includes recent data from 1993 through 2007. Trends in species richness and relative abundance should be apparent if operation of MNS has
had a discernable effect on the Lake Norman fish community. If there are discernable effects, are they consistent with the selec tive loss of individual species to impingement that could be interpreted as being causal in nature?

Hypothetically, selective harv esting of fish species by impingement could result in species or trophic imbalance in the community, or reduced standing crops of fish. If true, metrics involving species richness, relative abundance, and standing crop (absolute abundance) should reveal significant, sust ained changes in species occurrence and abundance, or a trophic imbalance. Also, a persistence or increase in top carnivores (piscivores) might indicate st ability or improvement in th e community, and vice versa.

In the database, the lake is divided into tw o zones (pelagic and lit toral, i.e., open water and near-shore, respectively). From 1993 until the present, the pelagic zone has been sampled by mobile hydroacoustics and purse se ine surveys, resulting in annual estimates of absolute abundance of the primary pelagic species (combined): threadfin shad, alewife, and gizzard shad. The littoral zone was sa mpled annually by boat electrofishing from 1993 through the present (see Section 3 for sampling method descriptions).

The results of these surveys in terms of fi sh abundance, species richness, and trophic structure of the fish community are discussed as follows.

Fish Abundance

The abundance of pelagic clupeid species, acco rding to annual hydroacoustic surveys in September, varied dramatically from 1993 to 1997, then appeared to stabilize after 1997Assessment of Adverse Environmental Impact

5-6 (Figure 5-1). Acoustic surveys prior to 1996 used only a down-looking transducer. For the 1996-2006 surveys, a multiplexed side-scan transducer was added to include fish residing within 2 m of the water surface. From 1996 on, abundance data should be directly comparable and would reflect the most recent status of the pelagic forage fish populations. Since 1997, population estimates fo r threadfin shad, alewife, and gizzard shad combined have ranged from 47,172,559 fish in 2004 to 91,335,000 fish in 1998.

Although gizzard shad were once a major comp onent of the forage fish community, especially in littoral areas (Siler et al. 1981), in recent ye ars they contribute very few fish compared to threadfin shad and alewife (Secti on 4, Table 4-8). Afte r first appearing in Lake Norman in 1999, alewife increased in a bundance to make up 12 to 25 percent of the purse seine catch, but was reduced to 5 percent or less in 2005-2007.

In the littoral zone of Lake Norman, elec trofishing surveys during 1993-2007 (Figure 5- 2) have shown a nearly three-fold variati on in the annual total catch for all species combined (2,849 in 1995 to 8,266 fish in 2003). However, there has been no sustained trend in the overall numeric al abundance of fish.

Bluegill and redbreast sunfish have been th e dominant species in electrofishing surveys since 1993, and also were abundant in the ea rlier 1978-1979 rotenone surveys (Siler et al. 1981). The annual variation in total electrofishing catch from 1993 to 2007 to some degree reflected the variation in catch of bluegill in partic ular (Figure 5-2). The annual
catch of redbreast sunfish a nd largemouth bass has shown less variation over the 15-year period (Figure 5-2).

Threadfin shad and bluegill were the two mo st abundant species of the eight target species (threadfin shad, alewife, channel catfish, blue catfish, white perch, bluegill, white bass, and striped bass) in th e 1993-2007 electrofishi ng catches (Figures 5-3 through 5-5). Since threadfin shad and alewif e are pelagic species, the hydr oacoustic data presented in Figure 5-1 may be a more accura te reflection of their annual abundance than the littoral zone electrofishing data (Figur e 5-3). Channel catfish, blue catfish, white bass, striped bass, and white perch were caught less freque ntly by electrofishing but show occasionally higher annual catch totals that do not indicate trends in th eir abundance. White perch had not been caught prior to 1998.

Species Richness

Since 1993 there has been an increase in the number of fish species found during electrofishing surveys, from 20-22 species annually prior to 1998 to as many as 29 species after 1998 (Figure 5-6). Species a dded since 1997 include alewife, bluehead chub, bowfin, fathead minnow, goldfish, green sunfish, rainbow trout, spotted bass, striped mullet, swallowtail shiner, walleye, wh ite catfish, white crappie, and white perch. Of these 14 species, bowfin, bluehead chub , wh ite catfish, and white crappie previously had been reported as occurring in Lake No rman during 1974-1980 (Table 3-1 in Section 3).5-7 Trophic Structure

Species caught by annual spring electrofishi ng surveys were divided into trophic guilds consisting of insectivores, omnivores, herbivores , and piscivores (Table 5-1) according to classifications used by NCDENR (2006). Insectivores dominated the annual electrofishing catch, representing 51 to 93 per cent of all fish caught and a 14-year mean of 78 percent (Figure 5-7). Omnivores and piscivores varied annually but each had a 14- year mean of 11 percent. The eastern s ilvery minnow was the only herbivorous species and comprised only 01.-0.2 percent of all fish caught in the years when they occurred (1993 and 2000).

Omnivores (primarily threadfin shad) were unusually abundant in 1993-1994 when they comprised 26-36 percent of the total electrofishing catches (Figure 5-7). The abundance of threadfin shad in 1993 and 1994 also was reflected in the pelagic fish population estimates (Figure 5-1). After 1994 omnivores comprised <15 percent of all fish caught annually.

From 1993 to 1999, piscivores represented 13 to 20 percent of all fi sh caught (Figure 5- 7). After 1999, they decreased to 6-11 per cent of the total catc h. The number of piscivores caught annually decreased from a mean of 623 fish in 1993-1999 to 409 fish in 2000-2007. The decrease in piscivores largel y reflected a decrease in the abundance of largemouth bass, the dominant piscivore.

Retrospective Summary

The fish community of Lake Norman has changed since the commencement of operation of MNS in terms of fish abundance, species richness, species composition, and trophic structure. Initially, the change s were related to the evoluti on of the fish community from a riverine community to a lacustrine community following the impoundment of the Catawba River in the early 1960s. Typical ri verine species were lost and lacustrine species became better established. Recent ch anges (since 1993) are readily tracked by examining the results of standardized a nnual sampling of the fish community using hydroacoustics, net gear, and electrofishing.

Despite long-term changes in the community, there is evidence of stabilization, particularly in this past decade. The fall population size of pelagic forage species stabilized after 1997. Since 1993, there also ha s been no sustained trend in the littoral zone catch size. However, there has been an increase in species richness since 1993, with the addition of 14 new species in the past 10 years. The trophic structure has become more stable after 1994, with insectivores numerically representing approximately 70-90 percent of the littoral zone catch, with th e remainder nearly equally divided between piscivores and omnivores.

Intensive recreational fishery management m easures and species introductions likely will modify the fish community of Lake Norman in the future, and have been largely responsible for changes experien ced in the past. However, th ere is no evidence that anyAssessment of Adverse Environmental Impact

5-8 community changes are relate d to operation of the MNS cooling water intake and impingement losses.



### Effects on Human Uses

Lake Norman, from which MNS withdraws its cooling waters, provide s important fishing opportunities to people from North Carolina and adjacent states. Popular targets of anglers include striped, largem outh and spotted bass; several species of catfish; and a variety of panfish species including bluegill, crappie, and perch. In addition, the lake supports a healthy community of other water-dependent species that provide passive use opportunities such as nature watching. He nce, in addition to potential effects on biological integrity, it is reasona ble to address the potential e ffects of impingement of fish at MNS on human uses of Lake Norman, especially fishing.

