Brown trout, Salmo trutta Linnaeus 1758, occurred worldwide, and is of significant conservation and socio-economic importance. Supplementary stocking of non-native hatchery fish has become increasingly important in the management of brown trout. This is also the case in Norwegian reservoirs, in order to compensate for reduced natural propagation. There is considerable interest in the behavior and ecological traits of supplementary stocked fish. This research aimed to test for possible strain differences in diel resource utilization among brown trout in a Norwegian reservoir. Native brown trout was compared with stocked native and non-native fish. The fish were caught with gillnets in the epibenthic and pelagic zones at night (20-04 h), early day (04-12 h) and late day (12-20 h) in summer and autumn. In the epibenthic zone, the largest catches of native/stocked native and stocked non-native fish were obtained during nocturnal and daytime hours, respectively. In the pelagic zone, native and stocked native fish were caught mainly during nocturnal hours. Very few stocked non-native fish were caught in the pelagic zone. Epibenthic fish of both strains fed mainly on surface insects throughout the 24-h period in summer. However, in autumn, Daphnia longispina and Bythotrephes longimanus became the dominant food items for both native and stocked native fish. Non-native stocked fish fed mainly on zoobenthos in autumn. In the pelagic zone in summer, native and stocked native fish were caught close to the surface, feeding mainly on surface insects during the night and zooplankton during the daylight hours in summer. In autumn, they stayed deeper at night and early day feeding largely on D. longispina. In late day they stayed closer to the surface, feeding mainly on surface insects. The habitat use and feeding strategy of brown trout in the study lake differed highly between native and stocked native vs. non-native stocked fish. We concluded that diel resource utilization in brown trout reflects an adaptation to local conditions. Such variations should be considered in any stocking programme of this species.
|Hesthagen T, Dervo BK., Diserud OH., Hegge O., Skurdal J. "Diel resource utilization of native, native stocked and non-native stocked brown trout Salmo trutta L. in a subalpine Norwegian reservoir" Journal of Zoology Studies 3.1 (2016): 1-12.|
|Hesthagen, T., Dervo, BK., Diserud, OH., Hegge, O., Skurdal, J. (2016). Diel resource utilization of native, native stocked and non-native stocked brown trout Salmo trutta L. in a subalpine Norwegian reservoir. Journal of Zoology Studies, 3(1), 1-12.|
|Hesthagen T, Dervo BK, Diserud OH, Hegge O, Skurdal J. Diel resource utilization of native, native stocked and non-native stocked brown trout Salmo trutta L. in a subalpine Norwegian reservoir. Journal of Zoology Studies. 2016; 3(1): 1-12.|