Diet and growth of stocked and wild 0+ pikeperch, Stizostedion lucioperca (L.)

Abstract

Wild and stocked 0+ pikeperch, Stizostedion lucioperca (L.), were sampled with a purse seine from Lake Oulujärvi, situated at the northern edge of the distribution range of the species. The stocked fry started immediate feeding on 0+ smelt, Osmerus eperlanus (L.) after their introduction into the lake in early August at about 50 mm length, whereas the smaller wild pikeperch fry continued to feed on zooplankton. Individual wet weight of the stocked pikeperch was about six‐fold compared with the wild pikeperch throughout August. The length of the ingested smelt was as on average 50%, and maximum 66%, of the pikeperch length. Wild 0+ pikeperch were too small to forage on 0+ smelt. Predation by older conspecifics on 0+ pikeperch was observed.

Ecologically and evolutionarily sustainable fishing of the pikeperch Sander lucioperca: Lake Oulujärvi as an example

“…We assumed that naturally recruited and stocked fish do not differ in mortality, but stocked pikeperch are often larger than their wild-born counterparts in their first autumn. This may imply that stocked fish have a better potential to start feeding on smelt and survive over their first winter than naturally recruited fish (Sutela and Hyvärinen, 2002). In evolutionary sense, pikeperch fingerling production may also be less susceptible to aquaculture-induced domestication effects having negative impacts on the survival of stocked salmonids (Fleming and Einum, 1997;Tymchuk et al, 2006), since often wild-caught parents are let to spawn in seminatural environments and fingerlings are not usually fed with artificial food (Ruuhijärvi and Hyvärinen, 1996).…”

“…After a long absence of pikeperch and the following reintroduction program, natural reproduction has been observed in Lake Oulujärvi since 1998 (Sutela and Hyvärinen, 2002). From a population biological perspective, the Lake Oulujärvi pikeperch stock is still rapidly increasing and likely soon facing even stronger density-dependence arising from the availability of suitable prey.…”

“…VPA was run only for the naturally hatched fish. The stocked fish were excluded using the assumption that during the years 1985-1993 no natural reproduction occurred (Sutela and Hyvärinen, 2002;Taskila, 2011). During the period the recapture rate of the stocked fish was on average 2.76% (∼3%, weighted with the number of stocked fish, FGFRI statistics).…”

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

“…Sutela and Hyvärinen [36] point out that in the northern edge of pikeperch's distribution range juvenile pikeperch does not shift to piscivory even when smelt is present (Figure 5), as the summers are cool and pikeperch does not hatch before early June and prey fish are given a head start. Vice versa, in the southern part of its distribution area, pikeperch is able to predate on even YOY ruffe, perch, roach, bleak (Alburnus alburnus (L.)), pumpkinseed sunfish (Lepomis gibbosus (L.)) and monkey goby (Neogobius fluviatilis (Pallas)) in its first growing season [4,8,37] as there seems to be no mismatch between predator and its prey.…”

Genetic effects of supportive stockings on native pikeperch populations in boreal lakes - three cases, three different outcomes

“…Until the late 1950s, Lake Oulujärvi (area 928 km 2 , mean depth 7.6 m) pikeperch sustained a flourishing fishery, with catches amounting to 100–150 tons year −1 (Sutela and Hyvärinen 2002). Thereafter, catches began to decline and the bottom, less than 100 kg year −1 , was reached in the early 1980s.…”