Impingement Monitoring at 

Manchester Street Station 

2006 

Prepared for 

Dominion Energy Manchester Street, Inc. 

Providence, Rhode Island 

by 

Normandeau Associates, Inc. 

Falmouth, Massachusetts 

March 2007 
Table of Contents

 Page

Summary 1 

Introduction 1 

Methods 2 

Results 

 Fish 

 Annual Impingement 5 

 High vs Low-pressure Collections 9 

 Multi-year Impingement Comparisons 11 

 Impingement rates vs flow and temperature 11 

Invertebrates 14 

Literature Cited 15 

Appendix 

Figures

 Page

 1. Aerial photo of the Providence River showing Manchester Street Station and approximate 

 location of high and low-pressure screen-wash return lines. 4 

 2. Percent of total for numerically dominant species of fish impinged on the 

 Manchester Street intake screens, 2006. 5 

 3. Estimated monthly impingement totals for Atlantic menhaden Atlantic herring, 

 winter flounder, Atlantic silverside, white perch, cunner, tautog, and total fish, 

 Manchester Street Station, 2006. Solid lines indicate the percent of total taken 

 each month for 1992, 1993, 1996-2005 pooled. 20-21 

 4. Length-frequency data for Atlantic menhaden (a), winter flounder January-April (b), 

 May-August (c), and September-December (d) impinged on the Manchester 

 Street intake screens, 2006. 22 

 5. Length-frequency data for Atlantic herring (a), silver hake (b), white perch (c), 

 and Atlantic tomcod (d) impinged on the Manchester Street intake screens, 2006. 23 
Figures (continued) 

 Page

 6. Percent of the annual total collected in high and low-pressure fish return lines 

 for numerically dominant fish plus "all others", 2006. 24 

 7. Range and mean percent of total number of fish impinged at Manchester Street Station 

 whichwere found in the low-pressure return line for selected numerically dominant 

 fish, 1996-2006. 24 

 8. Percent of total number of fish collected at Manchester Street Station which were found 

 in the low pressure return line for selected numerically dominant fish, 1996-2006. 25-26 

 9. Percent of total collected in the Manchester Street Station low-pressure return 

 line by month for Atlantic menhaden (top) and Atlantic silverside, 2006. Bars 

 indicate percent by month for pooled collections from 1995-2005. 27 

 

10. Percent of total collected in the Manchester Street Station low-pressure return 

 line by month for winter flounder (top) and tautog, 2006. Bars 

 indicate percent by month for pooled collections from 1995-2005. 28 

11. Estimated annual totals for 19 species of fish plus total fish impinged on the 

 Manchester Street intake screens, 1975-2006 (1980, 1994, 1995 excluded). 

 The geometric mean over the 1975-1993, 1996-2005 time series 

 is shown by a horizontal line in each case. 29-33 

12. Relationship between numbers of fish impinged (ln) and flow (top) and 

 water temperature, all species combined, Manchester Street Station, 2006. 34 

13. Relationship between numbers of fish impinged (ln) and station intake 

 flow (top) and numbers of fish impinged (ln) and water temperature, all 

 species combined, Manchester Street Station, 1992-2006. 35 

14. Annual totals for four numerically dominant species of macroinvertebrates, 

 Manchester Street intake screens, 1992, 1993, 1996-2006. 36 
 Normandeau Associates, Inc.

 Tables

 Page

 1. Total estimated numbers impinged by species, Manchester Street Station, 

 2006. Standard scores for 2005, comparable totals for 1992 through 2005 

 as well as the long-term mean (1975-1993, 1996-2005) are also shown 

 (see footnotes). 37 

 2. Estimated numbers of fish impinged on the Manchester Street intake 

 screens by species and month, January-December 2006. 38-39 

 3. Mean numbers of fish impinged per million gallons of through-plant 

 flow, Manchester Street Station, January-December 2006. 40 

 4. Total estimated monthly catch for numerically dominant finfish and 

 ‘all others’ partitioned by low and high-pressure wash systems, 

 Manchester Street Station, January-December 2006. 41 

 5. Estimated numbers of fish impinged on the Manchester Street Station 

 revolving screens January-December by species, 1975-2006 (1980 

 excluded). 42-45 

 6. Correlation coefficients between numbers of fish (all species) impinged 

 at Manchester Street Station in 24-hour periods, water temperature 

 and intake flow, 1992-2006. 46-47 

 7. Estimated numbers of invertebrates impinged on the Manchester Street 

 intake screens by species and month, 1992-2006. New screen and wash 

 system installed October 1994-mid-July 1995. No data available for 

 that period. 48-57 

 Appendix

 1. Hydrographic and operational data recorded at Manchester Street Station 

 January-December 2006. 
 3 Normandeau Associates, Inc.

Summary

 Impingement sampling at Manchester Street Station in 2006 covered the eleventh full 

year of station operation since the facility was repowered and the intake screens and wash system 

were modified to include low-pressure sprays, Ristroph screens, and a fish-return system. 

Collections were completed weekly year-round, with each sample typically consisting of one 24-

hour continuous screenwash period. A total of 43 species was represented in the 2006 catch. 

Atlantic menhaden, white perch and winter flounder accounted for 92% of the number of fish 

impinged. Numbers of fish collected in the high and low-pressure return systems were 

enumerated separately to examine system efficiency. Consistent with 1995 through 2005 results, 

collections clearly showed that the majority of impinged fish were returned to the Providence 

River via the low-pressure wash system and were therefore not subjected to the high-pressure 

sprays required to effectively remove impinged debris. 

 The overall 2006 total of 97,782 impinged fish, ranked tenth highest over the 30-year 

time series. The 2006 totals for impinged Atlantic menhaden ranked fourth highest over the 30-

year. Pooling data for the 1995-2006 time-period suggested that 48% of the variation in numbers 

impinged could be explained by seasonal changes in water temperature. Clearly, the major 

variations in numbers impinged remain unexplained and may perhaps be attributed to random 

and non-random movements of individual fish and fish schools coupled with natural seasonality 

and variation in population size. Collections of macro-invertebrates at Manchester Street in 2006 

were dominated by blue crab (n = 4,877) and seven-spine bay shrimp (n = 4,834). Annual totals 

for these species have been highly variable over the eleven complete sampling years. 

Introduction

 Impingement sampling at Manchester Street Station has been conducted since 1975 with 

the exception of 1980 when an impingement survival study was completed. Currently 

impingement sampling represents one phase of a biological monitoring program, which includes 

phytoplankton, periphyton, zooplankton, and ichthyoplankton sampling as required by RIPDES 

Permit No. RI0000434. The expanded study program resulted from the repowering of 

Manchester Street Station, which was completed in 1995. During the October 1994 through 

mid-July 1995 period the intake screens were replaced with new, continuously-operating 

Ristroph-type screens including high and low-pressure wash systems with separate return lines. 

The low-pressure return line, consisting of 12-inch reinforced fiberglass pipe, transports fish 

from the screen house to the hurricane barrier entrance. The high-pressure wash line traverses 

the intake channel to return impinged organisms to the river above the hurricane barrier. 

 This report summarizes results of finfish and macro-invertebrate sampling from January 

through December 2006, the eleventh complete year with the new intake screen system. Where 

appropriate, attention is focused on the Representative Important Species (RIS) covered in the 

316 Demonstration for the repowering project (NEC and NEP 1990) including conversion to 

equivalent adults in cases where young fish were impinged. The RIS are listed below. 
 2 Normandeau Associates, Inc. 

Alewife/blueback herring Atlantic silverside 

 Atlantic menhaden Striped bass 

 Atlantic herring Black sea bass 

 Bay anchovy Weakfish 

 Rainbow smelt Tautog 

 Silver hake Winter flounder 

 Mummichog 

Methods

 Impingement sampling was conducted following the regime begun in April 19921. One 

24-hour collection was completed weekly by directing high and low-pressure wash waters 

(Figure 1) to separate 4 ft x 4 ft partially submerged holding pens. The intake system consists of 

five circulating water pumps each with trash racks and a traveling screen in front. Any time a 

pump is in operation, its traveling screen operates continuously. After a minimum of 24 hours 

the pens were hauled and the catch processed. There were five occasions when sample times for 

both the low-pressure and high-pressure wash collections were less than 24 hours due to heavy 

loads of mussels, tunicates and debris. On two additional occasions there was no sample 

collected for the low-pressure system. On November 9, the debris load was so heavy the lowpressure net was weighed down and moved out of the discharge stream, and on November 16 the 

debris load was so heavy the net was lost during retrieval. 

 All fish were identified to the lowest taxon possible, counted, and measured to the nearest 

millimeter in total length (TL). With large collections, a minimum of 25 individuals was 

measured. Invertebrates large enough to be regularly impinged on the 3/8-inch intake screens 

were also identified and counted. Numbers of fish and invertebrates impinged per 24 hours were 

determined from the sampling interval; an extrapolated total was then obtained for the week by 

multiplying by seven. Estimated weekly totals were summed to provide monthly and annual 

totals. Hours of operation for each circulating water pump were obtained from the station log 

and used to estimate numbers impinged per million gallons (MG) of water circulated by the 

plant. 

 Where appropriate for representative important species the equivalent adult (EA) 

procedure was conducted to convert the numbers of young fish impinged to older individuals 

using survival values obtained from the literature. This allowed potential impingement losses to 

be equated to marketable and/or spawning-age fish which in turn can be compared with landings 

or spawning stock biomass where those data are available. Adjustments were made where 

possible to account for impingement survival. Assessment of impingement survival was 

completed at Manchester Street in early 1997 (MRI 1997). Since numbers of fish potentially lost 

to impingement were relatively low following the EA procedure, no effort was made to compare 

them with landings or stock size data in this report. Impingement losses are assessed in 

 

1

Prior to April 1992, collections were made by alternately rotating one or two of the five screens at one time through 

a complete revolution and removing any impinged fish by hand from the front face of the screens. Screens were 

typically washed every eight hours, the weekly sampling generally occurring 3-4 hours after a 0700 wash. 
 3 Normandeau Associates, Inc.

conjunction with entrainment losses in the Ichthyoplankton Entrainment Monitoring at 

Manchester Street report (see NAI 2007). 

 Before and after each 24-hour impingement sampling period hydrographic measurements 

were taken in the Manchester Street intake using a YSI 600XL. Measurements taken at the 

surface and 3-ft depth intervals to bottom included water temperature (±0.1 C), salinity (±0.1 

‰), pH (±0.1), and dissolved oxygen (±0.1 mg/l). 

 Hydrographic instruments were calibrated weekly using standard buffer solutions of pH 

7.0, and 10.0 for pH, a KCl solution of 0.42 N for conductivity, and the atmosphere for dissolved 

oxygen. Although factory set, temperature was checked with a certified thermometer and the 

data adjusted as required. 
 4 Normandeau Associates, Inc.

North Discharge 

South Discharge 

High Pressure Fish Return 

Low Pressure Fish Return 

Manchester 

Street Station

Intake 

gate

Intake Canal 

Figure 1. Aerial photo of the Providence River showing Manchester Street Station and 

approximate location of high and low-pressure screen-wash return lines. 
 5 Normandeau Associates, Inc.

Results

Fish

Annual Impingement

 

 A total of 43 fish species were recorded in the 2006 Manchester Street Station 

impingement collections. Atlantic menhaden (Brevoortia tyrannus), white perch (Morone 

americana), and winter flounder (Pseudopleuronectes americanus), accounted for 92, 3 and 2%, 

respectively, of the number of fish impinged (Figure 2). 

Manchester Street Screens

Fish Impingement 2006

Atlantic Menhaden 91.7%

White Perch 2.7%

Winter Flounder 2.1%

40 Remaining species 3.5%

Figure 2. Percent of total for numerically dominant species of fish impinged on the 

Manchester Street intake screens, 2006 

 Atlantic menhaden dominated the 2006 catch with an estimated annual impingement total 

of 89,663 fish (Table 1). They were only absent from collections in June and July (Figure 3, 

Table 2). Collections in August 2006 alone accounted for 88% of the annual total of menhaden 

impinged, yielding an impingement rate of 106 fish per hour for the month, which is equivalent 

to nine fish per million gallons of through-plant flow (Table 3). Over the year, total lengths 

ranged from 35 to 390 mm with a mean of 111 mm [standard error (s.e.) = 7.7, n = 192; Figure 

4a]. Individuals less than 100 mm in length, representing 87% of the total, were assumed to be 
 6 Normandeau Associates, Inc. 

young-of-the-year; those greater than or equal to 100 and less than 190, representing 4%, were 

assumed to be age 1, and those greater than 190 were assumed to age 2 +, accounting for 9%. 

