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SECTION V

ENTRAINMENT OF PALLID STURGEON THROUGH FLOODWAYS DURING 

THE 2011 LOWER MISSISSIPPI RIVER FLOOD

Executive Summary

Operation of floodways in the Lower Mississippi River (New Madrid, Bonnet Carré, and Morganza) 

could potentially entrain federally endangered pallid sturgeon (Scaphiryhnchus albus) constituting at 

“take” under the Endangered Species Act. Based on experience at the Bonnet Carré Spillway after the 

2008 opening, a recovery effort was launched to determine presence of pallid sturgeon in the 

floodways, successfully capture stranded sturgeon, and release them back into the Mississippi River. 

Each floodway had unique properties that required modified sampling approaches to effectively 

capture entrained sturgeon. Both the Bonnet Carré and Morganza floodways empty into large 

expanses of brackish water making detection very difficult; salinity tolerance of pallid sturgeon is 

unknown. Bonnet Carré and Morganza also have well-defined, low-flow channels that form when 

water recedes after closure making it relatively easy to capture entrained sturgeon if they move 

upstream towards the structure. However, pallids entrained in Morganza can move upstream in the 

Atchafalaya to the Old River Control Complex making it difficult to determine site-specific 

entrainment rates. Also, Morganza has a 7,000-acre forebay that becomes isolated from both the 

Atchafalaya and Mississippi Rivers at lower stages potentially trapping sturgeon. The New Madrid 

floodway in Missouri had widespread flooding with multiple inlets/outlets complicating effective 

sampling strategies. Despite these challenges, all three floodways were sampled multiple times to 

document sturgeon entrainment in the three major floodways and if possible, rescue sturgeon after 

closure of the structures. 

Pallid sturgeon were collected only in the Bonnet Carré floodway after the structure was closed. The 

majority of these fish were relocated back into the Mississippi River; some were retained for 

taxonomic studies by USFWS. Field surveys indicated that it was unlikely that pallid sturgeon, an 

obligate riverine species, would be entrained through Morganza because of the long distance between 

the main channel of the Mississippi River and the structure. Pallid sturgeon entrained through New 

Madrid likely exited the floodway at one of the three crevasses; no pallid sturgeon were found in the 

scour holes after the flood subsided. 

An additional study was conducted to determine the likelihood of Asian carp (silver and bighead 

carps) entering Eagle Lake when the Muddy Bayou structure was opened. Working with the 

Mississippi Department of Wildlife, Fisheries, and Parks, monitoring concluded that Asian carp came 

through the Muddy Bayou structure but none were detected or observed during subsequent surveys.

Detailed information on all of these activities associated with the 2011 Lower Mississippi River Flood 

is presented in the following chapters:

Chapter 1: Evaluation of Pallid Sturgeon Entering Birds Point- New Madrid Floodway

Chapter 2: Evaluation of Pallid Sturgeon Entrained Through the Morganza Floodway

Chapter 3: Entrainment of Sturgeon through the Bonnet Carré Spillway

Chapter 4: Evaluation of Asian Carp Entrained through the Muddy Bayou Control Structure
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Chapter 1: Evaluation of Pallid Sturgeon Entering Birds Point- New Madrid Floodway

Birds Point- New Madrid Floodway - May 16-19 2011. The Birds Point - New Madrid Floodway 

was opened on 2 May 2011. The ERDC Fish Ecology Team and personnel from Memphis District 

and Missouri Department of Conservation sampled in the vicinity of the three inflow/outflow 

crevasses created in the frontline levee of Birds Point – New Madrid Floodway on May 16-19, 2011. 

The Floodway was completely inundated with high water velocities (>2 m/s) near the crevasses and 

lower end during this sampling event. Efforts were made to sample for the federally listed pallid 

sturgeon. The areas sampled included the lower inflow/outflow crevasse near New Madrid and St 

John’s Bayou, the middle inflow/outflow crevasse in the vicinity of Big Oak Tree State Park and the 

upper inflow crevasse at Birds Point (Figures 1.1 – 1.3). The two lower crevasses were reached by 

boats launching at New Madrid; it was approximately 16 miles by boat from St. Johns structure to the 

crevasse adjacent to Big Oak State Park. The upper crevasse at Birds Point was reached by launching 

off the levee near sampling locations. Each reach was sampled overnight using five to six, 60 hook 

trotlines baited with worms and eight hoopnets of varying sizes (3’ hoops with 1” mesh and 4’ hoops 

with 4” mesh). Because of the high water velocities or shallow water conditions, gillnets and trawling 

were limited only to the middle crevasse near Big Oak Tree State Park.

Lower Crevasse (near New Madrid, MO and St John’s Bayou). A total of 32 individuals were 

collected at the lower crevasse representing only seven species (Table 1.1). The majority of the fish 

collected were in hoopnets (Figure 1.4). The dominant species collected was silver carp and 

accounted for half of our sample. Notable fishes included black buffalo and stonecat. No sturgeon 

were observed or captured. Low catch on trotlines could be attributed to high water velocities at the 

lower crevasse. Trotlines had the majority of bait still on the line and were fished in velocities ranging 

from 1-2 meters/second compared to hoopnets fishing in velocities of 0.5 – 3 meters/second with 

similar water depths ranging 6-14 feet. Maximum depth detected at sampling sites was 31 feet.

Middle Crevasse (Vicinity of Big Oak Tree State Park). Eighteen species of fishes were 

collected at the middle crevasse (Table 1.1). The majority of the specimens (n=59) were collected in 

two experimental gill nets (90’ long x 6’ deep with 6, 15’ long panels; mesh size ranged from 1” to 3 

1⁄2 “). These nets were set upstream of the crevasse in six feet of water with velocities 0.5 

meters/second and fished overnight. Hoopnets and trotline sets fished in the downstream path of the 

crevasse had water velocities ranging from 0.49-5 feet/second and also provide additional catch for the 

total effort (n=25). Water depths at sampling locations ranged from 6 to12 feet. Additional species 

not included in this report were collected by personal with the Missouri Department of Conservation 

using a 20’ small mesh trawl. Observation of their catch includes sunfishes and minnows. No 

sturgeon were observed or collected.

Upper Crevasse (at Birds Point). A total of 14 individuals were collected at the upper crevasse 

representing only four species (Table 1.1). Freshwater drum comprised 64% of the catch. The 

majority of the fish were collected on trotlines (n=12). Water depth in the vicinity of the gear was 

much shallower (2.5-6.9 feet) and velocities were much lower (<0.5 meters/second compared to the 

middle and lower crevasse (Figure 1-5). However, a scour hole did exist below one gap with water 

depths of 19 ft. Water dropped almost 1 foot overnight and we had difficulty retrieving the gear the 

next morning due to extreme shallow depths at some locations. Despite the low catch rates for the 

upper crevasse sets, a single shovelnose sturgeon was captured in the last hoopnet set on the last day 

of the trip (Figure 1.6). A rubber band was around the mid-section of the body (Figure 1.6), which was 
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removed before we tagged and released the shovelnose sturgeon back into the Mississippi River. 

Despite all the effort using different sampling gear (hoopnets, trotlines, gillnets and trawls), this was 

the only sturgeon collected during this sampling event. Only one shovelnose sturgeon was collected in 

the upper inflow crevasses at Birds Point (Table 1.1). The fish was later tagged and released back into 

the Mississippi River.

Birds Point- New Madrid Floodway - July 8, 2011 and July 11-12, 2011. MVD’s Commanding 

General and his staff visited Birds Point-New Madrid Floodway on July 7, 2011 and found a dead 

sturgeon at the upper crevasses of Birds Point. They delivered the sturgeon to ERDC Fish Ecology 

Team personnel for identification. We identified it as a shovelnose sturgeon, and the following 

business day the ERDC Fish Ecology Team returned to the Floodway to conduct additional sampling 

at the three crevasses.

The lower crevasses near New Madrid, MO were mainly small, shallow pools, which looked 

unsuitable for large fish like sturgeon. The small pools appeared to be created by the explosions when 

opening the lower crevasse. Many of the small pools had dried up, and those pools present were 

shallow, likely refilled with rain water, and had obvious signs of foraging wading birds (Figure 1.7). 

No sturgeon were found.

The middle crevasse (vicinity of Big Oak Tree State Park) was a large blue hole created by the 

scouring of the Mississippi River as it flowed through the crevasse. Because of its steep banks and 

size, we determined that additional sampling by boat would be necessary at a later date (Figure 1.8). 

