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Avon Point research update





    The following update concerns principally the insect
found on the shale reef. At the end of this update I've 
put the tables for the crustaceans finishing them up for
the year 1998.
     I want to thank the people who have taken the time to 
write and let me know they were interested in these notes.
Your comments have been appreciated.
                              John Lavelle 
                              Jan 24, 1998
                       ABLABSYMIA
                    MIDGE LARVAE           
    The follow table is derived from the waters that surrounded
the rock samples. I was faced with the choice of counting the
nests seen on the rocks or counting the animals that were shaken
from their nests and ended up in the surrounding waters. There
are problems with either. Counting the nests; the problem would 
be in finding them amid the Cladophora and in the laison. In 
counting those shaken loose into the water the problem is 
that I have no idea how many were not shaken out or whether 
the percentage of animals dislodged from the nests in the 
different samples were comparable. So faced with two 
comparatively bad choices I choose the one that was easiest 
to do, that is I counted the number of animals dislodged 
from the rocks and found in the water. Also I had begun in 
1993 and 1994 by counting the animals in the water so if I 
wanted to use that data at all I had to continue with the 
same method. Therefore the averages of the number of 
animals found below is less than the actual number of 
animals that live on the rocks. How much less I have no idea. 
Nor do I know how comparable the number of animal dislodged 
was between one sample and the next. In general the rocks 
were all treated in the same way in counting but a hundred 
minor variables existed between how one rock was transported 
from the bottom of the Lake to being viewed under a microscope. 
In other words don't make more of these numbers than this rather
sloppy method allows.
    All that being said the numbers are interesting if
one allows that the samples are comparable at all.


     Where a space is found in the table it means no samples
were taken that month.
       Average number found in 5 liter samples
      1993       1994     1995     1996    1997   1998

Mar                                                2 #
Apr.              0.36                             0 #
May  0.00         0.17     1.75     0.00    0 #    1.25
June 22.6         8.58    22.63     1.57    4.25  21
July 17.5        21.18     8.57    17.17   13.6   25
Aug. 14.4        36.58    32       28.2    22.7   32.3
Sept  4          79.25    15.66    28      12      8.5
Oct.  2.5        82.08                     50 #   13.7
Nov.                                              13
Dec.                                               8 #
               # Based on only one sample 

     Other than the year 1994, which for some unknown 
reason was an extraordinarily good year for these midges
all the years have a remarkably constant population 
density. At first glance that wouldn't appear to be so,
but if one takes into account the rather haphazard method
employed than the number swings can be viewed as sampling
errors. If I am right in this than what is surprising is
that with the great number of rounded gobies (10 to 15
per square meter) one would think that the number of 
midges would greatly decrease. Either the midges are
not foodstuff to the midges or their living in nests
provides protection from predation. This leads to the
question asked in earlier notes as to what the gobies
are eating.

                     Trichoptera 
                     Caddis Flies
    The number for these flies are probably more accurate
than the numbers for the midge laraes, at least for the 
years 1994 to 1996. I say this because on examining a
large rock on the lake's bottom rather than under a 
microscope the numbers were consistent. Also 
the nest of the animals being so large were easy to
find. The reason that I have more faith in the numbers
for the earlier years of this survey is that the number
of nests found was close to the number of animals found.
In 1997 and 1998 the number of nests found was close
to twice as high as the number of animals found. I have
no idea what happened to the animals. Since the method
for all the years was the same I think that this 
disappearance is an actual phenonema and not a sampling
problem.

 July 20 1994 - This rock was examined on the bottom
of the Lake. 
Rock size  50 cm. X 70 cm. underside area
                3cm. was the rocks thickness
           Hydropsyche      28
           Stenonema        12

For a comparison the Hydropsyche population works out to
.008 per square cm.  For the year the average worked out
to .009 per cm. 

   In the following table I have counted only the animals
seen. The number of Hydropsyche found on the reef has 
dropped quite a bit since 1994.

Genus - Hydropsyche
     These large (5 to 10 mm.) net weaving, nest building,
larvae are abundantly found on the reef. They always 
build their homes on the underside of rocks. The nests
are composed of mostly broken Zebra mussels shells and
very small rocks.  In every year far more animals are
found in the late summer and fall than in the spring 
and early summer.
        A                 B               C               D
Average rock area   Number of rocks  Number of caddis   C/(A*B)=D
 in cm. squared        samples         fly found
    
1994    87             76           62              .0093

1995    79             71           23              .0041

1996    94             63           13              .0021

1997    93             59           11*             .0020 

1998    85             87           15              .0020

==============================================

Caddis Fly     # 31
    This small (1 to 3 mm.) free living caddis gets it's 
designation from a drawing of the animal made 1992. This 
critter has the distinction of being the only animal, 
outside of the mollusks, that was examined by a professional. 
Regretfully she was unable to identify it other than to say 
it was a caddis fly.  
    The following table uses the same format as that
for the Hydropsyche.