 Numbers of young menhaden impinged were converted to equivalent age-2 fish, the age 

at which they enter the Narragansett Bay fishery (Durbin et al. 1983). The Atlantic States 

Marine Fisheries Commission (ASMFC 2004) provided an estimated annual instantaneous 

natural mortality rate (M) of 4.3 for young-of-the-year or age-0 fish and 0.98 for age-1 fish. 

Since the age-0 fish were impinged at various times during the year M = 4.3 was divided by 12 

to estimate a monthly mortality rate. The monthly rate was applied for the number of months 

remaining between the time a young fish was impinged and its next birthday, which was 

assumed to be June 1. Assuming no fishing mortality (F) prior to age 2 so that Z or total 

instantaneous mortality = M, the natural mortality rate, an annual survival rate of 37.5% (s = e-z) 

was applied to the equivalent age-1 impingement total plus any age-1 fish impinged to estimate 

numbers of age-2 fish. Results of the post-impingement survival study (MRI 1997) confirmed 

that menhaden are impingement sensitive (see for example Tatham et al. 1978), an average of 

only 1.9% surviving 48-hour holding periods at Manchester Street Station. With such a low 

survival rate no further adjustment was made to the numbers impinged. The potential loss of an 

estimated 78,261 age 0, and 3,628 age 1 menhaden in 2006 plus the 7,775 age 2+ fish impinged 

would be equivalent to the loss of 8,472 age-2 fish to the local fishery. Assuming a weight of 0.6 

pound for age-2 fish (ASMFC 2004), 8,472 menhaden would weigh 5,083 pounds. 

 White perch ranked second with an estimated annual total of 2,651 fish. They were 

present throughout the year. March collections with an estimated total of 1,048 fish accounted 

for 40% of the annual total (Figure 3, Table 2). White perch ranged in total length from 62 to 

410 mm, averaging 114 mm (s.e. = 3.0, n = 196). Following information presented by Clayton et 

al. (1978), length-frequency data indicated that about 92% of the fish impinged were 

approaching the end of their first year (less than 150 mm), 4% were age 2 (up to 200 mm), and 

4% were age 3+ (greater than 200; Figure 4c). 

 Male white perch mature at age 2 and females mature at age 4 (Mansueti 1961, Busch 

and Heinrich 1982, Klauda et al. 1988). Assuming an equal sex ratio, numbers impinged were 

converted to those two respective age classes with an annual mortality rate of 55% (Mansueti 

1961, Wallace 1971, Klauda et al. 1988). The post-impingement survival study indicated that 

25% of the white perch returned to the Providence River by the low-pressure fish return system 

survive following 48-hour holding periods. A slightly higher rate of 33% was recorded for the 

high-pressure system but the sample size was too small to be reliable (n = 9); therefore 25% was 

used in this analysis. Based on these values a total of 578 white perch of reproductive age were 

estimated to have been lost to impingement in 2004. 

 Winter flounder ranked third with an annual estimated impingement total of 2,088 fish, 

accounting for 2% of the year’s fish total. While flounder were impinged throughout the year 

but numbers were greatest in August (422 fish), that month accounting for 20% of the species’ 

total (Figure 3, Table 2). Following length-at-age data from Howell et al. (1992), Gibson 

(1993a), and Witherell and Burnett (1993), the vast majority of fish were immature (Figure 4). 

In August, when flounder were most numerous in impingement collections, age-0 fish, those less 

than 90 mm, accounted for all flounder collected. Partitioning the year’s catch into age classes 
 7 Normandeau Associates, Inc.

based on length, 62% of the total was classified as age 0, 31% as age 1, 6% age 2 and 1% age 3 

(Figure 4). 

 Results of the post-impingement survival study (MRI 1997) indicated that latent youngof-the-year winter flounder survival is 95% among individuals returned to the river via the lowpressure system, 92% among those subjected to the high-pressure system. Only 10% of the 

flounder collected during the survival study were age-1 and age-2 fish (n = 54); while sample 

size was small, a 100% latent survival rate was recorded. Conservatively applying survival rates 

of 95 and 92% to all flounder estimated to have been returned to the river by the low (1,562) and 

high-pressure systems (519), respectively, provided an estimated 2006 loss of 120 fish. 

 Annual survival rates for winter flounder of 0.054% for age 0, 0.2996% for age 1, and 

0.4035% for age 2 were applied to the impingement totals to estimate the equivalent number of 

adult fish (age 3) potentially lost to the local population. Age 3 corresponds to the age at which 

both 50% of the population reaches reproductive maturity and recruitment to the fishery occurs 

(Gibson 1989a; NOAA 1998). Survival rates for age 0, 1 and 2 individuals were derived by 

averaging values reported by Gibson (1993b) and Rose et al. (1996). Since annual survival rates 

are for the entire life stage, assuming an April 1 birthday, survival rates were generated for each 

month. All age-0 fish were aged to their first April birthday using monthly survival data and 

then annual rates were applied for all fish until age 3. Based on these data, the 2006 

impingement total adjusted for impingement survival would be equivalent to 28 age-3 fish. 

 Twelve species from the RIS list were not among the numerical dominants in the 2006 

impingement collections. These included tautog (Tautoga onitis), silver hake (Merluccius 

bilinearis), alewife (Alosa pseudoharengus), Atlantic silverside (Menidia menidia), blueback 

herring (Alosa aestivalis), striped bass (Morone saxatilis), bay anchovy (Anchoa mitchilli), 

mummichog (Fundulus heteroclitus), Atlantic herring (Clupea harengus), weakfish (Cynoscion 

regalis), rainbow smelt (Osmerus mordax) and black sea bass (Centropristis striata). Each of 

these species except rainbow smelt and black sea bass were represented in the 2006 collections 

although there were only three blueback herring, three striped bass, two bay anchovy, two 

mummichogs, two Atlantic herring and one weakfish collected. These fish provided estimated 

annual impingement totals of 18, 18, 14, 14, 12, and 7, respectively. The blueback herring were 

age-1 fish, impinged in April and ranged between 82 and 115 mm. The striped bass were 

impinged in February, March and May. They ranged from 345 to 530 mm in total length 

suggesting they were age-3+ fish (see for example Setzler et al. 1980). 

 Tautog were impinged in all months except November with an estimated annual 

impingement total of 663 fish. The largest monthly collections were obtained in May and June 

providing estimated totals of 175 and 134 fish, respectively (Figure 3). Total length 

measurements indicated that fish ranged from 52 to 320 mm with an average length of 142 mm 

(s.e. = 7.9, n = 80). Following Cooper (1967) who studied tautog from Rhode Island waters, 

individuals (male and female lengths averaged) reach 62 mm TL at age 1, 131 mm at age 2, 197 

mm at age 3, 244 mm at age 4, and 287 mm at age 5. Based on Cooper’s data the numbers of 

tautog impinged at Manchester Street were assumed to be distributed as follows: age 0 - 7%, age 

1 - 48%, age 2 - 25%, age 3 - 8%, age 4 - 10%, and age 5 - <1%. Tautog were not well 

represented during the impingement survival study completed in early 1997 (n = 12). Within 
 8 Normandeau Associates, Inc. 

that small sample, survival was 100% following 48-hour holding periods. To be conservative, 

only half the tautog impinged was assumed to have survived once returned to the river. 

 

 Utilizing otter trawl age-frequency data from Cooper (1967) an annual survival rate of 

0.83527 was calculated for tautog for ages 5 through 22. Although Cooper presented data for 

ages 1 through 4, there is good evidence that these younger age classes are not as susceptible to 

capture as older fish. This is based on the size of younger fish relative to otter trawl mesh sizes 

and the greater movement observed among older fish in comparison to younger fish, which tend 

to remain near the home site (Olla et al. 1974). In the absence of more reliable data, the survival 

rate for ages 5-22 was applied to ages 1-4 as well. The estimated annual survival rate of 0.83527 

was applied in succession to each age group to estimate the number of age-3 and age-6 tautog 

which might have resulted had impingement losses not occurred. These ages were selected 

because tautog mature at about age 3 (Chenoweth 1963, Hostetter and Munroe 1993) and enter 

the sport fishery at about age 6. These conversions result in a potential estimated loss of 193 

age-3 or 158 age-6 fish. 

 Silver hake were impinged from January through March and in December producing an 

estimated annual impingement total of 160 fish. They were impinged primarily in January (100 

fish; Table 2). Individuals ranged from 72 to 130 mm in length with a mean of 97 mm (s.e. = 

3.0, n = 24). Referring to information provided by Almeida (1987) and Helser (1996), fish 

around 100 mm TL impinged in winter were probably nearing the end of their first year. Silver 

hake between 100 and 150 mm were age-2 fish. Silver hake at age 2 enter the commercial 

fishery and 50% of those are mature (Almeida and Anderson 1978, NOAA 1998). Based on this, 

the number of juveniles potentially lost to impingement was converted to a number of equivalent 

age-2 fish. An annual survival rate of 0.67 obtained from Almeida and Anderson (1978) and 

Helser et al. (1996) produced an estimated loss of 121 age-2 fish. Since only five silver hake 

were taken during the impingement survival study and each one either died or was injured 

following 48-hour holding periods, all impinged silver hake were assumed to have died shortly 

after being returned to the river. 

 Alewives were impinged in January, March, April, July, August and December with an 

estimated annual impingement total of 115 fish. Individuals impinged ranged from 66 to 160 

mm in length (mean = 99 mm, s.e. = 5.8, n = 22). Following Clayton et al. (1978), small 

alewives (less than 150 mm) impinged would be age-0 fish. Young fish were equated to the 

number of reproductive age fish that might have survived had impingement not occurred. 

Estimates of annual survival rates between the time they migrate from natural river systems (age 

0) and age 3 when they begin to return to spawn were obtained from data provided by Cole et al. 

(1978) and Gibson (1989b). The proportion of the number of age-3 fish returning to the Parker 

River system in Massachusetts in 1978 to the number of age-0 fish leaving the same system three 

years earlier was approximately 0.05. From these data, an annual survival rate of 37% was 

obtained. Working with the Gilbert Stuart Brook alewife run in North Kingstown, Rhode Island, 

Gibson (1989b) estimated an annual survival rate of 38.2% for later year classes. Because the 

estimates based on Cole et al. (1978) and Gibson (1989b) were remarkably similar, these 

estimates were averaged (mean = 37.6%). This survival rate was applied successively beginning 

at age 1 for all fish collected to obtain an estimate of 19 age-3 alewives potentially lost to 

impingement effects during the year. Only nine river herring were collected during the 
 9 Normandeau Associates, Inc.

impingement survival study and each of those individuals died during the holding period (MRI 

1997). Therefore alewives and blueback were assumed to experience 100% mortality as a result 

of impingement. 

 Atlantic silversides were impinged in January, August, October and November yielding 

an estimated total of 52 fish (Figure 3). Two length frequencies (January–June and JulyDecember) were generated to determine what year classes were represented in the catch. Total 

length-frequency data indicated that silversides taken in 2006 were primarily members of the 

2005 year class (Conover 1979; Figure 6a, 6b). Young-of-the-year fish under 50-mm total 

length are rarely impinged but, because they fit through the intake screens, are susceptible to 

entrainment. Results from the impingement survival study completed at Manchester Street (MRI 

1997) suggested that latent survival rates of 28% and 17% were obtained for the low-pressure 

and high-pressure return lines, respectively. These data assume no sub-lethal impingement 

effects occurred after fish returned to the river, such as increased loss from predation or declines 

in feeding and growth rates leading to greater overall mortality rates. 

 Atlantic silversides mature at age 1 and spawn from late April through June (Conover and 

Kynard 1984). Over the course of their first (and typically only) winter, mortality can reach 99% 

(Conover 1979). Many of those remaining in the spring die during the spawning season (Bayliff 

1950, Conover and Ross 1982). Based on these data equivalent adults resulting from 

impingement losses were calculated as follows: Half the fish collected during January was 

assumed to survive to the beginning of the April 1 spawning season had impingement not 

occurred. All fish impinged in August were assumed to be adults and fish impinged from 

September through December were assumed to survive late fall and winter at a rate of 25%. 

These rates are considered conservative particularly for the small number of adults that survive 

until the fall of their second year since they are unlikely to survive to spawn a second time. 

These assumed rates were applied to the number impinged each month after adjusting for 

impingement survival. Applying these survival rates to the 20 silversides returned via the lowpressure line and 32 returned via the high-pressure line would reduce the potential estimated 

2006 losses to 19 equivalent adult fish. 

