Indiana Walleye

  Home ] Walleye stocking fund ] Newsletters ] Articles ] Calendar ] Directory ] Out of State guides ] Photo Album ] Photo's ] Walleye Outing ] Walleye song ] Walleye waters ] INDIANA WALLEYE SHOPPING CENTER ] Poll results ] Home ] 2006 highlights ] mwa open ] club crashers ] Walleye News ] [Message board] [Chat]

Walleye Waters provided by.......

 

 

 

 

 

Monroe Reservoir

Fish and Wildlife Research and Management Notes
 
  Author:
Brian M. Schoenung, Fisheries Biologist
 Date: March 7, 2002  Title:
Monroe Reservoir- 2001
 
INTRODUCTION

Lake Monroe is a 10,750 acre flood control reservoir in Brown and Monroe Counties southeast of Bloomington, Indiana. It is the largest lake in the state, and recreational activities such as boating and fishing are very important. Boat access is available at ten publicly-owned ramps located around the lake. In addition, several privately-owned recreational facilities such as boat rentals, sport shops, marinas, and campgrounds are available. Monroe Reservoir also serves as the primary water supply for the city of Bloomington.

At normal pool, the maximum depth of Lake Monroe is 54 feet with an average depth of 25 feet. The water level is regulated by the Corps of Engineers and is relatively stable, but may fluctuate up to 18 feet depending on storage needs. The lake is divided into two distinct basins which are separated by the State Road 446 causeway. The upper basin receives 90 percent of the runoff entering the lake and is shallower and more turbid than the lower basin. During summer, oxygen concentrations in the lower basin are usually adequate for fish survival down to depths of 20 to 25 feet. In the upper basin, adequate oxygen is normally present to a depth of about 15 feet.

Since impoundment in 1965, Lake Monroe has been managed primarily for largemouth bass and panfish fishing. A 14-inch minimum size limit on largemouth bass has been in effect since 1973. As often occurs in new reservoirs, Monroe provided excellent fishing for several years after impoundment. Fishing quality began to level off as less desirable species such as yellow perch, yellow bass, and gizzard shad began to increase in abundance. Since about 1982, the lake's fish community has been characterized by an overabundance of forage fish and too few predator fish.

Additional fish management practices at Lake Monroe have included several supplemental predator stockings. Early stockings included both northern pike and walleye, but were for the most part unsuccessful. One stocking of 4,500 10 to 18 inch pike in 1979 did provide moderate success with some returns to anglers. Stockings in the last decade or so have included both walleye and hybrid striped bass (Table 1). The intent of these stockings has been to provide additional fishing opportunities and utilize some of the surplus forage fish, particularly gizzard shad. In August of 1996, a 14-inch minimum size limit was placed on walleye at the lake.


Table 1. Walleye (WAE) and hybrid striped bass (HSB) stockings at Lake Monroe, 1982 through 2000.

Year
Species
Number
No/Acre
Size

1982

WAE
73,700
6.8
1 - 2"
1985
WAE
8,300
0.8
3"
1986
WAE
48,147
4.5
1 - 2"

1987

WAE
37,853
3.5
3"
1988
WAE
573,094
53.3
1 - 2"
1989
WAE
524,362
48.8
1 - 2"
1990
WAE
642,392
59.8
1 - 2"

1990

WAE
11,255,325
1,047.0
Fry
1991
WAE
461,102
42.9
1.5 - 2.5"
1992
WAE
541,766
50.4
1 - 2"
1993
WAE
523,720
48.7
1 - 2"
1994
WAE
441,284
41.0
1 - 2"

1995

WAE
538,467
50.1
1 - 2"
1996
WAE
746,075
69.4
1 - 2"
1997
WAE
801,791
74.6
1 - 2"
1998
WAE
285,675
26.6
1 - 2"
1999
WAE
563,030
52.4
1 - 2"
2000
WAE
547,347
50.9
1 - 2"
2001
WAE
293,001
27.3
1.5 - 2.5
 

