Early Life History of Yellow Perch in Eastern South Dakota Lakes

Yellow perch Perea flavescens are a popular South Dakota sportfish; however, inconsistent recruitment creates highly variable and unpredictable perch fishery quality. Before fishery managers can begin to develop and assess strategies to stabilize yellow perch recruitment, a better understanding of their early life history is required. I selected two natural lakes with differing yellow perch population types and monitored brood stock, spawning habits, and larval and juvenile life history patterns during 1995 and 1996. Pelican Lake was selected as a representative yellow perch population exhibiting inconsistent recruitment and Pickerel Lake as a population with relatively consistent recruitment. Yellow perch tended to be larger at a given age and grew more quickly in Pelican Lake than in Pickerel Lake during both years. Pickerel Lake was found to have a high density yellow perch population that maintained slow growth and size structures dominated by small (i.e.,cm) fish. Natural yellow perch spawning habitats were assessed with both surface observations and SCUBA in both study lakes and human-constructed structures were monitored by boat in Lake Goldsmith, South Dakota. In 1995, yellow perch in Pickerel Lake began spawning at 7°C and preferred periphyton-free woody structure along shorelines in the main body of the lake as spawning substrate. Egg masses examined in 1995 (N=l8) from Pickerel Lake were developing normally. No egg masses were found in Pelican Lake. Deciduous tree structures were placed into Lake Goldsmith to mimic natural structure types found in Pickerel Lake, and conifer tree bundles were simultaneously introduced for comparison. No apparent selection between tree types as a spawning substrate could be detected. It appears that yellow perch spawning activity preferentially occurs in the main body of the lake and that water levels play a potentially important role by influencing the amount of available spawning habitat. Yellow perch larvae were sampled in both lakes during both years with an ichthyoplankton surface trawl. Larval density in Pickerel Lake was significantly lower in 1995 than in 1996. Peak larval density in Pelican Lake was not significantly different between years. Larvae tended to migrate to offshore areas in Pickerel Lake, but did not exhibit a consistent movement pattern in Pelican Lake. The first food of larvae in Pickerel Lake was Copepoda nauplii, with fish switching to adult Copepoda by 7 mm total length (TL), and then to Cladocera and large calanoid Copepoda by 14-mm TL. However, in 1995, Copepoda nauplii density was extremely low and larvae began feeding on adult Copepoda at a much smaller TL. High proportions of empty stomachs (\u3e40%) in 7- to 9-mm TL post-sac larvae collected in late May and early June from Pickerel Lake in 1995, indicated that rations may have been inadequate. The 1995 diets of Pelican Lake larvae were similar to those found in Pickerel Lake, where first food was adult Copepoda, presumably in place of low-density nauplii. The size range of adult Copepoda in Pelican Lake, however, was much wider than in Pickerel Lake and the proportion of empty stomachs was not as high. In 1996, Pelican Lake larvae fed on Copepoda nauplii until 7-mm TL, followed by a switch at 8-mm TL to adult Copepoda and increasing numbers of the cladoceran Diaphanosoma birgei by 14-mm TL. Substantial numbers of large Cladocera were not present in the Pelican Lake environment and therefore additional dietary transitions did not occur until the fish reached advanced juvenile stages. Juvenile yellow perch were sampled by seining in mid-July and mid-August. Low catch per unit effort (CPUE) of juvenile yellow perch in Pickerel Lake in 1995 supports my contention that a sizable portion of the age-0 cohort was lost during the larval stages. Seining CPUE of age-0 yellow perch in Pickerel Lake during July of 1996 was more than 30 times that in 1995. No substantial losses of the age-0 cohort could be detected in either year in Pelican Lake. Juvenile diets in Pickerel Lake primarily consisted of several species of Cladocera and some adult Copepoda until fish reached an approximate TL of 50 mm, when chironomids, corixids, and amphipods were more utilized. Pelican Lake yellow perch fed extensively on adult Copepoda and Diaphanosoma ~ throughout their juvenile stage with a small proportion of their diet consisting of Corixidae and Chironomidae after perch reached 50-mm TL. Juvenile yellow perch in Pickerel Lake appeared to select turbid areas with macrophytic cover when perch densities were low (1995), but inhabited shorelines at random when density was high (1996). Pelican Lake juveniles did not show a preference for a particular shoreline habitat, possibly due to the typically turbid waters, low predator abundance, and high density of prey species, which may have lessened the need for anti-predator behavior. In summary, I believe that a substantial mortality event occurred for larval yellow perch in Pickerel Lake during late May and early June of 1995. Larval yellow perch CPUE declined substantially and length frequency histograms indicated missing larvae in the 8-10 mm length group. Empty stomach percentages, combined with low zooplankton densities possibly caused by environmental conditions, may be related to the loss of these larvae. Juvenile CPUE values in Pickerel Lake were also much lower in mid- and late summer of 1995 and the number of age-I yellow perch captured in spring trap netting in 1996 was substantially lower than in 1995. Although speculative, the evidence suggests that yellow perch year-class strength was set in the larval stage during mid- to late June in these two study lakes during the two years of research