Yellow perch, Perca flavescens (Mitchill), were collected for food habit determination from a transect in Indiana waters of Lake Michigan near Michigan City, Indiana between June and October in 1971 and June and September in 1972.The most important food items utilized on a mean annual basis were: unidentifiable organic material (UOM), alewife eggs, Pontoporeia affinis, fish (primarily alewife), insects (primarily chironomid larvae and pupae), and Eurycercus lamellatus. E. lamellatus, alewife eggs and UOM dominated 1971 stomach contents with P. affinis more important than E. lamellatus in 1972.Monthly stomach contents revealed heavy consumption of alewife eggs when available during the alewife spawning period, but these were replaced by P. affinis and fish (alewife) especially after July in both years.Differences between sexes of yellow perch captured by day and by night were minor and inconsistent.Differences between selected size groups (100-175, 176-225, 226-275 mm) manifested themselves in greater use of larger food items such as P. affinis and fish with larger length groups and as the summer progressed. The mean volumes of alewife eggs consumed, the most important food of yellow perch in this study, decreased significantly within each month both years as length of the yellow perch increased. In the large length groups, greater use of larger food items was made, but only fishes as a food item showed a signigicant difference between the two larger length groups.

Yellow perch, Perca flavescens, were collected by night trawling and gill netting at 5 m in a study area near Kintzele Ditch in Indiana waters of Lake Michigan during the months of June through September, 1975. Additional collections made by the Indiana Department of Natural Resources and the U.S. Fish and Wildlife Service using gill nets were included in some aspects of the study.Population characteristics were analyzed and compared to other studies. The rate of growth was significantly greater than in past Great Lakes' populations. The calculated length-weight relationships and growth rates were comparable to those reported by recent studies for southern Lake Michigan. Growth differed between males and females of the same age, and different ages were often represented in the same length interval. Nearly all male yellow perch were mature by age I and 130 mm. About half of the age II females and most at the 200 mm length interval were mature. Sex ratios were variable.Higher catch-per-unit-effort (cpe) was related to warmer water temperatures to the thermocline level. When water temperatures were mixed resulting in low inshore temperatures, cpe values were lower.There existed a great deal of sample variability within and between gear types as a result of seasonal population availability, gear characteristics, and non-random distribution of the population.Trawling, although more efficient than gill netting at sampling total numbers and widest range of lengths, was selective for smaller fish, and gill netting was selective for larger fish. Depth (from 5 m to 18.3 m) and particular gill net methods employed had little effect upon the sizes and length-percent frequency distribution sampled.Great differences between percentage age compositions compiled from trawl and gill net catches reflected the size selectivity of the gears. These results raised questions concerning the validity of management techniques involving percentage age composition and cpe index values to determine relative year class strength.The age groups I and II were represented by the proportion 8:2 (1:11) in the trawl catch which adequately sampled the sizes including the age I and II fish. Further study would be needed to determine the validity and usefulness to management considerations of this method of relative year class strength determinations. Recommendations for additional study were made.

