CROSS-ECOSYSTEM EFFECT of ALIEN FISH on INSECTIVORES living around HIGH MOUNTAIN LAKES
(2025) BION02 20242Degree Projects in Biology
- Abstract
- Growing research on ecosystem subsidies has emphasized the connection between aquatic and terrestrial ecosystems, with changes in one triggering responses in the other. In high mountain lakes, emerging aquatic insects are considered key aquatic subsidies and serve as an important nutrient resource for surrounding terrestrial ecosystem. The introduction of alien fish into these lakes, known to cause community shifts and declines in native aquatic communities such as aquatic macroinvertebrates, has raised concerns about the potential indirect effect on the surrounding terrestrial ecosystem. This study investigated whether the presence of introduced fish in high mountain lakes affects terrestrial insectivores, specifically predatory... (More)
- Growing research on ecosystem subsidies has emphasized the connection between aquatic and terrestrial ecosystems, with changes in one triggering responses in the other. In high mountain lakes, emerging aquatic insects are considered key aquatic subsidies and serve as an important nutrient resource for surrounding terrestrial ecosystem. The introduction of alien fish into these lakes, known to cause community shifts and declines in native aquatic communities such as aquatic macroinvertebrates, has raised concerns about the potential indirect effect on the surrounding terrestrial ecosystem. This study investigated whether the presence of introduced fish in high mountain lakes affects terrestrial insectivores, specifically predatory ground-dwelling invertebrates, through reduced emerging insect biomass flowing out of the lake. We sampled and compared ground-dwelling invertebrates and aquatic macroinvertebrate community across three lake categories: fishless lakes, lakes with established fish population, and lakes undergoing fish eradication. We hypothesized (1) a spatial pattern in predator abundance, with higher proportions near the shoreline due to increased food availability, and (2) lower predator proportions in areas around lakes with fish, due to reduced aquatic insect emergence and consequently reduced resources for predatory species. Aquatic emerging insect biomass was found to be significantly higher in fishless lakes, confirming the expected negative impact of fish on larval stages of emerging insects. Moreover, pitfall traps revealed a significantly higher proportion of ground-dwelling predatory invertebrates near the shoreline, compared to inland site, supporting the role of aquatic subsidies. However, no significant differences in predator proportions were found across the different lake categories. These findings underscore the importance of lake-derived subsidies for terrestrial insectivore communities and suggest that further research is needed to understand the ecological response of ground-dwelling predators to the presence of introduced alien fish. (Less)
- Popular Abstract
- From lake to land: Are introduced fish affecting animals on land?
Many high mountain lakes were originally fishless. However, in recent decades, fish have been introduced into these lakes for recreational fishing. This brought unexpected consequences for the ecosystem, affecting not only aquatic life but also animals on land.
The insects that inhabit lakes are often larval stages that will metamorphosize and eventually emerge as flying adults. On land they are a vital food source for many terrestrial animals living around the lakes. Fish heavily predate on insect larvae, consequently reducing the number of insects that make it out of the water. This could result in less food for insectivores, such as spiders, predatory beetles and... (More) - From lake to land: Are introduced fish affecting animals on land?
Many high mountain lakes were originally fishless. However, in recent decades, fish have been introduced into these lakes for recreational fishing. This brought unexpected consequences for the ecosystem, affecting not only aquatic life but also animals on land.
The insects that inhabit lakes are often larval stages that will metamorphosize and eventually emerge as flying adults. On land they are a vital food source for many terrestrial animals living around the lakes. Fish heavily predate on insect larvae, consequently reducing the number of insects that make it out of the water. This could result in less food for insectivores, such as spiders, predatory beetles and centipedes that live around these lakes.
As a part of the Life RESQUE ALPYR project, we studied 12 high mountain lakes in the Western Italian Alps. Four lakes were fishless, four lakes were undergoing fish removal, and four still had established fish populations. We placed traps near the lakes shore and farther away to capture ground-dwelling invertebrates, and we also sampled insect larvae to assess the prey availability, i.e. emerging insects.
What did we find?
Compared to lakes with fish, fishless lakes had much more emerging aquatic insects, confirming that fish reduce an important food source for animals on land. We also found more ground-dwelling predators near the lake shoreline, suggesting their habitat preference and importance of lake insects as a food source.
Interestingly, we didn’t observe any big differences in ground-dwelling predator numbers between lakes with and without fish. This suggests that while aquatic insects play a role in shaping nearby terrestrial communities, other factors may also influence predator abundance, and that more lakes are needed in future studies to get a clear picture of this relationship.
Although more research is needed to fully understand the impact of introduced fish on ground-dwelling predators, our study highlights the important connection between lake and surrounding land ecosystems. Changes in one environment often trigger to responses in the other and understanding these relationships is essential in designing effective conservation strategies for these unique high mountain areas.
Master’s Degree Project in Biology, 45 credits 2025
Department of Biology, Lund University
Advisor: Rocco Tiberti, Lucia Bello
Advisors Unit: Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria
Advisor at Lund university: Anders Persson, Department of Biology (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9212856
- author
- Lukšić, Gea
- supervisor
- organization
- course
- BION02 20242
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9212856
- date added to LUP
- 2025-09-19 11:57:54
- date last changed
- 2025-09-19 11:57:54
@misc{9212856,
abstract = {{Growing research on ecosystem subsidies has emphasized the connection between aquatic and terrestrial ecosystems, with changes in one triggering responses in the other. In high mountain lakes, emerging aquatic insects are considered key aquatic subsidies and serve as an important nutrient resource for surrounding terrestrial ecosystem. The introduction of alien fish into these lakes, known to cause community shifts and declines in native aquatic communities such as aquatic macroinvertebrates, has raised concerns about the potential indirect effect on the surrounding terrestrial ecosystem. This study investigated whether the presence of introduced fish in high mountain lakes affects terrestrial insectivores, specifically predatory ground-dwelling invertebrates, through reduced emerging insect biomass flowing out of the lake. We sampled and compared ground-dwelling invertebrates and aquatic macroinvertebrate community across three lake categories: fishless lakes, lakes with established fish population, and lakes undergoing fish eradication. We hypothesized (1) a spatial pattern in predator abundance, with higher proportions near the shoreline due to increased food availability, and (2) lower predator proportions in areas around lakes with fish, due to reduced aquatic insect emergence and consequently reduced resources for predatory species. Aquatic emerging insect biomass was found to be significantly higher in fishless lakes, confirming the expected negative impact of fish on larval stages of emerging insects. Moreover, pitfall traps revealed a significantly higher proportion of ground-dwelling predatory invertebrates near the shoreline, compared to inland site, supporting the role of aquatic subsidies. However, no significant differences in predator proportions were found across the different lake categories. These findings underscore the importance of lake-derived subsidies for terrestrial insectivore communities and suggest that further research is needed to understand the ecological response of ground-dwelling predators to the presence of introduced alien fish.}},
author = {{Lukšić, Gea}},
language = {{eng}},
note = {{Student Paper}},
title = {{CROSS-ECOSYSTEM EFFECT of ALIEN FISH on INSECTIVORES living around HIGH MOUNTAIN LAKES}},
year = {{2025}},
}