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Predatory Threat of Introduced Yellow Perch in a Salmonid‐Dominated Reservoir Food Web
Author(s) -
Hansen Adam G.,
Thompson Jedidiah S.,
Hargis Lauren N.,
Brauch Daniel,
Johnson Brett M.
Publication year - 2019
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1002/nafm.10257
Subject(s) - perch , brown trout , fishery , salmo , biology , predation , trout , oncorhynchus , pelagic zone , stocking , ecology , fish <actinopterygii>
Abstract Unauthorized or unanticipated introductions of sport fish can threaten native species and expose existing fisheries to unnecessary risk. Although introductions of apex predators draw more attention, introductions of coolwater mesopredators like Yellow Perch Perca flavescens could also be problematic yet are poorly studied. Here, we quantified the seasonal and size‐dependent diet and distribution of introduced Yellow Perch and evaluated their direct effects on age‐0 kokanee Oncorhynchus nerka in a 3,793‐ha mesotrophic reservoir during 2016, 15 years after the initial discovery of Yellow Perch. We compared these effects to those of Brown Trout Salmo trutta , which have been present in the reservoir since it was formed. Spatial overlap between kokanee and Yellow Perch occurred for less than 7 d during April and was confined to the inlet region as fry stocked upstream entered the reservoir. Predation from Brown Trout was 39‐fold greater than predation by Yellow Perch during this time. After fry funneled through the inlet, minimal spatial overlap was observed seasonally between Yellow Perch and age‐0 kokanee, particularly during summer, when a thermal refuge formed. Furthermore, age‐0 kokanee outgrew 58% of piscivorous‐sized Yellow Perch by June and outgrew 95% by October. Although age‐0 kokanee were more morphologically vulnerable to Brown Trout throughout the year, Brown Trout occupied nearshore areas away from pelagic kokanee. Yellow Perch exhibited a similar trophic role as Brown Trout by consuming mostly invertebrates (95.8% and 88.1%, respectively). The diet of each species contained over 25% Daphnia , but we saw no evidence that planktivory by Yellow Perch affected the abundance of Daphnia available to kokanee. Peak Daphnia densities in June 2016 (23.9–39.0 individuals/L) were the same as or higher than those recorded during 1993–2000, before Yellow Perch were discovered. Our study represents one of few in‐depth evaluations of introduced Yellow Perch in a montane reservoir. More empirical evaluations of the effects of introduced mesopredators are needed for refining risk assessments and guiding appropriate management actions.