Two different types of measures of the pot ential effects of impingement on human uses of the aquatic resources in Lake Norman, e quivalent loss and economic value, were used in this analysis. Estimates of the two types of measures were calculated for each of eight target species: threadfin shad, alewife, blue catfish, channel catfish, white perch, bluegill, striped bass, and white bass. Together, thes e eight species comprised approximately 83 percent of annual impingement at MNS in each year. The methods and parameter values used to develop these two measures are discussed in Appendix A. The resulting measures are described below.

Equivalent Loss Measures

Since impingement at MNS involves several spec ies of fish and a vari ety of sizes within each species, equivalent loss calculations provide a means to express these losses in biological terms that are more amenable to interpretation. In this assessment, two different equivalent loss measures were estimated for each target species:

 Equivalent yield provides a measure of th e additional weight of each species that could have been harvested by anglers in the absence of any impingement at MNS.

 Production foregone provides a measure of the additional biomass production that could have resulted from the impinged indi viduals in the absence of any impingement
at MNS.

Using the methodology and the most probable es timates for each of the input parameters described in Appendix A, estimates of equi valent fishery yield and production foregone for each of the five target species were generated using the monthly impingement estimates at MNS. The monthly estimates we re then summed to calculate total annual values.

Only six of the eight target species evaluated in this asse ssment directly support fisheries in Lake Norman. Annual fish ery yield that could result fr om the fish impinged at MNS totaled 111 lb (50.5 kg) under actual coo ling water flows based on sampling from5-9 December 2000 through November 2001 and 168 lb (76.4 kg) based on sampling from December 2001 through November 2002 (Table 5- 2). Under maximum (design) cooling water flows, annual fishery yield totale d 215 lb (97.7 kg) based on sampling from December 2000 through November 2001 and 183 lb (83.2 kg) based on sampling from December 2001 through November 2002. Most (> 90 percent) of this equivalent yield was through striped and white bass.

Annual production from the ta rget species impinged at MNS totaled 111 lb (50.5 kg) under actual cooling water flows base d on sampling from December 2000 through November 2001 and 152 lb (69.1 kg) based on sampling from December 2001 through November 2002 (Table 5-3). Under maximu m (design) cooling water flows, annual production foregone totaled 249 lb (113.2 kg) based on sampling from December 2000 through November 2001 and 166 lb (75.5 kg) based on sampling from December 2001 through November 2002. Three species, blue gill, channel catfish and striped bass, accounted for just over 80 percent of the to tal annual production fore gone. In the absence of impingement at MNS, this additional production could support ad ditional biomass of fish targeted by anglers and provide ener gy to support other ecosystem functions.

Economic Value

Calculation of economic value takes the es timates of equivalent yield and production foregone described above and assigns economic value based on estimates of “willingness to pay” for additional resources by the users of that resource. As such, this measure provides another perspective on the issue of adverse environmental impact by weighting the estimates of equivalent loss by the rela tive “importance” of each species assigned by humans. Calculation of economic value has a long history of use including for the assignment of economic benefits of th e Phase II rulemaking (EPA 2004a, 2004b, 2004c).

In this assessment, economic values were a ssigned to each of the four categories of benefit values relevant to §316(b) re gulations for existing facilities:

 market direct use benefits;

 nonmarket direct use benefits;

 indirect use be nefits; and,

 nonuse benefits.

The value of marketed goods is equivalent to the sum of predicted changes in “consumer and producer surplus.” Producer surplus is the difference between the price obtained for a good (e.g., fish) and the cost of producing that commodity. Consumer surplus is the difference between the perceived value of a good or service to the consumer and the cost of acquiring that good or service. Non-ma rketed goods, such as recreational fishing, normally require using indirect markets, such as travel, to infer their value. In addition, some positive changes in resources such as forage fish might increase the direct use values even though the resources themselves are not directly used. Fi nally, in addition to
these direct and indirect use -related values, there is a poten tial for environmental changesAssessment of Adverse Environmental Impact

5-10 to increase the welfare of individuals who do not use the resource at all. These latter
benefits are considered nonuse benefits. Me thods and input values used to calculate economic values for each of these benefits categories are described in Appendix A.

The annual economic value for all fish im pinged at MNS totaled $281 under actual cooling water flows based on sampling from December 2000 through November 2001 and $431 based on sampling from December 2001 through November 2002 (Table 5-4). Under maximum (design) cooling water flow s, annual production fo regone totaled $546 based on sampling from December 2000 through November 2001 and $470 based on sampling from December 2001 through Novemb er 2002. Most of this economic value (~74 percent) was attributable to the loss of striped bass or white bass.

Uncertainty in Economic Value

Given the large number of parameters needed to calculate economic values, coupled with the difficulty in obtaining precise estimates of the input values for each parameter, there can be considerable uncertainty in the es timates of economic value generated for any individual facility. It is for this reas on that EPA guidance on conducting such economic evaluations recommends that an uncertaint y analysis be conducted as part of the evaluation (EPA 2000). The purpose of such an uncertainty analysis is to make transparent all the underlying s ources of uncertainty in the calculation of economic value such that the reader can independently de termine whether the results have sufficient precision and accuracy to meet regulatory needs.

In this report, uncertainty wa s addressed using two methods. First, sensitivity analysis was conducted on key input parameters to determine the relative importance of the uncertainty in the values for each parameter to the estimates of economic value. Second, Monte Carlo analysis was used to evaluate the cumulative uncertainty in the estimates in economic benefit, combining the uncertainty in each of the input parameters. For simplicity, this uncertainty analysis focuse d on the estimates of economic benefit based on actual cooling water flows. Uncertainty for the maximum cooling water flow case should be almost identical. Results for each of the two methods are discussed below.

The results of sensitivity analysis are illustra ted in Figure 5-8. Uncertainty in recreational fishing price yielded the great est range in estimates of a nnual economic value, -60 to +164 percent based December 2000 through November 2001 sampling and -61 to 173 percent based on December 2001 through Novemb er 2002 sampling. Uncertainty in the fishing vulnerability yielded the second great est range, -90 to -4 percent based December 2000 through November 2001 sampling and - 92 to 6 percent based on December 2001 through November 2002 sampling. Uncertainty in these two parameters was clearly most important in determining the total uncertainty in the estimate of annual economic value. Uncertainty in the remaining five input pa rameters (natural mortality rate, fishing mortality rate, weight, trophic conversion fact or, and equivalent pr edatory exploitation rate) had relatively minor effects on estimates of annual economic value (< + 30 percent).5-11 The results of the Monte Carlo analysis are illustrated in Figure 5-9. The frequency distribution of the resulting annual estimates appeared generally symmetrical, although most of the estimates of economic value resu lting from this uncertainty analysis were higher than the most probable estimate. The median value from the Monte Carlo analysis was 49 percent higher for sampling from December 2000 through November 2001 and 62 percent higher for sampling from Decemb er 2001 through November 2002 than the most probable estimate. The 25th and 75th percentil es were 30 percent a nd 70 percent higher, respectively, for sampling from December 2000 through November 2001 and 40 percent and 84 percent higher, respectively, for sampling from December 2001 through November 2002. There was less than a 10 perc ent chance that the true annual economic benefit was more than 2.1 times the most probable estimate reported in Table 5-4. The
fact that most of the estimates of economi c value were higher than the most probable estimate is likely related to the non-symmetr ical effects of the tw o key parameters, the recreational price per pound and the fish vulnerability rate, described above.