High vs Low-Pressure Collections

 When repowered, the Manchester Street Station intake screens were fitted with separate 

high and low-pressure fish removal and return systems to maximize impingement survival. The 

impingement survival study completed early in 1997 indicated that, in most cases, fish returned 

to the river via the low-pressure system had a higher probability of survival than those returned 

via the high- pressure system (MRI 1997). 

 Numbers of fish collected in the high and low-pressure return systems in 2006 were 

enumerated separately to examine system efficiency. Extrapolated totals by sampling location 

were examined on an annual basis for the 2006 numerical dominants and all others pooled 

(Figure 6, Table 4). Annual low-pressure return efficiency results are included for those species 

common enough during the eleven complete years following repowering (1996-2006) to make 

comparisons (Figure 7). Percent removal by the low-pressure system was also examined on a 
 10 Normandeau Associates, Inc. 

monthly basis for Atlantic herring, winter flounder, Atlantic silverside, tautog, and Atlantic 

menhaden. These species were collected often enough over the course of the year to provide at 

least three separate monthly values (Figures 8 and 9). For each of these species collections were 

pooled from the 1995-2006 seasons to provide information on past results. Data from July 

through December 1995 were included since the new screen wash system was operational at that 

time. Monthly percentages based on estimated extrapolated totals of less than 110 fish were 

omitted from these figures since those values represent small, actual sample sizes of less than 15 

fish. 

 Consistent with the late half of July 1995 through 2005 results (NAI 2006), collections 

clearly showed that the majority of impinged fish were returned to the Providence River via the 

low-pressure wash system and were therefore not subjected to the high-pressure sprays required 

to effectively remove impinged debris (Figures 6, 7). Annual 2006 low-pressure return rates 

were highest for cunner and tautog (93%) followed by white perch (86%). The system was least 

efficient overall for Atlantic menhaden (46%). For all other species, a combined rate of 70% 

was recorded. Comparing low-pressure efficiency for 1996-2006, the eleven complete years 

available, for species collected regularly the time series shows percentages to be generally 

consistent with a range between 55 and 97% (Figure 8). Eight exceptions were observed. The 

1998, 2005 and 2006 values for menhaden (38, 51 and 46%, respectively) appear low compared 

to 1996 to 2004 values, and the 1999 and 2001 values for northern pipefish, (Sygnathus fuscus; 

34 and 30%, respectively) were low compared to its 1996-2004 efficiency percentages (2002 

thru 2005 numbers of fish collected were too few to evaluate wash efficiency). The 2002, 2003 

and 2004 values for Atlantic silverside (20, 30 and 47 %, respectively) appear to be low 

compared to the other 1996 to 2001 values. Lastly, the 2005 values for winter flounder (46%) 

were lowest compared to the 1996 to 2006 values. No clear explanation is apparent for the lower 

than expected values although some previous collections have coincided with large numbers of 

leaves and trash with which these fish may have become entangled. Entanglement of fish in 

aquatic vegetation was believed to reduce low-pressure wash efficiency at the waste energy 

(RESCO) facility in Saugus, MA (MRI 1988). 

 The monthly low-pressure efficiency values, where sufficient numbers of fish were 

impinged (extrapolated totals greater than 110), indicated that 2006 values were consistent with 

previous monthly estimates. Menhaden values for five months ranged from 0% (November) to 

99% (September). Low-pressure efficiency values for menhaden appeared low relative to 

previous seasons with the exception of September (Figure 9). The low efficiency for November 

was probably an anomaly due to problems caused by high debris loading during the month (see 

methods). Winter flounder values for eight months ranged from 63% (June) to 91% October). 

June and July were the only months to have below average low-pressure return efficiency values 

in 2006 compared with the pooled data from 1995-2005 (Figure 10). Tautog were caught in 

sufficient numbers in May and June (96 and 100%, respectively) to assess the monthly lowpressure efficiency. Both values exceeded the pooled data set (Figure10). 

 
 11 Normandeau Associates, Inc.

Multi-year Impingement Comparisons

 The number of species represented in the catch in 2006 (43) ranked fifth out of 29 years 

and exceeded the long term mean of 31 species dating back to 19752

. 

 Impingement totals by species for 2006 were compared with past data sets. Since 

repowering, there does not appear to be any apparent trends in RIS abundance based on 

impingement collections. Totals for 2006 as well as 1992 through 2005 are tabulated together 

with the geometric mean for the 1975 through 1993, 1996-2005 time series (Table 1). The 1992 

through 2006 sample years are tabulated together because the sampling regime changed in 1992 

(see Methods). Annual totals for 1975 through 2006 appear in Table 5 with the exception of 

1980 when an impingement survival study replaced the regular abundance program. Although 

shown, totals for 1994 and 1995 represent only a portion of the year because the screens were 

replaced between October 1994 and mid-July 1995. Estimated annual impingement values for 

19 selected species plus all species combined are presented in Figure 11 (1994 and 1995 were 

omitted here). The list of 19 includes the typical numerical dominants plus any RIS which have 

been numerically important in past years regardless of their rank in 2006. To facilitate 

comparison of 2006 values with past years, standard normal scores or standard deviates (also 

referred to as Z scores) were computed for each species. Standard scores express the degree of 

departure from the long-term mean in terms of the standard deviation (see for example Zar 1974, 

Chase and Brown 1992, Sokal and Rohlf 1995). Since the 29 annual totals (1975-1993, 1996-

2004, 1980 excluded) for any given species do not conform to the normal distribution in most 

cases because of occasional high values, totals were first log-transformed ln (x + 1). Spot checks 

(Ryan and Joiner 1976) confirmed that this procedure normalized each species' data set except 

for rarely encountered species, i.e. where many years contained zeros (Table 5); in these cases 

the standard scores are recognized as somewhat biased. 

 The annual fish impingement total for all species for 2006 was 97,782, ranking tenth over 

the 29-year time series (Figure 11). Reviewing individual species totals, those impinged in 

particularly high numbers in 2006 (positive standard scores) compared to past years included 

white perch, cunner, Atlantic menhaden and tautog. The 2006 totals for white perch ranked first, 

cunner fourth, menhaden sixth and tautog twelfth over the 29-years (Figure 11, Table 5). Winter 

flounder were impinged in relatively low numbers in 2006 ranking 23rd (2,088 fish, 50% of their 

long term mean of 5,192 fish, Figure 11). 

Impingement Rates versus Flow and Temperature

 For each year from 1992 to 2006 total numbers of fish impinged each week were 

compared with intake water temperature (mid-depth readings) and through-plant flow rates 

(Appendix Table 1) to determine if any relationship can be detected among these variables. Both 

temperature and flow have been shown to influence fish impingement rates at other power 

station intake structures (see for example Grimes 1975, Lifton and Storr 1978, Turnpenny 1983, 

Harmon et al. 1999). At higher intake velocities, fish are more likely to drift onto the screens 

and once there, greater water pressure or intake velocities will make it more difficult to swim 

 

2

 construction-shortened 1994 and 1995 seasons were excluded from the mean. 
 12 Normandeau Associates, Inc. 

away, particularly if a fish orients perpendicular to the flow at any point. Impingement often 

increases with declining water temperatures, presumably as a direct result of declining metabolic 

activity. Fish also move to deeper water in winter to escape cold surface waters while intake 

velocity at the face of the screens often increases with depth because the pump intakes are 

located near bottom. 

 Since repowering in 1995, the water temperature and numbers of fish impinged were 

significantly correlated in only 4 out of the past 12 years. Numbers of fish were first logtransformed before Pearson correlation coefficients (r) were calculated. Since some annual data 

sets deviated from normality even following ln transformation, nonparametric Spearman’s Rank 

correlation coefficients (rs) were also calculated (Table 6). A statistically significant negative 

correlation with water temperature was found in 1992, 1993, and 1997 indicating that numbers of 

fish impinged increased with declining temperatures. The relationship was strongest in 1992 

before the intake screens were upgraded (r = -0.695, probability, p < 0.001). That season 48% of 

the variation in numbers impinged could be explained by water temperature. The inverse 

relationship between numbers impinged and water temperature during those years supports the 

postulate that fish are more susceptible to impingement during cold-water months when their 

metabolism, reaction time, and swimming ability are at a minimum. High impingement totals 

for August 2006 were inconsistent with the cold water pattern since the high impingement rate 

was due to a large River population of menhaden. 

 The 1998, 1999, and 2001 data sets contrasted with 1992, 1993, and 1997 in that numbers 

impinged and water temperature were positively correlated. The positive relationship between 

water temperature and numbers impinged during those years may be attributable to strong 

positive correlations between temperature and flow; r = 0.755, p = 0.001 in 1998, r = 0.426, p = 

0.002 in 1999, and r = 0.308, p = 0.026 in 2001. Highest mean monthly flow rates in 1998, 

1999, and 2001 occurred in July, August, and September, the warmest time of year. Variation in 

intake flow with season of the year reflects to some extent regional power requirements and 

these are not consistent from year to year perhaps due to weather patterns. In years preceding 

1998 either no statistically significant correlation between flow and temperature (1994, 1996) 

was found or the relationship was inverse (1993, 1995, 1997), intake flow averaging higher 

during winter. It is also notable that juvenile Atlantic menhaden contributed a high percentage of 

the impingement catch from 1999 to 2006. These fish are most abundant inshore during summer 

and early fall when water temperatures are near their seasonal highs. 

 Statistically significant correlations with intake flow were observed in seven of the fifteen 

years examined - 1992, 1994, 1996, 1997, 1998, 1999 and 2001. In each case the relationship 

was positive suggesting that impingement increases with increasing flow. The 1994 data set 

presented the strongest case (r = 0.596, p = 0.001), 36% of the variation in number impinged 

being explained by intake flow. In 2006 there was no apparent correlation between ln flow and 

ln fish (r = 0.187, p = 0.184). Since neither the ln transformed number of fish impinged nor ln 

transformed station flow were normally distributed, the straight correlation coefficient should be 

viewed with caution. As Figure 12 displays, four flow regimes predominated during the year, 

three of the four with a wide range of impingement rates. While the remaining data show little 

relationship over the range of flows at which the plant operated, the indication is that 

impingement drops off at low flow. 
 13 Normandeau Associates, Inc.

Year 2002 proved to be only the third, with the exception of the short 1995 season and 

2000, in which neither water temperature (r = 0.240 p = 0.086) nor flow (r = -0.096, p = 0.499) 

were statistically correlated with numbers of fish impinged, inconsistent with previous years. 

The first time no correlation appeared was in 2000. The absence of a relationship with flow in 

2000 and 2002 was likely due, at least in part, to limited range in flow. Over the course of the 

respective years 69% and 48% of the impingement samples were collected under the same 

circulating water flow rate (10.8 million gallons per hour). Reasons for lack of correlation with 

temperature during those two years are not readily apparent but similar results were obtained in 

1994, 1996, and 2000 as well. 

 Data sets from 1995 through 2006 were pooled to encompass years following 

replacement of the intake screens with high and low pressure spray headers, Ristroph-type screen 

panels, and continuous operation. With the pooled data set numbers of fish impinged were 

positively but very weakly correlated with water temperature (r = 0.106, p = 0.01; Figure 12). 

However, regression analysis indicated that only 2% of the variation in numbers impinged from 

1995 - 2006 could be explained by water temperature. The pooled data set (Rs = 0.026, p = 

0.531), like the 2006 data, was not normally distributed and the Spearman rank coefficients were 

not statistically significant. The amount of variation in the data is remarkable and reflected in 

the low correlation coefficients. 

 Results of the individual annual analyses as well as the multi-year view indicate that 

much of the variation in numbers of fish impinged remains unexplained. Likely, other sources 

include random and non-random movements of individual fish and fish schools coupled with 

natural cycles of seasonal activity and variations in population size. Fish move in and out of the 

intake canal as they forage for food and likely encounter the intake screens as they do so. Other 

individuals no doubt encounter the face of the screens unintentionally as they seek to evade 

predators. In some locations strong winds associated with significant storm events have been 

associated with high rates of impingement (NUSCO 1987, NAI 1996). No wind effect has been 

noted at the Manchester Street intake, perhaps because it is well protected from all but southerly 

winds. 

