Activity and food choice of piscivorous perch (Perca fluviatilis) in a eutrophic shallow lake: a radio‐telemetry study

Abstract

SUMMARY 1. Radio transmitters were implanted in large perch (27–37 cm) in a shallow lake in Denmark. Between 6 and 13 perch were tracked every 3 h for 24‐h periods twice (summer) or once a month (winter) from August 1997 to July 1998. Activity levels were recorded as minimum distance moved per hour. 2. No significant differences in activity levels of individual fish were observed. 3. Highest activities were observed at daytime with peaks at dawn and dusk or midday. This diel pattern was most pronounced from October to April, whereas diel variations were less in the summer months, with no peaks occurring in midsummer. The general lack of activity at night supports the idea that perch is a visually oriented forager. 4. There was no significant relationship between daytime activity during the year and temperature or day length, but nighttime activity was correlated with temperature. In contrast with previous findings, activity levels varied little seasonally, except for high activity levels that occurred concomitantly with high temperatures in August. Instead, we found a significant relationship between the total distances moved per day and temperature, indicating that perch moved at the same average speed in the wintertime, but did so for shorter periods than in summer because of shorter day lengths. 5. Diet of the tagged perch shifted from fish dominance between August and January to invertebrates from February to June. There was no correlation between the diet shift and activity levels, indicating that feeding on invertebrate requires similar activity levels as predation on fish. 6. The results of this telemetry study throughout a year suggest that perch are more active during the winter than previously inferred from gill‐net catches. This observation underscores the importance of perch as a predator of 0+ planktivorous fish in lakes and has potential implications for pelagic food web structure and lake management by biomanipulation.

Cormorant predation on PIT-tagged lake fish

“…It could be argued that the observed patterns are overestimated due to adverse effects of tagging making the tagged fish more prone to predation. However, studies have demonstrated that perch tagged with relatively larger tags than used in this study performed well (Baras et al, 2000;Jacobsen et al, 2002) and for most tagged fish, the tag/bodymass ratio was well below recommended threshold . In contrast we would argue that our results are in fact underestimating the real magnitude of the predation.…”

The diet of reservoir perch before, during and after establishment of non-native tubenose goby

“…While there have been numerous studies on fish predation by perch (e.g. Horppila et al, 2000;Specziár and Rezsu, 2009;Didenko and Gurbyk, 2016), with observations including cannibalism on perch fry (Lohnisky, 1960;Craig, 2000) and/or predation upon YOY planktivorous cyprinids (Jacobsen et al, 2002;, very few have recorded perch foraging on benthic and/ or shelter dwelling fish species such as gobies (see Almquist et al, 2010;Taraborelli et al, 2010). Further, while the consumption of gobiids by predatory fishes in general has been widely studied in North American waters (e.g.…”

Extremely shallow spawning of perch (Perca fluviatilisL.) : the roles of sheltered bays, dense semi-terrestrial vegetation and low visibility in deeper water

“…Why perch inŘímov Reservoir restricted their spawning to shallow depths and why records of egg strands from water >3 m deep are so sporadic? Perch is a visually orientating fish (Ali et al, 1977;Jacobsen et al, 2002) and, as shown by Hergenrader (1969), perch spawning also takes place during daylight hours (most probably, visual communication plays an important role in perch spawning/courtship rituals). Visibility in the water column is therefore essential for spawning perch.…”

“…Perch is a visually orienting fish primarily active in daylight (Ali et al, 1977;Jacobsen et al, 2002). Also perch spawning takes place during daylight hours (Hergenrader, 1969).…”