Abstract

To understand food web dynamics, knowledge about factors influencing trophic interactions is fundamental. Using stomach content analysis, we investigated size-dependent predator-prey relations of two coastal predatory fish in the Baltic Sea: perch (Perca fluviatilis) and northern pike (Esox lucius). Perth undergo two ontogenetic diet shifts, from zooplankton to macroinvertebrates at ca. 50 mm; and then to fish at ca. 250 mm. For pike, all sizes (103-810 mm) fed almost exclusively on fish. The fish prey of perch and pike was predominantly three-spined stickleback in spring, and gobiids in late summer. The mean and maximum prey:predator size ratio was larger, while the minimum was smaller for pike compared with perch. Perch and pike fed on smaller-sized gobiids, three-spined and nine-spined stickleback compared within the environment. Our results on size-dependent diets of perch and pike is useful for quantitative analyses of food-web interactions and for ecosystem-based management.

Keywords

Eurasian perch (Perca fluviatilis); Northern pike (Esox lucius); food web dynamics; trophic interactions; stomach content analysis; size-dependent diets

Published in

Boreal Environment Research
2019, volume: 24, pages: 137-153

Authors' information