Top‐down and bottom‐up influences on populations of a stream detritivore

摘要: SUMMARY 1. Knowledge of the influence predatory fish in detritus-based stream food webs is poor. We tested whether larval abundance New Zealand leaf-shredding caddisfly, Zelandopsyche ingens (family Oeconesidae), was affected by presence brown trout, Salmo trutta and their primary detrital resource (Nothofagus leaves). 2. The density Z. biomass leaves were determined seven fishless streams four trout Cass region, central South Island, on occasions spanning 5 years. 3. Physicochemical conditions similar streams, but ANCOVA indicated that numbers positively related to leaf caddisfly significantly greater than for any given leaf. cases larvae also heavier per unit length those streams. 4. Our results provide evidence both top-down bottom-up influences a detritusbased web. Although detritivores may benefit from habitat provides degree protection predators, effects predators detritivore population still important. Thus, availability determine maximum attainable size, whereas predation likely reduce level below that.