### Conclusions

The results of this assessment provide no evidence that impingement at MNS is causing effects within Lake Norman that rise to a level that could be considered an “adverse environmental impact.” This conclusion is based on a careful evalua tion of all relevant lines of evidence, including the following observations:

1. Numbers of fish lost as a result of im pingement are exceedingly small compared to likely sizes of fish populations in Lake Norman. For all but two species, removal rates amounted to less than 1 fish per day. It is improbable that such a removal rate would constitute an advers e environmental impact on Lake Norman.

2. Total numbers impinged each year for th e two most abundant species, threadfin shad and alewife, amounted to less than 0.01 percent of th e population in the lake. Both species are highly prolific spawne rs with high growth rates and short life spans. This high reproductive potential can easily compensate for the relatively small losses at MNS with no long-term effects.

3. The aquatic community of Lake Norman ha s been relatively stable in terms of fish abundance and trophic structure, partic ularly in recent years. Fish abundance in pelagic areas has stabilized since 1997. There also has been no sustained trend
in the size of the littoral zone catch since 1993, while sp ecies richness has increased with the addition of several new species.

4. Intensive recreational fishery management and species introductions likely have been responsible for change s in the fish community e xperienced in the past. However, there is no evidence of changes related to operation of the MNS cooling water intake and impingement losses.

5. Estimates of total fishery catch that c ould result from the fish impinged at MNS had they survived amount to only 111 to 168 lb (50.5 - 76.4 kg) per year. ThatAssessment of Adverse Environmental Impact

5-12 amount translates to one-half pound per day or less. This level of harvest is less than what would be expected fr om a small number of anglers.

6. Estimates of the total production foregone as a result of fish impinged at MNS amounted to just over 111 - 152 lb (50.5 - 69.1 kg) per year of biomass. Almost all of this was a result of threadfin shad and alewife, both of which are highly abundant species in Lake Norman. That biomass translates to less than 0.2 ounces per surface acre (37 g/ha) across the entire reservoir.

7. The best estimate of the total economic value of fish impinged at MNS was $281 - 431 per year. Even considering the uncer tainty in these es timates, it is highly unlikely that the economic value exceeds $800 per year. These values must be considered insignificant compared to th e likely total economic value of the recreational fishery in Lake Norman.5-13 1992 1994 1996 1998 2000 2002 2004 2006 0 1x10 8 2x10 8 3x10 8 4x10 8 5x10 8 6x10 8 7x10 8Hydroacoustic Population Estimate

Figure 5-1 Annual Population Estimates of Pelagic Fish in Lake Norman Using Hydroacoustic Sampling, 1993-2006Assessment of Adverse Environmental Impact

5-14 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000

Total Bluegill Redbreast sunfish Largemouth bassElectrofishing Catch

Figure 5-2 Total Annual Elect rofishing Catch for Bluegill, Re dbreast Sunfish, Largemouth Bass, and All Species Combined at 30 100-m Transects in Lake Norman, 1993- 1997 and 1999-20075-15 1994 1996 1998 2000 2002 2004 2006 0 200 400 600 800 1,000Threadfin shadTotal Catch

0 10 20 30 40 50 60Alewife 0

2 4 6 8 10Blue catfish

Figure 5-3 Total Annual Electrofishing Catc h for Blue Catfish, Alewife, and Threadfin Shad at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-2007Assessment of Adverse Environmental Impact

5-16 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000

1994 1996 1998 2000 2002 2004 2006 0 40 80 120 160White perchTotal Catch

0

10 20 30 40 50 60BluegillChannel catfish

Figure 5-4 Total Annual El ectrofishing Catch for Blueg ill, Channel Catfish and White Perch at 30 100-m Transects in Lake Norman, 1993-1997 and 1999-20075-17 1994 1996 1998 2000 2002 2004 2006 0 2 4 6 8 10Total CatchWhite bass 0

2 4 6 8 10Striped bass

Figure 5-5 Total Annual Electrofishing Catch for Striped Bass and White Bass at 30 100- m Transects in Lake Norman, 1993-1997 and 1999-2007Assessment of Adverse Environmental Impact5-18ElectrofishingSpecies19931994199519961997199920002001200220032004200520062007Longnose garBowfinAlewifeGizzard shadThreadfin shadBluehead chubCommom carpEastern silvery minnowFathead minnowGolden shinerGoldfishGreenfin shinerSpottail shinerSwallowtail shinerWhitefin shinerBrassy jumprockQuillbackShorthead redhorseSilver redhorseBlue catfishBrown bullheadChannel catfishFlat bullheadFlathead catfishSnail bullheadFigure 5-6 Species Composition in the Littoral Zone of Lake Norman as Determined by Electrofishing in 1993-1997 and 1999-2007(Shading Denotes Species Presence)5-19Species19931994199519961997199920002001200220032004200520062007White catfishRainbow troutStriped mulletMosquitofishWhite bassWhite perchStriped bassRedbreast sunfishGreen sunfishPumpkinseedBluegillRedear sunfishHybrid sunfishWarmouthBlack crappieWhite crappieSpotted bassLargemouth bassHybrid black bassSwamp darterTessellated darterUnidentified darterWalleyeYellow perchTotal No. of Species20202021222324 28 23 29 25 24 2325Figure 5-6 continuedAssessment of Adverse Environmental Impact

5-20 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 0 10 20 30 40 50 60 70 80 90 100 % Herbivore % Insectivore % Omnivore % PiscivorePercent Trophic Level Composition

Figure 5-7 Percent Composition of Fish Trophic Guilds in the Littoral Zone of Lake Norman Based on Electrofishing Results of 1993-1997 and 1999-20075-21 Figure 5-8 Estimates of the Range of Effects of Uncertainty in Each Input Parameter on Estimates of Annual Economic Benefit at MNSAssessment of Adverse Environmental Impact

5-22 Figure 5-9 Results of Monte Carlo Analysis of Uncertainty in Key Input Parameters on Estimates of Annual Economic Benefits at MNS5-23 Table 5-1 Trophic Guild Assignments for Fish Species in Lake Norman

Taxa Trophic Guild Taxa Trophic Guild Longnose gar P White catfish I
Bowfin P Rainbow trout P Alewife F Striped mullet O Gizzard shad O Mosquitofish I Threadfin shad O Striped bass P
Bluehead chub O White bass P Commom carp O White perch P Eastern silvery minnow H Black crappie P Fathead minnow O Bluegill I
Goldfish O Green sunfish I Golden shiner O Hybrid black bass P Greenfin shiner I Hybrid sunfish I Spottail shiner I Largemouth bass P Swallowtail shiner I Pumpkinseed I
Whitefin shiner I Redbreast sunfish I Brassy jumprock I Redear sunfish I Quillback O Spotted bass P
Shorthead redhorse I Warmouth P Silver redhorse I Swamp darter I
Blue catfish P Tessellated darter I
Brown bullhead I Unidentified darter I Channel catfish P Walleye P Flat bullhead O White crappie P Flathead catfish P Yellow perch I
Snail bullhead I

