Laarman and Ryckman - Lake Superior State University

34 LAARMAN AND RYCKMAN
Table 1. Number of marked and recaptured fish
caught with trap nets in Manistee Lake,
1974-1978.
Species
Length Number
range •
(cm) Marked Recaptured
Bluegill 10.2-22.7 13,670 486
Pumpkinseed 10.2-22.7 20,105 1,125
Rock bass 10.2-25.2 1,830 190
Black crappie 12.7-32.8 5,827 693
Yellow perch 12.7-32.8 3,775 104
Walleye 25.4-58.2 3,063 366
Smallmouth bass 15.2-32.8 3,093 322
White sucker 38.1-58.2 1,772 77
a Fish outside of the length ranges were captured occasion-
ally, but in low numbers.
2O
R/M -266530 + 35.330 L- 1.4531' + 0.0193E
(R'=O.18)
•15 / • /
• / \
• / •• //
a. /•
•5 / /•
/
/
i I I I i
15 20 25 50 55
Length (cm)
Fibre 1, RelaQo•hip bet•ee• the pe•ce•Se
the population and the number of recaptured (R)
fish were determined. The end result was five R/ (•2 st•d•d errors).
M ratios (one per year) for each 2.5-cm length
group per species. No attempt was made to determine
R/M ratios from fish marked in one year bass (Fig. 3). Although the general trend was an
and recaptured in later years. Relationships be- increase in catchability with size, the extreme
tween R/M values and total lengths of fish were yearly variation gave a low R 2 value of 0.22.
determined by polynomial regressions. The R/M Rock bass from Fife Lake showed a uniformly
values for the mid-point of each 2.5-cm length upward trend, but data from Whitmore and Suggroup
represent relative efficiency indices, and arloaf lakes were more erratic (Latta 1959). Nets
the application of these indices is discussed be- were selective for walleyes greater than 55 cm,
low.
but a significant difference in catchability was
not detectable for smaller fish (Fig. 4).
RESULTS AND DISCUSSION
Total numbers of fish marked and recaptured
There was a general increase in catchability
from 1974 to 1978 are given in Table 1 by
species. Fish shorter and longer than the indicated
lengths were captured occasionally but in
very low numbers.
Calculated curves, with 95% confidence limio
9
8
RIM -2.773 + 0,173L
(R' = 0.12)
its, showing the relationships between R/M val- g7
ues and total lengths of fish are given in Figs.
1-8. Size selectivity was evident for all species
except smallmouth bass and white suckers
(Figs. 1 and 2). Low coefficient of determination
• 6
(R 2) values of 0.18 (smallmouth bass) and 0.12
(white sucker) indicated much variation in the
3
data for both species. Latta (1959) reported
2
more variation in R/M percentages for largemouth
bass (Micropterus salmoides) than for
i
other species in Whitmore and Fife lakes and no
40 45 50 55 60
general trend in size selectivity. In the same
Length (cm)
study, however, Latta (1959) reported size-spe- Figure 2. Relationship between the percentage
cific catchability for white suckers from Fife of recapture of marked white suckers (R/M)
Lake.
and length (L) in Manistee Lake, 1974-1978
Size selectivity was barely detectable for rock (+-2 standard errors).