 The large numbers of young-of-the-year menhaden impinged in late summer 1999 to 

2006 extending into the fall and winter of those years reflect to a certain extent the timing 

between the presence of strong year classes of fish susceptible to impingement and high seasonal 

intake flow rates. Menhaden travel in very dense schools and are often attracted both to intake 

and discharge currents. Once the schools arrive, there appears to be a slight observable pattern to 

numbers impinged. Their abundance in recent years could account for the small amount of 

explained variation in numbers impinged within discrete years as well as the pooled data set. To 

explore this possibility further correlation coefficients were recalculated individually for 1999 

through 2006 after removing menhaden from the data sets. In each case, no relationship was 

apparent between numbers impinged and temperature or flow (Table 6). 
 14 Normandeau Associates, Inc. 

Invertebrates

 Macroinvertebrates impinged on the Manchester Street intake screens in 2006 are 

tabulated by month in Table 7. For comparison, monthly estimated totals for 1992 through 2005 

are included since they are the only years during which invertebrates were enumerated from 

impingement collections. Numerical dominants in 2006 included blue crabs (Callinectes sapidus

– 4,877 animals), seven-spine bay shrimp (Crangon septemspinosa – 4,834 animals), and green 

crabs (Carcinus maenas – 596 animals). These three species accounted for 46, 45, and 6%, 

respectively, of the year’s invertebrate total. Blue crabs were impinged from April to December 

and were most abundant in August. Seven-spine bay shrimp were impinged from January to 

March. The majority of blue crabs (68%) were returned to the river via the low-pressure system 

in 2006, while only 19% of the seven-spine bay shrimp were removed by the low-pressure 

system. Green crabs were sampled in all months except March, and August to September. Lady 

crabs were only present in samples from January, August, October and December. 

 Impingement of invertebrates has been highly variable over the twelve complete years 

and two incomplete years for which data are available (Figure 14). Blue crabs were uncommon 

in 1992 (37 total), 1993 (70) and 2004 (83), relatively abundant in 1996 (9,098) and 1998 

(8,117), and most abundant in 1999, 2000, and 2001 (15,384, 17,818, 15,110, respectively). 

Blue crab abundance increased in 2006 for the second year in a row. Bay shrimp followed a 

similar pattern but declined after 1996 (42,708 animals) until 1998 (7,691 animals), and then 

increased in 1999 and 2000 (18,673 and 671,977, respectively). Bay shrimp, after being absent 

from the 2002 collections and relatively low in 2003 (282), were moderately abundant in 2005 

and 2006 (5,695 and 4,834, respectively). Green crabs (Carcinus maenas) were absent from the 

1992, 1993 and 2003 collections, appeared in increasing numbers in the shortened 1994 (five in 

nine months) and 1995 seasons (3,413 in six months), and were relatively abundant in 1997 

(5,505) and 1998 (5,456). Green crab abundance increased in 2005 and 2006 (277 and 596, 

respectively) relative to the 2000 – 2004 period when numbers ranged from 53 in 2000 to zero in 

2003. Lady crab numbers varied with no apparent trend. 
 15 Normandeau Associates, Inc.

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620p. 
 Norman

Atlantic Menhaden (RIS)

Monthly Estimated Impingement Totals

, , , , ,,, ,

,

,

, ,

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

10

100

1,000

10,000

100,000

Number of Fish

010203040506070

Percent Of Total

2006 1992-2005 ,

Atlantic Herring (RMonthly Estimated Impingement 

' 

' ' '

'

'

'

' '

Jan Feb Mar Apr May Jun Jul Aug Sep 

1

10

100

1,000

10,000

2006 1992-2005 '

Winter Flounder (RIS)

Monthly Estimated Impingement Totals

,

,

,

,

, ,

,

, ,

, , ,

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

10

100

1,000

Numbers of Fish

051015202530

Percent Of Total

2006 1992-2005 ,

Atlantic Silverside (

Monthly Estimated Impingement 

&

& & & & & & & & 

Jan Feb Mar Apr May Jun Jul Aug Sep 

10

100

Numbers of Fish

2006 1992-2005 &

Figure 3. Estimated monthly impingement totals for Atlantic menhaden, Atlantic herring, winter flounder, Atlanhake, cunner, tautog, and total fish Manchester Street Station, 2006. Solid lines indicate the percent of total take 1993, 1996-2005 pooled. 
 Norman

Silver Hake

Monthly Estimated Impingement Totals

'

'

'

'

' ' ' ' ' ' ' '

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1

10

100

1,000

10,000

0510152025303540

Percent Of Total

2006 1992-2005 '

Cunner

Monthly Estimated Impingement 

,

,

,

,

,

,

,

,

,

Jan Feb Mar Apr May Jun Jul Aug Sep 

0

4080

120160200240280320

Numbers Of Fish

2006 1992-2005 ,

Tautog (RIS)

Monthly Estimated Impingement Totals

,

,

, , ,

,

,

,

,

,

,

,

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0

50

100150200250300

Numbers Of Fish

051015202530

Percent Of Total

2006 1992-2005 ,

Total Fish

Monthly Estimated Impingement 

, 

, , , , , ,

,

,

Jan Feb Mar Apr May Jun Jul Aug Sep 

100

1,000

10,000

100,000

Number of Fish

2003 1992-2005 ,

Figure 3. Estimated monthly impingement totals for Atlantic menhaden, Atlantic herring, winter flounder, Atlanthake, cunner, tautog, and total fish Manchester Street Station, 2006. Solid lines indicate the percent of total take 1993, 1996-2005 pooled. 
 Norman

(a) 

Atlantic Menhaden

Length Frequency

January - December 2006

Manchester Street Screens

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

220

230

240

250

260

270

280

290

300

310

320

330

Length Class (mm)

05

1015202530

Percent of Total

Mean = 111 (s.e.= 7.67)

n = 192

 (b) 

Winter Flounde

Length Frequency

January - April 2006

Manchester Street Screens

30

50

70

90

110

130

150

170

190

210

230

250

270

Length Class (mm)

05

10152025

Percent of Total

Mean = 

(c) 

Winter Flounder

Length Frequency

May - August 2006

Manchester Street Screens

30

50

70

90

110

130

150

170

190

210

230

250

270

290

310

330

Length Class (mm)

05

10152025

Percent of Total

Mean = 98 (s.e. = 6.11)

n = 83

 (d) 

Winter Flounde

Length Frequency

September - December 2

Manchester Street Screens

30

50

70

90

110

130

150

170

190

210

230

25

Length Class (mm)

05

10152025

Percent of Total

Mean = 

Figure 4. Length-frequency data for Atlantic menhaden (a), winter flounder January- April (b), May-August (c), December (d) impinged on the Manchester Street intake screens, 2006. 
 Norman

(a) 

Atlantic Silverside

Length Frequency

January - June 2006

Manchester Street Screens

30 40 50 60 70 80 90 100 110 120 130 140

Length Class (mm)

0

102030405060

Percent of Total

Mean = 89 (s.e. =6.50)

n = 2

 (b) 

Atlantic Silversid

Length Frequency

July - December 200

Manchester Street Screens

30 40 50 60 70 80 90 100 11

Length Class (mm)

0

10203040506070

Percent of Total

Mean = 101 (s.e.= 10.34)

n = 3

(c) 

White Perch

Length Frequency

January - December 2006

Manchester Street Screens

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

180

190

200

210

220

230

240

250

260

270

280

290

300

Length Class (mm)

05

10152025

Percent of Total

Mean = 114 (s.e.= 2.96)

n = 196

 (d) 

Atlantic Herring

Length Frequency

January - December 20

Manchester Street Screens

30

40

50

60

70

80

90

100

110

Length Class (mm)

0

102030405060

Percent of Total

Mean = 

Figure 5. Length-frequency data for Atlantic silverside January-June (a), July-December (b), white perch (c), Atimpinged on the Manchester Street intake screens, 2006. 
 Normandeau Associates, Inc.

Manchester Street Station - 2006

Fish Return System Efficiency

Atlantic Menhaden

Winter Flounder

Atlantic Silverside

Atlantic Herring

Cunner

Tautog

White Perch

Silver Hake

Atlantic Tomcod

All Others

0

20

40

60

80

100

120

Percent Of Total

HP LP

Figure 6. Percent of the annual total collected in high and low-pressure return lines for numerically 

dominant fish plus “all others”, 2006 

Manchester Street Station

Low Pressure Efficiency

%

%

%

%

%

%

%

%

Atlantic Herring

Winter Flounder

Atlantic Silverside

Tautog

Atlantic Menhaden

Atlantic Tomcod

Northern Pipefish

Cunner

0

20

40

60

80

100

Percent of Total

High/Low 2006 %

Figure 7. Range and mean percent of total number of fish collected at Manchester Street Station which 

were found in the low pressure return line for selected numerically dominant fish, 1996-2006. 
 Normandeau A

Manchester Street Station

Low Pressure Return Efficiency

$ $

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

20406080

100

Percent Of Total

Atlantic Herring Mean 1996-2005 $

Manchester Street Stati

Low Pressure Return Efficiency

$ 

1996

1997

1998

1999

2000

2001

2002

2003

2004

20406080

100

Percent Of Total

Atlantic Menhaden Mean 1996-2005 $

Manchester Street Station

Low Pressure Return Efficiency

$ $

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

0

20406080

100

Percent Of Total

Atlantic Silverside Mean 1996-2005 $

Manchester Street Stati

Low Pressure Return Efficiency

$ 

1996

1997

1998

1999

2000

2001

2002

2003

2004

20406080

100

Percent Of Total

Atlantic Tomcod Mean 1996-2005 $

Figure 8. Percent of total number of fish collected at Manchester Street Station which were found in the low pre

selected numerically dominant fish, 1996-2006. 
 Normandeau A

Manchester Street Station

Low Pressure Return Efficiency

$ $

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

20406080

100

Percent Of Total

Cunner Mean 1996-2005 $

Manchester Street Stati

Low Pressure Return Efficiency

$ 

1996

1997

1998

1999

2000

2001

2002

2003

2004

20406080

100

Percent Of Total

Northern Pipefish Mean 1996-2005 $

Manchester Street Station

Low Pressure Return Efficiency

$ $

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

20406080

100

Percent Of Total

Tautog Mean 1996-2005 $

Manchester Street Stati

Low Pressure Return Efficiency

$ 

1996

1997

1998

1999

2000

2001

2002

2003

2004

20406080

100

Percent Of Total

Winter Flounder Mean 1996-2005 $

Figure 8. Percent of total number of fish collected at Manchester Street Station which were found in the low pre

selected numerically dominant fish, 1996-2006. 
 Normandeau Associates, Inc.

Atlantic Menhaden - 2006

Low Pressure Return Efficiency

,

,

,

,

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0

20

40

60

80

100

Percent Of Total

, 2006 1995-2005

Atlantic Silverside - 2006

Low Pressure Return Efficiency

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0

20

40

60

80

100

Percent Of Total

1995-2005

Figure 9. Percent of total collected in the Manchester Street Station low-pressure return line by month 

for Atlantic menhaden (top) and Atlantic silverside (bottom), 2006. Bars indicate percent by month for 

pooled data collections from 1995-2005. 
 Normandeau Associates, Inc.

