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Landscape‐Level Sampling for Status Review of Great Basin Redband Trout
Author(s) -
Dambacher Jeffrey M.,
Jones Kim K.,
Larsen David P.
Publication year - 2009
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/m08-077.1
Subject(s) - trout , abundance (ecology) , biomass (ecology) , rainbow trout , fishery , population , environmental science , habitat , threatened species , geography , structural basin , endangered species , sampling (signal processing) , ecology , confidence interval , population dynamics of fisheries , fish <actinopterygii> , biology , statistics , demography , mathematics , paleontology , filter (signal processing) , sociology , computer science , computer vision
In response to a petition to list Great Basin redband trout (subspecies of rainbow trout Oncorhynchus mykiss) as threatened or endangered, the U.S. Fish and Wildlife Service conducted a status review in 1998. To support that review, we conducted a survey of the abundances of redband trout in each of six subbasins of the Great Basin that included the states of Oregon, California, and Nevada. We used a generalized random‐tessellation stratified algorithm to select a target sample size of 35 sites/subbasin. Out of a target number of 210 sites, 185 were visited by three‐person crews that surveyed stream habitat and estimated the abundance of fish populations in sample reaches with lengths that were nearly 20 times the respective channel widths. A minimal sampling intensity was based on previously encountered levels of between‐site variance in estimates of redband trout abundance. The total population estimate of age‐1 and older (age‐1+) redband trout in the Great Basin was 971,313 fish, with a 95% confidence interval equaling ±15% of the mean estimate; 95% confidence limits ranged from 15% to 31% for population estimates in individual subbasins. Age‐1+ fish abundance in terms of numerical density showed no significant differences between any subbasins. However, there were significant differences in terms of biomass: Catlow Valley subbasin biomass was significantly higher than the Great Basin mean, whereas Goose Lake subbasin biomass was significantly lower than the basinwide mean. These comparisons were supported by like differences in average weight. Analysis of stream habitat characteristics and fish abundance revealed no relationships that were generally consistent throughout the Great Basin, although spatial patterns were evident within some stream systems where sampling intensity was sufficiently high.