The Blue River Darter Project: 2001 Update
Results
Darter Assessment
Zippin Analysis 2001
In our 2001 riffle studies, we collected three riffle areas where darters were
abundant in previous years. These areas are the same sites collected in 1999 and
2000. In our 2001 strip transects, we identified 205 specimens representing 10
fish species. This information is summarized with data from 1999 and 2000 in
Table 1.
Of the fish identified, the one found most frequently was the greenside darter
with 56 identified in the strip removals. Some 43 rainbow darters were
identified. Thirty-eight spotted darters were taken. This is the first time in
our samples that greenside darters and rainbow darters have outnumbered spotted
darters. Banded darters and banded sculpins were taken in about the same numbers
(25 and 19). Of the remaining species, stonerollers were fairly common. All
other species were taken sporadically at the various sites. We found one fantail
darter and an adult bluebreast darter at Milltown. Variegate darters were not
found at any of the sampling sites.
The total numbers of fishes identified were compared with collections in
previous years (Table 2). These data indicate that the numbers of several
darters have decreased since 1995.
In 2001, our estimated number of fish per 100 ft2 increased to 30.33. This
increase is primarily related to the dramatic increase in rainbow and greenside
darters at the permanent sampling sites. In 2000, greenside darters were most
common at Rothrock’s Dam. However, the number of spotted darters rebounded from
only 1.8 per 100 ft2 in 2000.
The Zippin population estimates for 1999, 2000 and 2001 are compared in Table
3.
In 1999, a significant drought event occurred leaving fish concentrated and
relatively easy to capture. In 2000, conditions were near normal, but fish catch
dropped at all sites in 2000 following the drought year. Based on literature
search evidence at that time, we predicted that this would happen. In 2001, the
population estimates rebounded as the numbers of rainbow and greenside darters
increased in the permanent sampling areas.
Interestingly, Trautman theorized that in Ohio bluebreast darters actually might
increase following the removal of mill dams because the removals enabled
upstream migration and recreated the fast water riffle systems common where mill
dams had been placed. This has not occurred in the Blue River where bluebreast
darter populations have remained very low.
In the 1985 study, the three dams were in reasonably good condition. Bluebreast
darters were found downstream from all sites. In the late 1980’s, two dams were
altered to facilitate canoe passage. Existing rocks at White Cloud were
repositioned providing the fast water canoe passage. An existing mill race at
White Cloud now remains dry except during high water.
At Rothrock’s Dam, most of the mill dam was removed. This had an immediate
impact upon the fish populations. Sand, silt and gravel that had been entrained
behind the dam covered the downstream riffles. Eventually much of this material
was carried downstream providing the fast water habitat that functions as a
passageway for canoers.
Milltown Dam is the remaining dam in this system. The major changes that have
occurred over the years have been silt deposition in the area below the dam. Old
photographs indicate the area below the dam was free of sediment. The changing
environment has created several microhabitats that did not exist in the 1980’s.
One of these is the short riffle that we selected as our monitoring site. This
area has easy access but does not appear to be a preferred habitat for the
spotted and bluebreast darters. The first significant habitat for these species
is downstream where we found both darters. Future work should focus on the
downstream riffle systems.
Some instruction about the demise of the bluebreast darter is provided by a food
habit study done in 1986. The original data is provided in Table 4.
This analysis of the stomach contents of 59 specimens of varying lengths
indicated that these darters consumed almost 60% dipteran larvae and that a
major food item was black flies—Simuliidae. The changing of the downstream
substrates to facilitate canoe passage may have changed the habitats creating a
steady flow instead of the turbulent flow observed when water flows over a dam.
This situation still exists at Milltown, and interestingly, blackfly larvae were
the dominant invertebrates in 2000.