1983

HSB
58,282
5.4
1 - 2"
1984
HSB
100,000
9.3
Fry
1984
HSB
44,450
4.1
2"
1985
HSB
107,000
10.0
1 - 2"
1986
HSB
53,850
5.0
1 - 2"
1988
HSB
10,710
1.0
2"
1989
HSB
75,250
7.0"
2
1990
HSB
53,760
5.0
1 - 2"

1991

HSB
53,750
5.0
1 - 2"
1992
HSB
54,716
5.1
1 - 2"
1993
HSB
90,306
8.4
1 - 2"
1994
HSB
6,618
0.6
2.3"
1995
HSB
*
1996
HSB
51,500
4.8
2.2"
1997
HSB
108,112
10.1
1.2"
1998
HSB
161,250
15.0
1.5"
1999
HSB
53,750
5.0
1.5"
2000
HSB
5,732
0.5
2 - 3
2001
HSB
96,942
9.0
1.3
* No fish were stocked

RESULTS AND DISCUSSION


Lake Survey

Dissolved oxygen concentrations were adequate for game fish survival to a depth of 16 feet. The Secchi disk reading, an index of water transparency, was nine feet. The increase in water clarity is probably related to an increase in aquatic vegetation coverage since the last survey.

Aquatic vegetation has increased substantially since the last survey. Several years of more stable water levels have resulted in a greater abundance and diversity of aquatic vegetation. Submersed aquatic vegetation consisted of American pondweed, brittle naiad, coontail, Eurasian water milfoil, small pondweed, and waterthread pondweed. Despite the increase in aquatic vegetation, overall coverage was still less than 1 percent of the lake's surface area. However, several of the coves within the lake had bottom coverage approaching 10 percent . Emergent aquatic vegetation consisted of American bulrush, American lotus, blunt spikerush, common reed, creeping water primrose, water smartweed, and American water-willow. Most of the emergent vegetation coverage was confined to the shoreline with the exception of American lotus which grew to a depth of six feet.

Fish sampling efforts produced 8,606 fish weighing an estimated 1,971 pounds. Twenty-five species and one hybrid were represented in the catch. Yellow bass were most abundant by number (27.2 percent ), followed by bluegill (22.0 percent ), gizzard shad (18.1 percent ), longear sunfish (9.9 percent ), white crappie (5.8 percent ), largemouth bass (4.3 percent ), logperch (3.6 percent ), channel catfish (1.8 percent ), yellow perch (1.8 percent ), and walleye (1.7 percent ). The remaining species were relatively insignificant in the catch by number, comprising less than 1 percent of the sample each. By weight, gizzard shad were most abundant (15.1 percent ), followed by channel catfish (13.5 percent ), yellow bass (13.2 percent ), largemouth bass (12.9 percent ), common carp (12.1 percent ), palmetto (hybrid striped) bass (8.6 percent ), walleye (7.6 percent ), bluegill (6.5 percent ), white crappie (3.2 percent ), flathead catfish (2.4 percent ), and longear sunfish (2.4 percent ). Each of the remaining species contributed less than 1 percent of the sample by weight.

The yellow bass sample consisted of 2,338 fish ranging from 1.6 to 9.5 inches in length. Gill net catch rates for yellow bass increased from 15.3 fish/lift in 1996 to 34.8 fish/lift in the current survey, comparable to the 1992 survey catch rate (Andrews 1996) (Table 2). The electrofishing catch rate for yellow bass increased from 14.6 fish/hour in 1996 to 214.6 fish/hour in the current survey. Only 5 percent of the yellow bass collected in the survey were 8 inches or larger compared to 68 percent in the 1996 survey and 12 percent in 1992. Yellow bass growth was consistent with the 1996 survey to age 3 but 0.7 inches shorter at age 4. Reproductive success appears to have been high for the last four years resulting in the highest catch rates for this species in recent history.


Table 2. Catch rates by gear type and year for select species at Lake Monroe (primary sampling methods in bold).