Water quality taken at the surface showed high dissolve oxygen (9.4 mg/l) and a water temperature of 

30.8 °C. A smaller scour hole existed near the large blue hole. We were able to sample it using two 

experimental gill nets (90’ long x 6’ deep with 6, 15’ long panels; mesh size ranged from 1” to 3 1⁄2 “). 

The dominant species collected was green sunfish, longnose gar and gizzard shad. Notable sport fish 

collected include largemouth bass and white bass. No sturgeon were observed or captured. Water 

quality was similar to the larger blue hole.

Our last sampling site was at the upper crevasse at Birds Point. In the upper crevasse there were many 

smaller blue holes (scour holes) created by the Mississippi River when the floodway was open. There 

was a massive fish kill in the lower blue hole at Birds Point where the Commanding General and staff 

had collected the dead shovelnose sturgeon. Based on low dissolve oxygen readings (<1.0 mg/l) at the 

bottom, it is likely that the fish kill was in response to the water being pumped out of the blue hole 

causing the mixing of bottom and surface water (Figures 1.9 and 1.10). Areas where dead fish were 

present on the shore or in blue hole were surveyed on foot for a total of four man hours. Because of 

the large number of dead fishes, we only kept track of the species present and ranked them in three 

categories (abundant, common, rare) (Table 1.2). All river sturgeons were counted, photographed, and 

measured if intact (Figures 1.11 and 1.12). If any dead sturgeon were questionable as being the federal 

endangered pallid sturgeon, they were brought back to the laboratory for verification. A total of 22 

species of fishes comprising 11 families were observed or collected including 19 shovelnose sturgeon 

(Table 1.2). Some of these sturgeons were the smallest we have observed entrained measuring 8 1/2 

inches fork length (Figure 1.13). Those specimens were identified as shovelnose sturgeon based on 

anal and dorsal fin ray counts. No pallid sturgeon were observed. 

Birds Point- New Madrid Floodway - July 27-28, 2011. A ramp was constructed at the middle 

crevasse (vicinity of Big Oak Tree State Park) by Memphis District contractors to provide boat access. 
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Water quality parameters for oxygen and temperature were measured vertically at several locations in 

water depths of 35-40 feet (maximum depth was approximately 40 feet). Stratification was evident 

throughout the crevasse. At depths greater than 10-11 feet, dissolved oxygen was less than 1 mg/l and 

water temperature was 60°F. Surface waters were 88 °F and dissolved oxygen was 8.43 mg/L. 

Because of its large size, the blue hole was divided into three reaches (upper, middle and lower). In 

each reach, 3-4 experimental gill nets were deployed for approximately two hours. Due to 

stratification, all nets were fished in the upper water column where dissolved oxygen was sufficient to 

sustain fish. Once nets were deployed, a boat-electroshocker was used for 20-35 minutes to stimulate 

movement of fish in hopes that they would encounter the gill nets. A total of 12 species of fishes were 

collected including shortnose gar, bigmouth and smallmouth buffalo, and freshwater drum. 

Recreational fishes included white bass, largemouth bass, flathead catfish, channel catfish, blue 

catfish, and bluegill. This fish assemblage is similar to borrow pits in the Mississippi River batture. 

Two live shovelnose sturgeon were captured during our sampling efforts. No pallid sturgeon were 

observed.

In upper crevasse at Birds Point, we surveyed six blue holes on foot. In a blue hole next to the one 

that produced 20 shovelnose sturgeon in early July (Table 1.2), we picked up one shovelnose sturgeon. 

In an adjacent blue hole we picked up two more shovelnose sturgeon for a total of three sturgeon 

(Table 2). We also observed 16 other species of fishes. It was apparent that the blue hole had been 

pumped likely contributing to the fish kill and refilled with rainwater and underwater seepage.

Sturgeon Summary

• May 16-19

o Birds Point - 1 shovelnose (live)

• July 12-13:

o Birds Point - 19 shovelnose plus the General’s = 20 shovelnose (all dead)

• July 27-29: 

o Birds Point - 3 shovelnose dead

o Big Oak - 2 shovelnose alive

TOTAL: 26 shovelnose sturgeon
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Table 1.1. Species and Number of Fishes Captured in the Three Crevasses of the Frontline Levee 

of Birds Point- New Madrid Floodway Using Trotlines, Gillnets, and Hoop Nets, May 16-19 2011

Species

Lower Crevasse

St. John’s

Middle Crevasse

Big Oak

Upper Crevasse

Bird Point

Family Acipenseridae (sturgeon)

Scaphirhynchus platorynchus, shovelnose sturgeon - - 1

Family Lepisosteidae (Gar)

Lepisosteus oculatus, spotted gar

Lepisosteus osseus, longnose gar

Lepisosteus platyrhincus, shortnose gar

-

-

-

7

2

13

-

-

-

Family Clupeidae (Herring)

Alosa chrysochloris, skipjack herring

Dorosoma cepedianum, gizzard shad

Dorosoma petenense, threadfin shad

-

-

-

4

1

8

-

-

-

Family Cyprinidae (Minnows)

Cyprinus carpio, common carp

Hypophthalmichthys molitrix, silver carp

Hypophthalmichthys nobilis, bighead carp

-

16

-

4

2

-

-

-

-

Family Catostomidae (Suckers)

Ictiobus bubalus, smallmouth buffalo

Ictiobus cyprinellus, bigmouth buffalo

Ictiobus niger, black buffalo

2

6

1

4

5

2

-

-

-

Family Ictaluridae (Catfishes)

Ameiurus natalis, yellow bullhead

Ictalurus furcatus, blue catfish

Ictalurus punctatus, channel catfish

Noturus flavus, stonecat

-

4

2

1

1

10

7

-

-

3

1

-

Percichthyidae (Temperate Basses)

Morone chrysops, white bass - 2 -

Centrarchidae (Sunfishes)

Lepomis macrochirus, bluegill

Pomoxis nigromaculatus, black crappie

-

-

1

1

-

-

Sciaenidae (Drums)

Aplodinotus grunniens, freshwater drum - 3 9

Total Number of Species 7 18 4
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Table 1.2. Species List of Entrained Fishes Collected or Observed from Birds Point- New Madrid Floodway 1

Species

May 16-18

ERDC, MDC, USACE

July 8,

General and Staff

July 11-12

ERDC

July 27-28

ERDC Total

Family Acipenseridae (Sturgeon)

Scaphirhynchus platorynchus, shovelnose sturgeon n=1 n=1 n=19 n=5 26

Family Polyodontidae (Paddlefish)

Polyodon spathula, paddlefish - - Common Common -

Family Lepisosteidae (Gar)

Lepisosteus oculatus, spotted gar

Lepisosteus osseus, longnose gar

Lepisosteus platyrhincus, shortnose gar

7

2

13

-

-

-

Common

Common

Common

Common

Common

Common

-

-

-

Family Hiodontidae (Mooneyes

Hiodon alosoides, goldeye - - Rare Rare -

Family Clupeidae (Herring)

Alosa chrysochloris, skipjack herring

Dorosoma cepedianum, gizzard shad

Dorosoma petenense, threadfin shad

4

1

8

-

-

-

Common

Abundant

Common

Common

Common

Common

-

-

-

Family Cyprinidae (Minnows)

Cyprinus carpio, common carp

Hypophthalmichthys molitrix, silver carp

Hypophthalmichthys nobilis, bighead carp

Pimephales vigilax, bullhead minnow

4

18

-

-

-

-

-

-

Common

Abundant

Common

Common

Common

Abundant

Rare

Common

-

-

-

- Family Catostomidae (Suckers)

Ictiobus bubalus, smallmouth buffalo

Ictiobus cyprinellus, bigmouth buffalo

Ictiobus niger, black buffalo

6

11

3

-

-

-

Rare

Common

Common

-

-

-

-

-

-

Family Ictaluridae (Catfishes)

Ameiurus natalis, yellow bullhead

Ictalurus furcatus, blue catfish

Ictalurus punctatus, channel catfish

Pylodictis olivaris, Flathead catfish

Noturus flavus, stone cat

1

17

10

-

1

-

-

-

-

-

Common

Common

Common

Rare

-

-

-

-

-

-

-

-

-

-

1

Percichthyidae (Temperate Basses)

