The young-of-the-year (YOY) yellow perch assessment was conducted in the nearshore waters of Lake Michigan in the south east region of Wisconsin from August 19, 2002 to September 9, 2002. A standard protocol was used for sampling using 25’X4’ beach seine with ¼" delta mesh and sampled 14 sites distributed along the shoreline from Kenosha in the south to Sheboygan in the north. At each location two pulls of 100’ each were taken in the shallow water perpendicular to the shore. All the fish captured were identified to the species level and counted. At least 50 individuals of yellow perch at each location were measured and total lengths (mm) were recorded. We collected anal spine samples from larger individuals of yellow perch for age determination. Some YOY yellow perch were preserved in 70% ethanol.
In addition to beach seining, for the first time in 2002, we used a modified Swedish monofilament gillnet to increase sampling area in the nearshore water, which was not accessible to beach seining. The modified nets consisted of approximately 40 ft long and 5 ft deep, with four panels of 6.25mm, 8mm, 10mm and 12mm mesh sizes (bar length). The sampling design called for setting at least two gill nets in the same general area of seining which were allowed to fish for one night. As for as possible we attempted to set one net on a rocky substrate and the other on a sandy bottom at depths ranging from 8 ft to 20ft of water. The gill nets were set on the same day of seining in a particular site. Once the net was paid out from the boat, a diver went down to make sure that the net was set properly on the bottom without any snags. The GPS coordinates, weather condition, water temperature, depth and substrate type were recorded at each site. At least two sites were selected from each major port – Kenosha, Racine, Milwaukee, Port Washington and Sheboygan. The nets were lifted on the following morning. All the fish were identified to species level and tallied. Yellow perch, both young and adults were measured (total length in mm). Anal spine samples were taken from larger individuals for age determination.
Results and Discussion:
We conducted seining survey in fourteen sites. Conditions were reasonably good in most sites. Some sites were choked with dead and decaying algae making seining difficult. Water temperature ranged from 510 F to 770 F in different sites. We completed two rounds of seining by revisiting the same site twice during a period of three weeks. A total of 21 species were captured in this survey. Young of the year alewife dominated the catch at all the sites followed by spottail shiner and longnose dace. The majority of the alewife ranged from 33 to 49mm in total length in mid August. A total of 67 YOY yellow perch were captured in the entire survey with an effort of 5350 ft. of seine haul. The catch per 100 ft. of seine haul turned out to be 1.28 YOY yellow perch in this year.
We caught 36 YOY yellow perch in Meyers Park, Racine on August 20 which ranged from 50 to 67mm, with mean and modal total length 55.6mm and 55mm. This area is shallow and sheltered with some rooted aquatic vegetation. The water temperature was 550 F. Other species that occurred at this site were alewife, longnose dace, sand shiner, fathead minnow, spottail shiner and common carp. The next sites that produced YOY yellow perch were Klode Park and Doctors Park which lie north of Milwaukee (9/20/2002). Both of these sites have sandy bottom with man-made rocky jetties. The seine net was pulled adjacent to the rocks. There was no rooted vegetation except for filamentous algae. The water temperature was 55 F. The other species recorded were alewife, longnose dace, spottail shiner and rainbow smelt. The YOY yellow perch ranged from 38 to 51mm with a mean total length of 44.8mm. These perch were approximately 10mm smaller than the one captured in Racine. We did not find any YOY perch in Port Washington and Sheboygan sites.
The second round of seining began on 9/03/2002 starting from Kenosha. We captured 2 YOY yellow perch in Eichelmann Park, Kenosha and 25 YOY yellow perch in Meyers Park, Racine. Both of these sites are shallow, mostly sandy and protected by the break walls. At this time the mean and modal total length of YOY perch had reached 61.7 mm and 61 mm respectively, which is about 6 mm greater than the perch found on August 20th at the same site. Although the weather conditions were congenial for seining, we did not get any more YOY yellow perch in the second round of seining.
Based on the index site sampling data it appears that the natural reproduction of yellow perch in this part of the lake is still a very poor. In recent years, only 1998 produced a decent year-class which was evident in the YOY index site survey (Figure 1). It is clear that the adult yellow perch need continued protection to facilitate recovery of the population.
In 2002, we added micromesh monofilament gillnet to sample deeper nearshore water, both sandy and rocky habitat. We set 18 gillnet sets in 11 locations for a total of 720 ft. of effort and captured 52 YOY yellow perch. The catch per 100 ft of effort works out to be 7.2 YOY yellow perch. YOY yellow perch were captured only in one site – Meyers Park, Racine. The majority of the YOY fish ranging from 56mm to 64mm were captured in the mesh size 6.25mm (bar length). The larger individuals ranging from 119mm to 146mm were captured in mesh size 12mm at this site. This size-class mainly consisted of age 1+ yellow perch that are 2001 year-class. The other sites which had yearling and older yellow perch included the sites inside Milwaukee Harbor, off Linnwood water filtration unit, and off Doctors Park. Spottail shiner was the dominant species in the gillnet catch followed by alewife, longnose dace and yellow perch. The other species that occurred in smaller number included blue gill, bluntnose minnow, darter, goby, mottled sculpin, rock bass, sand shiner, smallmouth bass, trout perch, chinook salmon and lake trout.