Species
1992
1996
2002
1992
1996
2001
1992
1996
2001
Yellow bass
33.8
15.3
34.8
3.6
0.7
0.2
27.3
14.6
214.6
Bluegill
1.5
1.3
0.4
205.3
18.6
31.3
57.5
162.8
215.1
Gizzard shad
36.4
9.7
15.4
9.9
0.3
0.1
307.0
44.2
169.3
White crappie
13.1
12.0
18.3
5.8
10.6
3.4
4.8
8.2
2.7
Largemouth bass
0.2
0.5
0.2
0.1
0.3
0.3
40.3
45.5
52.1
Walleye
2.0
0.7
2.8
0.0
0.1
0.1
1.5

12.3

11.1
Palmetto bass
3.8
0.3
2.0
0.1
0.0
0.0
0.3
0.7
0.1

A total of 1,890 bluegill was collected. They ranged from 2.2 to 8.1 inches in length. Both electrofishing and trap net catch rates of bluegill increased from the 1996 survey. Stock size bluegill (those between 3.0 and 6.0 inches in length) made up 85 percent of the catch. Only 16 percent of the bluegill collected were of harvestable size (6 inches or larger) as compared to 40 percent in 1996 and 61 percent in 1992 (Andrews 1996). Approximately 2 percent of the bluegill collected were 7 inches or larger compared to 14 percent in 1996 and 18 percent in 1992. Bluegill growth was above average to age 1 but decreased to below average by age 5 compared to bluegill growth at similar lakes. Bluegill recruitment appeared to be good over the last 4 years. However, only one age 6 bluegill (the oldest fish in the sample) was collected.

The gizzard shad sample consisted of 1,556 fish ranging from 1.6 to 14.0 inches in length. Eighty-three percent of the shad collected were between 7.0 and 9.0 inches in length and between ages 2 and 3. Very few age 0 or age 1 shad were collected during sampling. Although large schools of age 0 shad were observed during the survey, the 2000 year class of shad (age 1) was almost nonexistent. An unusually cold winter may have contributed to increased mortality for this year class. Gizzard shad growth was below average to age 1 and slightly below average thereafter compared to shad growth at similar lakes.

The longear sunfish catch consisted of 852 fish ranging from 1.9 to 6.1 inches in length. Electrofishing catch rates for longear sunfish have doubled in each of the last three surveys increasing from 23 fish/hour in 1992 to 43 fish/hour in 1996 to 115 fish/hour in the current survey. Despite the increase in catch rates, few longear reach a size large enough to interest anglers.

A total of 498 white crappie was collected. They ranged from 4.5 to 15.0 inches in length. White crappie 8 inches or larger accounted for just 8 percent of fish collected versus 36 percent in 1996 and 10 percent in 1992 (Andrews 1996, 1993). Crappie reproductive success appeared to be consistent, with year classes 1995 through 2000 represented in the catch. Crappie growth was considerably lower than in the previous survey. Crappie growth is now slightly below average for this type of lake compared to "average to above average" in the 1996 survey.

The largemouth bass sample consisted of 374 fish ranging from 1.8 to 20.5 inches in length. Fourteen percent of the bass collected were of harvestable size (14 inches or larger). Largemouth bass reproductive success appeared to be quite good through the last six years (year classes 1996 to 2001) while bass from year classes 1993 through 1995 were represented in fewer numbers. The largemouth bass electrofishing catch rate was 52.1 bass/hour compared to 45.5 bass/hour in 1996 and 40.3 bass/hour in 1992. Bass growth was slightly above average compared to bass growth at similar lakes and compared to previous Monroe surveys.

One hundred and fifty-six channel catfish were collected in the survey ranging from 4.9 to 29.2 inches in length. Catfish were well distributed throughout the size range indicating consistent recruitment. Channel catfish catch rates were comparable with catch rates from previous surveys.

The walleye catch consisted of 147 fish ranging in size from 7.5 to 24.3 inches. Walleye of harvestable size (14 inches or larger) comprised 46 percent of the sample. The gill net catch rate for walleye increased from 0.7 fish/lift in the 1996 survey to 2.8 fish/lift in the current survey while the electrofishing catch rate decreased slightly from 12.3 walleye/hour to 11.1 walleye/hour. Walleye stocking success appeared to be good with fish collected from the 1996 through 2000 year classes. The number of fish stocked through this period met or exceeded the stocking goals in all years except 1998. Walleye growth increased slightly since the last survey.