Morone chrysops, white bass

Morone mississippiensis, yellow bass

2

-

-

-

Rare

Rare

-

-

-

-

Centrarchidae (Sunfishes)

Lepomis macrochirus, bluegill

Micropterus salmoides, largemouth bass

Pomoxis nigromaculatus, black crappie

1

-

1

-

-

-

Common

Rare

Rare

Common

Rare

Rare

-

-

-

Family Percidae (perches)

Stizostedion canadense, sauger - - Rare Common -

Sciaenidae (Drums)

Aplodinotus grunniens, freshwater drum 12 - Common Common -

ERDC – Fish Ecology Team, EL; MDC – Missouri Dept. of Conservation; USACE – Memphis District Biologists
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Chapter 2: Evaluation of Pallid Sturgeon Entrained Through the Morganza Floodway

The ERDC Fish Ecology Team, with logistic support from Corps Rangers, New Orleans District, 

sampled the Morganza Spillway on July 14 and 18, 2011 for the federally listed pallid sturgeon. Areas 

sampled included below (downstream) the structure, the stilling basin and downstream canal, and the 

forebay above the structure using boat-electroshocker. Total shocking (pedal) time below the structure 

was 53 minutes and 19 minutes along the forebay above the structure (Figure 2.1). Water quality 

parameters varied below and above the structure (Table 2.1). Dissolved oxygen was 5 mg/l below the 

structure, and since these measurements were taken during early afternoon, hypoxic conditions 

probably occur during early morning hours. A total of six hauls was made with a 20-ft seine in the 

forebay. Areas where dead fish were present in scoured pools or on land below the structure were 

surveyed by two people on foot for a total combined time of nine 1/2 hours. Approximately one hour 

was expended in the forebay for dead fish. No sturgeon were observed or captured. 

Because of the massive number of dead fishes present, we only kept track of species and ranked 

abundance into three categories (abundant, common, and rare). A total of 35 species of fishes 

comprised of 14 families were observed or collected (Table 2.2). Gar were observed swimming near 

the structure (Figure 2.2), but most fish were dead (Figures 2.3 – 2.5). The dominant fishes observed 

were silver carp, gizzard shad and bigmouth buffalo. Common fishes included gar, catfishes, 
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silversides, and sunfishes. Rare fishes consisted of a few individuals of skipjack herring, mullet and 

flathead catfish. Based on previous life history studies, many of the fishes observed were backwater 

species. In addition, five species of freshwater mussels typically found in backwaters were observed 

(Table 2.3). Only a few riverine species were present. 

The absence of sturgeon is likely due to the position of the Morganza Structure relative to the 

Mississippi River. The structure is set back a considerable distance from the River compared to the 

Bonnet Carré Spillway. In addition, fish originating from the Mississippi River must travel through 

backwaters in the floodplain and over the potato levee. These barriers likely hamper movement 

towards the structure. Consequently, it is our opinion that entrainment of pallid sturgeon, which is an 

obligate riverine fish, through the Morganza Spillway would be a rare event. 

Table 2.1. Water Quality Data for Morganza Spillway, July 5, 2011

Parameters

Below

Structure

Above

Structure

Average Width (ft) 25 -

Average Depth (ft) 5.98 -

Average Velocity (ft/s) 0.79 -

Average Discharge (cfs) 354 -

Water Temperature (oC) 29.50 31.38

Dissolved Oxygen (mg/L) 5.10 7.44

pH 7.36 7.63

Conductivity (mS) 0.344 0.332

Turbidity (NUT) 18.39 49.9
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Table 2.2. Fish Species Documented in the Morganza Spillway

Species Status

Family Polyodontidae (Paddlefish)

Polyodon spathula, paddlefish Common

Family Lepisosteidae (Gar)

Lepisosteus oculatus, spotted gar

Lepisosteus osseus, longnose gar

Lepisosteus platyrhincus, shortnose gar

Common

Common

Common

Family Amiidae (Bowfin)

Amia calva, bowfin Common

Family Anguillidae (freshwater eels)

Anguilla rostrata, American eel Rare

Family Clupeidae (Herring)

Alosa chrysochloris, skipjack herring

Dorosoma cepedianum, gizzard shad

Dorosoma petenense, threadfin shad

Common

Abundant

Common

Family Cyprinidae (Minnows)

Cyprinus carpio, common carp

Hypophthalmichthys molitrix, silver carp

Hypophthalmichthys nobilis, bighead carp

Ctenopharyngodon idella, grass carp

Common

Abundant

Abundant

Rare

Family Catostomidae (Suckers)

Ictiobus bubalus, smallmouth buffalo

Ictiobus cyprinellus, bigmouth buffalo

Ictiobus niger, black buffalo

Carpiodes carpio, river carpsucker

Rare

Common

Common

Rare

Family Ictaluridae (Catfishes)

Ameiurus natalis, yellow bullhead

Ameiurus melas, black bullhead

Ictalurus furcatus, blue catfish

Ictalurus punctatus, channel catfish

Pylodictis olivaris, flathead catfish

Common

Common

Rare

Common

Rare

Family Belonidae (Needlefishes)

Strongylura marina, Atlantic needlefish Rare

Family Atherinidae (Silversides)

Menidia beryllina, inland silverside Common

Moronidae (Temperate Basses)

Morone chrysops, white bass

Morone mississippiensis, yellow bass

Rare

Rare

Centrarchidae (Sunfishes)

Lepomis cyanellus , green sunfish

Lepomis gulosus, warmouth

Lepomis megalotis, longear sunfish

Lepomis macrochirus, bluegill

Micropterus salmoides, largemouth bass

Pomoxis annularis, white crappie

Pomoxis nigromaculatus, black crappie

Abundant

Common

Rare

Common

Common

Rare

Common

Sciaenidae (Drums)

Aplodinotus grunniens, freshwater drum Rare

Family Mugilidae (Mullets)

Mugil cephalus, striped mullet Rare

Total Number of Species 35
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Table 2.3. Alive and Dead Freshwater Mussels Observed Above and Below the Morganza Spillway

Species Status

Family Unionidae

Pyganodon grandis, giant floater

Utterbackia imbecillis, paper pondshell 

Quadrula apiculata, southern mapleleaf 

Toxolasmus texasensis, Texas lilliput

Uniomerus tetralasmus, pond horn

Abundant

Common

Common

Common

Common
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Chapter 3: Entrainment of Sturgeon Through the Bonnet Carré Spillway

The Bonnet Carré Spillway diverts flood waters from the Mississippi River into a floodway that 

empties into Lake Pontchartrain to reduce river stages at New Orleans. The spillway has been opened 

twice over the past four years, although frequency of openings prior to this period was approximately 

once every 10 years. In 2008, it was open for 27 days beginning April 11th, maximum number of bays 

in operation was 160 out of 350, and maximum discharge through the structure was 160,144 cfs. In 

2011, it was open for 42 days beginning May 9th with a maximum of 330 open bays, which created 

discharges twice as high (315,930 cfs) compared to 2008. Once the structure is closed, discharge 

depends on the amount of water leaking through the pins. 

During both openings, the U.S. Army Corps of Engineers (Corps), Louisiana Department of Wildlife 

and Fisheries (LDWF), and Nicholls State University evaluated entrainment of the federallyendangered pallid sturgeon (Scaphiryhnchus albus) through the structure. In both cases, sturgeon were 

captured during the first week after closing with sampling continuing for numerous weeks. Sampling 

also occurred one week prior to the 2011 opening, but no sturgeon were captured. Multiple sampling 

gears were used including electroshocker, seines, trawls, and gill nets. 

Pre-Opening Sampling - May 4-5, 2011. Several reaches were sampled associated with the Bonnet 

Carré Spillway on May 4-5, 2011 for the federally listed pallid sturgeon. The reaches included the 

Mississippi River in the vicinity of the spillway structure, the upper portion of Barbars Canal, and the 

upper portion of Y Canal. Each reach was sampled using a boat-electroshocker at 60 Hz. At Barbars 

Canal and Y Canal, additional sampling gear was deployed which included experimental gillnets (90’ 

long x 6’ deep with 6, 15’ long panels; mesh size ranged from 1” to 3 1⁄2 “), a 2 1⁄2 trammel net, and 

hoopnets of varying sizes (3’ hoops with 1” mesh and 4’ hoops with 4” mesh). Because of the rising 

water, only four hoopnets were fished overnight in Barbars Canal.