Winter Flounder - 2006

Low Pressure Return Efficiency

,

, , , ,

, ,

,

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0

20

40

60

80

100

Percent Of Total

, 2006 1995-2005

Tautog - 2006

Low Pressure Return Efficiency

, ,

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0

20

40

60

80

100

Percent Of Total

, 2006 1995-2005

Figure 10. Percent of total collected in the Manchester Street Station low-pressure return line by 

month for winter flounder (top) and tautog (bottom), 2006. Bars indicate percent by month for pooled 

data collections from 1995-2005. 
 Norman

Alewife (RIS)

Manchester Street Intake Screens

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

0

300600900

1,2001,5001,8002,1002,4002,7003,0003,3003,600

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric Mean

 American Eel 

Manchester Street Intake Sc

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

199

1

Year

0

200400600800

1,0001,2001,4001,600

Number of Fish

Annual Total 1975-1993,1996-2005 Geomet

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

1

10

100

1,000

10,000

100,000

1,000,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric Mean

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

19

Year

10

100

1,000

10,000

100,000

1,000,000

10,000,000

100,000,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometr

Figure 11. Estimated annual totals for 19 species of fish plus total fish impinged on the Manchester Street intake 

(1980, 1994, 1995 excluded, see text). The geometric mean over the 1975-2005 time series is shown by a horizo
 Norman

Atlantic Silversides (RIS)

Manchester Street Intake Screens

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

10

100

1,000

10,000

100,000

1,000,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric Mean

Atlantic Tomcod

Manchester Street Intake Sc

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1

Year

0

400800

1,2001,6002,0002,4002,8003,200

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric 

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

0

200400600800

1,0001,2001,4001,600

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric Mean

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

199

1

Year

1

10

100

1,000

10,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric 

Figure 11. Estimated annual totals for 19 species of fish plus total fish impinged on the Manchester Street intake 

(1980, 1994, 1995 excluded, see text). The geometric mean over the 1975-2005 time series is shown by a horizo
 Norman

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

0

500

1,0001,5002,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric Mean

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

199

1

Year

10

100

1,000

10,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric 

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

10

100

1,000

10,000

100,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric Mean

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1

Year

0

200400600800

1,0001,200

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric 

Figure 11. Estimated annual totals for 19 species of fish plus total fish impinged on the Manchester Street intake 

(1980, 1994, 1995 excluded, see text). The geometric mean over the 1975-2005 time series is shown by a horizo
 Norman

Silver Hake (RIS)

Manchester Street Intake Screens

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

100

1,000

10,000

100,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric Mean

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

199

1

Year

10

100

1,000

10,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric 

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

0

400800

1,2001,6002,0002,4002,8003,200

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric Mean

Weakfish (RIS)

Manchester Street Intake Sc

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1

Year

0

400800

1,2001,6002,0002,4002,800

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric 

Figure 11. Estimated annual totals for 19 species of fish plus total fish impinged on the Manchester Street intake 

(1980, 1994, 1995 excluded, see text). The geometric mean over the 1975-2005 time series is shown by a horizo
 Norman

White Perch

Manchester Street Intake Screens

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

1

10

100

1,000

10,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geometric Mean

Windowpane

Manchester Street Intake Sc

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

199

1

Year

0

500

1,0001,5002,000

Number of Fish

Annual Total 1975-1993,1996-2005 Geomet

Winter Flounder (RIS)

Manchester Street Intake Screens

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

05

10152025

Number of Fish (Thousands)

Annual Total 1975-1993,1996-2005 Geometric Mean

1975

1976

1977

1978

1979

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1996

1997

19

Year

1,000

10,000

100,000

1,000,000

10,000,000

100,000,000

Annual Total 1975-1993,1996-2005 Geomet

Figure 11. Estimated annual totals for 19 species of fish plus total fish impinged on the Manchester Street intake 

(1980, 1994, 1995 excluded, see text). The geometric mean over the 1975-2005 time series is shown by a horizo
 Normandeau Associates, Inc.

Manchester Street Station

Fish Impingement vs. Intake Flow - 2006

,

, , ,

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,

, ,

,

, ,

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,

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,

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2 4 6 8 10 12 14 16

Station Flow (MG/Hr)

0

2.1

4.2

6.3

8.4

Loge Total Fish Per 24 Hours

Rs = 0.181

p = 0.198

Manchester Street Station

Fish Impingement vs. Water Temperature - 2006

,

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1 6 11 16 21 26

Water Temperature (C)

0

2

4

6

8

10

Loge Total Fish Per 24 Hours

Rs = -0.148

p = 0.314

Figure 12. Relationship between numbers of fish impinged (loge) and flow (top) and water 

temperature (bottom), all species combined, Manchester Street Station, 2006. 
 Normandeau Associates, Inc.

Manchester Street Station

Fish Impingement vs. Water Temperature - 1995 - 2006

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0 5 10 15 20 25 30

Water Temperature (C)

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Loge Total Fish Per 24 Hours

Rs = 0.026, p = 0.531

Manchester Street Station

Fish Impingement vs. Intake Flow - 1995 - 2006

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Station Flow (MG/Hr)

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2

4

6

8

10

12

14

16

Loge Total Fish Per 24 Hours

Rs = -0.005, p = 0.895

Figure 13. Relationship between numbers of fish impinged (loge) and flow (top) and water 

temperature (bottom), all species combined, Manchester Street Station, 1992-2006. 
 Norman

Blue Crab

Manchester Street Intake Screens

37

298

9,098

770

8,117

15,38417,81815,109

1,333

297

83

883

4,877

1992 1993 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

1

10

100

1,000

10,000

100,000

Seven-spine Bay Sh

Manchester Street Intake Scre

90

5

42,708

17,126

7,691

18,673

671,997

23,397

1992 1993 1996 1997 1998 1999 2000 2001 2002 

1

10

100

1,000

10,000

100,000

1,000,000

Green Crab

Manchester Street Intake Screens

1,954

5,505 5,456

655

53 57

22

12

277

596

1992 1993 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

10

100

1,000

10,000

Lady Crab

Manchester Street Intake Scre

4,654

37

61,098

1,689

393 405

21

351

13

1992 1993 1996 1997 1998 1999 2000 2001 2002 

10

100

1,000

10,000

100,000

Figure 14.Annual totals for four tnumerical dominant species of macroinvertebrates, Manchester Street intake sc1996-2006. 
Species 2006 2006 Z Score 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 

Atlantic menhaden 89,663 0.5941 194,189 56,889 56,968 11,642,543 884,212 130,042 9,808,927 979 5,527 71,643 White perch 2,651 1.1517 638 3,991 3,744 313 2,908 754 2,348 270 6,537 749 Winter flounder 2,088 -0.9310 29,942 15,997 11,283 8,850 14,622 3,948 9,716 5,902 13,398 15,360 Cunner 894 1.0793 1,267 821 404 4,192 2,420 674 1,942 756 358 610 Tautog 663 0.4618 810 891 895 1,993 1,449 337 753 1,295 2,075 465 Bluegill 287 0.4236 186 55 266 85 228 94 92 2,118 46 597 Atlantic tomcod 173 -0.0549 1,292 2,033 696 639 1,178 388 412 896 500 3,087 Silver hake 160 -0.9202 1,536 10,129 27,305 178 626 115 1,421 911 536 154 Oyster toadfish 146 1.2748 132 272 660 455 419 88 77 67 45 0 American eel 145 -0.4508 54 134 143 257 174 288 555 559 757 1,364 Alewife 115 -0.6000 456 439 406 70 2,601 343 107 102 128 134 Windowpane 95 -0.5055 151 129 34 0 959 127 119 191 1110 591 Crevalle jack 89 1.6302 8 0 20 0 0 10 96 0 19 0 Butterfish 67 0.4476 41 7 51 26 70 20 42 99 250 14 Atlantic silverside 52 -2.8871 6,145 768 5,086 242,786 3,875 1,096 7,317 1,970 58,036 30,712 Spotted hake 50 1.9384 0 0 14 68 0 179 35 0 0 27 Conger eel 47 3.6339 7 0 0 0 19 0 16 000Fourspot flounder 42 1.8013 7 7 7 0 0 38 11 6 0 0 Smallmouth flounder 41 0.9258 60 21 49 35 21 35 159 52 62 109 Hogchoker 27 -0.0244 45 65 192 281 41 12 196 238 51 184 Northern pipefish 27 -0.3662 57 59 7 90 114 176 998 831 719 495 Little skate 22 -0.2798 15 7 438 0 41 116 41 44 124 418 Striped searobin 20 0.0364 90 28 464 38 6,024 76 53 30 19 0 Grubby 19 0.3742 169 45 39 14 243 13 574 147 314 223 Striped killifish 19 -0.5461 34 7 121 306 101 13 47 26 42 113 Blueback herring 18 -0.9527 8 339 154 7 13 33 71 578 80 34 Striped bass 18 1.3479 7 0 0 34 7 11 8 7 35 15 Bay anchovy 14 -0.3426 0 25 14 16 0 0 81 207 32 303 Mummichog 14 -1.2516 104 42 164 154 293 144 7 289 605 691 Summer flounder 14 0.5295 31 45 26 148 0 7 84 19 40 17 Atlantic herring 12 -0.9705 170,912 29,570 4,157 39 499 24,026 22,667 66,150 1,565 10,708 Bluefish 12 0.1779 182 0 20 10 7 7 10,454 0 0 17 Atlantic moonfish 11 0.6238 0 23 43 91 7 21 41 103 0 44 Largemouth bass 10 0.8556 58 7 7 38 9 0 29 6 0 28 Brown bullhead 8 2.3290 0 0 0 0 11 0 0 000Gizzard shad 8 1.1970 34 7 51 0 0 50 7 000Golden shiner 7 1.2972 38 0 15 0 7 7 0 0 0 26 Pollock 7 1.0992 0 0 7 0 0 0 0 005Seaboard goby 7 1.6309 0 0 0 15 11 0 0 6 12 7 Weakfish 7 -0.9692 269 0 0 135 246 40 327 2,732 2,451 60 Lumpfish 5 0.1976 7 0 0 7 259 0 37 0 305 0 Striped cusk-eel 4 1.4275 0 7 0 0 0 13 14 000Threespine stickleback 4 -1.9575 88 416 346 110 749 1,703 398 212 800 545 Total 97,782 409,069 123,275 113,950 11,903,913 923,714 163,341 9,869,881 87,586 95,778 139,004 Grand Total 97,782 409,247 123,382 115,619 11,904,170 928,257 165,192 9,870,753 88,014 96,849 139,479 

Table 1. Total estimated numbers impinged by species, Manchester Street Station, 2006. Standard scores for 2006, comparable totals for 1992 through 200mean (1975-1993, 1996-2005 are also shown (see footnotes).

* Due to repowering upgrades, sampling in 1994 was only possible through September. Sampling in 1995 began in mid-July once new equipment became functional. These two years wetime series means.Grand total includes fish taken in other years but were no listed because they were not taken in 2006. Refer to Table 5 for a complete listing.
Table 2. Estimated numbers of fish impinged on the Manchester Street intake screens by species and month, January-December 2006

Species Jan Feb Mar Apr May Jun Jul Aug Sept Oct No

Atlantic Menhaden 78 79 96 34 14 0 0 79,063 7,295 80 2,57White Perch 49 7 1,048 721 636 35 27 45 6 25 14 Winter Flounder 290 292 253 76 121 218 137 422 112 59 70 Cunner 14 14 23 17 206 302 7 71 126 72 17 Tautog 14 46 20 37 175 134 57 100 37 31 0 Bluegill 20 0 0 0 0 141 38 0 0 13 68 Atlantic Tomcod 53 0 0 0 0 9 7 56 6 19 0 Silver Hake 100 39 14 0 0 0 0 0 0 0 0 Oyster Toadfish 0 0 0 7 42 16 20 18 7 29 7 American Eel 7 26 57 36 0 0 0 0 0 6 0 Alewife 7 0 7 69 0 0 7 12 0 0 0 Windowpane 0 7 0 4 27 8 7 42 0 0 0 Crevalle Jack 0 0 0 0 0 0 0 89 0 0 0 Butterfish 0 0 0 0 0 0 0 67 0 0 0 Atlantic Silverside 14 0 0 0 0 0 0 12 0 12 14 Spotted Hake 7 0 0 28 15 0 0 0 0 0 0 

Conger Eel 28 0 19 0 0 0 0 0 0 0 0 Fourspot Flounder 0 0 0 0 42 0 0 0 0 0 0 Smallmouth Flounder 7 0 12 7 15 0 0 0 0 0 0 Northern Pipefish 0 7 7 13 0 0 0 0 0 0 0 Little Skate 7 0 0 0 7 8 0 0 0 0 0 Hogchoker 0 0 0 0 0 0 7 12 8 0 0 Striped Searobin 20 0 0 0 0 0 0 0 0 0 0 Grubby 0 0 0 7 0 0 0 0 0 12 0 Striped Killifish 0 0 0 12 7 0 0 0 0 0 0 Blueback Herring 0 0 0 18 0 0 0 0 0 0 0 Striped Bass 0 7 4 0 7 0 0 0 0 0 0 Bay Anchovy 0 7 0 0 0 0 0 0 0 7 0 Mummichog 0 0 0 7 7 0 0 0 0 0 0 Summer Flounder 0 0 0 0 0 0 14 0 0 0 0 Atlantic Herring 0 0 0 5 7 0 0 0 0 0 0 Bluefish 0 0 0 0 0 0 0 12 0 0 0 Atlantic Moonfish 0 0 0 0 0 0 0 0 0 0 0 Largemouth Bass 0 0 0 0 0 0 0 0 0 0 10 Brown Bullhead 00008000000
Table 2. Estimated numbers of fish impinged on the Manchester Street intake screens by species and month, January-December 2006

