Predation in Freshwater Rivers: Brown Trout vs. Stonefly Nymphs

Predation in Freshwater Rivers: Brown Trout vs. Stonefly Nymphs

A classic predator-prey interaction in freshwater rivers is between the brown trout (Salmo trutta) and the stonefly nymph (order Plecoptera).

• Brown Trout: Carnivorous fish; visual predator; patrols riffles and pools.
• Stonefly Nymphs: Benthic insects; cling to rocks; high protein; emerge to adulthood by crawling onto shore or vegetation.

Interaction: Trout actively hunt nymphs, especially during emergence when nymphs are exposed. This predation regulates nymph populations, influences their behavior (drift timing, microhabitat use), and transfers energy up the food web. It is a key driver of stream community structure and trout growth.