Barbars Canal. A total of 53 individuals were collected in Barbars Canal representing ten 

species (Table 3.1). The majority of the fish collected were by boat-electroshocking. Shocking time 

for this reach was 1,897 seconds. Gillnets and trammel nets were fished overnight resulting in six 

individuals being captured. Low catch in these gears was attributed to trash entangled in the nets from 

floating plant debris displaced by the rising water levels. Overnight hoopnet sets (4) resulted in a 

single silver carp (Figure 3.1). The dominant species collected was striped mullet, follow by silver 

carp and smallmouth buffalo. Rare fishes included bigmouth buffalo and flathead catfish. No sturgeon 

were observed or captured. Discharge in Barbars Canal was 763 cfs on May 4, 2011 and rising (Table 

3.2).

Y Canal. Twenty-one species of fishes were collected in Y Canal (Table 3.1). Many of the 

species were represented by a single individual. Gizzard shad and striped mullet were the dominant 

species collected. No sturgeon were observed or collected. Boat-electroshocking was the most 

effective gear; however gill nets and hoopnets did provide additional catch for the total effort. Soak 

time for gillnets and shocking time was similar to the effort in Barbars Canal, however because of 

rising water within the floodway hoopnets were not fished overnight. On May 4, 2011, the discharge 

in Y Canal was 502 cfs and rising (Table 3.2). Discharge in Barbars Canal above the confluence of Y 

Canal was 763 cfs. Therefore, the approximate discharge in Barbars Canal below the confluence of Y 

Canal on May 4, 2011 was 1265 cfs (763+261 = 1265)
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Mississippi River Reach. Electroshocking was conducted along the Bonnet Carré Spillway (MS 

River side). Three reaches (each end and the middle) of the spillway was shocked for 300 seconds and 

all fish stunned were captured and identified. Additional shocking was conducted in the vicinity of 

entire spillway structure in search for sturgeon only. That shocking time accounted for 2,256 seconds 

(Figure 3.2). No sturgeon were observed or captured. A total of eight species of fish were collected 

for the combined three reaches (Table 3.1). 

Post-Closure: 2008 and 2011. Sampling began once the structure was closed. Three primary areas 

of the floodway were sampled regularly: stilling basin, canals (primarily Barbars and Y), and lakes 

(Figure 3.3). Over 24 days were expended by three crews working either together or separately 

representing LDWF, Nicholls State, and the Corps (ERDC and Bonnet Carré project staff primarily 

Bill Maus and Steve Stone).

Discharge patterns after the structure was closed differed substantially between the two years (Figure 

3.5). The 2008 hydrograph exhibited a slow decline over a period of four weeks, whereas the 2011 

hydrograph dropped to almost zero discharge in the floodway within a week. Pallid and shovelnose 

sturgeon catch generally followed the same trend as the hydrograph (Figure 3.5). Sturgeon were 

caught over a four-week period in 2008, whereas almost all sturgeon captured in 2011 occurred within 

the first week after closure. The greater magnitude of discharge through the floodway in 2011 may 

have been one contributing factor by displacing sturgeon to a greater extent. However, the abbreviated 

period of flow in the canals during 2011 also contributed to sturgeon catch patterns. Both pallid and 

shovelnose sturgeon are strongly rheotactic and orient into the direction of the flow. Water velocity in 

the canals below the structure essentially went to zero within a week after the 2011 closure and water 

levels dropped precipitously throughout the floodway. Therefore, displaced sturgeon were less likely 

to move towards the base of the structure as they did in 2008 when currents persisted for 4-5 weeks in 

the canals where most sturgeon were caught. Rapid drop in water levels in 2011 also hampered 

physical movement through or over road crossings that crisscross the floodway. Sturgeon essentially 

became stranded in 2011, with most individuals caught in the stilling basin below the structure or in 

floodway lakes that became disconnected with the canals. 

Higher discharge and longer opening in 2011 resulted in greater number of sturgeon caught. In 2008, a 

total of 14 pallid and 41 shovelnose sturgeon were collected over a 4-week period. In 2011, a total of 

20 pallid, 78 shovelnose, and one possible intermediate sturgeon were collected over a 1.5-week 

period. A notable collection was a tagged pallid sturgeon originally captured in the floodway during 

2008 and released back into the Mississippi River. Pallid to shovelnose ratio were similar between the 

two years; 1:3 in 2008 and 1:4 in 2011. Ratio in this reach of the lower Mississippi River is typically 

1:3. Mean length of pallid sturgeon collected in 2011 was 773 mm FL, compared to 712 mm FL in 

2008. Sizes in 2011 ranged from 449 – 924 mm FL corresponding to ages ranging from 3 to greater 

than 15 years. Mean size of shovelnose sturgeon caught in 2011 was slightly smaller (607 mm FL) 

than in 2008 (665 mm FL). 

Following the 2011 opening, we used acoustic telemetry to monitor movement of entrained 

shovelnose sturgeon (Scaphiryhnchus platorynchus), a species closely related to and sympatric with 

pallid sturgeon, within the floodway. Twelve VEMCO VR2Ws (remote receivers) were deployed 

from the Bonnet Carré floodway down Barbars Canal to Lake Pontchartrain to establish an automated 

acoustic telemetry array. Eighteen shovelnose sturgeon ranging in size from 501-830 mm FL were 

captured from upper Barbars, Y-Canal, and the Bonnet Carre' stilling basin and equipped with acoustic 
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telemetry tags (V9 coded acoustic transmitters, 289 day battery life) during the period 20-27 June 

2011. Tagged fish were then redistributed within the system near telemetry buoys (Barbars 1, 2, 4, 5, 

8 and Y-canal 1, see Figure 3.4). The array was deployed from 20 June 2011 through 25 May 2012 

and accumulated over 120,000 detections. No mortalities were reported and initially all individuals 

moved extensively near their original release point. There were no detection patterns to support 

movement of telemetry tagged individuals from the Bonnet Carre' floodway into Lake Pontchartrain 

after 13 July 2011. 

The initial acoustic array within the floodway was deployed on 20 June prior to sampling but the 

remaining gates at Lake Pontchartrain were not deployed until 13 July. This created an “open 

window” for undocumented movement into Lake Pontchartrain (21 June-13 July = 20-32 days 

depending on when fish were captured, tagged and released). Six individuals were unaccounted for 

after 13 July suggesting they moved quickly through the floodway and into Lake Pontchartrain before 

the final gates were deployed. None were documented returning back to the floodway. Those fish that 

remained in the system experienced sporadic, localized movement. However, overall movement of 

telemetry tagged fish began to decrease by early August as water levels within the floodway 

decreased, in part creating isolated pools and remnant channels, and as water temperatures increased 

(31 C). Salinity during this period where the floodway enters Lake Pontchartrain was ≥ 2 ppt; 

detections during this period on the receivers nearest to Lake Pontchartrain were few to none.

The USFWS issued a non-jeopardy, emergency Biological Opinion for the 2008 opening with an 

estimated incidental loss of 88 adult pallid sturgeon. A Biological Opinion will likely be issued for the 

2011 opening. Differences in hydrograph and catch rates should be considered for future operations. 