Species Jan Feb Mar Apr May Jun Jul Aug Sept Oct No

Gizzard Shad 00000000008Golden Shiner 70000000000Pollock 00070000000Seaboard Goby 00000000000Weakfish 70000000000Lumpfish 00500000000Striped Cusk-eel 00040000000Threespine Stickleback 00040000000Total Fish 729 531 1,565 1,113 1,336 871 328 80,021 7,597 365 2,78Number of Species 18 11 13 20 16 9 11 14 8 12 9 
Table 3. Mean numbers of fish impinged per million gallons of through-plant flow, Manchester Street Station, January -December, 20

Species Jan Feb Mar Apr May Jun Jul Aug Sep Oct 

Atlantic Menhaden 0.0116 0.0099 0.0114 0.0056 0.0015 0.0000 0.0000 8.8398 1.0132 0.0091 White Perch 0.0066 0.0009 0.1255 0.1138 0.0696 0.0047 0.0037 0.0049 0.0008 0.0027 Winter Flounder 0.0407 0.0475 0.0330 0.0112 0.0131 0.0301 0.0191 0.0441 0.0155 0.0065 Cunner 0.0019 0.0022 0.0026 0.0023 0.0226 0.0425 0.0009 0.0069 0.0174 0.0079 Tautog 0.0019 0.0065 0.0026 0.0055 0.0190 0.0185 0.0078 0.0092 0.0051 0.0040 Bluegill 0.0028 0.0000 0.0000 0.0000 0.0000 0.0196 0.0052 0.0000 0.0000 0.0018 Atlantic Tomcod 0.0080 0.0000 0.0000 0.0000 0.0000 0.0011 0.0010 0.0062 0.0008 0.0020 Silver Hake 0.0140 0.0053 0.0015 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 American Eel 0.0009 0.0035 0.0069 0.0045 0.0000 0.0000 0.0000 0.0000 0.0000 0.0006 Oyster Toadfish 0.0000 0.0000 0.0000 0.0008 0.0046 0.0021 0.0028 0.0020 0.0009 0.0034 Alewife 0.0009 0.0000 0.0008 0.0109 0.0000 0.0000 0.0009 0.0012 0.0000 0.0000 Windowpane 0.0000 0.0013 0.0000 0.0006 0.0030 0.0010 0.0010 0.0036 0.0000 0.0000 Crevalle Jack 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0099 0.0000 0.0000 Atlantic Silverside 0.0019 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0012 0.0000 0.0013 Butterfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0074 0.0000 0.0000 Spotted Hake 0.0010 0.0000 0.0000 0.0041 0.0016 0.0000 0.0000 0.0000 0.0000 0.0000 Conger Eel 0.0038 0.0000 0.0026 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Fourspot Flounder 0.0000 0.0000 0.0000 0.0000 0.0046 0.0000 0.0000 0.0000 0.0000 0.0000 Smallmouth Flounder 0.0009 0.0000 0.0013 0.0009 0.0015 0.0000 0.0000 0.0000 0.0000 0.0000 Northern Pipefish 0.0000 0.0009 0.0008 0.0020 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Hogchoker 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0010 0.0012 0.0010 0.0000 Black Crappie 0.0028 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Striped Searobin 0.0027 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Little Skate 0.0009 0.0000 0.0000 0.0000 0.0007 0.0010 0.0000 0.0000 0.0000 0.0000 Striped Killifish 0.0000 0.0000 0.0000 0.0017 0.0007 0.0000 0.0000 0.0000 0.0000 0.0000 Blueback Herring 0.0000 0.0000 0.0000 0.0023 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Grubby 0.0000 0.0000 0.0000 0.0009 0.0000 0.0000 0.0000 0.0000 0.0000 0.0013 Striped Bass 0.0000 0.0009 0.0005 0.0000 0.0008 0.0000 0.0000 0.0000 0.0000 0.0000 Summer Flounder 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0019 0.0000 0.0000 0.0000 Mummichog 0.0000 0.0000 0.0000 0.0008 0.0007 0.0000 0.0000 0.0000 0.0000 0.0000 Bay Anchovy 0.0000 0.0009 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0007 Atlantic Moonfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Largemouth Bass 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Atlantic Herring 0.0000 0.0000 0.0000 0.0006 0.0008 0.0000 0.0000 0.0000 0.0000 0.0000 Bluefish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0012 0.0000 0.0000 Gizzard Shad 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Golden Shiner 0.0009 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Weakfish 0.0009 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Pollock 0.0000 0.0000 0.0000 0.0008 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Seaboard Goby 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Brown Bullhead 0.0000 0.0000 0.0000 0.0000 0.0008 0.0000 0.0000 0.0000 0.0000 0.0000 Cusk-eels 0.0000 0.0000 0.0000 0.0006 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Threespine Stickleback 0.0000 0.0000 0.0000 0.0006 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Lumpfish 0.0000 0.0000 0.0005 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 
42

Table 4. Total estimated monthly catch for numerically dominant finfish and 'all others' partitioned by low and

 high-pressure wash systems, Manchester Street Station, January - December 2006.

Atlantic Menhaden Atlantic Silverside Winter Flounder Atlantic Herring

Low High Percent Low High Percent Low High Percent Low High Percent 

Pressure Pressure Low Pressure Pressure Low Pressure Pressure Low Pressure Pressure Low

Jan 31 47 39.7% 7 7 50.0% 206 83 71.3% 0 0

Feb 52 26 66.7% 0 0 250 41 85.9% 0 0

Mar 65 31 67.7% 0 0 220 32 87.3% 0 0

Apr 33 0 100.0% 0 0 70 6 92.1% 0 5 0.0%

May 0 13 0.0% 0 0 106 15 87.6% 0 0

Jun 0 0 0 0 134 83 61.8% 0 7 0.0%

Jul 0 0 0 0 86 51 62.8% 0 0

Aug 33,655 45,407 42.6% 0 11 0.0% 302 119 71.7% 0 0

Sep 7,212 82 98.9% 1 0 100.0% 99 13 88.4% 0 0

Oct 68 12 85.0% 12 0 100.0% 53 5 91.4% 0 0

Nov 0 2,574 0.0% 0 13 0.0% 9 60 13.0% 0 0

Dec 225 126 64.1% 0 0 27 11 71.1% 0 0

Total 41,341 48,318 46.1% 20 31 39.2% 1,562 519 75.1% 0 12 0.0%

Cunner Tautog White Perch Silver Hake

Low High Percent Low High Percent Low High Percent Low High Percent 

Pressure Pressure Low Pressure Pressure Low Pressure Pressure Low Pressure Pressure Low

Jan 14 0 100.0% 14 0 100.0% 49 0 100.0% 69 31 69.0%

Feb 7 7 50.0% 32 14 69.6% 7 0 100.0% 33 6 84.6%

Mar 17 6 73.9% 13 6 68.4% 930 118 88.7% 7 6 53.8%

Apr 11 6 64.7% 37 0 100.0% 652 68 0 0

May 193 13 93.7% 169 6 96.6% 492 144 0 0

Jun 287 14 95.3% 133 0 100.0% 35 0 0 0

Jul 6 0 100.0% 50 7 87.7% 27 0 0 0

Aug 71 0 100.0% 100 0 100.0% 22 22 0 0

Sep 126 0 100.0% 37 0 100.0% 6 0 100.0% 0 0

Oct 72 0 100.0% 18 13 58.1% 25 0 0 0

Nov 7 10 41.2% 0 0 7 7 0 0

Dec 18 6 75.0% 11 0 100.0% 37 0 100.0% 6 0 100.0%

Total 829 62 93.0% 614 46 93.0% 2,289 359 86.4% 115 43 72.8%

Atlantic Tomcod All Others

Low High Percent Low High Percent 

Pressure Pressure Low Pressure Pressure Low

Jan 41 11 78.8% 86 27 76.1%

Feb 0 0 45 6 88.2%

Mar 0 0 75 33 69.4%

Apr 0 0 148 67 68.8%

May 0 0 118 55 68.2%

Jun 0 8 0.0% 123 47 72.4%

Jul 7 0 100.0% 86 7 92.5%

Aug 0 55 0.0% 158 88 64.2%

Sep 6 0 100.0% 13 0 100.0%

Oct 19 0 54 11 83.1%

Nov 0 0 36 55 39.6%

Dec 23 0 100.0% 30 18 62.5%

Total 96 74 56.5% 972 414 70.1%
Table 5. Estimated numbers of fish impinged on the Manchester Street Station revolving screens January-December by species, 1975-2006 (1980 excluded 1).

Species 1975 1976 1977 1978 1979 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 2 1995 3 

African pompano 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 Alectis ciliarisAlewife 1,459 518 1,484 491 518 335 817 770 213 1,640 3,498 636 1,113 226 659 197 6 0 150 26  Alosa pseudoharengusAmerican eel 119 168 238 245 707 1,106 718 647 209 187 106 330 103 124 62 324 34 51 24 391  Anguilla rostrataAmerican shad 0 0 0 0 0 0 208 56 0 14 0 0 0 0 0 0 0 0 0 0 

 Alosa sapidissimaAtlantic cod 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Gadus morhuaAtlantic herring 28 28 21 121 0 19 0 46 84 16,515 11 1,948 104 830 288 452 187007 1 Clupea harengusAtlantic mackerel 0 0 0 19 0 0 0 0 0 0 0 0 0 0 0 0 0 0 13 0 

 Scomber scombrusAtlantic menhaden 50,630 12,734 24,619 18,876 494 1,285 54 2,147 827 18,831 29,440 1,510 2,344 9,974 2,976 38,836 159,328 247 25 138 7 Brevoortia tyrannusAtlantic moonfish 0 0 0 0 0 0 0 0 0 216 0 0 0 0 0 0 0 0 0 44 

 Selene setapinnisAtlantic silverside 1,305 1,106 21,129 1,854 1,212 12,196 24,583 9,687 97 4,677 4,471 11,273 24,824 14,873 12,365 3,089 3,215 804 1,071 1,528 3 Menidia menidiaAtlantic tomcod 0 14 0 244 247 297 2,359 255 1,367 2,197 329 307 158 36 281 0 15 39 742 348  Microgadus tomcodBanded killifish 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

Fundulus diaphanusBay anchovy 0 98 658 0 308 461 159 585 60 59 0 0 95 1,385 161 350 96 0 0 563  Anchoa mitchilliBlack crappie 0 0 0 0 0 0 0 0 0 0 0 0 54 113 0 0 0 0 0 13 

 Pomoxis nigromaculatusBlack sea bass 0 0 21 0 19 0 0 0 0 0 0 0 0 0 0 0 0 0 0 33  Centropristis striataBlack spotted stickleback 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Gasterosteus wheatlandiBlueback herring 168 70 273 791 492 1,089 7,799 500 301 502 164 233 1,012 164 247 164 0 0 6 110  Alosa aestivalisBluefish 0 0 42 17 73 157 869 810 40 265 30 75 0 128 48 0 0 0 0 7 

 Pomatomus saltatrixBluegill 84 154 287 338 967 492 1,100 224 744 58 89 803 49 254 50 0 69 0 29 70  Lepomis macrochirusBlue runner 0 24 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 50 

 Caranx chrysosBrown bullhead 0 0 0 0 33 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7  Ameiurus nebulosus
Table 5. (continued).

Species 1975 1976 1977 1978 1979 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1 1995 2 

Brown Trout 00000000000000000000

 Salmo truttaButterfish 0 112 112 37 114 90 0 0 52 283 367 0 95 386 48 40 0 0 0 18  Peprilus triacanthusChain pickerel 0 0 0 19 0 0 56 0 0 140000000000

 Esox nigerCommon carp 0 0 0 0 50 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Cyprinus carpioConger eel 0 0 0 0 0 0 0 14 0 0 0 0 0 0 0 0 0 0 0 0  Conger oceanicusCrevalle jack 0 0 21 0 0 112 252 94 0 0 0 0 0 68 0 0 0 0 0 0  Caranx hipposCunner 28 14 168 124 34 51 380 0 0 0 0 0 0 0 51 246 19 0 128 529 

 Tautogolabrus adspersusFourspine stickleback 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 12 0  Apeltes quadracusFourspot flounder 0 14 0 0 0 22 0 48 0 0 0 0 0 42 0 0 19 0 0 0  Paralichthys oblongusGizzard shad 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Dorosoma cepedianumGolden shiner 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Notemigonus crysoleucasGrubby 0 0 0 0 0 0 0 0 0 73 0 88 0 0 0 0 0 12 10 34  Myoxocephalus aenaeusHogchoker 0 0 0 0 17 21 0 0 61 22 1,367 365 577 0 192 388 8 12 0 57  Trinectes maculatusInland silverside 00000000000000000050

 Menidia beryllinaKillifish 14 - - - - - - - - - - - - - - - - - - - - 

 Fundulus spp.Largemouth bass 0 0 21 19 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Micropterus salmoidesLittle skate 14 0 0 17 179 150 124 0 63 795 401 550 394 168 62 0 39 13 3 40  Raja erinaceaLonghorn sculpin 00000000000000000070 Myoxocephalus octodecemspinosusLookdown 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Selene vomerLumpfish 0 0 19 19 17 0 0 0 0 14 0 0 61 0 0 0 0 0 0 0 

 Cyclopterus lumpusMullet 0 0 0 19 0 0 60 0 14000000000000

 Mugil spp.
Table 5. (continued).

