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Avery, Ed L.; Hunt, Robert L. / Population dynamics of wild brown trout and associated sport fisheries in four central Wisconsin streams

Results,   pp. 6-19 PDF (6.7 MB)

Page 6

       fishing day was assumed during the re-  where n  = number of car counts
  and was computed by the formula:
       mainder of May and in September.                      possible/day
       Day length each month varied with the      Ci    = mean number of
cars      n = 2
       time intervals represented by the 6:30                present at each
       a.m. and 8:30 p.m. car counts. These                  count period
 c                  (CiTi) (Aowed) (OWED)
       were determined by the earliest angler        T     - c          
              i   1
       on the stream and the last angler leav-    Ti    = the time interval
rep-  _
       ing the stream, respectively. All other               resented by
each car   where OWED    = number of days in
       car counts represented 2.0-hour time                  count, usually
2 hours                    opening weekend.
       intervals.                                   A      = mean number
of an-
         Monthly fishing pressure (as ang-                  glers/car on
       ler-hours) was estimated by the                       days (wd) or
week-         In 1977, riparian landowners on
       formula:                                              end days plus
          Radley Creek and the Mecan River
                                                             holidays (wed)
         were issued a "fisherman's log" to
           n = 8                                    WD    = number of weekdays
      record fishing effort and size, number,
                  2(CiTi) (Awd) (WD)                        in the month
            and species of trout caught by rela-
                          (Awi) (WD)                WED = number of weekend
         tives, friends, etc. Vehicles present on
                                                            days + holidays
in     these riparian properties were not in-
                       i n - 8+                                 the month.
              cluded in the 2-hour counts on census
             t  m n                  days. Pertinent data recorded by the
                  (CiTi) (Awed) (WED)                                   
            riparian landowners were added to the
           i = 1                                Fishing pressure on opening
week-    estimated values from the census to
                                              end in May was considered separately
 achieve monthly and season totals.
       TROUT POPULATIONS*                     Mecan River to 114 lb/acre
in Radley   mons and Radley creeks to 5.2 in. in
                                             Creek, with a composite average
in all  the Mecan River. Average yearling
                                             four streams of 96 lb/acre.
These    densities ranged from 860/mile in the
      Standing Stocks                        brown trout densities and standing
    Mecan River to over 1,500/mile in the
                                             stocks are generally greater
than those  other streams. Lowry (1971) found
                                             found in northern Wisconsin
streams  61 % of the spring population of brown
         Spring 1976-78                      (Frankenberger 1968; Mason and
        trout in McKenzie Creek in northwest-
                                             Wegner 1970; Lowry 1971; Thuemler
   ern Wisconsin consisted of yearlings
         The average spring density of age I  1976); but, although numerical
densi-  which averaged 4.6 in. However, trout
      and older brown trout ranged from    ties are higher, standing stocks
in  densities in McKenzie Creek were gen-
      1,270/mile in the Mecan River to     weight are lower than in Class
I    erally less than half those observed in
      2,500/mile in Emmons Creek (Table    streams of southern Wisconsin
      this study.
      3). The average density in the four  (Brynildson and Mason 1975; C.
L.      The average percentage of the
      streams as a whole during the 3-year  Brynildson, pers. comm.).   
       spring populations consisting of age
      period was 2,020/mile. Average stand-   Relatively few trout in the
5.5- to  II's ranged from 18% in Wedde Creek
      ing stock ranged from 59 lb/acre in the  6.4-in. range were present
in the spring  to 29% in Emmons Creek (Table 4).
                                              in any of the study streams.
This inter-  Average densities ranged from 311/
                                              val proved to be a natural
break be-  mile in the Mecan River to 703/mile in
                                              tween age I and age II+ fish
at this  Emmons Creek, while the average size
      *Native brook trout were captured occa-  time of year, with most yearlings
being  of the 2-year-olds ranged from 7.3 in.
      sionally in each of the streams but were un-  less than the minimum
legal length of  in Emmons Creek to 8.6 in. in the Me-
      important in terms of numbers or standing  6.0 in. Yearlings were numerically
 can River. Age III's accounted for
      stock. Rainbow trout, captured only in the  dominant each spring in
all streams;  averages of 5-9% of the spring popula-
      Mecan River, were of greater importance  their minimum average was
61 % in  tions, and their average densities
      than brook trout but were still insignificant  Emmons Creek and their
maximum  ranged from 80/mile in the Mecan
      relative to the brown trout population  average, 77% in Wedde Creek
(Table  River to 216/mile in Emmons Creek.
      present. Only brown trout are discussed in  4). Average size of yearling
stocks in  Average size ranged from 9.6 in. in Em-
6     this report.                           April ranged from 4.6 in. in
both Em-   mons Creek to 10.7 in. in the Mecan

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