The yellow perch population in Lake Michigan continues to be a major concern. Our winter 2005 assessment centers around examining the age distribution and year class strength of the yellow perch population with emphasis on 3 year-olds. On a very encouraging note, the 2002 year class (now 3 year-olds), were fairly well represented, although not as strongly as the 1998 year class (Table 1). The overall sex ratio of male to female was 64:36, which was just the reverse in 2000 and 2001 as a result of strong 1998 year class entering the fishery. Of the 245 perch aged in the 2005 assessment, 64% belonged to 1998 year class, 27% belonged to 2002 year class and 4% belonged to 2001 year class.
The percent composition in the 2004 sport harvest perch comprised 67%, and 2001 and 2002 year classes represented 13% each. Where as the percent composition of 2005 sport caught perch was somewhat different in that the 1998 year-class contributed only 37%, and 2001 and 2002 year classes contributed 20% and 40%, respectively (Figure 1).
Good numbers of mature adults (comprised mostly of fish from the1998 year class) congregated on the spawning grounds during our spawning assessment in May-June 2005. We also documented the 2001 and 2002 year-classes, though in smaller numbers, on the spawning grounds. A sub sample of 110 yellow perch caught during the spawning season was aged using anal spines. 69% of the aged perch belonged to the 1998 year class, 16% belonged to the 2001 year class and 11% belonged to the 2002 year class. The WDNR dive team made several dives during this period and recorded one of the greatest egg mass abundances in recent years (Table 2).
The young-of-the-year yellow perch assessment was conducted in the late summer using a 25-foot bag net with ¼" delta mesh. We sampled at 14 sites from Kenosha to Sheboygan. At each site, two 100-ft pulls were taken twice in the season for a total of 4,975 ft of effort. We captured 1,934 YOY yellow perch, i.e. 39 YOY yellow perch per 100ft of seine haul. This was the greatest catch per effort that we have recorded since the assessment began in 1989 (Figure 2). The majority of fish were captured in the Milwaukee and Racine areas. In addition, we set 100 ft gillnets (6mm and 10mm bar mesh) at two index sites (Wind Point and Fox Point) on 9/15/05 and captured 195 YOY yellow per 100 ft of gillnet, which was more than ten-fold the previous highest catch year. The total length of these YOY yellow perch varied from 50mm to 90mm.
The commercial fishery for yellow perch remains closed, and there is no evidence to support re-opening at this time. The sport bag remains at five fish. Sport fishing is closed from May 1 – June 15. This closure period is now a permanent rule, and will remain in effect for the foreseeable future. Protection of spawning stocks during the peak of the spawning season is critical to any population. Lake Michigan has undergone major changes in the last decade; most have not been conducive to yellow perch recruitment. The existence of a well-represented 2001 and 2002 year class is very encouraging.