2007-30

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Michigan Department of Natural Resources
Status of the Fishery Resource Report
2007-30
Page 1
Bennett Lake
Livingston County, T4N, R5E, Section 1, 2
Shiawassee River, Last surveyed 2006
Joseph M. Leonardi
Environment
Bennett Lake is a 150 acre lake located in Deerfield Township of Livingston County three miles
southeast of Argentine. The lake lies within the boundaries of the Shiawassee River watershed and
North Ore Creek sub-watershed. North Ore Creek flows northerly entering Bennett Lake at the
southeast shore, then exits to the north, flowing into Lobdell Lake and eventually discharging to the
Shiawassee River.
Public access to Bennett Lake is obtained using the Lobdell Lake Pubic Access Site (PAS) and
motoring through the connecting channel (North Ore Creek) to the main basin. Michigan Department
of Natural Resources (MDNR), Parks and Recreation Division administers the Lobdell Lake PAS,
which services approximately 30 vehicles. The boat launch and parking lot are paved with capabilities
for launching most boat sizes used for general recreation.
The geographic region of Bennett Lake is characterized by gently sloping ground moraine interspersed
with outwash channels and numerous end-moraine ridges. Undulating topography formed alternating
well-drained rises and poorly drained depressions of variable soils. Soils on raised moraines generally
consist of medium texture sand and loam while depressions along end moraine ridges are typically fine
texture, high in organic content. Outwash channels developed by glacial retreat generally formed the
river and stream drainage pattern of the watershed. Groundwater inflow is moderate resulting in a
cluster of lakes in the immediate area surrounding Bennett Lake.
Bennett Lake is typified as a warm water, medium size, deep lake of mesotrophic characteristics. The
lake shoreline is irregular in shape and can be divided into east and west portions (Figure 1). The west
portion forms a semi-circular main basin reaching 57 feet in depth while the east portion forms a
shallow water marsh complex with a single deep-water zone of 20 foot depth. The shoreline is
moderately developed with approximately 60 residences. The north and south shores of the west
portion are most developed with approximately 30 dwellings. The east basin is undeveloped and
considered valuable marsh and emerging wetland habitat.
Limnological parameters measured in August 2006, included temperature and oxygen profiles (Table
1). Thermal stratification in Bennett Lake occurred in mid-summer with thermocline development
between 15 and 30 feet. Critical oxygen concentrations for fish (< 3 ppm) were observed at depths
greater than 27 feet. The 2006 temperature and oxygen profiles are comparable to historical profiles
and indicate significant portions of the deep water zones become oxygen deprived and unsuitable for
most fish species when the lake stratifies.
Total alkalinity of Bennett Lake has historically ranged from 160 ppm to 240 ppm indicating
moderately hard water. In August 2006, total alkalinity measured 143 ppm. The lower alkalinity
measurement is most likely a natural fluctuation that could be attributed to a number of things such as
Michigan Department of Natural Resources
Status of the Fishery Resource Report
2007-30
Page 2
precipitation, lake turnover, or elemental cycling within the lake. Water pH ranged from 7.4 to 8.1
indicating good buffering ability. Other limnological parameters measured in 2006 included nitrate
(16.2 ug/L), total nitrogen (8.5 ug/L), total phosphorus (29.1 ug/L), chlorophyll a (2.77 ug/L), and
secchi disk (19 ft.).
The Carlson Trophic State Index (TSI) is a quantitative index for the purpose of classifying and
ranking lake trophic status using variables of chlorophyll a, total phosphorus, and secchi disk (Carlson
1977). The TSI scale ranges along a scale from 0 to 100 with lowest values reflecting oligotrophic
conditions and highest values reflecting hypereutrophic conditions. The TSI value for Bennett Lake
was 43 suggesting fair to good water quality and productive mesotrophic conditions.
Aquatic vegetation is the dominant form of fish cover in Bennett Lake. The overall fertility of the lake
along with its relatively shallow average depth make it well suited for aquatic vegetative growth.
Cursory observations during a 2006 survey effort indicated coontail was abundant in the littoral zone
with common occurrence of large-leaf pondweed, white lily, Eurasian milfoil, chara, and filamentous
algae. Emergent vegetation, particularly cattail and bulrush, were common to the west basin forming
ideal waterfowl marsh habitat. The North Ore Creek channel between Bennett and Lobdell lakes is
routinely treated with herbicides for nuisance aquatic vegetation.