Macroinvertebrate Bioassessment
The results of the macroinvertebrate assessment for 2001 indicated three sites
with very good macroinvertebrate diversity. The macroinvertebrate bioassessments
were compared with our last major sampling period-1995. The percent comparisons
to a pristine reference increased at all sites. See Figure 1 for a
comparison. Sites 6 and 7 at Rothrock’s Dam
and Milltown showed a marked increase in invertebrate quality since 1995. Both
sites increased from a slightly impaired to a non-impaired status. Site 3 showed
a slight increase in invertebrate quality since 1995; however this site
originally was in the non-impaired range.
Individual Macroinvertebrate Metrics
To further analyze these trends, the individual metric data were placed in
Table 5 and Table 6 for analysis and interpretation.
Taxa Richness
All three sites investigated in 2001 showed an increase in the number of taxa.
Sites 3, 6, and 7 increased by 6, 5, and 4 taxa respectively. This suggests an
increase in water quality, habitat diversity, and habitat sustainability since
1995.
EPT Taxa
The EPT taxa at all sites was substantial, and White Cloud was in the range
expected for a pristine stream with a number of available habitats. In a
pristine stream, we would expect to find at least eight families of
Ephemeroptera, Plecoptera and Tricoptera (EPT taxa). Site 3 had 9 families from
the EPT group, one more than in 1995. At Site 6, the number of families in the
EPT group increased from 4 to 8. This is perhaps due to the removal of the dam
at this site and continued sorting of the sand and sediments. Site 7, however,
showed a decrease in the number of families in the EPT group from 7 in 1995 to 6
in 2001.
Autecology of Dominant Families
Studying the autecology of the dominant taxa at the various sites provides some
instruction regarding water quality in the Blue River. The riffle beetle,
Elmidae, was the dominant taxon at Sites 3 and 6 in 2001. These larvae are
collectors of coarse sediment and detritus. They are among the moderately
tolerant families, and are fairly resistant to sediment pollution. Site 3 had a
dominant taxa of Chironomidae in 1995, which are significantly more tolerant of
pollutants than are the Elmidae. However, at Site 6, the dominant taxa in 1995
were the Heptageniids who are about as tolerant to pollutants as the Elmidae.
Milltown (Site 7) showed the most dramatic change in dominant taxa from 1995 to
2001. In 1995, the dominant taxa were the Simuliids which are extremely tolerant
to water pollution. In 2001 the dominant taxa were the Perlidae, a family that
is extremely intolerant to pollutants.
Family Biotic Index
The Family Biotic Index (FBI), an indicator of the level of organic pollution,
yielded values mostly in the moderate range. The indices overall substantiate
some organic enrichment, but not at the level where the stream is severely
degraded. The FBI for all three sites has decreased slightly since 1995. This is
a further indicator that there has been a decrease in the amount of organic
pollutants since 1995.
Community Loss
All sites were compared with Site 3 as a reference in both 1995 and 2001. Site 7
showed a dramatic reduction in community loss in 2001 as opposed to 1995 while
Site 6 remained in the same range of community loss in 2001.
Shredders (Coarse Particulate Organic Matter Community)
Shredders skeletonize, shred, and consume leaves. We found very few members of
this functional group in the Blue River during both 1995 and 2001. One reason
could be that we did most of the study in the late summer and early fall when
leaves had already been processed. We need to continue the study in the late
winter and spring, when processing is occurring, to determine the abundance of
the shredding community. Shredders were present, and we noted that stoneflies
had infiltrated leaf packs in those samples that we took after leaf fall had
begun.
Similarity and Diversity Assessment 1995-2001
Similarity
As a continuation of the macroinvertebrate bioassessment, similarity and
diversity analyses were performed on macroinvertebrate data from 1995 and 2001.
As noted in Table 7, percent similarity at the three sites ranged from 36%-52%.
In a six-year study period, this amount of similarity is considered an
indication of good ecological integrity and stability of the riffle ecosystems. Jaccard coefficient ranged from 0.42-0.5. Study of the individual species arrays
revealed some interesting findings. The most interesting finding was a dramatic
decrease in a shredder stonefly family Pteronarcyidae, and dramatic increases in
two families. Perlidae, a stonefly predator was virtually absent in 1995, but
became a dominant taxon in 2001.