Rapid decreases in discharge below the structure, which happened in 2011, will probably result in 

more sturgeon becoming stranded and non-recoverable. Gradual decreases in discharges, like 2008, 

will provide rheotactic cues for sturgeon to move upstream towards the structure, congregate, and 

become easier to catch. Regardless of the discharge patterns, however, it has been demonstrated twice 

under different circumstances that rapid rescue of entrained pallid sturgeon can be successfully 

accomplished to minimize impacts to this endangered species. 
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Table 3.1. Number of Fishes Captured in Barbars Canal, Y Canal, and Mississippi River

in the Vicinity of the Bonnet Carré Spillway Using All Gear Types, May 4-5, 2011

Species Barbars Canal Y Canal MS River @ Spillway

Family Lepisosteidae (Gar)

Lepisosteus osseus, longnose gar 2 1 -

Family Clupeidae (Herring)

Alosa chrysochloris, skipjack herring

Dorosoma cepedianum, gizzard shad

Dorosoma petenense, threadfin shad

2

2

2

1

12

1

-

9

1

Family Cyprinidae (Minnows)

Cyprinus carpio, common carp

Hypophthalmichthys molitrix, silver carp

-

6

1

1

1

1

Family Catostomidae (Suckers)

Carpiodes carpio, river carpsucker

Ictiobus bubalus, smallmouth buffalo

Ictiobus cyprinellus, bigmouth buffalo

Ictiobus niger, black buffalo

2

6

1

-

1

3

1

-

-

-

-

1

Family Ictaluridae (Catfishes)

Ictalurus furcatus, blue catfish

Ictalurus punctatus, channel catfish

Pylodictis olivaris, flathead catfish 1

1

2

-

-

-

-

Poeciliidae (Livebearers)

Gambusia affinis, Western mosquito fish - 1 -

Percichthyidae (Temperate Basses)

Morone saxatilis, striped bass

Morone chrysops, white bass

-

-

-

-

1

1

Centrarchidae (Sunfishes)

Lepomis cyanellus, green sunfish

Lepomis macrochirus, bluegill

Lepomis megalotis, longear sunfish

Lepomis microlophus, redear sunfish

Lepomis symmetricus, bantam sunfish

Micropterus salmoides, largemouth bass

Pomoxis annularis, white crappie

-

-

-

-

-

-

-

1

4

1

1

1

1

1

-

-

-

-

-

-

-

Sciaenidae (Drums)

Aplodinotus grunniens, freshwater drum - 1 -

Mugilidae

Mugil cephalus, striped mullet 29 12 5

Total Number of Species 10 21 8
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Table 3.2. Water Quality Data for Barbars Canal, Y Canal and Mississippi River 

in the Vicinity of the Bonnet Carré Spillway on May 5, 2011

Variable Barbars Canal Y Canal MS River @ Spillway

Water Body Width (ft) 93 93 -

Depth (ft)

Mean 

Minimum

Maximum

7.5

11.4

4.5

9.6

7.4

-

-

Velocity (ft/s)

Mean 

Minimum

Maximum

0.83

0.69

1.1

0.71

0.39

1.4

-

-

-

Discharge (cfs) 7631 502 -

Water Temperature (oC) 18.39 18.94 22.22

Dissolved Oxygen (mg/L) 6.75 8.40 7.06

pH 7.12 7.41 7.48

Conductivity (mS) 0.344 0.344 0.342

Turbidity (NTU) 47 42.2 38.2

1 Discharge measured above the confluence of Y Canal
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Chapter 4: Evaluation of Asian Carp Entrained through the Muddy Bayou Control 

Structure

Sand boils at Buck Chute Mississippi River Levee adjacent to Eagle Lake was problematic during the 

2011 flood. To prevent potential levee failure, the Muddy Bayou Control Structure was open to direct 

water from Steele Bayou into Eagle Lake to equalize pressure on the levee. There were concerns 

about introducing Asian Carp (bighead and silver carp) from a known area infested by these species 

(i.e., Steele Bayou) into Eagle Lake during the opening and the resulting impacts to the fisheries, as 

well as potential dangers to water skiers and boaters from jumping silver carp.

Fish Survey After the Opening of Muddy Bayou Control Structure on May 2, 2011. To evaluate 

the presence of Asian Carp in Eagle Lake, the ERDC Fish Ecology Team and personal from 

Mississippi Department of Wildlife, Fisheries and Parks (MDWFP) sampled four reaches including: 

above the structure to Steele Bayou, the vicinity of Steele Bayou upstream and downstream of Muddy 
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Bayou, below the structure to the mouth of Muddy Bayou, and Eagle Lake near the confluence of 

Muddy Bayou. Sampling gear included boat electroshocking, gillnets, and transects using visual 

counts of jumping silver carp disturbed by the boat motor.

While the Muddy Bayou Structure was open, gillnets were not effective due to trash and leaves 

becoming entangled in the webbing. Only six species of fish were captured, but no Asian Carp. Visual 

counts and boat electrofishing provided an additional opportunity to detect Asian Carp (Table 4.1).

Fish Survey During the Closure Of Muddy Bayou Control Structure on August 10, 2011. The 

ERDC Fish Ecology Team and the MDWFP returned to sample the same reaches of Muddy Bayou in 

search for Asian Carp. Sampling gear and methods were the same as before using boat 

electroshocking, gillnets and transects using visual counts of jumping silver carp disturbed by the boat 

motor. No carp were detected in Muddy Bayou or in Eagle Lake near its confluence with Muddy 

Bayou, but high abundance of silver carp were documented in Steele Bayou above the structure (Table 

4.2). With the reduction of water velocities and depths, gillnets were an effective sampling gear. A 

total of 80 individuals were netted comprised of eight species of fishes. No Asian carp were present in 

gillnet samples. Boat electrofishing validated the absence of Asian Carp in Muddy Bayou but showed 

high abundance of silver and bighead carp in Steele Bayou (Figure 4.1, Table 4.3). 

Conclusions. It is likely that Asian carp occur in Eagle Lake considering the duration of the opening 

and the high density of these species found in the source water (i.e., Steele Bayou). However, 

problematic infestations of these species are not obvious at this time. Our sampling did not detect 

Asian carp in Eagle Lake after the structure was closed. We are not aware of any reports of jumping 

silver carp in the Lake. Furthermore, it is doubtful that Asian carp could establish reproductive 

populations in the Lake because they typically spawn in rivers with flowing water. If a successful 

spawn did occur, high predation rates on the fry are likely considering that the lake fishery is managed 

for predator species including largemouth and white bass. Future sampling of Muddy Bayou and 

Eagle Lake will be conducted to further investigate the occurrence and abundance of Asian carp in the 

Lake and below the Muddy Bayou Structure. 

Table 4.1. Visual Accounts of Silver Carp Leaping Out of the Water

Using Boat Electroshocking and Visual Counts on May 2, 2011

Muddy Bayou at Mouth n=7

Below Muddy Bayou Structure n=4

Above Muddy Bayou Structure n=0

Steele Bayou upstream of Muddy Bayou transect distance 0.4 mile n=3

Steele Bayou downstream of Muddy Bayou transect distance 0.4 mile n=0

Table 4.2. Visual Accounts of Silver Carp Leaping Out of the Water

Using Boat Electroshocking and Visual Counts on August 10, 2011

Muddy Bayou at Mouth n=0

Below Muddy Bayou Structure n=0

Above Muddy Bayou Structure n=0

Steele Bayou upstream of Muddy Bayou transect distance - 1 mile n=118

Steele Bayou downstream of Muddy Bayou transect distance - 1 mile n=42

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Table 4.3. Fish Species Observed in Boat Electroshocking or Gillnet Samples on August 10, 2011

Species

Muddy Bayou

at Mouth

Below Muddy

Bayou Structure

Above Muddy

Bayou Structure

Steele Bayou Upstream

of Muddy Bayou

Steele Bayou Downstream

of Muddy Bayou

Family Polyodontidae (Paddlefish)

Polyodon spathula, paddlefish * - - - -

Family Lepisosteidae (Gar)

Lepisosteus oculatus, spotted gar

Lepisosteus osseus, longnose gar

Lepisosteus platyrhincus, shortnose gar

**

**

**

***

**

**

***

*

**

***

*

**

***

**

***

Family Clupeidae (Herring)

Dorosoma cepedianum, gizzard shad

Dorosoma petenense, threadfin shad

***

***

***

***

***

***

***

***

***

***

Family Cyprinidae (Minnows)

Cyprinus carpio, common carp

Hypophthalmichthys molitrix, silver carp

Hypophthalmichthys nobilis, bighead carp

Ctenopharyngodon idella, grass carp

**

-

-

**

**

-

-

**

**

-

-

**

**

***

*

**

**

***

**

**

Family Catostomidae (Suckers)

Ictiobus bubalus, smallmouth buffalo

Ictiobus cyprinellus, bigmouth buffalo

Ictiobus niger, black buffalo

***

**

**

***

***

***

***

***

***

***

**

***

***

***

***

Family Ictaluridae (Catfishes)

Ictalurus furcatus, blue catfish

Ictalurus punctatus, channel catfish

-

***

*

***

*

***

-

-

-

-

Percichthyidae (Temperate Basses)

Morone Hybrid, white bass x stripe bass * - - - -

Centrarchidae (Sunfishes)

Lepomis macrochirus, bluegill

Micropterus salmoides, largemouth bass

-

-

*

*

-

-

-

-

-

-

Sciaenidae (Drums)