Source: NCDENR (2006)

I = Insectivore

P = Piscivore

O = Omnivore

H = HerbivoreAssessment of Adverse Environmental Impact

5-24 Table 5-2 Estimates of Potential Total A nnual Equivalent Fishery Yield (lb) from Individuals Impinged for Each Target Species at MNS

Species Dec 2000 - Nov 2001 Dec 2001 - Nov 2002

Actual

Flow Maximum Flow Actual Flow Maximum Flow

Alewife 0 0 0 0

Blue catfish 2 3 3 3 Bluegill 3 6 3 3

Channel catfish 4 7 3 3 Striped bass 24 44 52 57

Threadfin shad 0 0 0 0

White bass 78 153 104 114 White perch 1 2 3 4

Total 111 215 168 1835-25 Table 5-3 Estimates of Potential Total Annua l Production Foregone (lb) from Individuals Impinged for Each Target Species at MNS

Species Dec 2000 - Nov 2001 Dec 2001 - Nov 2002

Actual

Flow Maximum Flow Actual Flow Maximum Flow

Alewife 2 4 5 5

Blue catfish 7 15 12 12 Bluegill 24 51 28 30

Channel catfish 24 48 16 18 Striped bass 53 98 79 85

Threadfin shad 9 21 2 3

White bass 4 7 3 4 White perch 2 5 7 8

Total 125 249 152 166Assessment of Adverse Environmental Impact

5-26 Table 5-4 Estimates of Economic Value (2009$) of Fish Impinged at MNS

Species Dec 2000 - Nov 2001 Dec 2001 - Nov 2002

Actual

Flow Maximum Flow Actual Flow Maximum Flow

Alewife a 0 0 0 0

Blue catfish 1 1 1 1 Bluegill 14 30 16 17

Channel catfish 2 5 2 2 Striped bass 53 96 112 122

Threadfin shad a 0 0 0 0

White bass 154 304 208 227 White perch 3 6 11 12 Equivalent predator b 6 11 7 8 Non-target species c 48 93 82 82

Total 281 546 431 470

a Economic benefits for threadfin shad and alewife on ly occur through forage benefits to the equivalent predator.

b Equivalent biomass production for all Target Species converted to an equivalent biomass of a recreationally important predator.

c Economic value associated with all impinged fish s pecies that were not selected as target species.6-1 

# 6

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Thompson, J.S., J.A. Rice, D.S. Waters, J.C. Tayl or, J.E. Hightower, L.A. Davis, and P.S. Rand. 2005. Energetics of reservoir striped bass popula tions: Phase I final report. Prepared for Division of Inland Fisheries, North Caroli na Wildlife Resources Commission by North Carolina Cooperative Fish and Wildlife Research Unit, North Carolina State University, Raleigh, NC.Tidwell, J.H. and S.D. Mims. 1990. A comparison of second-year growth of blue catfish and channel catfish in Kentucky. Th e Progressive Fish-Culturalist 52:203-204.

Tidwell, J.H. and S.D. Mims. 1990. A comparis on of send-year growth of blue catfish and channel catfish in Kentucky. Progres sive Fish-Culturist 52(3):203-204.6-7 United States Environmental Protection Agen cy (EPA). 1977. Guidance for Evaluating the Adverse Impact of Cooling Water Intake St ructures on the Aquatic Envirnment: Section 316(b) P.L. 92-500. Draft. Washington, D.C.

United States Environmental Protection Agency (EPA). 1992. Framework for Ecological Risk Assessment. Risk Assessment Foru m, EPA/630/R-92/001. Washington, D.C.

United States Environmental Protection Agency (EPA). 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. Washington, D.C.

United States Environmental Protection Agen cy (EPA). 2000. Guidelines for Preparing Economic Analysis. EPA/240/R-00/003. Washington D.C., 227 pp.

United States Environmental Protection Agency (EPA). 2004a. National Pollutant Discharge Elimination System – Final Regulations to Es tablish Requirements for Cooling Water Intake Structures at Phase II Existing Facilit ies. 40 CFR Parts 9, 122, 123, 124, and 125.

United States Environmental Protection Agency (EPA). 2004b. Regional Analysis Document for the Final Section 316(b) Phase II Existing Facilities Rule. Office of Water. EPA/821/R02/003. Feb. 12.

United States Environmental Protection Agency (EPA). 2004c. §316(b) Phase II Final Rule, Regional Studies, Part H: Inland Studies.

United States Environmental Protection Agency (EPA). 2006. Regional Benefits Analysis for the Final Section 316(b) Phase III Existi ng Facilities Rule. EPA-821-R-04-007. June.

Van Horn, S.L., J.R. Finke, and D. Degan. 1996. Summer habitat selectio n of striped bass in Lake Norman. Proceedings of the Annual Conf erence of Southeastern Fish and Wildlife Agencies 1996: 92-97.

Van Horn, S.L., B.K. Baker, and M.Rash. 1999. Growth and condition response of Lake Norman striped bass to increased stocking rate s and more restrictive harvest regulations. Proceedings of the Annual Conference of S outheastern Fish and Wildlife Agencies
1999:193-199.

Van Horn, S.L. 2001. Lake Norman striped ba ss management: a conf lict between fishery managers and anglers. Proceedings of the Annual Conference of Southeastern Fish and Wildlife Agencies 2001:316-323.

Wismer, D.A. and A.E. Christie. 1987. Temperature relationships of Great Lakes fishes: a data compilation. Great Lakes Fishery Commission, A nn Arbor, Michigan. Special Publication No. 87-3. July 1987. 165 p.A-1 

# A

APPENDIX A: METHODS TO ESTIMATE EQUIVALENT LOSS AND ECONOMIC VALUE OF FISH IMPINGED AT MARSHALL

Introduction

This appendix describes the methods used to develop estimates of annual equivalent loss and economic value of fish impinged at the McGuire Nuclear Station (MNS). For this assessment, annual impingement estimates we re developed using recent impingement monitoring data collected at MNS over th e period 10 December 2000 – 29 November 2002 (Section 4).



### Estimates of Target Species Equivalent Losses

In order to calculate economic value, estimates of annual impingement loss at MNS for the eight target species (threadfin shad, alewif e, blue catfish, cha nnel catfish, bluegill, striped bass, white bass and white perch) must be converted to equivalent measures that can be assigned economic value for these spec ies. For species of commercial and/or recreational importance, the equivalent measure selected was the yield to the fishery that would have been expected had the individuals not been impinged. For species that serve as forage for other, generally larger, aqua tic organisms, the measure selected was the production of biomass available as food for hi gher trophic levels that would have been expected had the individuals not been impinged. Methods used in this report to calculate these two measures are consistent with thos e used by EPA in the Phase II rulemaking and are described below.

