The onset of piscivory in a freshwater fish species: analysis of behavioural and physiological traits

Abstract

The onset of piscivory in fish, resulting in a shift from zooplankton or invertebrate to fish prey, was studied on pikeperch (Sander lucioperca) using behavioural (attack, capture and swimming activity), morphological (allometry) and digestive enzymatic (trypsin, α-amylase and pepsin) analyses between larvae displaying or not piscivorous behaviour at different ages (23, 30, 37, 44 and 52 days post-hatching). The shift from zooplanktonic food items (Artemia nauplii) to a piscivorous diet did not occur at the same time for all individuals within the same cohort. Predation tests, conducted under controlled conditions (20ºC; ad libitum feeding), showed that some larvae attacked fish prey as early as the age of three weeks (11.0 ± 1.3 mm TL), while others did not start until the age of six weeks (16.6 ± 1.9 mm TL). Piscivorous individuals were bigger, with larger heads, longer tails, higher acid protease and lower alkaline protease activities, than non-piscivorous conspecifics. In conclusion, high inter-individual variability in morphological and digestive system developments linked to predatory ability development could induce cannibalism in fish.

Pulsed supplies of small fish facilitate short-term intraguild predation in salmon stocked streams

“…This suggests that the insectivorous white-spotted charr in our study are not adapted to effectively digest sh prey. In addition, the active digestive enzymes of shes are different during insectivorous and piscivorous life stages (Colchen et al 2020), suggesting that sh may be unable to change their active enzymes in response to rapid shifts in diet. Thus, despite their high consumption of masu salmon fry, white-spotted charr may lack the ability to effectively digest them, meaning that they are unable to convert the energy contained in masu salmon fry into growth.…”

Does Size Matter? Small and Large Larvae of Pikeperch (Sander lucioperca) in a Comparative Gene Expression Analysis

“…In pikeperch, the first cannibalism was found to occur among individuals attaining 15 mm total length under rearing conditions in aquaculture [8]. In a study by Colchen and colleagues [6], piscivorous pikeperch larvae exhibited a more advanced digestive system, characterised by increased digestive enzyme activity, along with larger heads and tails compared to their non-piscivorous counterparts.…”

“…This influences the overall mortality rate in pikeperch aquaculture and consequently affects its economic success. Previously, differences between cannibalistic and non-cannibalistic pikeperch were considered to result from developmental differences [6,7]. In pikeperch, the first cannibalism was found to occur among individuals attaining 15 mm total length under rearing conditions in aquaculture [8].…”

“…For this purpose, we comparatively investigated the expression patterns of genes relevant for developmental processes in larval pikeperch [14][15][16]. Hereby, we tried to exclude the influence of piscivory/cannibalism on the expression levels by sampling individuals before the onset of cannibalism based on the age and size of first-time cannibalistic individuals provided by the literature [3,6,8]. By combining size comparisons and gene expression analyses, our approach can contribute to elucidating potential relationships in the genetic regulation of growth differences in aquaculture pikeperch.…”

Impact of exploration behavior, aptitude for pellet consumption, and the predation practice on the performance in consecutive live prey foraging tests in a piscivorous species

“…However, pikeperch is an obligate piscivore, shifting to piscivore earlier compared to other species, and cannibalism often occurs as a population regulatory factor (Feiner and Höök, 2015 ). Under laboratory conditions, the shift starts with the size of 11.0 mm, and, at the size of 19.9 mm, 90% of the stock is already piscivorous if the prey is available (Colchen et al 2020 ). In nature, obligate piscivority can be observed in 13.5 mm fish (Specziár, 2011 ), but fully develops in fish of 35–100 mm or longer (Ginter et al 2011 ; Mittelbach and Persson 1998 ; Specziár, 2011 ).…”