Selective Food Preferences of Walleyes of the 1959 Year Class in Lake Erie

Abstract

Stomachs were examined from 1,473 walleyes (Stizostedion vitreum vitreum) of the 1959 year class collected in western Lake Erie from June 1959 to October 1960. In the same period, the relative abundance and lengths of potential forage species were determined from trawl catches. The walleyes fed almost entirely on fish. In 1959 the food was dominated first (in June and July) by yellow perch (Perca flavescens) and then, in sequence, by spottail shiners (Notropis hudsonius) and emerald shiners (Notropis atherinoides). In 1960, the walleyes fed mostly on yearling spottail shiners and emerald shiners in the spring and summer but young alewives (Alosa pseudoharengus) became the dominant food in the fall. The length of forage fish increased with the length of walleyes and walleyes of a given length usually ate forage fish within a restricted range of lengths. This size preference was shown by walleyes of the same length in the same and different months. The increase in length of forage fish with length of walleye was not proportionate. Walleyes 2.5 inches long ate forage fish 0.44 times their length whereas walleyes 15.5 inches long ate forage fish only 0.28 times their length. The diet of the walleyes changed according to species and lengths of forage fish available. Since young of several species hatched in different months and grew at different rates, abundance and suitability as forage sometimes changed rapidly.

SELECTIVE PREDATION FOR VERTEBRAL PHENOTYPE INGASTEROSTEUS ACULEATUS: REVERSAL IN THE DIRECTION OF SELECTION AT DIFFERENT LARVAL SIZES

“…A value of0.33 was chosen to produce a moderate probability of prey escape in encounters with predators, so that variation in prey performance could be expected to influence survival in all experiments. This value is near the average ratio reported for the diet of other percoid fishes at small predator lengths (0.4 to 0.5 for predators 60 to 100 mm in length; Parsons, 1971;Popova and Sytina, 1977).…”

“…However, the relatively shallow body of stickleback larvae, the lack of spine and lateral plate development in larvae of the sizes used here, mouth gape measurements of other sunfishes (Werner, 1974), and the occurrence of higher prey/ predator size ratios in the diet of wild predators than in these experiments (Parsons, 1971;Popova and Sytina, 1977) all suggest that predators were not strongly gape-limited in these experiments. Gape limitation was not a factor in selection for VR because selection for VR was unrelated to size selection (Fig.…”

“…Therefore, selection may be less strong in the wild where larvae are exposed to a wide size range of potential predators than in these laboratory experiments where predator size was restricted. However, gut analyses show that prey size typically increases with predator size among piscivorous fishes in the wild (Parsons, 1971;Popova and Sytina, 1977;Knight et al, 1984). This indicates that the size range of predators actually preying upon fish of a given size is a restricted portion of the size range present in the wild.…”

Influence of Larval Gizzard Shad (Dorosoma cepedianum) Density on Piscivory and Growth of Young-of-Year Saugeye (Stizostedion vitreum × S. canadense)

“…Saugeye, as well as walleye (Parsons 1971 ;Knight et al f 984; B.M. , can consume fish 33-50% of their total length.…”

“…Generally stocked into Ohio reservoirs at 30-50 mrn (Stahl et al 1992), saugeye (Lynch et al 1982; B.L. ) and walleye (Smith and Pycha 1960;Parsons 197 1;Mathias and Li 1982;Jackson et al 1992) are piscivorous at 239 and 234 mm, respectively, on fish 33-5096 of their total length (Parsons 1971 ; Knight et al 1984; B.M. .…”