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Demographic changes following mechanical removal of exotic brown trout in an Intermountain West (USA), high-elevation stream

Ecology of Freshwater Fish

By:
, ,
DOI: 10.1111/eff.12143

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Abstract

Exotic species present a great threat to native fish conservation; however, eradicating exotics is expensive and often impractical. Mechanical removal can be ineffective for eradication, but nonetheless may increase management effectiveness by identifying portions of a watershed that are strong sources of exotics. We used mechanical removal to understand processes driving exotic brown trout (Salmo trutta) populations in the Logan River, Utah. Our goals were to: (i) evaluate the demographic response of brown trout to mechanical removal, (ii) identify sources of brown trout recruitment at a watershed scale and (iii) evaluate whether mechanical removal can reduce brown trout densities. We removed brown trout from 2 km of the Logan River (4174 fish), and 5.6 km of Right Hand Fork (RHF, 15,245 fish), a low-elevation tributary, using single-pass electrofishing. We compared fish abundance and size distributions prior to, and after 2 years of mechanical removal. In the Logan River, immigration to the removal reach and high natural variability in fish abundances limited the response to mechanical removal. In contrast, mechanical removal in RHF resulted in a strong recruitment pulse, shifting the size distribution towards smaller fish. These results suggest that, before removal, density-dependent mortality or emigration of juvenile fish stabilised adult populations and may have provided a source of juveniles to the main stem. Overall, in sites demonstrating strong density-dependent population regulation, or near sources of exotics, short-term mechanical removal has limited effects on brown trout populations but may help identify factors governing populations and inform large-scale management of exotic species.

Geospatial Extents

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Demographic changes following mechanical removal of exotic brown trout in an Intermountain West (USA), high-elevation stream
Series title:
Ecology of Freshwater Fish
DOI:
10.1111/eff.12143
Volume
24
Issue:
2
Year Published:
2015
Language:
English
Publisher:
Wiley
Contributing office(s):
Coop Res Unit Seattle
Description:
12 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Ecology of Freshwater Fish
First page:
252
Last page:
263
Country:
United States
State:
Utah
City:
Logan
Other Geospatial:
Logan River
Online Only (Y/N):
N
Additional Online Files(Y/N):
N