Species 1975 1976 1977 1978 1979 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1 1995 2 

Mummichog 1,057 1,160 6,433 4,355 8,479 6,198 60,974 115 0 750 165 683 42 331 482 0 165 326 200 139  Fundulus heteroclitusNorthern kingfish 0 0 0 0 17 0 0 0 0 0 0 0 0 0 48 0 0 0 0 0 

 Menticirrhus saxatilisNorthern pipefish 48 56 56 0 17 41 114 0 48 84 47 73 0 120 234 101 7 110 539 529  Syngnathus fuscusNorthern puffer 00000000000000000000 Sphoeroides maculatusNorthern searobin 0 14 0 0 0 0 0 0 0 0 0 0 0 0 208 0 0 0 0 41 

 Prionotus carolinusOyster toadfish 0 0 0 0 0 0 0 0 0 0 0 0 0 54 0 0 0 0 0 0  Opsanus tauPollock 0 0 0 0 0 49 277 0 0 0 0 0 0 0 0 0 0 0 0 0  Pollachius virensPumpkinseed 0 0 0 0 0 0 140 0 0 0 0 0 0 0 0 0 0 0 21 0  Lepomis gibbosusRainbow smelt 0 28 35 34 644 150 31 0 0 0 0 0 53 78 0 0 0 0 0 11  Osmerus mordaxRed hake 0 294 413 78 1,387 96 620 0 0 87 15 0 51 175 0 0 0 20 0 6 

 Urophycis chussRock gunnel 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 Pholis gunnellusRound herring 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Etremeus teresSand lance 0 0 0 0 16 17 0 0 0 0 0 0 63 0 0 0 0 0 0 0  Ammodytes sp.Scup 0 0 0 0 0 0 0 0 0 0 0 0 0 0 51 92 672 0 0 7 

 Stenotomus chrysopsSeaboard goby 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

 Gobiosoma ginsburgiSea lamprey 00000000000000000000 Petromyzon morinusSheepshead minnow 00000000000000000000 Cyprinodon variegatusSilver hake 992 3,080 6,272 2,370 11,987 424 2,810 2,263 156 2,900 1,723 508 1,174 1,300 1,522 0 626 212 23 47  Merluccius bilinearisSmallmouth flounder 14 0 0 0 0 0 0 0 0 0 0 68 0 32 0 0 0 21 0 0 

 Etropus microstomusSmooth dogfish 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6 

 Mustelus canisSpot 00000000000000000000 Leiostomus xanthurus
Table 5. (continued).

Species 1975 1976 1977 1978 1979 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1 1995 2 

Spotted hake 28 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Urophycis regiaStriped anchovy 00000000000000000000

 Anchoa hepsetusStriped bass 0 0 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0 13 

 Morone saxatilisStriped cusk-eel 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7 0 

 Ophidion marginatumStriped killifish 0 196 762 877 826 1,703 2,589 99 0 89 23 0 369 442 463 0 25 37 25 14  Fundulus majalisStriped searobin 290 14 21 33 36 0 0 0 0 0 150 0 0 0 0 471 718 43 0 0 

 Prionotus evolansSummer flounder 0 0 0 0 0 0 0 0 361 245 0 0 0 0 0 0 0 0 0 0  Paralichthys dentatusTautog 34 56 56 145 6,394 720 1,895 56 95 84 0 316 1,343 495 152 214 20 92 258 445  Tautoga onitisThreespine stickleback 28 98 56 52 3,004 240 51 56 0 716 141 520 2,661 187 75 0 110 136 59 0  Gasterosteus aculeatusWeakfish 1,543 28 1,253 751 42 624 2,470 48 0 49 16 60 0 0 52 464 82 0 0 6 

 Cynoscion regalisWhite crappie 00000000000000000000

 Pomoxis anularisWhite hake 14 28 217 23 417 0 0 0 0 75 0 0 0 0 0 0 0 0 0 0 

 Urophycis tenuisWhite perch 14 0 217 0 130 178 40 312 240 163 11 56 53 137 41 160 392 2,896 232 19  Morone americanaWhite sucker 0 0 0 0 84 44 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Catostomus commersoniWindowpane 129 196 259 208 1,388 817 89 93 81 1,967 673 798 523 1,148 78 163 123 38 65 70  Scophthalmus aquosusWinter flounder 2,381 1,148 1,503 3,017 15,101 3,273 11,207 4,212 1,572 25,340 748 7,106 5,516 2,365 10,823 2,422 1,660 1,935 912 4,295 1 Pleuronectes americanusYellow perch 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  Perca flavesensTotal 60,421 21,748 66,647 35,193 55,467 32,467 122,845 23,137 6,811 78,911 43,985 28,306 42,768 35,468 32,139 47,610 167,635 7,151 4,566 9,741 13Number of species 22 27 28 29 35 31 29 23 21 31 23 22 24 28 28 17 24 19 26 36 

1Due to impingement survival study conducted in 1980, no standard impingement studies were conducted.2Due to repowering upgrades sampling in 1994 was only possible through September.3Sampling in 1995 began in mid-July once new equipment became functional.
Appendix 2. Errata – 2002 – 2005 Annual Impingement Reports 

Report Title: Impingement Monitoring at Manchester Street Station - 2002 

Page 5, last paragraph the sentence reading: 

In September, 62% of the annual total of menhaden was impinged, 

yielding an impingement rate of 3,312 fish per hour and 5,046 fish per 

million gallons of through-plant flow (Table 3). 

This sentence should read: 

In September, 62% of the annual total of menhaden was impinged, yielding an 

impingement rate of 3,312 fish per hour and 1,262 fish per million gallons of throughplant flow (Table 3). 

Report Title: Impingement Monitoring at Manchester Street Station - 2003 

Page 5, last paragraph the sentence reading: 

In January 51% of the annual total of menhaden was impinged, yielding an 

impingement rate of 29 fish per hour and 11 fish per million gallons of throughplant flow (Table 3). 

This sentence should read: 

In January 51% of the annual total of menhaden was impinged, yielding an impingement 

rate of 29 fish per hour and 2 fish per million gallons of through-plant flow (Table 3). 

Report Title: Impingement Monitoring at Manchester Street Station – 2004 

On page 6, first paragraph the sentence reading: 

In January alone 51% of the annual total of menhaden was impinged, yielding an 

impingement rate of 27 fish per hour and 19 fish per million gallons of throughplant flow (Table 3). 

This sentence should read: 

In September alone 40% of the annual total of menhaden was impinged, yielding an 

impingement rate of 27 fish per hour and 3 fish per million gallons of through- plant flow 

(Table 3). 

Report Title: Impingement Monitoring at Manchester Street Station – 2005 

On page 6, first paragraph the sentence reading: 

In October alone 54% of the annual total of menhaden was impinged, yielding an 

impingement rate of 141 fish per hour, which is equivalent to 627 fish per million 

gallons of through-plant flow (Table 3). 
This sentence should read: 

In October alone 54% of the annual total of menhaden was impinged, yielding an 

impingement rate of 141 fish per hour, which is equivalent to 125 fish per million gallons 

of through-plant flow (Table 3). 

Corrected versions of each year’s respective Table 3 follow. 
Table 3. Mean numbers of fish impinged per million gallons of through-plant flow, Manchester Street Station, January-December 2002.

Species Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean

Atlantic Menhaden 11.4491 9.1825 5.3102 0.1268 1.1937 0.0174 0.0395 2940.7064 5046.3233 353.8788 13.5754 117.1423 708.2455

Atlantic Silverside 0.0416 0.0056 0.0088 0.0250 0.0346 0.2165 0.0580 1.3769 0.0495 0.0470 0.0469 112.0563 9.4972

Winter Flounder 0.2350 0.1122 0.0782 0.0040 0.0158 0.6273 1.2681 1.6371 0.0000 0.1519 0.0291 0.6763 0.4029

Cunner 0.0374 0.0939 0.1399 0.2197 0.1333 0.8985 0.1744 0.7670 0.0000 0.0000 0.0143 0.0201 0.2082

Tautog 0.0215 0.0113 0.0327 0.0422 0.0739 0.0254 0.0806 0.4572 0.0000 0.0470 0.0263 0.2433 0.0885

Atlantic Tomcod 0.0106 0.0000 0.0000 0.0000 0.0043 0.2177 0.0614 0.0132 0.0000 0.0000 0.0000 0.0410 0.0290

Oyster Toadfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0920 0.1056 0.0180 0.0000 0.0000 0.0000 0.0000 0.0180

White Perch 0.0113 0.0662 0.0694 0.0061 0.0075 0.0327 0.0000 0.0000 0.0000 0.0000 0.0032 0.0138 0.0175

American Eel 0.0000 0.0169 0.0051 0.0208 0.0135 0.0033 0.0120 0.0134 0.0000 0.0000 0.0000 0.0487 0.0111

Mummichog 0.0039 0.0054 0.0050 0.0100 0.0072 0.0174 0.0040 0.0000 0.0495 0.0000 0.0000 0.0000 0.0085

Silver Hake 0.0035 0.0056 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0037 0.0752 0.0073

Weakfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0264 0.0000 0.0000 0.0421 0.0033 0.0060

Threespine Stickleback 0.0582 0.0054 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0053

Black Sea Bass 0.0074 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0069 0.0402 0.0045

Atlantic Moonfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0502 0.0000 0.0042

Northern Pipefish 0.0074 0.0000 0.0037 0.0100 0.0022 0.0043 0.0076 0.0132 0.0000 0.0000 0.0000 0.0000 0.0040

Summer Flounder 0.0000 0.0000 0.0000 0.0000 0.0000 0.0100 0.0000 0.0312 0.0000 0.0000 0.0069 0.0000 0.0040

Crevalle Jack 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0470 0.0000 0.0039

Hogchoker 0.0000 0.0000 0.0000 0.0000 0.0000 0.0088 0.0000 0.0276 0.0000 0.0000 0.0095 0.0000 0.0038

Spotted Hake 0.0035 0.0000 0.0152 0.0052 0.0000 0.0087 0.0119 0.0000 0.0000 0.0000 0.0000 0.0000 0.0037

Bluegill 0.0000 0.0000 0.0000 0.0000 0.0094 0.0000 0.0000 0.0000 0.0000 0.0000 0.0195 0.0135 0.0035

Alewife 0.0000 0.0000 0.0000 0.0000 0.0000 0.0043 0.0047 0.0264 0.0000 0.0000 0.0000 0.0000 0.0030

Striped Killifish 0.0039 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0192 0.0000 0.0000 0.0000 0.0000 0.0019

Striped Searobin 0.0216 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0018

Largemouth Bass 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0036 0.0000 0.0000 0.0000 0.0032 0.0135 0.0017

Atlantic Herring 0.0000 0.0000 0.0000 0.0000 0.0022 0.0098 0.0080 0.0000 0.0000 0.0000 0.0000 0.0000 0.0017

Striped Bass 0.0039 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0132 0.0000 0.0000 0.0000 0.0000 0.0014

Smallmouth Flounder 0.0000 0.0000 0.0051 0.0000 0.0050 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0065 0.0014

Fourspot Flounder 0.0000 0.0000 0.0000 0.0000 0.0000 0.0135 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0011

Butterfish 0.0035 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0064 0.0008

Bay Anchovy 0.0000 0.0000 0.0000 0.0000 0.0000 0.0087 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0007

Seaboard Goby 0.0039 0.0000 0.0000 0.0000 0.0000 0.0043 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0007

Anchovies 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0080 0.0000 0.0000 0.0000 0.0000 0.0000 0.0007

Scup 0.0035 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0037 0.0000 0.0006

Rock Gunnel 0.0000 0.0000 0.0038 0.0000 0.0022 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0005

Bluefish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0055 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0005

Spot 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0047 0.0000 0.0000 0.0000 0.0000 0.0000 0.0004

