Pesticides in urban streams and early life stages of pacific coho salmon

Abstract

Abstract-Pesticides are frequently detected in urban streams and are believed to be primarily the result of homeowner use. Although concentrations in most cases are low (<1 mg/L), there is concern that pesticide inputs threaten efforts to restore and enhance salmon habitat. The authors exposed early life stages of coho salmon (Oncorhynchus kisutch) to a pesticide mixture (''cocktail'') representative of those pesticides most frequently reported in urban streams in western Washington State, USA. Life stages were continuously exposed to pulses of the cocktail simulating those in urban streams in fall and winter when coho salmon eggs and sac fry are present. Nominal concentrations of eight herbicides, two insecticides, a fungicide, and a breakdown product were the maximum detected. Fertilization, hatching success, survival, deformities, and growth of fry were not significantly affected. A reduction in fertilization success (19-25%) was not reproducible even when gametes were exposed to 100 times the maximum concentrations detected. Based on the end points examined in the present study, the results suggest that direct exposure to the pesticides most frequently detected in urban streams in western Washington does not impair early life stages of coho salmon and is not a major factor governing the recovery of salmon populations. The extent to which pesticide exposure would affect smoltification, outmigration, and ocean survival needs to be determined. Environ. Toxicol. Chem. 2013;32:920-931. # 2013 SETAC

Growth and survival of pacific coho salmon smolts exposed as juveniles to pesticides within urban streams in western Washington, USA

“…Similarly, earlier life stages including fertilization, hatching success, growth, and survival to 5 wk post swim-up were also unaffected [18]. Prerelease, condition factor, survival, sex ratio, brain AChE activity, and gonado-and hepatosomatic indices were not affected.…”

“…The cocktail consisted of those pesticides detected in at least 30% of the urban creeks monitored (see Figure 6 in Franz [16]) and included 8 herbicides, including 2 triazines (prometon and simazine), 2 insecticides (both AChE inhibitors), a fungicide, and a breakdown product. None of the endpoints (fertilization, hatching success, growth, and survival to 5 wk post swim-up) were significantly affected [18]. Although results suggested that exposure to the pesticides most frequently detected in urban streams in western Washington does not directly impair early life stages of coho salmon, the extent to which pesticide-exposed fry would suffer reduced survival during smoltification, outmigration, or in the ocean was not reported.…”

“…From studies in 2007 to 2008, 3 cohorts of fry (A, B, and C [18]) were maintained from 35 d post swim-up to tagging and release as smolts. In each cohort, pesticide-treated fish had been exposed either at fertilization of eggs through 35 d post swim-up of fry (2007-2008: cohorts A and C; single cohort in 2008-2009), or at fertilization through swim-up (2007-08: cohort B) [18]. Within each of these cohorts, gametes had been split between pesticide exposure and clean water controls, such that each treatment group was genetically similar to its control group.…”

“…The measured concentrations and the continuous pulsed exposure we employed likely represent a worst-case exposure for salmon gametes and fry within urban streams in western Washington [18]. However, we do not know the actual duration of pulses of pesticides in these urban streams.…”

“…Previously, we [18] continuously exposed gametes and early life stages of coho salmon to pulses of a pesticide mixture ("cocktail") representative of that within urban streams in western Washington in fall through early spring when concentrations are greatest [16] and early life stages are present. The cocktail consisted of those pesticides detected in at least 30% of the urban creeks monitored (see Figure 6 in Franz [16]) and included 8 herbicides, including 2 triazines (prometon and simazine), 2 insecticides (both AChE inhibitors), a fungicide, and a breakdown product.…”