The potential near-shore forage fish populations were investigated by bottom trawling during the months of June through August of 1984-86 in Lake Michigan, near Michigan City, Indiana. Data were collected on the six moat common species including: yellow perch (Perca flavescens); alewife (Aloes pseudoharenqus); rainbow smelt(Osmerus mordax); bloater (Coreaonus,hovi); spottail shiner (Notroois hudsonius); and trout-perch (Perconsis omiscomavcus). Results of the 1984-86 sampling period were compared with data for 1973 in an attempt to document changes in population density, species composition, annual catch, seasonal abundance, and population structure.The total trawl catch for all species increased nearly seven-fold since 1973 even though sample methods and collection effort were unchanged. A dramatic increase in yellow perch abundance was primarily responsible for the elevated levels sampled for all species from 1984-86.The species composition of the catch shifted since 1973. In 1973, spottail shiners were the most abundant species (41%) and trout-perch and alewives were the next most abundant species comprising 20% and 17% of the catch, respectively. Yellow perch, which comprised only 12% of the catch in 1973, increased to 81% of the catch in 1986. Bloater also showed a great increase in relative importance since 1973 when they were rare in the catch. Other species, including alewife, were relatively minor components of the total catch each year from 1984-86. The trawl catch results revealed that alewife and trout-perch declined 71% and 87%, respectively, comparing 1973 with 1984-86. During the same period, yellow perch increased 72-fold and bloater over 3000-fold. By comparison, the spottail shiner population was stable with no long-term changes, but rainbow smelt populations fluctuated widely.Seasonal abundance of adult fish (age I or older) generally decreased from June to August for each fish species and year sampled with the exception of yellow perch which peaked in July of 1973, and in August of 1985-86. Young-of-the-year fish were generally captured in late July and August.Population structure changes were evaluated by examining pooled length-frequency data. Yellow perch length-frequency distributions indicated that strong year classes were produced every year from 1983 to 1986. The 1985 year class was well over twice as large as any of the other years sampled. Spottail shiner and rainbow smelt length-frequency distributions remained approximately stable since 1973, while alewife length-frequency distributions fluctuated annually. Capture of bloaters was almost entirely limited to June, and consisted primarily of age I+ fish in 1984-86.These results reveal significant changes have occurred in the potential near-shore forage fish populations in Indiana waters of Lake Michigan since the early 1970's. Although several factors may be involved in the shifts noted, the major contributing factor is likely predator-prey interactions as a result of salmonid predator density.

Relative weight (Wr) of yellow perch (Perca flavescens) was evaluated for fish collected from the Indiana waters of Lake Michigan in June, July and August of 1976 and 1984-1991. Computation of Wr was completed for individual fish in 20 mm intervals over the size range from 100-219 mm using Wr = (W/Ws) 100 where W=weight of a fish in grams and Ws=standard weight for a fish of the same length. Length was highly correlated with weight in all years for males, females and sexes combined (r=0.97-0.99). Distributions of predicted weights for fish at 130 mm and 250 mm were at or near modes of the populations used to construct the Ws equation for yellow perch. Relative weights consistently decreased with increasing size in all years for males, females and sexes combined. Using 1976 length-weight data when the yellow perch population was sparse and fast growing as a standard (100%) for comparison, relative condition factors (Q) increased with increasing size in some years and decreased with increasing size in others for males females and sexes combined and it did not appear to be length dependent. When comparing Wr at 100 mm and 200 mm by sex and month, f hales had higher Wr than males at 100 mm in seven of nine years in June, six of nine years in July and only four of nine years in August. Female fish also had higher Wr than males at 200 mm in eight of nine years in June and July and six of nine years in August. There appeared to be no consistent pattern or trend of Wr increasing or decreasing by month for males, females or sexes combined. When Kn was evaluated for 100 mm and 200 mm fish by sex and year, male fish had higher Kn than females at 100 mm in all eight years. Male and female fish at 200 mm were more similar; male fish had higher Kn in three years, lower Kn in three years and equal Kn in two years. No relationships were found at 200 mm comparing Wr or Kn and CPE (quality/ h) for males (r=0.43; r=0.42), females (r=0.12; r=0.13) or sexes combined (r=0.28; r=0.22). Simple linear correlations of proportional stock density (PSD) with Wr and Kn revealed relative weights increased with PSD for 100 mm (r=0.51) and 200 mm (r=0.72) fish. Relative condition factors also increased with PSD for 100 mm fish, however the relationship was weak (r=0.30) but a strong correlation was found between Kn and PSD (r=0.81) for 200 mm fish. Based on these results, it appears that either Kn or Wr may be used inassessing the condition of yellow perch from the Indiana waters of Lake Michigan. / Department of Biology

