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Michigan Department of Natural Resources Jackson County (T2S, R2E, Sec. 29, 32) Surveyed May 1995 Michael P. Herman Environment Grass Lake is located in west-central Jackson County approximately 8
miles east of the City of Jackson. It is approximately 348 acres in size
but is one of the most shallow lakes in the county with an average depth
of only about 4 feet. The deepest basin, only 13 feet, is located near
the extreme northern end (see map of Grass
Lake). The lake basin is comprised mainly of marl, although some sand,
gravel, and peat are also present. Grass Lake has an inlet on it's north end which directly connects to
Mud Lake and Tims Lake. The only outlet of Grass Lake, located on it's
south end, empties into the Grass Lake Drain. This drain flows into the
Leoni Millpond and eventually enters Michigan Center Lake to the southwest.
Grass Lake is part of the upper Grand River watershed. Several other lakes
in close proximity to Grass Lake have similar physical features. Goose,
Gilletts and Brills lakes are all rather large lakes which have extensive
areas of shallow water and similar substrates. The name "Grass Lake" may have originated from the vast bulrush beds
which once covered this lake. Local residents have reported a significant
reduction of bulrushes in the last few decades. Although the bulrush appears
to be a very hearty plant, substrate disturbances, occasional "mowing"
by motorboats, and low concentrations of any one of several aquatic plant
herbicides are known to kill bulrushes. High-speed boating activity undoubtedly
has resulted in a reduction of this plant in Grass Lake. Other vegetation
types found in Grass Lake include the algae Chara, Eurasian milfoil
(Myriophyllum spictatum), and several species of common pond weeds
(Potomogeton). All of these are moderately abundant. The majority of Grass Lake is bordered by sedge marsh habitat which has
significantly restricted human development of the shoreline. Approximately
40 permanent and summer homes presently exist along this lake. There is
a county park on the southeast side of the lake which has a gravel boat
ramp and parking for approximately 12 cars. This site is maintained by
the Jackson County Parks Division. Earlier in this century, the fishery resources of Grass Lake were apparently
heavily influenced by winterkills. A winterkill can occur when thick coverings
of ice and snow blanket shallow lakes which have somewhat enriched waters.
Snow and ice restrict the amount of sunlight reaching the aquatic plants,
thereby reducing photosynthesis and the amount of dissolved oxygen plants
add to the water. During long winters the dissolved oxygen supply becomes
depleted by the respiration (breathing) of aquatic animals, plants, and
bacteria which are decomposing organic materials on the lake bottom. Fish
die from suffocation if dissolved oxygen falls below a critical level
before the ice breaks up and re-aeration can occur. The likelihood of
winterkill is increased by any form of fertilization (eg., from lawns,
farms, septic systems, and waterfowl) which stimulates plant growth in
the summer and, thereby, plant decomposition in the winter. Major winterkills occurred at Grass lake in 1916 and 1936, and a few
winterkilled fish were observed in the spring of 1945. Winter oxygen levels
were measured by the Fisheries Division several times from 1948 through
1964. During that period, oxygen levels low enough to stress fish occurred
only in the late 1940s and early 1950s. More recently, a mild winterkill
was reported in the early 1980s. Records indicate that bluegill, largemouth bass, and yellow perch were
stocked in the late 1930s and early 1940s by the Fisheries Division. This
was common practice until research demonstrated that stocking these species
was unnecessary. The earliest fish growth data on record was taken from
a few bluegills collected in 1957. Most of these were growing below state
average rates. A fishery survey conducted in 1971 resulted in the capture
of large numbers of warmwater fish species typical of lakes in the area.
The survey report stated that bluegill and perch populations "appeared
stunted," however fish growth was not analyzed. Fishing was reported as
poor for panfish and fair for bass and pike. Another extensive fishery survey was conducted in 1986 following several
riparian complaints of poor fishing. Results were very similar to those
of the 1971 survey. Bluegill and perch were rather small and slow growing
when compared to average fish growth rates in Michigan. Some large bass
and northern pike were represented in the fish sample. Fisheries personnel from the Jackson District have successfully raised
redear sunfish since 1984 and have stocked approximately 2.5 million fingerlings
in over 30 area lakes. This fast-growing panfish, originally native to
as far north as the Indiana-Michigan border, has become increasingly popular
among anglers since their first introduction to a few southern Michigan
lakes in the early 1950s. Preliminary evaluations have generally shown
good survival of stocked redears, and their natural reproduction has been
confirmed in several lakes. In the fall of 1987, approximately 35,000
redear sunfish fingerlings were stocked in Grass Lake from rearing ponds
in the Jackson District. A survey in 1990, just 3 years later, resulted in an impressive catch
of redear sunfish. A total of 55 redears averaging nearly 8 inches long
were caught in trap nets. These fish appeared very healthy and robust
and fish scale analysis showed that they were growing 1 inch above the
state average rate. As in 1986, the 1990 survey resulted in a good catch
of pumpkinseeds that exhibited growth rates above the state average. The
shallow, weedy habitat in Grass Lake seems to favor both redear and pumpkinseed.
Both species utilize foods found in those areas of lakes, such as snails
and aquatic insects. Results of the 1990 survey showed a persistence of the chronic problem
of small bluegills in this lake. Bluegills averaged just 5.6 inches and
appeared to be in only fair condition. In general, bluegill populations
in most area lakes average 6 inches or larger. Bluegills exhibited growth
rates that were nearly 1 inch below the state average, which represents
a slight growth decline since the 1986 survey. Although only one northern
pike was captured in 1990, several were captured during the 1986 survey.