Fifty-two common carp were collected in the survey ranging from 2.0 to 31.5 inches in length. Carp comprised 12.1 percent of the total sample by weight compared to 18 percent in 1996 and 12 percent in 1992. Carp appear to be maintaining a stable population in the reservoir.

The hybrid striped bass catch consisted of 48 fish ranging from 4.0 to 27.1 inches in length. Almost all of the hybrids were collected from one gill net set at the face of the dam. Hybrid striped bass catch rates are tied closely to the number of fish stocked each year. Very few hybrids were collected from the 2000 year class due to the small number of individuals stocked while the 1998 and 1999 year classes were fairly well represented. Stockings met or exceeded goals in these two years. Other year classes represented in the catch included 1997, 1996, 1994 and 1993. No hybrid striped bass were stocked in 1995. Growth for hybrid striped bass was consistent with that of past surveys at this lake.

Other game species collected in the survey included yellow perch, warmouth, black crappie, redear sunfish, flathead catfish, black and yellow bullhead, green sunfish, and white bass. These species are likely to persist and may make occasional contributions to the creel. Other game species known to exist in the reservoir but not collected in this survey include smallmouth bass and spotted bass. The fact that no specimens of these two species were collected in the survey attest to their relative abundance in the reservoir.

Additional nongame species collected in the survey included logperch, spotfin shiner, brook silverside, golden redhorse, golden shiner, spotted sucker, and tadpole madtom. These species may augment the forage base at times but otherwise make no significant contributions to the fishery.



Tailwater sampling

The water temperature at the time of sampling was 56 0F with a discharge of 550 cfs. The tailwater discharge had been high for several weeks prior to sampling. Tailwater sampling consisted of 0.5 hour of day D.C. electrofishing on each bank beginning at the spillway. Only game species were collected during sampling. Fish sampling efforts produced a total of 59 game fish representing three species. Largemouth bass were most abundant followed by walleye, and spotted bass. The largemouth bass sample consisted of 39 fish ranging from 2.8 to 15.2 inches in length. Largemouth bass growth was slightly below average compared to bass growth in impoundments. The walleye sample consisted of 11 fish ranging in length from 15.3 to 20.6 inches in length. Walleye growth was slightly above average compared to walleye growth in impoundments. The spotted bass sample consisted of nine fish ranging from 2.8 to 9.7 inches in length. Spotted bass were not aged. Almost all of the fish collected were captured along the rip-rapped section of the tailwater within the first 100 yards of the dam outlet.

 

CONCLUSION AND DISCUSSION

Lake Monroe possesses a diverse fish population of approximately 30 game and nongame species. The dominant forage species in the fishery include yellow bass, gizzard shad, bluegill, white crappie, and longear sunfish. Gizzard shad serve as the primary forage species for most game species in the reservoir. Between the native and stocked predator species in the lake, considerable predatory pressure is applied to the shad population. However, the availability and preference of predator species to utilize shad as forage decreases predatory pressure on other forage fish in the lake. Populations of bluegill, longear sunfish, yellow bass and white crappie appear to have little or no correlation to predator populations, implying that their populations are density dependent. Therefore the number of individuals of a given species recruited in any given year controls the performance of that species for that year class. Years with high reproductive success result in intense competition and poor growth while years with low recruitment and less competition results in good growth and more quality size fish.

The diet of both crappie and yellow bass switches from insects to small forage fish as they grow larger. A population bottleneck often occurs at this time where several age classes begin to stack up at the same size. This bottleneck is the result of limited food resources which leads to intense competition. A small percentage of fish may eventually reach a length where they can utilize larger gizzard shad as forage, at which point they quickly grow beyond this bottleneck and reach a larger average size. The length frequencies for these species indicate that most individuals succumb to natural mortality before this occurs. Yellow bass and white crappie longevity is limited with few individuals surviving beyond age 6. The densities of these two species are further compounded by the fact that they serve as both prey and predator. Without adequate predation, crappie and yellow bass densities remain high which further increases competition. A research project designed to more closely examine predator/prey interactions could shed additional light on the factors limiting quality size panfish at Monroe.