Daily and seasonal movements of adult alewives, Alosa pseudoharengus, were studied at depths of 5 to 18 m in Indiana waters of Lake Michigan near Michigan City. Collections were made June to October, 1971, with gill nets and a bottom trawl and June to September, 1972, with gill nets.There was no significant difference (P > 0.05) between trawl and gill net catch rates in 1971 regardless of time of day. Significantly more fish were caught during early summer than late summer. Noon gill net catches did not differ significantly between stations. At 10 m, midnight gill net catches were larger than noon catches and bottom gill net catches were greater than surface catches.In 1972, June and July gill net catches were greater than August and September catches. Spawning was essentially completed by August, and inshore populations of spawning adults returned to deeper offshore areas.Midnight catches were greater than noon catches at all depths. During the day, alewives were farther offshore than the 15 m station, but at night they moved inshore. Crowding of alewives inshore at night resulted in significantly larger catches at the 5 m than at the 15 m station.Food habit studies in 1971 and 1972 revealed zooplankton comprised the major portion of the alewife diet. The copepod Cyclops bicuspidatus was the main zooplankter consumed. Bosmina longirostris and Eurycercus lamellatus were major cladoceran food items. Major non-zooplankton food items were Cryptochironomous, Chironomous, and larval alewives.Zooplankton and cladoceran percent volume in stomachs increased to maxima in July of each year followed by a general decline. Copepods were the dominant food in June. Chironomid larvae were a major component of the diet in May, 1972, and August of both years. The largest percent volume of alewife larvae in stomachs occurred in September.A comparison of daily movements and food habits by percent composition of food items in alewives collected July, 1971, revealed the dominant zooplankton species in alewife stomachs were Bosmina longirostris, Chydorus sphaericus, Alona affinis, Eurycercus lamellatus, Polyphemus pediculus, Cyclops,bicuspidatus, and Limnocalanus macrurus. B. longirostris and P. pediculus, which accumulate at the surface at night, were consumed by alewives in greatest quantity at midnight and sunset when the alewife is near the surface. The benthic species C. sphaericus, A. affinis, and E. lamellatus were consumed in greatest quantity at sunrise when the alewife is near the bottom.Ball State UniversityMuncie, IN 47306

Fish were collected at 1 and 5 m stations along three transects in Lake Michigan near Michigan City, Indiana. The five major species captured by trawling and/or seining between June and October, 1973 included: yellow perch, Perca flavescens; rainbow smelt, Osmerus mordax; alewife, Alosa pseudoharengus; spottail shiner, Notropis hudsonius; and trout-perch, Percopsis omiscomaycus.The alewife and spottail shiner were major species collected by seining, comprising 94.5% and 4.9% of the catch, respectively. The majority of individuals captured were young-of-the-year (yoy), especially alewives taken predominantly during the daytime.The bottom trawl captured a greater number of species than the seine. Catch-per-unit-effort (cpe) of most species was greatest in night trawling.The yellow perch comprised 16% of the total trawl catch. Spawning adults predominated in June and July with a deep water migration of this species beginning in August. The yoy first appeared in the catch in August.Rainbow smelt represented 24% of the total trawl catch. Adults were present in June catches and yoy were first captured in July. Off-shore movement was underway by October.Alewives comprised 13% of the total trawl catch. Spawning adults were taken in greatest numbers during June and July with a slight off-shore movement beginning in August. Young fish were first captured in the trawl in August.The most abundant species captured with the trawl was the spottail shiner comprising 27% of the total catch. Larger fish were well represented in the catch from June through August with a strong off-shore movement in October. Young fish were first captured in August.Trout-perch represented 16% of the total trawl catch. Catches were restricted to adults and no yoy were captured except in September at one sample site. Off-shore migration of trout-perch had begun by October.There were significant similarities in cpe and size distribution of fish captured at Dunes and Kintzele Ditch transects. In general, catches at the Michigan City transect were lower and size distribution was less consistent compared to the other transect catches.Ball State UniversityMuncie, IN 47306

Age, growth, and abundance data were collected on yellow perch, Perca fla vescen, in Indiana waters of Lake Michigan in 1987 and 1988. The data collected were compared to data on yellow perch in Indiana waters of Lake Michigan dating back to 1975.Changes in growth, mortality, and abundance between 1975 and 1988 were clearly illustrated by the data. Growth has decreased; back-calculation indicates that "quality" (> 200 mm) perch in 1975 were about age II, however, "quality" perch in 1988 were over age V. Annual mortality values produced from following a cohort or comparing age classes indicate that mortality has decreased since 1981, most sharply in 1987 and 1988. Changes in growth and mortality are likely resultant of large changes in abundance. Indices of abundance (biomass and catch-per-uniteffort) reveal that the yellow perch population has become much more dense in the late 1980's than the 1970's and early 1980's. The percentage of quality perch has decreased, however, the abundance of quality perch has increased and peaked in 1988. / Department of Biology

