Community structure affects trophic ontogeny in a predatory fish

Area of Science:

• Ecology
• Evolutionary Biology
• Fisheries Science

Background:

• Ontogenetic niche shifts are crucial for predator development but their drivers, particularly community structure, are understudied.
• Top predators like brown trout (Salmo trutta) experience significant dietary changes throughout their lives.

Purpose of the Study:

• To investigate how lake fish community structure affects the ontogenetic niche shifts of brown trout.
• To determine if prey availability and competition modulate trophic position and individual dietary specialization in brown trout.

Main Methods:

• Stable isotope and stomach content analyses were used to assess brown trout diets.
• Logistic regression and generalized additive mixed models analyzed relationships between body length, trophic position, and community composition across nine subarctic lakes.

Main Results:

• The presence of a small prey fish species, specifically three-spined sticklebacks (Gasterosteus aculeatus), was the primary factor influencing the size of ontogenetic niche shifts.
• Brown trout exhibited stronger positive relationships between body length, trophic position, and individual dietary specialization in three-species communities compared to simpler systems.

Conclusions:

• Lake fish community structure significantly modulates the ontogenetic diet trajectories and individual niche specialization of top predators like brown trout.
• Prey fish availability, rather than competitor-prey species, is a key determinant of ontogenetic niche shifts in brown trout.