        A                 B               C               D
Average rock area   Number of rocks  Number of caddis   C/(A*B)=D
 in cm. squared        samples       fly #31 found
    
1994    87             76                86               .013

1995    79             71               100               .018

1996    94             63                23               .004

1997    93             59                 9               .002

1998    85             87                 4               .0005



      There has been a large decrease in the number of these
free living caddis flies over the years.


                 Other Unidentified Caddis Flies

     In 1995 and in greater numbers in 1996 there were
caddis flies found on the reef that I refered to as 
the sloppy nest builders. Whereas the Hydropsyches
built their nest out of very small rocks and 
Zebra mussel shells these caddis flies built their 
nest out of long strands of algae. Three animals were
found in 1995 and in 1996, eleven animals were found.
In appearance they look very much like the net building
Hydropsyche and may very well be a different species
in the same genus. None were seen in 1997 or 1998.

    In 1994 thru 1996 5 or 6 other species of caddis 
flies were found living in portable nests. They were found
very seldomly. None were found in 1997 or 1998.


                      EPHEMEROPTERA                        
                       STENONEMA        
                        MAYFLY

   These insects are found generally in late summer and fall
free=living on the rocks of the reef. In the following table
I am again using the format used above for the caddis flies.

        A                 B               C           D
Average rock area   Number of rocks  Number of    C/(A*B)=D
 in cm. squared        samples      mayfliesfound
    
1994    87             76              17           .003

1995    79             71              21           .004

1996    94             63               6           .001

1997    93             59              33           .006   

1998    85             87             215           .029 


    The great increase in the number of mayflies was not 
scattered in samples throughout the year. The large numbers
were clustered in the dates shown below.

1998    Area
       in cm.
Aug 16   72     108	
        100      20
Aug 23   72      26	
         96       0	
Aug 30  117      11	
         91       0	
Sept 6  192       3	
	78        0	
Sept 13	80       12	

                        
    If I eliminate these dates totally from the samples than
the total number of mayflies found is 32. Using the formally
from above gives the number, .005. But I don't know if it makes
any sense to do this.
    Obviously the number of mayflies is increasing but it will
take someone better trained in statistics to tell by how 
much.

====================================================                         ROTIFERS

   Plankton sample size 12.5 liters
   In the chart below the number column is the total 
number of all rotifers found in the month. The average
is the total rotifers divided by the total number of
samples taken that month. Generally there were two samples
taken every week or 8 to 9 samples a month
              
           1994               1995            1996          
      number  average   number  average  number  average 
April   60      10        75     8.33     250    31.25
May     78       8.6     660    82.5    *1362   151.33
June   532      48.36    491    54.55    1335   148.33
July *4144     460.44    501    55.66    2787   348.37
Aug   2065     229.44    176    19.55    2697   385.28
Sept   124      15.5     379    47.38    1217   135.22
Oct     82       9.11    279    31        267    29.66
Nov.    66       7.3     102    11.33     103    12.87
Dec.     1        .12      3     0.6       10     1.11

            1997             1998
      number  average   number  average
Jan     13      2.2        3     0.5
Feb      0      0          4     0.6 
Mar      6       .7        3     0.3
Apr.    36      4        310    38.8
May    726     38       2594   324.3
June  2229    247.7     1274   141.6
July  1271    141.2     1610   178.9  
Aug.   707    101       1793   224.3
Sept  1245    155.6      970   121.5
Oct.   759     84.3      925   102.8
Nov.    11      1.2       37     4.1 
Dec.     3       .3        2      .25
* The July 1994 and the May 1996 are so high because in
both these month on one date there was an enormous
number of rotifers.
  July 20 1994 there were 3043 rotifers in just one 12.5 
liter sample.
  May 26 1996 there were 1073 rotifers in the sample.


    The following tables below are the same as the ones I posted
on glin-announce several months ago but here they are more 
current taking the numbers to the end of 1998. 
   
                        COPEPODS
                 Monthly Averages for Copepods
   The following data is based on 12.5 liter samples taken twice
a week. All the samples where taken in the morning from the
same location.
	        Calanoid Copepods 1993 to 1997
       1993      1994     1995        1996    1997    1998
Mar.                        2.2        2.6      .9    1.56
Apr.             7.7        3.7        3.5     4.5    24.1
May            104.3       84.8       37      40.5    11.6 
June   12.75    71.4       56.7       60.7  *144      27.8
July    4.85    22.4        2.4       28.4     8.5     4.6
Aug     4       16.7        5         28.1     7.1     2.6
Sept   26.57    32.1       13.6        6.8    11      12
Oct    15.55    11           9.3      34.6     6.3    21
Nov     9.11     9.9        5.3        2.9     4.9    14.3
Dec     5.57     6.3        7.2        5.6      .8    20.1

Average of the  31.3       20.9      23.04    25.3    15.34
Calanoids Apr. thru Dec.
1994 to 1998

