Piscivory and the development of bimodality in the size distribution of 0+ pikeperch (Stizostedion lucioperca L.)

Abstract

Durin an eight years period the onset and development of piscivory of O+ pikeperch was studied in the naturafienvironment of a shallow, eutrophic Dutch lake.In some ears the piscivory started as early as halfway June at a pikeperch size of circa 20 mm. The O+ ikeperci predated mainly on the smaller O+ smelt because these were the most slender preyfish avaifable. The O+ ikeperch is less and the O+ perch is much less available because of their larger circumference. Sm$O+ bream and roach became only available when their growth was retarded. The positive1 skewed size distribution of the O+ pikeperch halfway June is recursory for the development of girnodalitg in the size distribution later in the season. A seconcfmodus of larger, piscivorous, O+ pikeperch ecame relatively important in years when smelt was abundant. The surv~val rate of this category was appearantly higher than that of the smaller planktivorous individuals. ZusammenfassungNahrungswabl und bimodale Liingenverteilung in der 0-Gruppe vom Zander (Stizostedion lnciopercu L.)In einem flachen eutrophen, niederlindischen See wurde iiber 8 Jahre die Entwicklung der Zander des 1. Lebensjahres (Agr. 0+) zum Raubfisch untersucht.In mehreren Jahren begann die Umstellung von der E m a r u n g aus Planktonkrebsen auf Fischnahrung bereits Mitte Juni be1 einer Linge der Zander von etwa 20 mm. Die Nahrung dieser Jungfische bestand hauptsachlich aus den kleinen und schlanken Stinten der O+ Gruppe. Der Zander kann im ersten Lebensjahr andere Fische der 0-Grup e wie Artgenossen, Barsche, Brassen und Plotzen erst dann fressen, wenn diese im Wachstum zurdgeblieben sind.Die bimodale L&genverteilung in der 0-Gruppe der Zander bildet sich aus einer ab Mitte Juni auftretenden, ositiven Schiefe heraus. Besonders in Jahren mit massenhaften Vorkommen von Stinten den Kategorie war die Uberlebensrate deut ich hoher, als bei den kfeineren Zandern der Altersgruppe, die sich von Zooplanktern ernahrten.warder Gipfe P , der vonden Vorwiichsern qebildet wurde, sehr aus epragt. Innerhalb der fischfressen- ResumePiscivorie et diveloppement de bimodaliti dans la distribution de taille du sandre O+ (Stizostedion lucioperca L.) Pendant une periode de huit annees on a etudie le debut et le developpement de piscivorie du sandre O+ dans le milieu nature1 d'un lac hollandais peu profond et eutrophique. I1 y avaient des annies que la piscivorie du sandre commengait d6jh en mi-juin h une taille d'environ 20 mm. Le sandre O+ se nourissat surtout d'Cperlan O f plus petit, parce que celui-ci Ctait le Poisson de proie le plus disponible. Le sandre O+ est moins et la perche O+ est encore plus moins disponible h cause de leur plus grande U.S. Copyright Clearance Center Code Statement: 0175-8659/85/0103-O119 $02.5010 Z. angew. Ichthyol. 3 (1985) 119-131 0 1985 Verlag Paul Parey, Hamburg und Berlin ISSN a1 7~~~5 9 120 W . L. T. van Densen circonference. La petite brtme O+ et le petit gardon O+ devenaient seulement disponibles lorsque leur croissance ttait reiardCe. ui est en mi-juin positivement oblique, ap...

Effects of size-selective mortality on estimates of the growth rate of zander, Sander lucioperca (L.) from Lake Jeziorak

“…This phenomenon commonly occurs in the fish of the genus Sander and related genera. For example it was described by Fox (1989) in walleye, Stizostedion vitreus (Mitchill, 1818) cultured in experimental ponds and by van Densen (1985) in zander fry at a Dutch brackish-water Lake Issel. No data are available in the literature about the second year of life (1+) of these fish.…”

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].…”

“…However, due to eutrophication and climate change complex modifications in the feeding modes of fish are expected to take place [11]. Thus, there is a heightened need to research into longterm and developmental changes in diet, as pikeperch have a quite rigid ontogenetic feeding pattern [10] that is very sensitive to environmental changes, particularly to those influencing food web components. Nevertheless, there are only a few long-term data series on pikeperch fry diet and prey community that could be used as basis to study how eutrophication and/or climate change directly or indirectly might influence the diet, diet shift and growth of juvenile pikeperch.…”

“…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].…”

“…In the 19th century smelt (Osmerus eperlanus eperlanus m. spirinchus (Pallas)), which is considered to be the primary first prey fish for pikeperch [10,27], was rather common in Lake Võrtsjärv [28]. Before the mid20th century, as a result of heavy fishing pressure [29], smelt disappeared from the lake.…”