Table1. Mark-recapture Largemouth bass data from the Des Plaines River.
|
Size (cm)
|
Number of individuals day 1
|
Number of individuals day 2
|
Population density estimate
|
|
Unmarked
|
Marked
|
|
< 10
|
73
|
64
|
22
|
570
|
|
10-20
|
35
|
28
|
13
|
|
|
20-30
|
20
|
22
|
18
|
|
|
> 30
|
6
|
4
|
2
|
|
|
Total
|
134
|
118
|
55
|
|
Using these data, estimate the density (number/hectare) of each size class plus the overall density. [Note: 1 hectare = 10,000 m2.]
Sample calculation
For < 10 cm size class,
N = [73 x (64 + 22)] / 22
N = 285
The sample was taken from a 1,000 m x 5 m stretch of river which equals 5,000 m2.
One hectare is 10,000 m2, so we need to double our density estimate. 285 x 2 = 570 fish in the < 10 cm size class.
Bluntnose minnow
Complete the following table
Table 2. Mark-recapture Bluntnose minnow data from the Des Plaines River.
|
Size (cm)
|
Number of individuals day 1
|
Number of individuals day 2
|
Population density estimate
|
|
Unmarked
|
Marked
|
|
< 3
|
252
|
174
|
63
|
|
|
3-6
|
196
|
145
|
54
|
|
|
6-9
|
177
|
132
|
58
|
|
|
> 9
|
34
|
26
|
11
|
|
|
Total
|
659
|
477
|
186
|
|
1. Which species was more numerous is the Des Plaines River? How much more abundant?
2. Based on the data, which species grows to a larger size?
3. Which species do you think is the prey and which is the predator? Why?