Yellow perch spawning
assessment, Green Can Reef – 2008
In 2008, we began yellow perch spawning assessment on 5/21/2008 and continued till 6/17/2008. We sampled five times – 5/21, 5/29, 6/6, 6/10 and 6/17. The effort varied from 500 ft of gillnet to 1,000 ft per each lift for a total of 4,000 ft. Even though the effort was greater in 2008, the number of yellow perch captured in this traditional spawning reef was much lesser compared to the previous years. The mesh sizes used were similar to the 2007 sampling – 2, 2.5, 2.75, 3 and 3.25 inches. However, the total number of yellow perch captured in five lifts was only 326. In contrast to previous years, fewer males were captured (64%) in 2008. The bottom temperature was 34 0F on 5/21/08 and increased to 53 0F by 6/17/08. The cooler bottom temperature probably delayed congregation of perch in large numbers near the spawning reef. No spent females were observed until 6/10/08.
|
Sampling date |
Number (all) |
Number (male) |
Number (female) |
|
May 21st |
67 |
43 |
24 |
|
May
29th |
96 |
73 |
23 |
|
June 5th |
54 |
17 |
37 |
|
June 10th |
76 |
51 |
25 |
|
June 17th |
33 |
20 |
13 |
We took 154 age samples, and we were able to determine ages of 152 perch. In 2008, for the first time in several years, the 1998 year-class perch which are 10-year-old were replaced by the 2002 year-class perch as the most dominant age group. In addition, 2003, 2004 and 2005 year-classes also comprised fair number of perch in the spawning population. Thus, there were multiple year-classes represented in the spawning population, a positive sign of a recovering population.
2008 – Yellow Perch Egg
Deposition Survey:
The WDNR dive team continued the
effort using the protocol similar to 2003 to quantify egg deposition in the
Green Can Reef area.
|
2008 Diving for yellow perch egg deposition |
|||||
|
Date |
Divers |
Depth |
Location |
Area searched (ft) |
# of egg masses |
|
June 2, 2008 |
Brad E. |
50 to 38 feet |
E of Green Can Reef |
30 |
1 |
|
Mike B. |
30 |
1 |
|||
|
June 2, 2008 |
Mike Kitt |
35 to 25 feet |
South of Green Can |
24 |
2 |
|
Mike Neal |
24 |
1 |
|||
|
June 2, 2008 |
Brad E. |
35 to 20 feet |
South and West of GCR |
24 |
3 |
|
Cheryl P./ Ben H |
24 |
3 |
|||
|
June 2, 2008 |
Mike Kitt/Scott H |
50 to 50 feet |
South and East of GCR |
40 |
1 |
|
Mike B/Mike N. |
24 |
1 |
|||
|
June 18, 2008 |
Brad E |
53 to 45 feet |
East of Green Can Reef |
16 |
0 |
|
Mike B / Ben H |
16 |
0 |
|||
|
June 18, 2008 |
Tim K. |
40 to 30 feet |
East and South of GCR |
20 |
0 |
|
Ryan V. |
20 |
0 |
|||
|
June 18, 2008 |
Brad E. |
45 to 35 |
West and South of GCR |
16 |
0 |
|
Mike B / Ben H |
16 |
2 |
|||
Total area searched = 28,800m2
Total eggs found = 15
Egg masses per 1000 m2 = 0.52
Extremely low number of egg skeins was found during the two days of diving survey (6/2 and 6/18). Only fifteen eggs skeins were observed by surveying 28,800 square meters, which amounts to 0.52 egg skeins per 1000 square meters. Whereas in 2007, 10.81 egg skeins per 1000 square meters were documented. The lower number of eggs in the survey area is probably the reflection of a lower number of spawning adults along the reef.