Robert F. Carline

Piscivory by Walleyes and Yellow Perch in Western Lake Erie

Abstract We examined stomach contents of 906 age-0 and older walleyes Stizostedion vitreum vitreum and 1,575 age-2 and older yellow perch Perca flavescens, collected from western Lake Erie in 1979–1981, to measure preferences for prey type and size and diet overlap among different size groups of these two percids. Seasonal diets closely followed changes in forage-fish availability. Walleyes ate age-1 shiners Notropis atherinoides and N. hudsonius in spring, but switched to age-0 clupeids Dorosoma cepedianum and Alosa pseudoharengus in summer and autumn. Diet selection was governed by abundance of appropriate-size prey and preferences for forage species. Yellow perch ate invertebrates in spring but clupeids and shiners thereafter; electivity values for prey were low compared with those of walleyes, indicating that yellow perch were the more opportunistic feeders. Diet overlap was greatest among walleye age groups (0, 1, and 2-and-older) and least between walleyes and yellow perch. We hypothesize that densi...

Predation by Pellet-Reared Tiger Muskellunge on Minnows and Bluegills in Experimental Systems

Abstract Studies in Wisconsin lakes have shown that stocked tiger muskellunge (F1 hybrids of female muskellunge, Esox masquinongy x male northern pike, E. lucius) reared on live food survive better than those reared entirely on dry pellet food. We evaluated the ability of pellet-reared hybrids to convert to a minnow (Notropis spp. and Pimephales promelas) or bluegill (Lepomis macrochirus) diet in laboratory aquaria and hatchery ponds. In aquaria, 86–310-mm (total length) tiger muskellunge selected cyprinids that were about 40% of their own length and bluegills that were about 30% of their length, sizes closely predicted by an optimal foraging construct (time from prey capture to complete prey ingestion ÷ prey dry weight). Using these prey sizes, we tested hybrids (130, 150, and 170 mm long) in conversion experiments in aquaria and ponds. During experiments, prey were maintained at a constant density and predators were sampled periodically to determine the proportion eating fish. Tiger muskellunge converte...

Estimation and Interpretation of Proportional Stock Density for Fish Populations in Ohio Impoundments

Abstract We used fish population and food consumption data from five Ohio impoundments plus results from computer simulations to (1) examine sources of sampling error in estimating Proportional Stock Density (PSD), an index of fish population structure, (2) evaluate the relative effects of growth, mortality, and recruitment on PSD, and (3) assess use of PSD to predict outcomes of predator-prey interactions when the largemouth bass (Micropterus salmoides) is the major piscivore in medium to large impoundments (>50 hectares) with complex fish communities. When largemouth bass were collected with electrofishing gear, estimates of PSD varied considerably. During the spring, PSD was positively related to water temperature. PSD was lowest during summer when large bass were not vulnerable to electrofishing gear and increased in autumn when water temperatures declined. The PSD of a largemouth bass population in one impoundment ranged from 11 to 36% over a 4-year period as growth, exploitation, natural mortality, ...

Habitat Selection by Smallmouth Bass in Response to Physical Characteristics of a Simulated Stream

Abstract Habitat selection by smallmouth bass Micropterus dolomieui in shallow pools of the Flat River, Michigan, during summer 1981 and 1982 was related to the distribution of substrate type, depth, and current velocities. When current velocity was increased through manipulation, smallmouth bass reduced time spent in a habitat, foraged less, and moved more. Manipulation of light intensity between sunlit and shaded habitats did not influence use of habitats by smallmouth bass. When smallmouth bass behavior and habitat choice were observed without habitat manipulation, the fish chose gravel- to boulder-sized substrate and they avoided sand and silt substrates. Areas deeper than 45 cm were preferred by Flat River smallmouth bass; however, preference for deep areas was directly related to fish length in 1982. Areas of reduced current velocity, generally less than 15 cm/s, also were preferred. Smallmouth bass spent much of their time in foraging-related activities; up to 40% of fish between 10 and 18 cm long ...

Largemouth Bass Predation on Stocked Tiger Muskellunge

Abstract To better understand why stocked esocids survive poorly, we estimated mortality rates of tiger muskellunge (F1 hybrid of female muskellunge Esox masquinongy x male northern pike E. lucius) that were placed into two Ohio reservoirs (mean fish total lengths, 171 and 179 mm; 62 fish per hectare). Because pond experiments showed that hybrids stocked at night experienced mortality rates as high as those released during the day, we stocked tiger muskellunge into lakes during the day. Mortality of stocked hybrids (estimated by catch per effort of electrofishing) exceeded 95% within 40 days in both lakes. Population estimates of largemouth bass Micropterus salmoides coupled with stomach-content data revealed that these predators accounted for 26% and 45% of the numbers stocked in the two lakes. In addition, some hybrids died from thermal stress. Improved survival of tiger muskellunge should result if they are stocked at lengths greater than 250 mm to reduce predation losses, and late in fall when thermal...