History
Bennett Lake fish community assessments have been conducted by MDNR, Fisheries Division in
1979, 1990, 1997, and 2006. These assessments document the presence of 23 native fish species, 1
colonized species, and one introduced species (Table 2). It is likely other species are present but have
not been documented due to collection bias. Of the fish species present, each would be considered
common to the region and typical of warmwater fish assemblages in southern Michigan. Walleye
have not been stocked in Bennett Lake and their presence reflects movement from Lobdell Lake where
they were introduced. The lake herring or "cisco" has not been not been found since 1979 and is
believed extirpated.
Extensive fisheries management has not occurred on Bennett Lake. There has been no fish stocking
and past assessments have indicated a fair to good fishery for most sportfish present. Bennett Lake is
extremely popular for recreational use and maintains a very good reputation for largemouth bass,
northern pike, bluegill, black crappie, and pumpkinseed sunfish. Numerous largemouth bass angling
tournaments occur annually and often combine catches from both Lobdell and Bennett lakes.
Current Status
In May 2006, Fisheries Division conducted a fisheries assessment using trap net, gill net, seine, and
electrofishing gear. Three inland trap nets were fished for three nights at three locations. One
experimental mesh gill net was used to sample deep water zones at two locations for one night. Three
25-foot seine tows were made at three locations and three ten minute nighttime electrofishing runs
were conducted at three locations. All fish were measured to the nearest inch group and scales samples
were collected for age-growth analysis on common sportfish.
Michigan Department of Natural Resources
Status of the Fishery Resource Report
2007-30
Page 3
A total of 1,606 fish representing 22 species were collected. Bluegill, bowfin, brown and yellow
bullhead, carp, largemouth bass, and yellow perch were the most abundant comprising 96% of the total
catch by number and 89% of the catch by weight (Table 3). Other species collected included black
crappie, blackchin shiner, central mudminnow, golden shiner, grass pickerel, green sunfish, lake
chubsucker, longnose gar, northern pike, rock bass, walleye, warmouth, and white sucker.
A total of 1,200 bluegill averaging 5.9 inches comprised 75% of the total catch (Table 3). Fifty
percent of these fish met or exceeded the acceptable harvest size of 6 inches. Age-growth data
indicates bluegills were growing below State average having a mean growth index of -0.9 (Table 4).
Age frequency indicates sufficient recruitment is occurring with good representation of bluegill aged 4
to 7 years (Table 5). Bluegill longevity peaks at age 7 and older fish appear to experience high
mortality from either harvest or natural causes.
A total of 89 pumpkinseed sunfish averaging 6.1 inches comprised 6% of the total catch (Table 3).
Sixty-six percent of these fish met or exceeded the minimum harvest size of 6 inches. Age-growth
data indicates pumpkinseed sunfish are growing slightly above State average having a mean growth
index of +0.2 (Table 4). Age frequency indicates sufficient recruitment to harvest size with good
representation of age 3 and 4 fish (Table 5). Fully recruited pumpkinseeds are well represented as age
5 and 6 fish. Pumpkinseed longevity peaks at age 6 and older fish appear to experience high mortality
either by harvest or natural causes.
A total of 38 yellow perch averaging 3.5 inches comprised 2% of the total catch (Table 3). Ninety-two
percent of these fish were captured with electrofishing gear and all fish were aged between 1 to 3 years
accounting for the small average size. Age-growth data indicates yellow perch were growing below
State average having a mean growth index of -0.9 (Table 5). The absence of yellow perch older than
age 3 indicates high mortality most likely the result of natural causes.
A total of 29 largemouth bass averaging 11.6 inches comprised 2% of the total catch (Table 3).
Twenty-eight percent of these fish met or exceeded the minimum harvest size of 14 inches. Agegrowth data indicates largemouth bass are growing below State average having a mean growth index
of -1.1 (Table 4). Slow growth was observed at early age with age 3 fish averaging 8.2 inches
compared to the State average 9.4 inches. Although age frequency was based upon a relatively small
sample, multiple year classes were represented and recruitment to harvest size appears acceptable
(Table 5).
Other important sportfish occurred in low abundance. Fifteen black crappie averaged 9.0 inches, eight
northern pike averaged 26.1 inches, and one walleye measured 24.5 inches. Non-sportfish found in
relative abundance included 106 brown and yellow bullhead, 41 bowfin, and 35 carp.
Analysis and Discussion
Direct comparison of the 2006 fisheries assessment to previous assessments is tenuous due to
collection bias. Seasonal timing, gear selection, and procedural differences greatly affect catch rates.
However, the 2006 catch does allow for discussion of the current fish community and some
comparison to previous findings is possible.