The measure “yield to the fishery” is define d as the annual total yi eld (in weight) that could have occurred in the commercial or r ecreational fishery from those individuals lost to impingement in the absence of compensatory changes in to tal mortality. This yield is calculated using the Equivalent Yield Mode l (EYM), which integrates Baranov’s catch equation (Ricker 1975) with estimates of the mean weight by age (Dey 2002, EPRI 2004). This method is conservative in that potential density-dep endent changes in mortality or growth rates th at often occur in natural popul ations were not included. Using the EYM, fishery yield equivalent to the annual impingement loss at MNS for each target species was estimated as follows:



#    

   

###      

 f l n

i i i i
i i n

j i j j 

### Z F V W A S NL EY

1 1Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-2 where:

EY = Equivalent yield to fishery

NL j = Number of each age or life stage category (j) lost annually to impingement
at MNS

S

j → i = Total survival from age or life stage category (j) to age (i)

n

j = Number of age or life stag e categories (j) impinged at MNS

V

i = Vulnerability of age (i) to fishing

F

i = Instantaneous fishing mortality rate for age (i)

Z

i = Instantaneous total mortality rate for age (i)

A i = Total mortality rate for age (i) = 1-e-Zi

W

i = Average weight for individual of age (i) captured in the fishery

nf

= Maximum number of ages (i) vulnerable to fishery.

The EYM results in an estimate of yield define d in the same units used to describe the average weight of the individuals and integrates yield across all ages. In this assessment, the EYM was not applied to threadfin shad or alewife as neither supports any direct commercial or recreational fishing.

The measure of biomass production that could ha ve resulted from individuals impinged at MNS was calculated using the Production Fo regone Model (PFM) (Dey 2002, EPRI 2004). As with the EYM, this method is also conservative in th at potential densitydependent changes in mortality or growth ra tes that often occur in natural populations were not included. Using the PFM, potenti al biomass production from individuals impinged was estimated for each of the target species as follows:



#     

#  

i i Z G

i i n

j i j j L

i i Z G e W G S NL

P i i l

 

 

 

 

##   1

1

1

and the total production foregone (P) can be found by summing over all the age categories that are impinged:



# 

  m

i i P P

1A-3 where:

P

= Total production foregone

P i = Production foregone for individuals impinged at MNS in age category (i)

G i = Instantaneous growth rate in weight for age category (i)

NL j = Number of each age category (j ) lost to impingement at MNS

S

j → i = Total survival from age category (j) to age (i)

n

j = Number of age categories (j) impinged at MNS

W

i = Average weight of indi viduals in age category (i)

Z

i = Average instantaneous mortality rate for age category (i)

m = Total number of age categories impinged at MNS

L = Final age category.

The PFM was applied to all target species th at as individuals serv e as food for other aquatic organisms during at leas t part of their life cycle.

Both the EYM and PFM are consistent with th e benefits calculation procedures used by EPA in their regional analys is of the benefits of th e Phase II Rule (EPA 2004b). Estimation of the biological input parameters for each of the target species is described below.

Assignment of Age Categories for Impinged Individuals

One of the necessities of equivalent loss cal culation is that the direct measures of impingement mortality must be assigned to individual age categories as defined in the production foregone and equivalent yield models. In this assessment, age was assigned using length information for each target species obtained from the current impingement monitoring together with estim ates of maximum length at age for these same species
obtained from the scientific literature and from an analysis of the length-frequency patterns for each species.

Life Table Information

Biological input parameters for the Producti on Foregone and Equivalent Yield models include life stage durations, in stantaneous natural and fishin g mortality rates, and the fraction vulnerable to the fishery for each life stage and age, as well as mean weights atAppendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-4 the beginning of each life stage and age for each target species. Each of these model inputs were determined as described below.

Life Stage Durations

Estimates of impingement were developed for this assessment on a monthly basis. Consequently, the duration of each month was set as 30.4 days, the average monthly duration across the entire year. However, it is important to rec ognize that fish do not become vulnerable to impingement until they are approximately 25 mm long and typically 1 to 2 months of age. Hence, the number of monthly increments in the first year of life is less than 12. Spawning months and months at which each species first became vulnerable to impingement at MN S were assigned as follows:

Species Peak Spawning Month Average Month When Individuals Reach 25 mm TL

Threadfin shad Jun Jul

Alewife Jun Jul
Blue catfish Jul Aug
Channel catfish Jul Aug
Bluegill Jun Aug
Striped bass Mar May
White bass May Jul
White perch May Jul

Natural Mortality Rates

A range (maximum, most probable, and minimum) of instantaneous natural mortality rates for each target species were ob tained from the following sources:

Threadfin shad – Daily instantaneous natura l mortality rates were obtained from EPRI (2005) Table 4-43. For age 0, the most proba ble value was assumed to be the midpoint between the maximum and minimum values listed. For ages 1 and 2, maximum and minimum values were assumed to be 25 per cent higher and 25 per cent lower than the most probable value, respectively.

Alewife – Most probable daily instantaneous na tural mortality rates were obtained from EPRI (2005) Table 4-24. For all ages, maxi mum and minimum values were assumed to be 25 percent higher and 25 per cent lower than the most probable value, respectively.

Blue catfish – The maximum, most proba ble and minimum estimates of the daily instantaneous natural mortality rates were assu med to be the same as that for the closely
related channel catfis h, discussed below.A-5 Channel catfish – The maximum, most probable and minimum estimates of the daily instantaneous natural mortality rates for all ages were obtained from EPRI (2005) Table
4-25.

Bluegill – The maximum, most probable and minimum estimates of the daily instantaneous natural mortality rates for all ages were obtained from EPRI (2005) Table
4-41.

Striped bass – The maximum, most probabl e and minimum estimates of the daily instantaneous natural mortality rates for all ages were obtained from Moore et al. (1991), Hightower et al. (2001), a nd Thompson et al. (2005).

White bass – The maximum, most probabl e and minimum estimates of the daily instantaneous natural mortality rates for all ages were obtained from EPRI (2005) Table
4-31.

White perch – The maximum a nd most probable estimates of the daily instantaneous natural mortality rates for Age 0 were base d on survival rates pr ovided in EPRI (2005) Table 4-12. The minimum value was assumed to be the same distance less than the most probable value as the maximum was higher. The most probable estimates for all older ages were based on survival rates provide d in EPRI (2005) Table 4-12. The maximum and minimum values were assumed to be 25 percent higher and lower than the most probable value, respectively.

These most probable values were used to provi de the best estimates of equivalent loss, while the maximum and minimum values were considered in the uncertainty analysis.

Fishing Mortality Rates

A range (maximum, most probable, and mini mum) of instantaneous fishing mortality rates for the three species that directly support fishing were selected as follows:

Blue and channel catfish – The maximum, most probable, and minimum estimates of annual fishing mortality were set to 0.15, 0.10, and 0.05, respectively. These annual exploitation rates were then converted to daily instantaneous fi shing mortality rates required for this analysis.

Bluegill – The maximum, most probable, and minimum estimates of annual fishing mortality were set to 0.5, 0.13, and 0.1, resp ectively. These annual exploitation rates were then converted to daily instantaneous fishing mortality rates required for this analysis.

Striped bass – The maximum, mo st probable, and minimum estim ates of fishing mortality were set to 0.87, 0.66, and 0.16, respectively.Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-6 White bass – The most probable estimate of instaneous fishing mortality was calculated from Z value in Quist et al. (2002) and M value in Carlander (1997). The maximum estimate was set to 20% higher than the mo st probable and the minimum estimate was 20 % less than the most probable.

