Stable isotopes and gut contents indicate differential resource use by coexisting asp (Leuciscus aspius) and pikeperch (Sander lucioperca)

Abstract

Differential use of habitat and prey resources is an important mechanism that may allow coexistence of sympatric species. Unlike interactions between smaller cyprinid and percid fishes, the resource use by coexisting predatory asp (Leuciscus aspius) and pikeperch (Sander lucioperca) is relatively unknown. Here, gut content and stable isotope analyses were used to study ontogenetic dietary shifts and interspecific trophic niche overlap between asp and pikeperch coexisting in two reservoirs. The hypothesis that both species show an ontogenetic dietary shift from small invertebrates to large fish prey, but at the same time use different prey resources to reduce potential competitive interactions, was validated. The isotopic niches of the two predators showed no, or only a moderate, degree of overlap (0%-65%). The ontogenetic changes in the degree of interspecific isotopic niche overlap were different in the two reservoirs, suggesting that trophic segregation can be dynamic and variable among systems. Gut contents revealed that small (<100 mm standard length) asp consumed mostly terrestrial invertebrates and emerged aquatic insects, whereas small pikeperch foraged on zooplankton, larval and pupal stages of aquatic insects and fish. Larger individuals (>100 mm) of both species were predominantly piscivorous, with asp consuming more cyprinid prey and pikeperch more percid prey.Coexisting asp and pikeperch populations are able to utilise different prey resources, thereby reducing potential negative competitive interactions. K E Y W O R D Sdietary ontogeny, foraging strategy, interspecific competition, piscivory, stable isotopes

The diet of predatory fish in drinking water reservoirs – how can they contribute to biomanipulation efforts?

“…Asp undergo considerable ontogenic shifts in diet through their lifetime, with four trophic guilds represented by i) zooplanktivory in earliest life stages, ii) an ephemeral period (May-June) of extended feeding on surface arthropods at 16-40 mm SL, and iii) facultative and iv) obligate piscivory at 121-500 mm SL (Specziár & Reszu 2009). This partitioning corresponds with that of Vašek et al (2018), who observed mostly terrestrial invertebrates and emerged aquatic insects being consumed by juvenile asp of < 100 mm SL, while larger individuals of > 100 m were predominantly piscivorous. The discovery of zander as prey in asp diet, albeit a single occurrence, may also point to possible predation on other piscivorous fish species (Vašek et al 2018).…”

“…This partitioning corresponds with that of Vašek et al (2018), who observed mostly terrestrial invertebrates and emerged aquatic insects being consumed by juvenile asp of < 100 mm SL, while larger individuals of > 100 m were predominantly piscivorous. The discovery of zander as prey in asp diet, albeit a single occurrence, may also point to possible predation on other piscivorous fish species (Vašek et al 2018). In this study, terrestrial insects occurred regularly in the diet of both juveniles (110-130 mm SL) and adult asp (max.…”

“…In Hungary (Lake Balaton, Specziár 2011), the rate of cannibalism in zander ranged between 0.1 and 88 % (mean 19 %, summary data for all size categories between 5-800 mm SL), while at other sites in the Czech Republic (e.g. Lipno Reservoir), values of up to 34 %m have been recorded (Vašek et al 2018). In Ukraine (Kaniv Reservoir), values ranged from 5.7 %FO (zander < 40 cm SL) to 14.8 %FO (40-54 cm SL), with small zander the third most common prey (both by %m and %FO) after roach and perch in the largest zander size groups (Didenko & Gurbyk 2016), as also found in our study (Tables 3, 4).…”

“…Overall, however, piscivory represented 80.7 %m of the diet, confirming its suitability for food web manipulation in drinking water reservoirs. Asp predation, therefore, has no, or no significant, effect on the populations of other predatory species, with coexisting asp and zander populations, for example, utilising different prey resources, thereby reducing potential negative competitive interactions (Vašek et al 2018). It is very difficult (rather impossible) to state any conclusion regarding optimal selection of appropriate species for biomanipulation purposes based just on food analyses.…”

Applying stable isotopes of carbon (δ13C) and nitrogen (δ15N) to examine the role of pikeperch (Sander lucioperca Linnaeus, 1758) in structuring the food web of Lake Eğirdir (Central Anatolia), Turkey

“…In addition, Kaymak et al (2018) used stable isotopes to examine the relationships between environmental variables at locations above and below the Almus Dam and the food web structure of local fish assemblages. Vašek et al (2018) compared the stable isotope and stomach contents of pikeperch from 2 different sources. The purpose of this study was to investigate trophic status and the role of S. lucioperca L., 1758 in structuring the food webs of Lake Eğirdir during 2 seasons (spring and autumn) using stable isotopes.…”