The population dynamics of alewives Alosa pseudoharengus and spottail shiners Notropis hudsonius were investigated in Indiana waters of Lake Michigan from 1984-1996. Insights to population dynamics of both species were found by applying age and growth information to length-frequency distributions of index trawl catches within and between years. Both alewife and spottail shiner populations showed general increasing trends over the period, reaching peak levels in 1996. Interaction potential was examined for alewives, spottail shiners, and the yellow perch Perca flavescens, another important nearshore species. Trends in relative catches of these species were correlated to provide insight to possible interactions. There appears to be negative relationships between alewife and yellow perch populations, as well as between yellow perch and spottail shiner populations. No relationships were found between alewife and spottail shiner populations. / Department of Biology

Food habit analyses of the young-of-the-year alewife in lake Michigan show zooplankton was the primary component of the diet in 1972 and 1973. Cyclops bicuspidatus contributed the largest portion of the diet in both years. The dominant cladocerans consumed in each year were Bosmina longirostris, Daphnia retrocurva, Chydorus sphaericus, Polyphemus pediculus, and Diaphanosoma brachyurum. Diaptomus spp. was the only other copepod of importance. Chironomid larvae and pupae provided minor volumes in both years.Monthly food habits revealed a general decline in cladoceran percent volume from August to October at the Michigan City and Dunes transects. Bosmina longircstris was the predominant cladoceran in August of both years at both stations. Chydorus sphaericus was a major food item in September, 1972 at the Michigan City transect, and August and September, 1972 at the Dunes transect. Daphnia retraocurva was a primary prey species in August of each year and in September, 1973 at Michigan City, and in August and September of both years at the Dunes transect.Polyphemus pediculus percent volume was greatest in August and September, 1973 at both stations. At the Michigan City transect, Cyclops bicuspidatus was the dominant food item, and was more important in September than August in both years. In contrast, C. bicuspidatus contributed a major portion of the alewife diet at the Dunes transect in each year, but was more important in August than September. Diaptomus spp. percent volume was greatest at the Michigan City transect in October of both years. Chironomids were major food items only in August, 1972 at the Dunes transect.Young-of-the-year alewife food habits in relation to fish length indicated that smaller YOY alewives selected smaller cladocerans and copepods, whereas larger alewives preferred larger cladocerans, copepods, and chironomids.Ball State UniversityMuncie, IN 47306

Food habits were examined for the spottail shiner, Notropis hudsonius, in Indiana waters of Lake Michigan from June to October, 1973. Insects were the primary volumetric component of the diet. Chironomus spp. larvae and chironomidae pupae were the most important insect food items consumed. The most important zooplankton organism consumed was the benthic cladoceran Eurycercus lamellatus. Alewife, Alosa pseudoharenqus, eggs were the only other significant food consumed.A monthly comparison of food items taken by spottails showed that Chironomus spp. larvae was an important food item in all months and the primary item in September and October. Chironomidae pupae were important from June through September with greatest percent volume consumed in July, The cladoceran, Eurycercus lamellatus was an important food from July through September, reaching its highest percent volume of the diet in August. Alewife eggs were the major food of spottails in June but were also important in July.Young-of-the-year spottails fed primarily on zooplankton for the first month of their existence, but their diet changed in succeeding months and was similar to that of the adults.Analysis of competition between spottail shiners, yellow perch and alewives revealed important overlap in food items in June, August, September and October. Competition in June was between spottail shiners and yellow perch (100-250 mm) for alewife eggs. In August, the spottail shiner and alewife (140-220 mm) competed for chironomids and the spottail shiner and yellow perch competed for Eurycercus lamellatus. September competition was between spottail shiner and yellow perch (26-100 mm) for chironomids and between yellow perch (26-100 mm) and alewives (140-220 mm) for alewife larvae. Finally, in October, major competition was between yellow perch (100-250 mm) and alewives (140- 220 mm) for alewife larvae.Ball State UniversityMuncie, IN 47306