Grubby 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0040 0.0000 0.0000 0.0000 0.0000 0.0000 0.0003

Blueback Herring 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0038 0.0000 0.0000 0.0000 0.0000 0.0000 0.0003

Windowpane 0.0000 0.0000 0.0038 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0003

Lumpfish 0.0000 0.0000 0.0037 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0003

Red Hake 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0036 0.0000 0.0000 0.0000 0.0000 0.0000 0.0003
Table 3. Mean numbers of fish impinged per million gallons of through-plant flow, Manchester Street Station, January -Decemb

Species Jan Feb Mar Apr May Jun Jul Aug Sep Oct Atlantic Menhaden 11.0210 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1.9433 5.1018 6.5513 Silver Hake 1.4274 0.3800 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0086 Winter Flounder 0.4274 0.2246 0.1548 0.2543 0.0534 0.0512 1.1029 0.4007 0.4635 0.5196 Atlantic Silverside 0.4326 0.0979 0.0055 0.0000 0.0000 0.0028 0.0038 0.0543 1.3968 0.7539 Atlantic Herring 0.0000 0.0000 0.0000 0.0000 0.0000 0.3239 1.9815 0.0190 0.0000 0.0000 White Perch 0.0217 0.2109 0.5270 0.0104 0.0331 0.0000 0.0000 0.0039 0.0000 0.0037 Tautog 0.0429 0.0090 0.0564 0.0711 0.0745 0.0898 0.0270 0.0077 0.0039 0.0193 Atlantic Tomcod 0.0064 0.0000 0.0000 0.0104 0.0000 0.0777 0.1684 0.0394 0.0042 0.0039 Weakfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0115 0.1097 0.0859 0.0843 Oyster Toadfish 0.0000 0.0000 0.0000 0.0000 0.0069 0.0772 0.1972 0.0587 0.0105 0.0075 Striped Searobin 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0144 0.1471 Alewife 0.0031 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0703 0.0345 Cunner 0.0222 0.0040 0.0000 0.0588 0.0485 0.0460 0.0079 0.0039 0.0035 0.0151 Threespine Stickleback 0.0158 0.1184 0.0796 0.0000 0.0000 0.0034 0.0000 0.0000 0.0000 0.0000 Scup 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0038 0.0041 0.0297 0.1459 Bluegill 0.0000 0.0000 0.0048 0.0104 0.0118 0.0451 0.0605 0.0041 0.0000 0.0043 Blueback Herring 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0306 Hogchoker 0.0000 0.0000 0.0000 0.0000 0.0072 0.0063 0.0555 0.0297 0.0000 0.0081 Mummichog 0.0000 0.0000 0.0000 0.0104 0.0640 0.0253 0.0000 0.0000 0.0000 0.0000 Black Sea Bass 0.0324 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0077 American Eel 0.0031 0.0085 0.0174 0.0000 0.0035 0.0039 0.0000 0.0000 0.0039 0.0039 Striped Killifish 0.0000 0.0204 0.0228 0.0104 0.0048 0.0034 0.0000 0.0000 0.0000 0.0000 Windowpane 0.0000 0.0000 0.0000 0.0238 0.0048 0.0000 0.0038 0.0000 0.0000 0.0000 Butterfish 0.0032 0.0000 0.0000 0.0000 0.0000 0.0034 0.0032 0.0039 0.0000 0.0000 Little Skate 0.0000 0.0072 0.0055 0.0000 0.0000 0.0000 0.0164 0.0000 0.0000 0.0000 Striped Bass 0.0092 0.0000 0.0109 0.0000 0.0000 0.0000 0.0000 0.0033 0.0000 0.0000 Smallmouth Flounder 0.0130 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Atlantic Moonfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0038 0.0000 0.0077 Grubby 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0077 0.0000 0.0000 0.0000 Spot 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0236 0.0000 0.0000 Rainbow Smelt 0.0000 0.0040 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Golden Shiner 0.0000 0.0000 0.0000 0.0158 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 
Table 3. (continued).

Species Jan Feb Mar Apr May Jun Jul Aug Sep Oct Gizzard Shad 0.0000 0.0135 0.0031 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Summer Flounder 0.0000 0.0000 0.0000 0.0000 0.0035 0.0000 0.0032 0.0077 0.0000 0.0000 Brown Trout 0.0000 0.0000 0.0000 0.0123 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Crevalle Jack 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0041 0.0000 0.0074 Bluefish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0035 0.0000 Bay Anchovy 0.0000 0.0000 0.0000 0.0000 0.0000 0.0034 0.0000 0.0000 0.0000 0.0000 Black Crappie 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Striped Anchovy 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Spotted Hake 0.0000 0.0040 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Pollock 0.0000 0.0000 0.0000 0.0000 0.0000 0.0039 0.0000 0.0000 0.0000 0.0000 Largemouth Bass 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Pumpkinseed 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Lookdown 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0036 African Pompano 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0035 0.0000 Northern Pipefish 0.0032 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Fourspot Flounder 0.0032 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 
Table 3. Mean numbers of fish impinged per million gallons of through-plant flow, Manchester Street Station, January -December, 2004.

Species Jan Feb Mar Apr May Jun Jul Aug Sep Oct Atlantic Menhaden 18.7053 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0306 12.8177 6.1592 Atlantic Herring 0.0000 0.0000 0.0000 0.0000 3.8122 2.9162 8.6223 0.0000 0.0000 0.0000 Winter Flounder 7.8879 1.2770 0.3080 0.3902 0.2279 0.3936 0.9435 0.5267 0.1521 0.6360 Silver Hake 11.7029 0.0832 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0076 White Perch 1.3735 0.5189 0.8452 0.0469 0.0182 0.0138 0.0035 0.0036 0.0000 0.0000 Atlantic Tomcod 0.0116 0.0038 0.0058 0.0036 0.0214 0.2343 0.1298 0.0040 0.0374 0.0184 Atlantic Silverside 0.2506 0.0867 0.0080 0.0438 0.0000 0.0000 0.0000 0.0000 0.0314 0.0935 Tautog 0.0098 0.0373 0.0081 0.0303 0.0419 0.0358 0.1393 0.0316 0.0130 0.0347 Cunner 0.0000 0.0131 0.0144 0.0370 0.0696 0.0677 0.1051 0.0237 0.0269 0.0307 Threespine Stickleback 0.0000 0.1793 0.0252 0.0251 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Alewife 0.0000 0.0076 0.0000 0.1921 0.0143 0.0113 0.0000 0.0000 0.0000 0.0000 Blueback Herring 0.0000 0.0000 0.0162 0.1628 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Oyster Toadfish 0.0000 0.0000 0.0000 0.0000 0.0157 0.0611 0.0407 0.0197 0.0000 0.0140 Windowpane 0.0137 0.0264 0.0122 0.0000 0.0000 0.0031 0.0000 0.0076 0.0000 0.0000 American Eel 0.0039 0.0108 0.0039 0.0000 0.0000 0.0136 0.0171 0.0079 0.0054 0.0000 Northern Pipefish 0.0263 0.0000 0.0000 0.0069 0.0000 0.0031 0.0000 0.0000 0.0000 0.0076 Scup 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Hogchoker 0.0000 0.0000 0.0000 0.0000 0.0000 0.0205 0.0000 0.0000 0.0000 0.0080 Bluegill 0.0000 0.0000 0.0000 0.0079 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Grubby 0.0000 0.0076 0.0000 0.0073 0.0000 0.0000 0.0098 0.0000 0.0000 0.0000 Summer Flounder 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0111 0.0079 0.0034 0.0000 Mummichog 0.0039 0.0038 0.0039 0.0036 0.0039 0.0031 0.0000 0.0000 0.0000 0.0000 Smallmouth Flounder 0.0134 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Striped Searobin 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Bay Anchovy 0.0000 0.0000 0.0000 0.0000 0.0000 0.0100 0.0000 0.0000 0.0038 0.0000 Atlantic Moonfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0047 Rainbow Smelt 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Fourspot Flounder 0.0067 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 American Shad 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Butterfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Striped Cusk-eel 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Gizzard Shad 0.0039 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Little Skate 0.0000 0.0038 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Red Hake 0.0000 0.0038 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Largemouth Bass 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Striped Killifish 0.0000 0.0038 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Black Sea Bass 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Black Crappie 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 
Table 3. Mean numbers of fish impinged per million gallons of through-plant flow, Manchester Street Station, January -December, 20

Species Jan Feb Mar Apr May Jun Jul Aug Sep Oct NAtlantic Menhaden 266.7750 43.3299 0.0000 0.0000 0.0000 0.0000 0.0473 255.6805 2.8281 627.1177 17.2Atlantic Herring 0.1150 0.0000 0.0000 0.0000 0.0000 267.7883 780.1928 0.0768 0.0000 0.0000 0.0Winter Flounder 23.9413 41.0309 109.9073 5.2803 2.8075 0.6601 6.6245 14.2218 1.8802 0.6943 0.3Atlantic Silverside 5.5234 37.9303 0.2029 0.0000 0.0000 0.0000 0.0000 0.2746 0.1212 0.0445 0.0Silver Hake 0.9920 13.5641 0.2897 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Atlantic Tomcod 0.9364 0.2058 0.6201 0.8115 0.4985 0.1056 0.2776 3.1473 0.1191 0.0000 0.1Cunner 0.1392 0.0413 0.0424 0.1869 0.6698 0.4322 0.0748 3.2914 1.0734 0.8692 0.3Tautog 0.1150 0.3700 0.3032 0.1522 0.2224 0.1464 0.0473 0.5095 0.9981 1.1249 0.4White Perch 0.0383 0.2450 3.5404 0.0000 0.0000 0.0000 0.0000 0.0000 0.0405 0.0000 0.0Alewife 0.1533 0.1624 0.0000 0.0000 0.1108 0.0000 0.0000 0.0393 0.1214 0.0445 0.0Weakfish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1298 0.1200 0.1122 0.6Bluefish 0.0000 0.0000 0.0000 0.0000 0.0000 1.3675 0.0000 0.0000 0.0403 0.0000 0.0Bluegill 0.0000 0.0000 0.0000 0.4837 0.0338 0.0718 0.0000 0.0000 0.0000 0.2882 0.2Grubby 0.0383 0.1502 0.4765 0.2462 0.0554 0.0346 0.0000 0.0000 0.0000 0.0000 0.0Windowpane 0.0383 0.0000 0.2028 0.1884 0.0000 0.0000 0.0000 0.0393 0.3917 0.0000 0.0Oyster Toadfish 0.0000 0.0000 0.0000 0.0000 0.0554 0.1713 0.0834 0.0786 0.0805 0.0858 0.1Threespine Stickleback 0.0000 0.3966 0.2473 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Mummichog 0.0000 0.0000 0.0395 0.2946 0.0000 0.0684 0.0374 0.0588 0.0000 0.0000 0.0Striped Searobin 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.2357 0.0000 0.0445 0.0Smallmouth Flounder 0.2300 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Largemouth Bass 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.3448 0.0Northern Pipefish 0.0383 0.0000 0.0763 0.0457 0.0372 0.0000 0.0000 0.0393 0.0000 0.0000 0.0American Eel 0.0383 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0393 0.0386 0.0000 0.1Summer Flounder 0.0000 0.0690 0.0000 0.0000 0.0000 0.0692 0.0000 0.0000 0.0000 0.0758 0.0Rainbow Smelt 0.1839 0.0406 0.0369 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Hogchoker 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0998 0.0000 0.1174 0.0413 0.0Butterfish 0.0383 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1230 0.0000 0.0000 0.0Golden Shiner 0.0000 0.0000 0.0000 0.2235 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0American Shad 0.0000 0.0406 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1Gizzard Shad 0.0625 0.0406 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0345 0.0Black Crappie 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1034 0.0Black Sea Bass 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Striped Killifish 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0390 0.0000 0.0Little Skate 0.0625 0.0000 0.0000 0.0457 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Scup 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0786 0.0000 0.0000 0.0Yellow Perch 0.0000 0.0000 0.0000 0.0593 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Atlantic Cod 0.0000 0.0000 0.0000 0.0000 0.0554 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Crevalle Jack 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Lookdown 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Blueback Herring 0.0000 0.0000 0.0000 0.0457 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Common Carp 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0413 0.0Lumpfish 0.0000 0.0413 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Pumpkinseed 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0413 0.0Conger Eel 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Striped Bass 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0Fourspot Flounder 0.0000 0.0000 0.0000 0.0000 0.0000 0.0373 0.0000 0.0000 0.0000 0.0000 0.0