Aplodinotus grunniens, freshwater drum - - - - *

Ranking of species other than bighead and silver carp:

Not Observed - Rare *

Common ** Abundant *** 
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Participants

Name Affiliation Project

Joshua Koontz Memphis District New Madrid

Mark Smith Memphis District New Madrid

Mike Thron Memphis District New Madrid

Danny Ward Memphis District New Madrid

Dave Herzog Missouri Department of Conservation New Madrid

Dave Knuth Missouri Department of Conservation New Madrid

David Ostendorf Missouri Department of Conservation New Madrid

Russell Beauvais New Orleans District Morganza

Joe Harvey New Orleans District Morganza

Steve Stone New Orleans District Morganza/Bonnet Carré

Richard Boe New Orleans District Bonnet Carré

Chris Brantley New Orleans District Bonnet Carré

Bill Maus New Orleans District Bonnet Carré

Thomas Parker New Orleans District Bonnet Carré

Gary Vitrano Louisiana Wildlife and Fisheries Bonnet Carré

Matt Duplessis Louisiana Wildlife and Fisheries Bonnet Carré

Tim Ruth Louisiana Wildlife and Fisheries Bonnet Carré

Jeff Thompson Louisiana Wildlife and Fisheries Bonnet Carré

Dave Schultz, PI Nicholls State University Bonnet Carré

Stephen Byrne Nicholls State University Bonnet Carré

Chris Levron Nicholls State University Bonnet Carré

Clint Troxler Nicholls State University Bonnet Carré

Paul Hartfield USFWS, Jackson, MS Bonnet Carré

Debbie Fuller USFWS, Lafayette, LA Bonnet Carré

Monica Sikes USFWS, Lafayette, LA Bonnet Carré

Robert Smith USFWS, Lafayette, LA Bonnet Carré

David Walther USFWS, Lafayette, LA Bonnet Carré

Jerry Brown Mississippi Wildlife, Fisheries, and Parks Eagle Lake

Don Henke Mississippi Wildlife, Fisheries, and Parks Eagle Lake

Ryan Jones Mississippi Wildlife, Fisheries, and Parks Eagle Lake

Brian LaBarre Vicksburg District Eagle Lake

Kent Parrish Vicksburg District Eagle Lake

Jay Collins ERDC All

Steven George1 ERDC All

Jan Hoover 1 ERDC All

Alan Katzenmeyer ERDC All

Jack Killgore1 ERDC All

Phil Kirk ERDC All

Bill Lancaster ERDC All

Bradley Lewis ERDC All

Todd Slack1 ERDC All

1 Co-authors of this report

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F-VI-1

SECTION VI

MISSISSIPPI DEPARTMENT OF MARINE RESOURCES

OFFICE OF MARINE FISHERIES

2011 MISSISSIPPI RIVER/BONNET CARRÉ SPILLWAY FLOOD OPERATION

AUGUST 2011

TABLE OF CONTENTS

INTRODUCTION ....................................................................................................................................2

IMPACTS TO COASTAL HABITATS...................................................................................................3

IMPACTS TO MARINE RESOURCES..................................................................................................5

FIGURES AND TABLES.................................................................................................................. 9-25

Reference: National Marine Fisheries Service. 2010. Fisheries Economics of the United States, 2009. 

U.S. Dept. Commerce, NOAA Tech. Memo. NMFS-F/SPO-118, 172pp. Available at:

https://www.st.nmfs.noaa.gov/st5/publication/index.html. 
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INTRODUCTION

The severe and cumulative impacts of sequential natural and manmade disasters which have struck the 

Gulf of Mexico since 2004, have taken a tremendous biological and economic toll on Mississippi’s 

coastal resources, harvesters, and industry. This report focuses on the Bonnet Carré Spillway opening 

(and other environmental factors), during the Mississippi River flooding event of 2011.

High snowfall this past winter coupled with excessive spring rainfall throughout the mid-west resulted 

in record flooding in the U.S. The 2011 Flood waters exceeded most of the records for gauge readings 

and volumes, even surpassing the 1927 and 1937 floods according to the U.S. Army Corps of 

Engineers. Rivers experiencing the most severe impact include the Upper Missouri and Souris rivers, 

the Red River in North Dakota and Minnesota, the Minnesota River, the Upper Mississippi River, the 

Des Moines River, the Lower Missouri River, the James River, the Big Sioux River, the lower Ohio 

River, and the Lower Mississippi River. The result of all this water has been greatly increased flows 

down most of the country’s major rivers which forced releases from many of the reservoirs and control 

structures, straight down the Mississippi River Valley and into the Gulf of Mexico.

Along the Gulf coast, a number of federal flood control structures were opened to handle the load and 

prevent flooding of communities along the river. The Bonnet Carré Spillway, located approximately 

30 miles above New Orleans was opened on May 9, 2011 and not closed again until June 20, 2011. 

The Bonnet Carré serves to reduce pressure on existing levees by lowering the river stage and 

decreasing flow velocities to New Orleans and surrounding communities. The 7,000 feet long 

spillway structure located on the east bank of the Mississippi River, contains 350 concrete bays, of 

which 330 were opened to release the excess river water into the western end of Lake Pontchartrain. 

Each bay of the spillway is 20 feet wide. In addition, the Morganza Spillway, located along the 

western bank of the Mississippi River, some 20 miles north of Baton Rouge, was opened for only the 

second time since it was completed in the mid-1950s. The Morganza is used to divert water from the 

Mississippi River into the Atchafalaya Basin to protect communities downriver (Figure1).

The maximum discharge rate of the Bonnet Carré Spillway was estimated at 316,000 cubic feet per 

second (cfs) (note: 1 cubic foot = 7.48 gallons.) This maximum flow occurred with only 330 out of the 

350 bays opened. The design maximum flow of the spillway is 250,000 cfs, which is a difference of 

some 66,000 cfs; or over 26% greater than the volume the structure was designed to carry. The Bonnet 

Carré spillway had a discharge rate at or exceeding 250,000 cfs for a total of 21 days (Figure 2). For 

illustrative purposes, an Olympic sized swimming pool has a volume of approximately 88,229 cubic 

feet or 660,000 gallons, depending on its depth; and during that 21 day period, the Bonnet Carré 

spillway was discharging that volume about every two seconds. These numbers and calculations are 

important to consider because it is a common practice to compare the total number of spillway bays 

opened during one flood event versus another past event when evaluating the severity of the impact. 

Even though some 400 feet of the spillway remained closed, the 2011 opening was indeed a major 

event which exceeded most other full spillway openings.

Coupled with the great inflow of freshwater into the Gulf from the north was the fact that the five Gulf 

States were under extreme to exceptional drought and record high temperatures (Figures 3 and 4). 

Rainfall along the coast was minimal if not absent from at least early April 2011. The potential effects 

of floodwaters were most likely buffered due to the drought conditions and the resulting unusually low 

local river flows. This reduced the coastal rivers contribution to the flood waters impact.
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The air temperatures during that time exceeded 100°F on numerous occasions, setting up high salinity 

and high temperature waters across most of the Gulf’s traditional oyster harvesting grounds. The stage 

was set for another hardship for the Gulf’s oyster fishery.

Salinities in the production reef areas in western-most Mississippi Sound were at normal levels at the 

beginning of April 2011. However, with the Mississippi River rising and subsequent opening of the 

Bonnet Carré in early May 2011, the salinities in areas like St. Joseph’s reef declined steadily from 

about 13.0 parts per thousand (ppt) on April 23, 2011 to 1.0 ppt by May 23, 2011 (Figure 5). The 

freshwater remained over that area until June 17, 2011 and finally reached the ‘normal’ salinity levels 

around July 4, 2011. 

The Mississippi oyster season for public reefs closed in April 2011. However, one Mississippi oyster 

farm lease holder; near Waveland, MS, was issued a Lease Harvest Permit, and began harvesting the 

lease oysters on May 14, 2011, and ceased harvest activities June 2, 2011 due to the oysters beginning 

to open and die.

In addition to lower salinities, many of the waters in Mississippi Sound as far east as Gulf Shores 

Alabama have experienced large plankton blooms which have simultaneously driven down the 

dissolved oxygen and caused fish kills and ‘jubilees’. Low oxygen conditions such as these aren’t 

good for sessile organisms like oysters.