White perch –The maximum, most probable, and minimum estimates of annual fishing mortality were set to 0.20, 0.15, and 0.10, respec tively. These annual exploitation rates were then converted to daily instantaneous fishing mortality rates required for this analysis.

As with natural mortality, the most probabl e values were used to provide the best estimates of equivalent loss, while the maxi mum and minimum values were considered in the uncertainty analysis. Since there is little or no harvest of either threadfin shad or alewife in Lake Norman, fishing mortality rate s for both of these species were set to 0.

Fishing Vulnerability Rates

Fishing vulnerability rates refer to the frac tion of each age at a size vulnerable to be harvested by anglers. For the fishing vulnerability rate s used in this assessment, individuals were assumed to be not vulnerable (rate = 0) up to a set age and completely vulnerable (rate = 1) above that age. Th e maximum and minimum ages of complete vulnerability were estimated using best pr ofessional judgment based on length at age information from the scientific literature. Resulting estimates are as follows:

Species Youngest Age of Vulnerability Oldest Age of Vulnerability

Blue catfish 4 5

Channel catfish 5 6
Bluegill 3 7
Striped bass 3 7

White bass 2 7
White perch 3 4

For the most probable vulnerability rates, ha lf of the individuals were assumed to be vulnerable at the youngest age while the remain ing half did not become vulnerable until the oldest age.

The most probable values were used to provi de the best estimates of equivalent loss, while the maximum and minimum values were considered in the uncertainty analysis. Since there is little or no harvest of either threadfin shad or alewife in Lake Norman, fishing vulnerability rates for both of these species were set to 0.A-7 Weight at Beginning of Age

A range (maximum, most probable, and minimu m) of estimated weights at the beginning of each age were obtained for each target species from the following sources:

Threadfin shad – The most probable mean wei ght at the time of first impingement was assumed to be 1 g each while those for subse quent ages were obtained from Thompson et al. (2005). The maximum and minimum weights were assume d to be 20 percent higher and 20 percent lower than the most probable value, respectively.

Alewife – The most probable mean weight at the time of first impingement was assumed to be 1 g each while those for subsequent ag es were based on length-at-age data from O’Gorman et al. (1997) coupled with a lengt h-weight relationship from Thompson et al. (2005). The maximum and mini mum weights were assumed to be 20 percent higher and 20 percent lower than the most probable value, respectively.

Blue catfish – The most probable mean wei ght at the time of first impingement was assumed to be 1 g each and the maximum a nd minimum mean weights were assumed to be 20 percent higher and lower, respectivel y, than the most probable values. The maximum and minimum weights at age for all other ages were based on mean lengths at age for ages < 10 from Grist (2002) and for ages 11 – 18 from Graham (1999). Maximum mean weights were calculated fr om these lengths using a length-weight relationship from Graham (1999) while the mi nimum mean weights were calculated from these lengths using a length-weight relati onship from unpublished data for the Missouri River. The most probable mean weights were assumed to be at the mid-point between the maximum and minimum values.

Channel catfish – The most probable mean wei ght at the time of first impingement was assumed to be 1 g each while for subsequent ages mean weights were based on mean lengths at age provided by Pi erce et al. (2003) for the Miss ouri River and a length-weight relationship for Georgia rivers obtained from www.fishbase.org . For all ages, the maximum and minimum mean weights were as sumed to be 20 percent higher and lower, respectively, than the most probable values.

Bluegill – The most probable mean weight at the time of first impingement was assumed to be 1 g each while those for subsequent ag es were based on length-at-age data from Hales and Belk (1992). The maximum and mi nimum weights were assumed to be 20 percent higher and 20 percen t lower than the most proba ble value, respectively.

Striped bass – The most probable mean weight at the time of first impingement was assumed to be 1 g each while those for subse quent ages were based on length-at-age data from Van Horn et al. (1999) coupled with a length-weight relationship from Thompson et al. (2005). The maximum and minimum weights were assume d to be 20 percent higher and 20 percent lower than the most probable value, respectively.Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-8 White bass – The most probable mean weight at the time of first impingement was assumed to be 1 g each while those for subse quent ages were based on length-at-age data from Carlander (1997) The maximum and mi nimum weights were assumed to be 20 percent higher and 20 percen t lower than the most proba ble value, respectively.

White perch – The most probable mean weight at the time of first impingement was assumed to be 1 g each while those for subs equent ages were obtained from Carlander (1997). The maximum and mini mum weights were assumed to be 20 percent higher and 20 percent lower than the most probable value, respectively.

For all species, weights at the beginning of each month within an age were interpolated using an instantaneous growth rate based on the weights at the begi nning and end of that age. The most probable values were used to provide the best estimates of equivalent loss, while the maximum and minimum values were considered in the uncertainty analysis.



### Economic Valuation Methods

The potential economic values of impingement at MNS were calculated for each of the benefit categories described using standard economic con cepts outlined in EPA (2004b, Part A: Evaluation Methods, Chapter A9: Be nefit Categories and Valuation). Methods used to estimate values associated with each of the four benefit cat egories (market direct use benefits, nonmarket direct use benefits, in direct use benefits, a nd nonuse benefits) are discussed below.

Direct Use Values

Direct use values accrue to individuals who di rectly use the aquatic resources affected, in other words, recreational anglers. The econom ic value of this bene fit category is then equivalent to the economic value of the harv est by anglers that would have resulted from the fish that were impinged. The biological benefit values were defined in terms of pounds to be consistent with reported fishery economic statistics. Using these estimates of increased fishery harvest, the economic va lue of the direct use benefit category was estimated for each sub-component (m arket and nonmarket) as follows.

Market Values (Commercial Fishing)

Market benefits refer to economic benefits that can be directly measured from data obtained in the marketplace. Changes in the magnitude of commercial fish and shellfish harvests are the principal market benefits relevant to §316(b) regulations. Since impingement losses at cooling water intake stru ctures had the potential to increase stock size, and hence commercial harvests, positive market benefits could potentially accrue had they not been impinged. At present, co mmercial fishing on Lake Norman appears to be non-existent. Hence for this assessment, the market value of any increase in commercial fishing was assumed to be essent ially non-existent and no further estimation of this category was required.A-9 Non-Market Direct Use Values (Recreational Fishing)

This category includes benefits derived through use of the resource that are not reflected in the market for the resource. Relative to §316(b) regulations, the most common benefit that could accrue from impinged fish would be through increases in recreational fishing opportunities. Increased abundance of adult fish that could result had impingement
losses not occurred can lead to increased catch rates for indi vidual anglers as well as an
increase in the number of fishing trips by anglers.

Unfortunately, benefits from increased recreatio nal use of the resour ce are not directly reflected in the primary market, i.e., the ma rket for recreational fishing. However, EPA
concluded that there is considerable liter ature to support valui ng this benefit through estimation of an angler’s “willingness to pa y” for recreational opportunities. Thus, the non-market direct use value for additional recreational catch can be defined as the increase in the total “willingness to pay” across all anglers resulting from any greater recreational opportunities due to reduction in impingement losses. The recreational values used represent the marginal bene fit per unit change in recreational catch.

