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Query: "author" (Straile Dietmar) .

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1.
Small but voracious : invasive generalist consumes more zooplankton in winter than native planktivore
Žiga Ogorelec, Alexander Brinker, Dietmar Straile, 2022, original scientific article

Abstract: In recent years, Lake Constance has experienced an invasion and domination of three-spined stickleback (Gasterosteus aculeatus) in the pelagic zone, which has coincided with a decline in the native whitefish (Coregonus wartmanni) population. Similar massive invasions of sticklebacks into pelagic zones have been recognized also in marine areas or small lakes worldwide. However, their diet overlaps with native species is rarely evaluated, especially in the winter season, which often presents a bottleneck for fish survival. In this study, we compared the diet of pelagic sticklebacks with the diet of the substantially larger native whitefish in different seasons, to evaluate the threat of the recent stickleback invasion on whitefish populations. By monthly sampling of zooplankton and both fish species diets, we could demonstrate that sticklebacks select similar prey throughout most of the year and consume more prey than whitefish during the winter. With relations between prey availability and prey selection, interspecific and intraspecific seasonal diet variability and indices like a prey-specific index of relative importance, we discuss the importance of zooplankton species traits and abundance for whitefish and stickleback predation. This study shows that sticklebacks, despite their small size, represent a serious potential diet competitor to native planktivorous fish. Sticklebacks quickly adapt to new environments, and thus we advocate precautions regarding their introduction into similar lakes as Lake Constance, as this could cause irreversible ecological changes.
Keywords: Bythotrephes longimanus, Lake Constance, overwintering strategy, pelagic whitefish diet, planktivory, predator size, seasonal prey selection, stickleback invasion
Published in DiRROS: 18.07.2024; Views: 142; Downloads: 112
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2.
Can young-of-the-year invasive fish keep up with young-of-the-year native fish? A comparison of feeding rates between invasive sticklebacks and whitefish : a comparison of feeding rates between invasive sticklebacks and whitefish
Žiga Ogorelec, Lars G. Rudstam, Dietmar Straile, 2022, original scientific article

Abstract: Invasion of non-native species might alter food web structure and the strength of top-down control within lake ecosystems. As top-down control exerted by fish populations is often dominated by young of the year fish, the impact of new fish species might depend on the feeding rates of the juvenile fish. Here we provide comparative analyses of feeding rates of juvenile whitefish (Coregonus wartmanni) – a native and specialised planktivore and an invasive generalist (sticklebacks, Gasterosteus aculeatus). We studied feedings rates of whitefish and sticklebacks in aquaria experiments using 2 cm to 8 cm fish feeding on seven zooplankton species common to Lake Constance. As whitefish hatch several months earlier than sticklebacks, 0+ whitefish are larger than 0+ sticklebacks throughout the year and hence are predicted to have higher feeding rates on especially large zooplankton species. We show that sticklebacks as small as 2 cm were able to feed on the largest zooplankton species of Lake Constance. Further, stickleback feeding rates were similar to both the same size 0+ whitefish and the larger 0+ whitefish co-occurring with smaller 0+ sticklebacks. Hence, 0+ sticklebacks will compete with 0+ whitefish for the same zooplankton species, therefore the invasion of sticklebacks is unlikely to change the relative feeding pressure by individual 0+ fish on zooplankton species.
Published in DiRROS: 16.07.2024; Views: 109; Downloads: 69
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