DMR staff collected a total of 200 square meter samples during May 2011 (100 samples) and repeated 

again during July 2011(100 samples) which indicated significant oyster mortalities. Preliminary oyster 

mortalities estimate for market sized oysters (≥ 3” total length) of the major commercial reefs in the 

western Mississippi Sound were determined to be in excess of 85%.

The salinity in these areas of the Mississippi Sound was driven well below the five ppt, the threshold 

which has been shown in past studies to cause extensive oyster mortalities. Biological sampling 

continues in Mississippi and the full impact of this freshwater event is still unknown. 

IMPACTS TO COASTAL HABITATS

During May 2011, the Mississippi Department of Marine Resources (MDMR) conducted a square 

meter sampling program of oyster reefs located in the western Mississippi Sound. A total of 100 

square meter samples were collected by SCUBA divers at 50 randomly chosen sites within 30 second 

(30”) sized grids overlaid onto known western oyster reef boundaries. During July 2011, the MDMR 

repeated this sampling, with findings and comparisons illustrated in Figures 6 -8.

Living oysters as well as obviously recent dead oysters were measured and recorded. Instantaneous 

mortality estimates were derived by comparing the numbers of living versus recent dead oysters in the 

samples. Instantaneous mortality estimates for May 2011 ranged from 7% to 40%, and from 36% to 

98.7% for the month of July 2011. Likewise, estimates of the number of sacks (1.98 ft.3) of live market 

sized (≥ 3” length) oysters present were calculated for each reef area or complex (Figure 7). These 

ranged from 8.1 to 448 estimated live market oyster sacks per acre for May 2011 (weighted average 

249.5), and from 2.7 to 43.8 sacks per acre for July 2011 (weighted average 34.1) Figure 8.
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F-VI-4

The weighted average estimate of living market oysters as well as mortalities was based on sampling 

results while taking the total reef area or complex acreages into consideration. This was performed by 

each reef or complex and for the total western oyster reef acreage of 7,797 acres. May 2011 sampling 

resulted in an estimate of 1,945,085 sacks of market sized oysters. While in July 2011, these numbers 

dropped dramatically some 86%, or loss of 1,678,878 sacks to an estimated total of only 266,207 

remaining sacks.

The extent and severity of flood waters was effectively monitored through constant recorder 

instruments, recording YSI data sondes and sampling. Figures 9-21 illustrate low salinity and later; 

high temperatures and low dissolved oxygen events. Salinity levels on many of the oyster reefs were 

below two and three parts per thousand (ppt) for a period of approximately two to three weeks. 

Additionally, water temperatures reached 30°C at many locations in middle to late June 2011. 

Mississippi Department of Environmental Quality (MDEQ) YSI data sondes were deployed at the 

request of the MDMR, in the vicinity of various oyster reef locations and later recovered (Figures 21-

25). However, two of the MDEQ YSI data sondes are missing, and were not recovered.

The MDMR postponed an ongoing oyster cultch plant in May 2011 due to the opening of the Bonnet 

Carré spillway. In August 2011, the MDMR restarted restoration activities for oysters. Brood stock 

oysters were relayed to the hardest impacted areas in the western Mississippi Sound. This work is 

expected to help re-inoculate other affected benthic organisms as well. Significant oyster cultch plants 

of several areas were begun in August 2011, and will continue into September 2011. Oyster reef 

cultivation work will be conducted by the MDMR during the months of August 2011 and September 

2011. Cultivation will consist of towing a bagless oyster dredges over existing oyster shells covered 

with fouling organisms, such as a heavy algae growth or low salinity tolerant hooked mussels, to help 

expose a clean hard surface which will be conducive to an improved spat set rate. 

Several years of recovery are anticipated before the return of a “normal” oyster season. Long term 

effects are unknown, especially for the larval stages. Ongoing monitoring activities will be required to 

maximize restoration efforts. A potential exists for multi-species year class losses. 

The MDMR Shellfish Bureau conducts two routine phytoplankton samples each month. Data analyses 

of these samples are compiled in cooperation with the NOAA Phytoplankton Monitoring Network 

(PMN). These samples are taken from the northern-most and the southern-most boundaries of the 

Pass Christian oyster reef. In light of the Bonnet Carré’ Spillway opening, additional sampling was 

added from the St. Joe oyster reef. This sample is taken once each month to monitor for the presence 

of introduced phytoplankton species from the fresh water influx. 

Results from the samplings showed a significant decrease in common phytoplankton and an 

introduction of a few freshwater species. The freshwater phytoplankton observed included 

Pediastrum spp. and Scenedesmus spp.

As the dissolved oxygen and salinity began to return to normal levels, there was an increase in algal 

blooms in the western Mississippi Sound. On June 27, 2011, a phytoplankton bloom was reported in 

the western Mississippi Sound. Aerial photographs were taken of this bloom but identification of type 

was not recorded (Figure 26). On July 27, 2011, a bloom of Chattonella spp. was investigated at the 

Gulfport and Long Beach shorelines. This bloom caused a significant fish kill. 
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-5

Certain species of Chattonella have been shown to produce brevetoxin which will cause fish kills and 

is harmful for human consumption. No brevetoxins were detected in this Chattonella bloom. When an 

algal bloom begins to crash, the decaying process depletes dissolved oxygen which in turn, causes 

hypoxic conditions and will suffocate marine animals and plants.

On June 22, 2011 an aerial survey was conducted along the western Mississippi Sound to take some 

pictures of the influence of freshwater. Figure 27 shows what is believed to be the mixing of the 

turbid freshwater with the clearer high salinity water of the Gulf of Mexico.

Due to the likely introduction of aquatic invasive species, such as Asian carp, through this year’s 

spillway opening, surveillance monitoring will be conducted to assess the extent and impact of their 

introduction in order that corrective measures may be taken to limit their further spread to other 

coastal bays and river systems.

IMPACTS TO MARINE RESOURCES

Impacts to the Mississippi Blue Crab Fishery. When the Bonnet Carré Spillway opened on May 9, 

2011 it was anticipated that this freshwater would negatively influence the summer’s shrimp and crab 

harvest in the Mississippi Sound. Immediate fishery impacts were expected to be seen by movement 

of mobile species to areas of higher salinities. However, shrimp landings data continued stable 

through May and June 2011 through the present to be normal to slightly higher than normal (source: 

NOAA). Future Mississippi shrimp landings will continue to be monitored on a monthly basis. 

The DMR decided to use 2001-2009 to calculate the historical average of dockside landings and value 

for both crab and oysters. This decision was based the negative impacts of Hurricane Katrina in 2005 

and the BP oil spill in 2010, which greatly misrepresents the historical averages for the last five years. 

Mississippi blue crab landings for May 2011 were 46,934 lbs., a 35% decrease compared to average 

landings for May in the years 2001 through 2009 (73,525 lbs.). Value for Mississippi May 2011 blue

crab landings was $38,584.00, a 44% decrease compared to average values for May in the years 2001 

through 2009 ($69,824.00).

Mississippi blue crab landings for the period May-August 2011 averaged were 34,688 lbs./month, a 

53.5% decrease compared to average landings for May-August in the years 2001 through 2009 

(74,563 lbs./month). To date, based on an estimated 53.5% decrease (combined May through August 

2011), total damage assessment for 2011 when compared to average annual value for the years 2001-

2009 of $603,000 per year it has been determined to have had a total economic impact of $515,200 on 

the blue crab fishery of Mississippi. It is possible that the freshwater affected the natural migration 

and life cycle stages of blue crab and will affect future catches in Mississippi. The decreased harvest 

could warrant the Mississippi blue crab fishery to be considered harmed, disrupted or failed, per the 

requirements of the National Marine Fisheries Service Policy Guidance for Disaster Assistance Under 

Magnuson-Stevens Act 312(a) and Interjurisdictional Fisheries Act 308(b) and 308(d). Should that 

determination be made by NOAA, it would reflect injury to approximately 291 Mississippi resident 

commercial crab trap license holders and 86 resident commercial crab trawl license holders (Table 1). 

An appropriate recovery plan to restore and enhance the fishery will be drafted upon determination of 

the level of injury is made. 
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-6

Impacts to the Mississippi Oyster Fishery. The seafood industry has experienced more than its fair 

share of both natural and man-made disasters since Hurricane Katrina made landfall in 2005. The 

support that the MDMR received from the Department of Commerce has been a major catalyst in the 

recovery of Mississippi’s commercial and recreational fisheries. In 2010 the deepwater horizon 

disaster caused major difficulties for the entire northern gulf coast. In the spring of 2011 we had the 

impact of the opening of the Bonnet Carré Spillway which introduced large volumes of fresh 

Mississippi River water into the western Mississippi Sound home to 95% of the States oyster reefs. 

