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Intraguild indirect effects through trophic cascades between stream-dwelling fishes
Osamu Katano1, Tomoyuki Nakamura, Shoichiro Yamamoto
1National Research Institute of Fisheries Science, Fisheries Research Agency, Komaki, Ueda, Nagano 386-0031, Japan. katano@fra.affrc.go.jp
The Journal of Animal Ecology
|August 15, 2006
Summary
Omnivorous fish like gudgeon, dace, and chub can boost ayu growth by reducing invertebrate competitors, leading to increased algal biomass via trophic cascades. This highlights indirect ecological effects in stream ecosystems.
Area of Science:
- Ecology
- Aquatic Ecology
- Fisheries Science
Background:
- Indirect ecological effects, particularly trophic cascades, play a crucial role in structuring aquatic communities.
- Omnivorous fish can influence lower trophic levels, impacting algal biomass and fish growth.
- Understanding these interactions is vital for effective stream ecosystem management.
Purpose of the Study:
- To investigate the strength and role of indirect effects mediated by omnivorous fish on algal biomass through trophic cascades.
- To assess the indirect effects of gudgeon, dace, and chub on the growth of ayu (Plecoglossus altivelis altivelis).
- To explore the predictability of these indirect effects based on fish feeding behaviors and food overlap.
Main Methods:
- Introduction of four fish species (ayu, gudgeon, dace, chub) with varying omnivory levels into experimental pools.
- Quantification of algal biomass and invertebrate populations in the presence and absence of different fish species.
- Measurement of ayu growth rates under different experimental conditions.
Main Results:
- The presence of gudgeon, dace, and chub significantly reduced algal-feeding invertebrates, leading to increased algal biomass via trophic cascades.
- Ayu growth rates were substantially higher (25.9–44.1 times) in pools containing gudgeon, dace, or chub compared to pools with ayu alone.
- Indirect effects on ayu growth were predictable by food overlap but also influenced by specific feeding behaviors and trait-mediated interactions.
Conclusions:
- Omnivorous fish exert significant indirect effects on stream ecosystems, influencing algal biomass and the growth of other fish species.
- Trophic cascades initiated by omnivorous fish can enhance the growth of species like ayu by alleviating competition for resources.
- Predicting the strength of these indirect effects requires considering not only food overlap but also species-specific feeding ecology and interactions.
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