Premium
Demographic changes following mechanical removal of exotic brown trout in an I ntermountain W est ( USA ), high‐elevation stream
Author(s) -
Saunders W. Carl,
Budy Phaedra,
Thiede Gary P.
Publication year - 2015
Publication title -
ecology of freshwater fish
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 55
eISSN - 1600-0633
pISSN - 0906-6691
DOI - 10.1111/eff.12143
Subject(s) - brown trout , trout , electrofishing , stocking , salmo , biology , abundance (ecology) , population , ecology , fishery , fish <actinopterygii> , demography , sociology
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 ( S almo trutta ) populations in the L ogan R iver, U tah. 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 L ogan R iver (4174 fish), and 5.6 km of R ight H and F ork ( 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 L ogan R iver, 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.