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Failure of Submersed Macrophytes to Provide Cover for Rainbow Trout throughout Their First Winter in the Henrys Fork of the Snake River, Idaho
Author(s) -
Griffith J. S.,
Smith R. W.
Publication year - 1995
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 - 10.1577/1548-8675(1995)015<0042:fosmtp>2.3.co;2
Subject(s) - macrophyte , rainbow trout , fish measurement , cobble , fishery , environmental science , aquatic plant , juvenile , trout , ecology , habitat , fish <actinopterygii> , biology
Submersed aquatic plants that are abundant in some stream reaches have a potential to provide winter concealment cover for juvenile salmonids. We monitored an index of macrophyte abundance in a portion of the Henrys Fork of the Snake River during two winters that differed in severity and assessed the densities of age‐0 rainbow trout Oncorhynchus mykiss associated with the macrophytes. The macrophyte index averaged 84–87%, in November 1989 and 1992, and an average of 10–13 fish/100 m 2 were concealed there. In 1990, macrophyte cover declined to 59% in January and 46% in early February; fish density declined by about one‐third by January and dropped to nearly zero in February. In 1992–1993, the macrophyte index declined to an average of 39% following anchor ice formation in December and to 32% in January. Fish density in December was reduced to about half of the November density and to about 1 fish/100 m 2 in January. Movement of marked fish in 1989–1990 was predominantly from macrophytes into cobble and boulder cover along the bank. During these 2 years, cover provided by submersed macrophytes in the study area was not adequate to hold age‐0 rainbow trout throughout the winter. During winter of 1992–1993 no natural bank habitat was available because of low water flows, and we believe that none of the 1992 cohort of rainbow trout survived in the study area.