Electrofishing catch rates for largemouth bass at Monroe Reservoir have increased slightly from previous surveys indicating that densities may be increasing. Growth of largemouth bass remains slightly above average and can be attributed to low bass densities and an abundance of forage. Anglers should continue to experience good fishing for largemouth bass with good opportunities to catch quality size fish. A work plan to take a closer look at the largemouth bass population will begin in the spring of 2002 with sampling again taking place in 2005 followed by a creel survey the same year. This project should provide additional insight into the status of the Monroe bass population as well as strategies to improve bass fishing at the lake.

Lake Monroe should continue to provide good angling for channel and flathead catfish. Populations of both species appear to be stable with good recruitment, particularly for flathead catfish. Both populations also appear to have good survival to adult size with channel catfish collected up to 29 inches and flathead catfish up to 33 inches.

Walleye stocking success at Monroe has been good with stocking goals being met or exceeded in five of the last seven years resulting in a stable population at the reservoir. The stocking rate for walleye at Monroe Reservoir is 50 fingerlings/acre. Only the 1998 and 2001 stockings failed to meet this objective. Catch rates for walleye have been stable and have even increased slightly over the previous two surveys. Walleye growth has also increased slightly since the 1996 survey. Harvestable size walleye (14 inches or larger) comprised 46 percent of the walleye collected in the survey. Walleye are a popular sport fish at Lake Monroe with 5.9 percent of anglers targeting this species in the last angler survey (Schoenung 2001). Anglers should find good fishing for walleye over the next several years.

Fishing for hybrid striped bass at Monroe Reservoir should be very good over the next several years. Hybrid stockings have met or exceeded goals (5 fish/acre) in each of the last six years with the exception of 2000 when only a token stocking was made. Survey catch rates have been relatively consistent over the last 10 years and the hybrid bass population appears to be stable. Hybrid striped bass growth has also remained consistent. Hybrids up to 27 inches (11 pounds) were collected in the survey. The popularity of the hybrid fishery has been steadily increasing and accounted for 11.6 percent of angler trips in the 2000 angler survey (Schoenung 2001).

A recent change in Lake Monroe has been the dramatic increase in aquatic vegetation. Aquatic vegetation was fairly abundant at Monroe until several years of extreme variability in water levels beginning in 1996. From that time until just a few years ago aquatic vegetation had been sparse to nonexistent in the reservoir. The change in vegetation coverage could have significant impacts on the fish population at Lake Monroe. The fishery at Monroe had been steadily improving up to the 1996 survey. The most recent survey seems to document a backslide for some species including white crappie, bluegill, and yellow bass. The elimination of aquatic vegetation may play a role in this backslide. It will be interesting to see what changes take place in the fishery over time provided the level of aquatic vegetation can be maintained. Another fisheries survey is planned for Lake Monroe in 2006.

 

LITERATURE CITED

Andrews, S. J. 1993. Monroe Reservoir fish management report, 1992. Fisheries Section, Indiana Department of Natural Resources. Indianapolis. 21pp.

Andrews, S. J. 1996. Monroe Reservoir fish management report, 1996. Fisheries Section, Indiana Department of Natural Resources. Indianapolis. 28pp.

Schoenung, B. M. 2001. Fishing pressure and fish harvest at Lake Monroe, 2000 fish management report. Fisheries Section, Indiana Department of Natural Resources.Indianapolis. 15pp.

 

Walleye stocking fund ] Newsletters ] Articles ] Calendar ] Directory ] Out of State guides ] Photo Album ] Photo's ] Walleye Outing ] Walleye song ] Walleye waters ] INDIANA WALLEYE SHOPPING CENTER ] Poll results ] Home ] 2006 highlights ] mwa open ] club crashers ] Walleye News ]



 

 

Up
Bass lake
Big Turkey lake
Brookville
Cagles mill
Clear lake
Dewert lake
Eagle Creek Reservoir
Huntingburg lake
Huntington Reservoir
Kokomo Reservoir
Lake of the Woods
Maxinkuckee
Mississinewa
Monroe Reservoir
Pike Lake
Salamonie Reservoir
Lake Shafer
Waubee