Michigan Department of Natural Resources
Status of the Fishery Resource Report
2007-30
Page 4
In southern Michigan warmwater lakes, bluegill are one of the most abundant fish species present and
play a key role in community structure and overall sportfishing quality (Schneider 1981). Schneider
(1990) suggests indices of bluegill characteristics can be used to classify populations. The "Schneider
Index" uses size scores of length frequency and relates them to an adjective ranking system ranging
from "very poor" to "superior". Using the Schneider Index for classifying bluegill populations using
trap net data, Bennett Lake scored 4.25 for a good rank (Table 6).
Bluegill size structure has fluctuated between assessments in 1990, 1997, and 2006 (Table 6). In 1990,
bluegill size structure ranked "poor/acceptable" but improved significantly to "excellent" in 1997. In
2006, a decline to "good" was observed. The time span between assessments makes it difficult to
ascertain cause but differences are most likely attributed to natural cycles of abundance and harvest.
Age data from 1997 indicates a high percentage of older and larger fish in the catch. It is reasonable to
expect higher natural mortality and increased harvest mortality when the size structure is skewed
toward older and larger fish. When older and larger fish are removed from the population faster than
new recruits enter, a decline in size structure is likely. In 1990, when the bluegill size structure was
skewed toward younger and smaller fish, mortality was likely lower allowing higher recruitment into
the fishery. Presently, bluegill appear as the most abundant species in the lake and provide good
recreational angling opportunity to catch harvestable fish.
A small but healthy pumpkinseed sunfish stock provides additional recreational angling opportunities
in Bennett Lake Pumpkinseed sunfish abundance, size distribution, and age frequency have remained
similar since 1990 indicating a stable fishery. Pumpkinseed growth was slightly above State average
suggesting the relatively low abundance observed is not dependent on available food.
The largemouth bass fishery of Bennett Lake appears in satisfactory condition. Relative abundance,
size distribution, and age frequency were similar to the 1997 assessment and indicate a healthy and
stable fish community. Historically, largemouth bass growth in Bennett Lake has been below State
average and likely reflects environmental and climatic influences. Bennett Lake is highly regarded by
local bass anglers for large fish and remains a popular tournament fishing water in southern Michigan.
One of the significant differences between the 1997 and 2006 assessment was a decline in black
crappie catch in 2006. Over 200 black crappie averaging 7.0 inches were collected in 1997 compared
to 15 black crappie averaging 9.0 inches in 2006. The lower 2006 catch may reflect a decline in black
crappie abundance but more likely is the result of collection bias.
Yellow perch seldom provide viable recreational fisheries in inland waters in the southeast Michigan
area. None of the cluster of lakes surrounding Bennett Lake are known for yellow perch and most
reflect Bennett Lake's size structure. High mortality is observed after age 3 and is believed to be the
result of natural mortality due to unsuitable coolwater habitat, unavailable food, and predation.
Preferred water temperatures for yellow perch are 66-70F. During summer months, the Bennett Lake
epilimnion averages mid-70F with a small limited hypolimnion layer of preferred temperature and
oxygen available for yellow perch. Additionally, food preferences of 2-3 inch yellow perch typically
shift from zooplankton to larger macroinvertebrates which appear in limited supply based on cursory
observations.
Michigan Department of Natural Resources
Status of the Fishery Resource Report
2007-30
Page 5
Northern pike typically do not exhibit high abundance in assessments unless they are specifically
targeted after winter ice-out. Since only eight northern pike were captured in the 2006 assessment, it is
difficult to provide comment. The northern pike observed were robust and healthy and the limited data
obtained indicated good growth patterns. A small viable northern pike fishery exists and likely
provides additional recreational fishing opportunities.
Other fish species found in Bennett Lake appear in satisfactory abundance. Brown and yellow
bullheads function as bottom feeders and play an important role in the fish community. Carp, also a
bottom feeder, appear in moderate abundance. Bowfin and longnose gar are important predator fish
which help balance panfish populations.
Management Direction
Fisheries management of Bennett Lake should continue to concentrate on warmwater and coolwater
species with emphasis on bluegill, pumpkinseed sunfish, black crappie, largemouth bass, and northern
pike. Although the bluegill size structure has shown signs of decline, no immediate management
actions are warranted nor are any recommended. Management goals should strive to maintain a
bluegill fishery with and acceptable (or better) rating using the Schneider Index methodology. Future
assessments should make a greater effort to target northern pike and largemouth bass to understand
their population dynamics.
References
Carlson, R.E. 1977. A trophic state index for lakes. Limnology and Oceanography. 22:361-369.
Schneider, J.C. 1981. Fish communities in warmwater lakes. Michigan Department of Natural
Resources, Fisheries Research Report 1890, Ann Arbor.
Schneider, J.C. 1990. Classifying bluegill populations from lake survey data. Michigan Department
of Natural Resources, Fisheries Division, Fisheries Technical Report No. 90-10, Ann Arbor.
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