Gill nets, the primary gear type used to sample pike populations, were
not used in the 1990 survey. Anglers interviewed during the 1990 survey
reported consistent catches of northern pike. In an effort to increase the chances for redear sunfish survival as well
as to provide some genetic diversity to the existing population, more
fingerling redear sunfish were stocked into Grass Lake in 1991 and 1992. Grass Lake was last surveyed in May of 1995 with four standard trap nets
(8 x 5 x 3 foot, 1.5-inch mesh) and two experimental gill nets (125-feet
long, six panels). All of the nets were fished for 1 night. Gamefish species
captured during this survey in descending order of abundance included
bullhead, redear sunfish, bluegill, black crappie, pumpkinseed sunfish,
yellow perch, northern pike and rock bass (Tables 1a and 1b). Anaysis
of growth rates and age composition may be found in tables 2 and 3. Evaluation of the redear sunfish fingerlings previously stocked into
this lake was the primary objective of the 1995 fisheries survey. Redear
sunfish were found to have grown and survived very well in Grass Lake.
Over 160 redears were captured in trap nets. They averaged nearly 9 inches
in length and one-half pound in weight, with several fish over 10 inches
long. Most of the redears caught in 1995 were four-years old and are likely
survivors from fingerlings stocked in 1991. Five year classes of redears
were represented in the 1995 fish sample indicating that natural reproduction
is occurring (Table 3). Redears exhibit growth rates nearly 1 inch above
the state average (Table 2). The goal of creating a "trophy" panfish has
been achieved. Bluegills comprised 16% of all fish caught in trap nets and they averaged
6 inches. Nearly 60% of the bluegills caught in trap nets were at least
6 inches long, an acceptable size to most anglers (Table 1a). Based on
growth analysis using fish scales, bluegills caught in trap and gill nets
during the 1995 survey exhibited growth rates that were approximately
0.7 inches below the state average (Table 2). The slow bluegill growth
observed in 1995 was consistent with past surveys. Grass Lake supports an excellent bullhead population. Bullheads were
the most abundant fish species caught in trap nets and they averaged nearly
10 inches. This species is often overlooked by anglers even though they
are fun to catch and are excellent table fare. Black crappie caught in
trap nets averaged 8.5 inches and over 80% of them were larger than 7
inches, the size that anglers consider large enough to keep. Crappies
exhibited above average growth rates and appeared to be in very good physical
condition. Pumpkinseed sunfish averaged over 6 inches and exhibited slightly above
average growth rates. Over 70% of the pumpkinseeds caught during this
survey were of acceptable size to anglers. A few yellow perch were captured,
ranging in size from 6 to nearly 11 inches. Perch averaged nearly 8 inches
and were represented by four age groups. Although not enough fish were
captured to be statistically significant, all age groups of perch exhibited
average or above average growth trends. Bluegills are targeted for sampling in inland lakes because of their
role in determining fish community structure and overall sportfishing
quality (Schneider 1981). Even though the goal of lake surveys is to sample
all fish species and all sizes present, many times the bluegill population
is the only one adequately sampled because bluegills are typically one
of the most abundant. A ranking system has been developed that allows
fish managers to get an idea of the relative quality of a lake's fish
population (Schneider 1990). On a scale of 1 to 7, the quality of the
bluegill population in Grass Lake based on the trap net catch was calculated
as 2.5, or marginally "acceptable". Results of past surveys suggest that a stable fishery exists in Grass
Lake. Survey records show that species composition has remained relatively
unchanged with the notable exception of stocked redear sunfish. Even though
bluegill growth has remained markedly poor since growth was first observed
in the late 1950's, Grass Lake has consistently produced good numbers
of bluegills that have been an acceptable size to anglers. Bluegills have
generally been quite abundant and have provided anglers with significant
angling opportunities throughout the years. Growth trends for perch, pumpkinseeds,
largemouth bass, pike, and crappie are remarkably similar to those from
past surveys of Grass Lake; that likewise suggests that a stable fishery
exists. Age composition and survival characteristics of all species listed
in Table 2 appear to be normal based on scale sample frequencies. The
longevity of black crappie appears to be above average. Redear sunfish seem ideally suited to Grass Lake. The excellent growth
exhibited by this species is unexpected based upon historical growth characteristics
of most other species in the lake. Redear sunfish should continue to grow
and attain very large sizes when compared to other panfish species. Redears
do not seem to demonstrate growth stunting as do most other sunfishes. Redear natural reproduction has been successful in Grass Lake and the
growth and survival of this species should be monitored by surveying the
lake again in approximately 5 years. Although the fishery of Grass Lake is somewhat average, this lake supports
a variety of catchable gamefish that are available to anglers. Bluegill,
black crappie, northern pike and redear sunfish are quite abundant and
anglers are satisfied with the existing fishery. No radical fishery management
is recommended at this time. Report completed: December 30, 1996. 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 Technical Report
90-10, Ann Arbor. Table 1a.-Number, weight and length of fish collected from Grass
Lake with trap nets, May 10, 1995.
Table 1b.-Number, weight and length indices of fish collected
from Grass Lake with gill nets, May 10, 1995.
Table 2.-Average total length (inches) at age, and growth relative
to the state average, for five species of fish sampled from Grass Lake
with trap and gill nets, May 10, 1995. Number of fish aged is given in
parentheses.
Table 3.-Estimated age frequency (percent) of five species of
fish caught from Grass Lake with trap and gill nets, May 10, 1995.
Last Update: 08/05/02
tinchert@michigan.gov |
