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Using accelerated life testing procedures to compare the relative sensitivity of rainbow trout and the federally listed threatened bull trout to three commonly used rangeland herbicides (Picloram, 2,4‐D, and clopyralid)
Author(s) -
Fairchild James F.,
Allert Ann,
Sappington Linda S.,
Nelson Karen J.,
Valle Janet
Publication year - 2008
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/07-342.1
Subject(s) - rainbow trout , picloram , clopyralid , trout , toxicology , acute toxicity , biology , zoology , toxicity , ecology , fishery , botany , medicine , fish <actinopterygii> , weed control
We conducted 96‐h static acute toxicity studies to evaluate the relative sensitivity of juveniles of the threatened bull trout ( Salvelinus confluentus ) and the standard cold‐water surrogate rainbow trout ( Onchorhyncus mykiss ) to three rangeland herbicides commonly used for controlling invasive weeds in the northwestern United States. Relative species sensitivity was compared using three procedures: standard acute toxicity testing, fractional estimates of lethal concentrations, and accelerated life testing chronic estimation procedures. The acutely lethal concentrations (ALC) resulting in 50% mortality at 96 h (96‐h ALC50s) were determined using linear regression and indicated that the three herbicides were toxic in the order of picloram acid > 2,4‐D acid > clopyralid acid. The 96‐h ALC50 values for rainbow trout were as follows: picloram, 41 mg/L; 2.4‐D, 707 mg/L; and clopyralid, 700 mg/L. The 96‐h ALC50 values for bull trout were as follows: picloram, 24 mg/L; 2.4‐D, 398 mg/L; and clopyralid, 802 mg/L. Fractional estimates of safe concentrations, based on 5% of the 96‐h ALC50, were conservative (overestimated toxicity) of regression‐derived 96‐h ALC5 values by an order of magnitude. Accelerated life testing procedures were used to estimate chronic lethal concentrations (CLC) resulting in 1% mortality at 30 d (30‐d CLC1) for the three herbicides: picloram (1 mg/L rainbow trout, 5 mg/L bull trout), 2,4‐D (56 mg/L rainbow trout, 84 mg/L bull trout), and clopyralid (477 mg/L rainbow trout; 552 mg/L bull trout). Collectively, the results indicated that the standard surrogate rainbow trout is similar in sensitivity to bull trout. Accelerated life testing procedures provided cost‐effective, statistically defensible methods for estimating safe chronic concentrations (30‐d CLC1s) of herbicides from acute toxicity data because they use statistical models based on the entire mortality:concentration:time data matrix.