Lake morphometry and resource polymorphism determine niche segregation between cool- and cold-water-adapted fish

Area of Science:

• Ecology
• Climate Change Biology
• Fisheries Science

Background:

• Arctic and subarctic temperatures are rising due to climate change.
• This facilitates the expansion of warmer-water fish species into new regions.
• The impact of resource availability and species interactions on these expansions is not well understood.

Purpose of the Study:

• To evaluate ecological interactions between invading perch (Perca fluviatilis) and native European whitefish (Coregonus lavaretus).
• To determine how resource availability and fish community structure influence niche overlap and coexistence.
• To assess the role of lake depth in mediating these interactions.

Main Methods:

• Studied fish communities in 10 subarctic lakes with varying whitefish morphs and presence of perch.
• Analyzed stomach contents and used stable-isotope analysis to assess resource use.
• Quantified invertebrate prey availability to understand niche partitioning.

Main Results:

• Perch consistently occupied the littoral niche.
• Large sparsely rakered (LSR) whitefish used littoral and pelagic resources in monomorphic whitefish lakes.
• In sympatry with perch, LSR whitefish shifted to pelagic resources in deep lakes but overlapped niches in shallow lakes.
• Densely rakered (DR) whitefish, a zooplanktivore, excluded LSR whitefish from pelagic zones, increasing LSR-perch niche overlap in deep lakes.

Conclusions:

• Resource availability, particularly lake depth and fish community composition, governs ecological interactions between native and invading species.
• These factors lead to varied outcomes of species range expansions, even at similar latitudes.
• Lake morphometry and fish community structure are crucial for predicting species distribution shifts under climate change.