Mississippi’s oyster industry (Table2) is an important component to the entire seafood industry in the 

State with a total economic impact of $100 million dollars (2003) and after Katrina was reduced to 

$12.17 million in 2007. The commercial seafood industry in Mississippi had an overall total 

economic impact of $289 million in 2009 (NMFS 2010). 

Fisheries staff conducted an assessment of the public oyster reefs in Mississippi prior to the opening of 

the Bonnet Carré Spillway in May 2011. This assessment provided an estimate of 1,945,086 sacks of 

oysters on the public reefs. In July 2011 a post spillway opening assessment was conducted this 

estimate resulted in 266,207 sacks of oyster. Mortality as a result of excessive fresh water from the 

Bonnet Carré Spillway opening and other environmental factor caused a loss of 1,678,878 sacks of 

oysters. Mississippi’s oyster resource had approximately 86% mortality in a two month period. Based 

on these high mortalities it will require a minimum of three years for a full recovery of the oyster 

resource, given no additional environmental stressors. Figures 28 and 29 depict the poor condition of 

oyster during the July reef assessment. 

With a net loss of 1,678,878 sacks of oysters or 13,431,024 pounds of oyster meat and based on the 

Mississippi’s average annual prices per pound of meat harvested of $2.78 (NOAA 2010). The direct 

economic impact from the spillway opening on the oyster fishery is estimated at $37,338,246. The 

economic multiplier was determined using the data for Mississippi in the NOAA publication Fisheries 

Economics of the U.S 2009 the most current report. The economic multiplier was calculated using 

Mississippi’s 2009 commercial harvesters sales $60,857,000 divided by the 2009 total landing revenue 

$37,998,000 the result is an economic multiplier which includes post harvest activities results in an 

economic multiplier of 1.6. Therefore the one-year economic impact to the oyster industry from the 

opening of the Bonnet Carré Spillway and other environmental factors is estimated at $59,411,194, a 

more detailed economic impact report will be put together in the near future. 
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-7

FIGURES AND TABLES

Figure 1. Map of Spillway Locations and Functions
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-8

Figure 2. Bonnet Carré’ Spillway Operations

0

50

100

150

200

250

300

350

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

Bays Open

Flow (Ft.

3 per Second)

2011 Bonnet Carre Spillway Operation

Flow (cfs) Bays Open
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-9

Figure 3. 2011 U.S. Drought Map
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-10

Figure 4. 2011 U.S. Drought
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-11

Figure 5. St. Joseph Reef Salinities
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-12

Figure 6. Percent Recent Oyster Mortality

0

10

20

30

40

50

60

70

80

90

100

Pass Christian 

Complex

Pass Marianne Reef St. Joseph's Reef Telegraph Reef

16 18

7

40

54

43

98.7

36

Percent Recent Oyster Mortalities May vs. July 2011

From Square Meter Samples

May July
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-13

Figure 7. Estimated Sacks of Oysters Per Acre

0

50

100

150

200

250

300

350

400

450

Pass Christian 

Complex

Pass Marianne 

Reef

St. Joseph's Reef Telegraph Reef

448

91

121

8.1

36.4 43.8

2.7 15.5

Estimated Sacks of Legal ≥3" Oysters/Acre

May vs. July 2011 from Square Meter Samples

May July
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-14

Figure 8. Estimated Sacks Per Acre (Legal Oysters)

0.0

50.0

100.0

150.0

200.0

250.0

May 2011 July 2011

249.5

34.1

Estimated Sacks Per Acre (Sack Oysters)

Mississippi Western Commercial Reefs

May vs. July 2011 (Sack = 1.98 ft.3, ~300 Legal 3" Oysters)
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-15

Figure 9. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-16

Figure 10. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-17

Figure 11. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-18

Figure 12. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-19

Figure 13. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-20

Figure 14. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-21

Figure 15. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-22

Figure 16. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-23

Figure 17. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-24

Figure 18. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-25

Figure 19. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-26

Figure 20. USGS
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-27

Figure 21. St. Joseph’s Reef Hydrology

0.00

5.00

10.00

15.00

20.00

25.00

30.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

5/17 5/19 5/21 5/23 5/25 5/27 5/29 5/31 6/2

Temperature (°C)

Salinity (‰), O2(mg/l)

St. Joseph' Reef Data Sonde

May 19 - 31, 2011

Salinity Optical DO Temperature
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-28

Figure 22. Pass Christian Tonging Reef Hydrology

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

5/17 5/19 5/21 5/23 5/25 5/27 5/29 5/31 6/2 6/4 6/6

Temperature (°C)

Salinity (‰), O2(mg/l)

Pass Christian Tonging Reef Data Sonde

May 19 - June 3, 2011

Salinity Optical DO Temperature
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

Environmental and Cultural Resources

F-VI-29

Figure 23. Pass Christian Tonging Reef Hydrology

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

6/11 6/16 6/21 6/26 7/1 7/6 7/11 7/16 7/21 7/26

Temperature (°C)

Salinity (‰), O2 (mg/l)

Date 2011

Pass Christian Tonging Reef Data Sonde

June 13 - July 22, 2011

Salinity Optical DO Temperature
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-30

Figure 24. Henderson Point Reef Hydrology

0.00

5.00

10.00

15.00

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25.00

30.00

35.00

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6.00

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16.00

18.00

6/11 6/16 6/21 6/26 7/1 7/6 7/11 7/16

Temperature °C

Salinity (‰) and O2 (mg/l)

Date 2011

Henderson Point Reef Data Sonde

June 13 - July 22, 2011

Salinity Optical DO Temperature
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2011 Post Flood Report

Appendix F

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F-VI-31

Figure 25. Pass Marianne Reef Hydrology

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

6/11 6/16 6/21 6/26 7/1 7/6 7/11 7/16 7/21 7/26

Water Temperature (°C), Salinity (‰), O2 (mg/l)

Date 2011

Pass Marianne Reef Data Sonde

June 13 - July 22, 2011

Temperature Salinity Optical DO
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2011 Post Flood Report

Appendix F

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F-VI-32

Figure 26. June 27, 2011 Aerial Photo of Algae Bloom and MDMR Boat Collecting Phytoplankton Sample

Figure 27. Photograph of Turbid Water Around the Western Tip of Deer Island in Biloxi, MS June 22, 2011
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-33

Table 1. Mississippi Blue Crab Dockside Landings, Value and Number of Participants

Year

Annual

Landings (lbs)

Value

($)

Resident Commercial

Crab Trap Licenses

Resident Commercial

Crab Trawl Licenses

2001 433,656 390,941 208 No such license yet

2002 716,127 568,419 217 No such license yet

2003 876,521 680,032 253 No such license yet

2004 865,106 705,705 262 No such license yet

2005 429,231 436,003 189 56

2006 1,126,818 927,943 122 45

2007 737,442 741,136 110 58

2008 450,037 446,756 138 53

2009 545,328 572,852 155 64

2010 DWH DWH 138 67

2011 n/a n/a 291 86

Table 2. Mississippi Oyster Dockside Landings, Value and Number of Participants

Year

Annual 

Landings 

(lbs meat)

Value

($)

Resident 

Commercial 

Dredge Licenses

Resident 

Commercial 

Tong Licenses

Non-Resident 

Commercial 

Dredge Licenses

Non-Resident 

Commercial

Tong Licenses

2001 2,653,270 4,195,464 165 67 33 68

2002 2,737,839 4,455,647 172 51 44 49

2003 4,042,136 7,227,588 207 59 48 71

2004 3,029,391 6,073,242 180 60 32 56

2005 610,384 1,447,132 28 3 0 5

2006 0 0 16 17 0 1

2007 299,088 818,544 139 56 23 33

2008 2,610,349 6,869,160 97 13 19 13

2009 2,191,724 6,100,264 274 66 118 82

2010 DWH DWH 273 99 111 104

2011 n/a n/a 278 87 122 98

 
Mississippi River and Tributaries System

2011 Post Flood Report

Appendix F

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F-VI-34

Figure 28. Stressed and Dead Oyster in the Shell

Figure 29. Gaping “Dead” Oyster