Pikeperch Sander lucioperca trapped between niches: foraging performance and prey selection in a piscivore on a planktivore diet

Abstract

The foraging behaviour of planktivorous pikeperch Sander lucioperca during their first growing season was analysed. Field data showed that S. lucioperca feed on extremely rare prey at the end of the summer, suggesting the presence of a bottleneck. In experiments, foraging ability of planktivorous S. lucioperca was determined when fish were feeding on different prey types (Daphnia magna or Chaoborus spp.) and sizes (D. magna of lengths 1 or 2Á5 mm) when they occurred alone. From these results, the minimum density requirement of each prey type was analysed. The energy gain for three different foraging strategies was estimated; a specialized diet based on either large D. magna or Chaoborus spp. or a generalist diet combining both prey types. Prey value estimates showed that Chaoborus spp. should be the preferred prey, assuming an energy maximizing principle. In prey choice experiments, S. lucioperca largely followed this principle, including D. magna in the diet only when the density of the Chaoborus spp. was below a threshold value. Splitting the foraging bout into different sequences, however, resulted in a somewhat different pattern. During an initial phase, S. lucioperca captured both prey as encountered and then switched to Chaoborus spp. if prey density was above the threshold level. The prey selection observed was mainly explained by sampling behaviour and incomplete information about environmental quality, whereas satiation only had marginal effects. It was concluded that the observed diet based on rare prey items was in accordance with an optimal foraging strategy and may generate positive growth in the absence of prey fish in suitable sizes.

Diet patterns and ontogenetic diet shift of pikeperch, Sander lucioperca (L.) fry in lakes Peipsi and Võrtsjärv (Estonia)

“…pikeperch can feed on prey fish up to 50% as large as they are. However, smelt with its slender and elongated body is more easily caught and pikeperch fries are capable to predate on smelt of more than 50% of its own length (van Densen, 1985;Persson & Brönmark, 2008). The shortage of the potential prey fish generally delays the food shift to piscivory (Frankiewicz et al, 1996;Mehner et al, 1996).…”

“…pikeperch has access to adequate food and can achieve faster growth in the first summer, they have a better chance of avoiding predators and surviving the winter (Werner & Gilliam, 1984;Frankiewicz et al, 1997;Specziar, 2005). Therefore, the size and structure of the pikeperch population is strongly dependent on the success at the juvenile stage (van Densen, 1985;Persson & Brönmark, 2008). Nevertheless, few studies have focused on the diet of juvenile pikeperch in large shallow lakes.…”

Prey selectivity by juvenile Atlantic cod Gadus morhua in three coastal habitat types

“…Predators may also display prey selectivity even if they are generalists (Turesson et al 2002, Persson & Brönmark 2008. Since the attack rates for our 2 prey types are different (Table 1), cod may encounter the 2 prey types at different rates when prey densities are similar, generating selectivity without involving active choice by the predator (Johansson et al 2004, Persson & Brönmark 2008. Prey-dependent attack rates (Table 1) would thus result in grass shrimp being encountered more frequently than brown shrimp, and the prediction of a higher inclusion of grass shrimp in the diet of cod at low prey densities, especially in the sand habitat (Fig.…”

Shifts in Prey Selection and Growth of Juvenile Pikeperch (<i>Sander lucioperca</i>) over Half a Century in a Changing Lake Võrtsjärv

“…Comparison of the diets of juvenile pikeperch in Lake Võrtsjärv and in other shallow eutrophic European lakes [2,6,[8][9][10] indicates that the diet of zooplanktivorous pikeperch in Lake Võrtsjärv was somewhat more similar to that in other lakes in 1950s than in the recent period. The type of food consumed by juvenile pikeperch is argued to depend mostly on the availability of zooplankton species [2].…”

“…In this respect, the diet and ontogenetic dietary shift of juvenile pikeperch, Sander lucioperca (L.), have been studied quite extensively in many north temperate waters [2][3][4][5][6][7][8][9] as the size and structure of pikeperch populations are strongly dependent on their success at the juvenile stage [5,10]. However, due to eutrophication and climate change complex modifications in the feeding modes of fish are expected to take place [11].…”