Psephenidae, a scraper, increased in number 5-10 fold. The increase in numbers
of scrapers could be related to the attached algae fauna on the rocks. In this
study, we noted high nitrate and phosphate levels in the river during storm
discharge periods. Nitrate and phosphate, while not toxic themselves, create
changes in the river continuum. The phosphate and nitrate provide nutrients for
algae. More algae might logically lead to more scrapers. These species might in
turn provide the food supply for a predatory stonefly. It is recommended that a
periphyton study be undertaken in the future.
Diversity
For diversity, we used Shannon's index. As noted in the methods, Shannon’s index
is a method used to estimate the probability of removing the same two animals at
random. The data indicate that diversity, although high, decreased slightly from
1995 to 2001 at all three sites. The numbers were so close, however, that we
would not consider the reduction to be significant. While diversity is very
similar, the dominant taxa have changed due to environmental factors such as
increased nitrate and phosphate.
Habitat Assessment
The three sites were evaluated using two habitat assessment methods--The Habitat
Assessment Field Data Sheet as well as the Qualitative Habitat Evaluation Index
(QHEI). These methodologies are described in more detail in the methods section.
These habitat evaluations are rapid visual assessments developed using the
available field data sheets. The field data sheet includes nine areas of
consideration ranked as excellent, good, fair, or poor. The rankings are summed
and compared as a percentage of a pristine high quality reference site. If these
percentages are higher than or equal to 88%, they are considered to be
comparable to the reference standard. If the percentage is 75-88%, it is
considered supporting. If the percentage is 60-73%, it is partially supporting
and if the percentage is less than or equal to 58%, it is considered
non-supporting.
The QHEI is a measure of the qualitative habitat corresponding to the physical
features that affect fish and invertebrate populations. The QHEI data sheets are
broken down into metrics or categories that are then broken down into individual
components. Metrics of the QHEI include substrate, in-stream morphology, channel
morphology, riparian zone, bank erosion, pool/glide and riffle/run quality, as
well as gradient. For each of these components the status of the river is
assessed and a score is assigned based on that status. The scores are added
together to give an aggregate QHEI. The score is interpreted using a scale that
corresponds to suitability of a warm water habitat for aquatic organisms. QHEI
scores greater than 60 indicate that a stream is suitable for warmwater habitat
without use impairment.
Overall Assessment
Both strategies for evaluating these areas indicate that the habitat is suitable
and that there is little impairment. All sites have ample habitat to support a
variety of species. Major changes at White Cloud and Rothrock’s are related to
alteration of the old dams. The Milltown site has undergone considerable
deposition below the dam. This has actually increased the number of available
habitats by providing more waterwillow for cover and creating slower water
riffles inhabited by rainbow and greenside darters. Future students should note
that the study riffle at Milltown is a recent development and possibly should
focus on the more stable riffle system farther downstream
Water Quality Analysis
Water quality data are summarized in the attached table. According to the state
and federal governmental agencies, Blue River from miles 11.5—57 is high quality
and should be preserved. As one can observe from the above data taken at various
times, all samples are within the EPA’s standards for quality water. Dissolved
oxygen values were near saturation. The pH was in the alkaline range primarily
because this stream receives a substantial quantity of spring water with ample
dissolved bicarbonates. The numbers of fecal coliform did not exceed 200/100ml,
the standard for recreational use. There was not an excess of nitrates or
phosphates to cause algae to flourish. The sample areas studied are of good
water quality and should be able to support a diverse, healthy, and balanced
habitat. During low and moderate flow period, the water is relatively clear.
Water quality problems develop when the stream receives considerable runoff from
point source thunderstorms and heavy rains. When this occurs, the river becomes
turbid and carries significant numbers of fecal coliform bacteria and has
elevated nutrients. We recommend that a future class consider monitoring a storm
discharge period to assess this phenomenon. A sediment study might also provide
good background information.
Water Quality
Analysis Table
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