For this assessment, total “willingness to pa y” for each target species was calculated by multiplying the estimated biological benefits (pounds) of impinged fish by the expected value per pound recreational fishermen were wi lling to pay for that increased harvest:

S S S RP BBR RFB  

where:

RFB S = Economic benefits ($) to recreationa l fishing for each target species (S)

BBR S = Biological benefits (lbs) to recreati onal fishing for each target species (S)

RP S = Value per pound recreational anglers are willing to pay for the increase in harvest of the target species (S).

The biological benefits to the recreational fi shery for each target species estimated for MNS (Table 5-2) are likely to be a very sm all fraction of the estimated recreational catch of comparable species in Lake Norman in re cent years. Hence, there is no reason to expect that changes in recreational fishing ha rvest that could result had the fish not been impinged at MNS would be sufficiently large so as to affect the price the anglers are willing to pay. Therefore, the values that r ecreational anglers are currently willing to pay for each species should be a reasonable measur e of the values they would be willing to pay assuming impingement was eliminated. Th is is the same assumption used by EPA in calculating the national benefits of the Phase II Rule (EPA 2004b).

For this assessment, we used the same recreational values per fish as used by the EPA in the Phase III Rule (EPA 2006) which were then adjusted to reflect current (2009$). All of the recreationally-cau ght target species in this assessment except striped bass fall intoAppendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-10 EPA’s "Panfish" category. Striped bass assign ed values from the "Small game" category. Values used in this assessment were:

Species Group Recreational Value (2009 $/fish)

Maximum Most Probable 5 Minimum

Panfish 1.82 0.99 0.54

Small game 12.97 5.39 0.54

To convert these values to a weight basis to be consistent with the biological benefits calculation, each of these recreational values were divided by an estimated average weight per harvested fish based on be st professional judgment as follows:

Species Average Weight per Fish Harvested (lb/fish)

Maximum Most Probable Minimum

Blue catfish 1.82 0.99 0.54

Channel catfish 1.82 0.99 0.54

Bluegill 1.82 0.99 0.54

White bass 1.82 0.99 0.54

Striped bass 12.97 5.39 2.15

White perch 1.82 0.99 0.54

The resulting values ($) per pound of fish for each target species are as follows:

Species Recreational Value (2009$/lb)

Maximum Most Probable Minimum

Blue catfish 0.91 0.33 0.13

Channel catfish 1.82 0.66 0.27

Bluegill 18.22 5.37 1.79

White bass 4.55 1.99 0.89

Striped bass 7.41 2.16 0.61

White perch 9.11 3.32 1.34

The most probable values were used to provide the best estimates of equivalent loss while the maximum and minimum values were c onsidered in the uncertainty analysis.

5 Used EPA’s mean value as most probable.A-11 Indirect Use Benefits

This category includes benefits that accrue to humans fr om the use of the resource indirectly. Relative to §316(b) regulations, the indirect bene fit that could result from fish that were not impinged would be through an increased consumption by higher trophic levels of production that result from these organisms. This increased consumption could result in greater growth and survival rates among fish in these hi gher trophic levels, and hence, increase fishing opportunities. Pr oduction consumed by higher trophic levels results from pelagic forage species, such as threadfin shad and alewife, as well as individuals of recreationally important sp ecies that die of natural causes.

Unfortunately, there are no generally accepted me thods to assign a value directly to this benefit. Instead, the value of this benefit is assigned indi rectly by quantifying the amount of commercially and/or recr eationally important species th at could be supported by the production potentially generated by these impi nged organisms, which were subsequently harvested by man. Hence, the value of the production equivalent to the fish impinged is equal to the value of commerc ial and/or recreational harves t that could be supported by that production.

The value of the indirect benefits of impinge d fish at MNS uses the following three-step

process.

Step 1 – Estimation of Total Biomass of Higher Trophic Levels Supportable by the Annual Productivity Equivalent to the Impingeme nt. The total biomass of higher trophic levels supportable is calculated by usi ng a trophic transfer method as follows:



#   TTC

PFB HTB

S S 

###   

# 

 5

1

where:

HTB = Total annual higher trophic level biomass (pounds) supported by production foregone attributable to impingement

PFB S = Biomass production foregone for each target species (S) attributable to impingement

TTC = Trophic transfer coefficient.

This approach is identical to that used by EPA in the Sect ion 316(b) Final Phase II Rule (EPA 2004b).

For this assessment, production foregone esti mates equivalent to impingement at MNS for each of the target species were calcul ated using the Production Foregone Model as described above and listed in Table 5-3. These estimates of production foregone were based on annual impingement estimates from MN S. A trophic transfer coefficient of 10Appendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-12 percent, consistent with EPA (2004b), was then used to convert the total biomass forgone to an amount of higher trophic level biom ass supportable by that production foregone. The coefficient means that an average of 10 percent of the production foregone would have ended up as predator biomass. For th e uncertainty analysis, a range for the trophic transfer coefficient of 5 to 15 percent was assumed.

Step 2 – Estimation of Equivalent Pred ator Harvest Supporte d by Annual Productivity Equivalent to the Reduction in Impingement. As previously noted, the value of indirect benefits is determined by the value of th e commercial and/or recreational harvest supported by the increased productivity. Hen ce, the total higher trophic level biomass estimated under Step 1 needs to be converted to an estimate of actual yield to the fishery expressed as equivalent predator harvest. This is accomplished by assuming that the total higher level biomass is converted to biom ass of a popular commercial or recreational species and then multiplying the value by the annual fishery exploitation rate for that species as follows:

EP ER HTB EPY  

where:

EPY = Equivalent predatory yield (pounds) attributable to impingement compliance

HTB = Higher trophic level biomass (pounds) at tributable to impingement compliance

ER EP = Fishery exploitation rate for th e selected equivalent predator.

For this assessment, striped bass was select ed as the equivalent predator endpoint upon which the estimate of indirect value is based. In reality, any potential production increase of course would be transferred among many sp ecies, including some with little or no recreational or commercial importance. Howe ver, this species is a popular target of recreational anglers in Lake Norman. He nce, this species should be a reasonably representative species for a ssigning recreational importance, and hence value, for this assessment. Using the life table information, the annual exploitation rate for striped bass was estimated to be 20 percent. For the uncer tainty analysis, a range of 10 to 30 percent was assumed. We believe that the selection of the striped bass as th e equivalent predator provides a reasonably conservative estimate of indirect-use value, since the “willingness to pay” (WTP) estimates for this species is at the upper boundary of the range of WTP values for other species addr essed in this assessment.

Step 3 – Estimation of Indirect Use Economic Benefit. Estimates of the economic value of the increased recreational harvest resulti ng from increases in forage biomass were calculated using the methods previously desc ribed for direct-use non-market benefits. For this assessment, the value per fish for striped bass (the equivalent predator) was based on the values per fish assigned to this species in EPA (2006). These were then converted to a value per pound a ssuming an average weight per harvest striped bass of 5 lb each as follows:A-13 Maximum Most Probable Minimum

Value per fish (EPA 2006) 18.80 5.04 1.33

Value per pound 3.76 1.01 0.27

Non-Use Benefits

As previously discussed, this category, al so known as passive use values, includes all benefits above and beyond any accrued through use of the resource. Most commonly
cited non-use benefits incl ude bequest and existence va lues. EPA acknowledges that these benefits can be estimated best by us ing contingent valuation methods on a sitespecific basis. However, they concluded th at such studies are un likely to be conducted for specific facilities and were clearl y beyond the scope and budget of EPA for development of the §316(b) re gulations (EPA 2004a).