Habitat Preferences, Survival, Growth, Foods, and Harvests of Walleyes and Walleye × Sanger Hybrids

Abstract We compared habitat preferences, survival, growth, foods, and harvests of stocked walleyes Stizostedion vitreum and walleye ♀ × sauger S. canadense ♂ hybrids in Pleasant Hill Reservoir, Ohio. Both fishes were stocked at similar rates and sizes (about 40 mm mean total length) in late May or early June 1979–1982. Neither group showed consistently better survival. Growth was similar until age 2. Thereafter, hybrids grew faster than walleyes. Age-0 walleyes occurred mostly over fine substrates in early summer and coarse substrates by fall. Habitat selection by age-0 hybrids was similar to that of walleyes, except hybrids preferred finer substrates in fall. Older hybrids and walleyes moved offshore at temperatures above 22°C. Diets of both fishes were similar, but hybrids ate more littoral fishes, whereas walleyes ate more pelagic fishes. Age-1 and older hybrids and walleyes ate mostly invertebrates in spring. Age-0 gizzard shad Dorosoma cepedianum were the most important prey for all ages of both gro...

Predation by Tiger Muskellunge on Bluegill: Effects of Predator Experience, Vegetation, and Prey Density

Abstract Many pellet-reared tiger muskellunge (F1 hybrid of female muskellunge Esox masquinongy and male northern pike E. lucius) do not survive stocking in reservoirs dominated by bluegill Lepomis macrochirus prey. Poor survival may occur because few hybrids capture bluegills. In a previous study done in hatchery ponds, only 10% of naive hybrids (those never before exposed to live prey) captured bluegills during 15 days. In similar ponds, we tested the effects of predator experience (using hybrids previously exposed to bluegill prey), vegetative cover, and bluegill density on the number of hybrids capturing prey. Few experienced or naive hybrids captured bluegills at low prey density, regardless of the presence or absence of vegetation. When bluegill density was increased from 1 to 5 prey/m2 in ponds or to 40/m2 in aquaria, many hybrids captured bluegills. Our pond study suggests that most hybrids will not fare well when stocked in lakes where only bluegill forage is present. Received April 19, 1983 Acce...

Responses of Fish Populations to Mitigation Structures in Two Small Channelized Streams in Ohio

Abstract Responses of fish populations to mitigation structures (rock deflectors and artificial riffles) were compared in two small channelized streams in Ohio to determine potential recreational benefits of such structures. In Chippewa Creek, we compared fish populations 1 and 3 years after construction in sections with and without rock deflectors. In River Styx, previously altered around 1950, we compared fish fauna 1 year before and 1 year after channelization in sections with and without mitigation devices. Sections with rock deflectors in Chippewa Creek supported significantly more species and higher numbers and biomass of fish than did sections without structures. In River Styx, fish populations before construction and 1 year afterwards were similar; low flows prior to channelization and above-average flows afterwards probably had more influence on fish populations than the habitat changes. Stations with deflectors or artificial riffles tended to support greater densities of fish than stations witho...

Evaluation of Scale Shape for the Identification of Walleye Stocks from Western Lake Erie

Abstract We used the method of Jarvis et al. to characterize scale shapes of five stocks of walleye Stizostedion vitreum vitreum from western Lake Erie, to assess the effects of age, sex, and year of collection on scale shape, and to determine the level of accuracy for assignment of test individuals to their respective stocks based upon their scale shape. Neither sex, age, nor year of collection had significant effects on scale shape of walleyes from the Maumee River, Ohio. Using discriminant analysis we found some differences among scale shape from the five western Lake Erie stocks. The three Ohio stocks (Maumee and Sandusky rivers and Toussaint reef) were more similar in scale shape to each other than to the Lake St. Clair stocks (Clinton and Thames rivers), but classification rates of test individuals to their respective stocks were low. Differences in scale shape were more apparent when we compared an eastern-basin stock (Presque Isle, Pennsylvania) with western-basin groups, yet rates of successful c...

Experimental Assessment of Mortality and Hyperglycemia in Tiger Muskellunge Due to Stocking Stressors

Abstract Tiger muskellunge (the F1 hybrid of female muskellunge Esox masquinongy and male northern pike E. lucius) have survived poorly when stocked in reservoirs. To understand why, we quantified, in the laboratory, both mortality and plasma glucose responses to three common stocking stressors: Dipnet handling, confinement, and temperature increase. No young-of-year hybrids died within 48 h when the temperature was abruptly increased 10°C and only 5% died when the temperature was increased 12°C, but 98% died within 4 h when the temperature was increased 15°C. Thus, we concluded that thermal stress is an important determinant of poststocking mortality. Mortalities in response to three multiple-stressor treatments–(1) handling and temperature increase, (2) handling, confinement at a fish density of 83 g/L, and temperature increase, and (3) handling, confinement at 135 g/L, and temperature increase–did not differ from each other or from mortality associated with a temperature increase alone. Thus, handling ...