   *  Except for the extraordinary number of animals found on one
sampling date the number of calanoid copepods would have shown 
a marked decline in 1997. That date was June 15. The sample 
had the extraordinary number of 880 calanoids in the 12.5 liter
sample. The total number of calanoids found for the entire year 
in about 50 samples minus the June 15 date was 1130, thus the one 
sample had more animals than all the samples for the entire 
year. I have belabored the point of the nonrandomness of the
zooplankton in the 1996 report and so will not cover that ground
again. What I want to point out here is that if the June 15 sample
is dropped from the reporting than the copepods had a steep 
drop in their numbers in 1997 and the average for the month of  
June would be 52 per sample rather than 144 per sample. The 
average for the year would drop from 25.3 per sample to 11.4
per sample. Whether this dropping of the sample from the total
counts is valid I leave up to the reader but if the June 15
sample is ignored than the calanoids have had a major decline 
in 1997.

                    Cyclopoid Copepods
     The cyclopoid copepods had a sharp drop in the numbers
found in the samples. The table does not include the
cyclopoid T. Mexicanus pranis. This small copepod was found
very sporadically in the samples until this year. Though when
it was found it could be found in large numbers.
     Comparison of Cyclopoids Copepods from 1993 to 1997
      1993       1994        1995    1996      1997      1998

April             8.6        9.77     3		.3	   2.1  
May              38.33      56.75    50.33     8.9	  34.7		
June   51.5      38.77     182      109.36    35.4        59.1
July   25        26.6       19.55    17.13    30.2         6.3
Aug.   38.5      13.7       19.11     5	       7.7	   3.7
Sept.  17.28     12.5        7.12    17.33     2.9         1.2
Oct.    8.55     13.1        3.77     8.88     2.3         3.4
Nov.   12.88      7.7        5.66     1.5      4.3         1.6
Dec.   10.71      5.13       4.4      7.66     1.1         3.3

Average for the  18.277     34.23    24.46    10.3        12.82
years 1994 to 1998
Apr. to Dec.
                   Copepod Nauplii
    No attempted was made to distinquish between cyclopoid and 
calanoid copepods. 
                        Nauplii
Monthly averages
         1993      1994       1995       1996   1997    1998
Jan.                                     3.25    3.8     0.3
Feb.                                      .75    1.9     1.4
Mar.                                     9.5     1.4      .9
Apr.               36.16      28         8.25   61.3    33.4
May               133.97     161.25     63.55   13.8    53.4
June     13        61.3      129.44    121.22   64.8    38.5
July     2.71      27.66      29.4      51      48.6     5.2
Aug.     4.5       49.55      70.44     30      15       9.8
Sept.    6.57      26         40.12     49.66   10      38.4
Oct.     4.77      10.22      13.11     44       8.8    14.8
Nov.     6.44       2.88       4.44      1.625   2.8     1.4
Dec.     4.57       5.62       2.4       1.66     .2      .25

Yearly average     39.26       53.17     41.21   25.03  16.26
from Apr to Dec.


    The numbers for all the copepods are still lower in current
years than they have been since 1994 except for a slight 
increase in the cyclopoid copepods in 1998 over 1997.
====================================================
The year ahead:
   You may have noticed a sharp spike in the Calanoid copepods
number at year end. This increase in numbers is one of the 
really frustrating things about working in the Lake because
the samples were getting even more interesting in January 
but the big cold moved in and froze the whole Lake area up for
about one mile out.

   Below is the sample taken on Jan 1, 1999 and Jan. 6 1999:

Jan 1, 1999
Calanoids (L.siciloides)    13
T. Mexicanus pranis          2
Cyclopoid (D. thomasi)       4



Jan 6, 1999
Calanoids (L.siciloides)    70
T. mexicanus                 1
Cyclopoid (D. thomasi)       8
Bosmina longristris          5
Daphnia (species ?)          6

     Something was happening with the Calanoid population and
while I probably will never know why this increased population
was occurring it would have been nice to see how long it would
last. Hopely the ice will break up in the nexts couple of days
allowing me to take one or two more samples in January. As it
stands now the numbers are showing a great increase over all the
years prior. Several of these Calanoids were bearing small 
clutches of eggs.

     A final note on this sample. When I first viewed the
Daphnias I thought they were some new and very strange type
of animal. But seperating them out and studying them better
I saw that all the Daphnias were molting at the same time.
They looked so bizarre because they still had their old 
skeletons attached to them. 


Jan 24, 1999.
     What ever was happening with the crustacean population
is over. The ice has broken up near shore and it is
possible to again take water samples. Below are the animals
found in todays sample.

Calanoids (L.siciloides)     2
Cyclopoid (D. thomasi)       2
Nauplii                      1
Daphnia (species ?)          1   (had 3 eggs)

Rotifers
   Unidentified              1

Nematode                     3