In the final rule, EPA provided that "In cases where an impingement mortality and entrainment characterization study does not iden tify substantial harm to a threatened or endangered species, to the sustainability of populations of important species of fish, shellfish, or wildlife, or to the maintenan ce of community structure and function in a facility's waterbody or watershed, monetizati on [of non-use benefits] is not necessary." [69 Fed. Reg. Vol. 131 (9 July 2004) page 41648]. However, they do require a qualitative discussion of these benefi ts if they are believed to exist.

The impingement monitoring studies provide no evidence that impingement at MNS is causing “substantial harm” to threatened and endangered species or to aquatic populations and communities of the Lake Norm an. Therefore, consistent with the EPA approach for the Section 316(b) Phase II Rule, non-use values were not included in this economic valuation.

Adjustment for Other Species

The total annual economic benefits for the target species is th e sum of the annual economic benefits for all benefit categorie s described above. These target species, however, do not account for all fish impinged at MNS but only 83.02 (2000-2001 sampling) and 82.52 (2001-2002 sampling) percent. The following equation was used to account for the benefits resulting from reduc tions in impingement for the remaining 0.4 percent of fish impinged at MNS:



# 

  

###       

  4

1 

### 1 996

. 0 1

TS TS TS non 

### Ben Ben

where:

Ben non - TS = Economic benefits accruing to non-target speciesAppendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-14 Ben TS = Economic benefits accruing to four target species and the equivalent predator.

The total annual economic value of fish imping ed at MNS is the sum of the benefits to the target species plus the bene fit to the equivalent predator and the benefit to non-target species.



### Uncertainty Analysis

EPA’s Phase II §316(b) Rule requires that a faci lity seeking a site-specific determination based on benefits valuation also submit “an an alysis of the effects of significant sources of uncertainty on the results of the study” [ §125.95(b)(6)(iii)(C)]. Un certainty refers to the lack of knowledge about measures and comp onents that go into each element of the benefits valuation procedures. Under Phase II , the purpose of the uncertainty analysis is to make transparent all the underlying sour ces of uncertainty in the calculation of economic value such that the appropriat e regulatory authority can independently determine whether the results have sufficient precision and accuracy to meet regulatory needs (EPA 2004b) and form sufficient basi s for sound regulatory decisions. The purpose of this section is to evaluate the eff ects of uncertainty in key input parameters on the estimates of economic value for MNS.

Uncertainty is not unique to the calculati on of economic value under Phase II §316(b). Some uncertainty exists in almost all predic tions of future conditions based on past or existing information and this is especially tr ue when dealing with environmental science
and economic issues. In both environmental scien ce and economics, inhe rent variability and limited understanding of underlying proce sses, coupled with difficulty in making accurate measurements of underlying paramete rs, makes consideration of uncertainty in these cases especially important. Uncertain ty analysis is beco ming an increasingly important part of cost-benefit assessments as th ey play a greater role in the environmental regulatory process.

EPA (2000) identified the following mini mum requirements applicable to most uncertainty analyses related to environmental regulations:

 To present the outcomes or conclusions base d on expected or most plausible values;

 To provide descriptions of all known key assumptions, biases, and omissions;

 To perform sensitivity analysis on key assumptions; and

 To justify the assumptions used in the sensitivity analysis.

Uncertainty arises in assessments from three general sources: natural variation, uncertainty in model structure, and uncertain ty in model parameters. Natural variation
results from natural differences across elem ents within a populat ion or in a population across time. For example, not all members of the United States population are expected to value increased recreationa l fishing opportunities to the same degree. Alternatively, wide year-to-year differences in entrainm ent and impingement densities at the sameA-15 station are common. These differences in abund ance can result in large differences in the annual economic value. Both of these exam ples can yield uncertainty in the total economic value estimated under §316(b).

Uncertainty related to model stru cture arises from the lack of knowledge as to what is the most appropriate form of the model to accura tely describe the process being modeled. For example, the form of the relationship betw een the number of trips and travel cost in a simple travel cost model has been assumed to be linear, semi-log, or log by various analysts (Rosenberger and Loomis 2001). Howe ver, the most appropriate form is still a matter of debate. Likewise, alternatives that reduce total cooling water flow can result in reduced impingement. Most commonly, an assumption of a linear relationship with cooling water volume is made. However, this assumption also remains an area of debate.

Finally, uncertainty in model parameters can re sult from difficulty in measurement or in inherent variability in the model parameter. This is likely to be the most frequently encountered source of uncertainty in econom ic valuation under the Phase II Rule. Examples of this source of uncertainty include estimates of life stage-specific life table parameters for equivalent loss estimation and measurements of angler’s “willingness to pay” obtained from surveys.

In this section we address three broad areas of uncertainty: parameters used to estimate direct and indirect use benefits, questions regarding the use an d magnitude of nonuse benefits, and the economic factors used to estimate the lifetime benefits, focusing primarily on uncertainty in model parameters. Each of these areas is discussed below.

Inputs to Direct and I ndirect Use Benefits

Key input parameters addresse d in this section include:

 Natural mortality rate,

 Fishing mortality rate,

 Age of recruitment to the fishery,

 Mean weight at beginning of each stage,

 Trophic conversion factor,

 Exploitation rate for equivalent predator, and

 Recreational value per pound.

Two other key input parameters, impingeme nt rates and age composition, were not addressed in this uncertainty analysis as reliable information on the uncertainty was unavailable from the hi storical studies.

Uncertainty for this assessment was addressed by two means. First, a sensitivity analysis was conducted on individual input parameters . Second, a Monte Carlo analysis wasAppendix A: Methods to estimate equivalent loss and economic value of fish impinged at Marshall

A-16 conducted to determine the likely overall uncer tainty in the estimates of annual economic value resulting from the current levels of uncertainty. The results of each of these analyses are provided below.

Sensitivity Analysis

A sensitivity analysis was conducted individually on each of the seven input parameters listed above. Multiple calculations of annual equivalent loss and economic value were made using the extreme values (i.e., maxi mum and minimum) for each parameter while holding all other parameters constant at their most probable values. The purpose of this sensitivity analysis was to determine the pa rameters for which the current levels of uncertainty have the greatest effect on each of the estimates.

Monte Carlo Analysis

Monte Carlo analysis was used to assess the overall uncertainty in the estimates of total annual equivalent loss and economic benefits ba sed on the current levels of uncertainty in each of the seven input parameters. For each of these parameters, random values were selected from a triangular distribution, wh erein the maximum and minimum values for the distribution were set to the maximu m and minimum values for each parameter
described earlier and the mode of the distri bution was set to the mid-point used as the best estimate for each parameter. Values for each parameter were randomly selected separately for each species and life stage a nd the Monte Carlo analysis was run using 1,000 iterations to define the resulting fre quency distribution in annual estimates of equivalent loss measures and economic benefit.