Channel Suspended Sediment and Fisheries: A Synthesis for Quantitative Assessment of Risk and Impact

Abstract

Our meta‐analysis of 80 published and adequately documented reports on fish responses to suspended sediment in streams and estuaries has yielded six empirical equations that relate biological response to duration of exposure and suspended sediment concentration. These equations answer an important need in fisheries management: quantifying the response of fishes to suspended sediment pollution of streams and estuaries has been difficult historically, and the lack of a reliable metric has hindered assessment for risk and impact for fishes subjected to excess sedimentation. The six equations address various taxonomic groups of lotic, lentic, and estuarine fishes, life stages of species within those groups, and particle sizes of suspended sediments. The equations all have the form z = a + b (logex) + c(logey); z is severity of ill effect, x is duration of exposure (h), y is concentration of suspended sediment (mg SS/L), a is the intercept, and b and c are slope coefficients. The severity of ill effect (z) is delineated semiquantitatively along a 15‐point scale on which is superimposed four “decision” categories ranging from no effect through behavioral and sublethal effects to lethal consequences (a category that also includes a range of paralethal effects such as reduced growth rate, reduced fish density, reduced fish population size, and habitat damage). The study also provided best available estimates of the onset of sublethal and lethal effects, and it supported the hypothesis that susceptible individuals are affected by sediment doses (concentration × exposure duration) lower than those at which population responses can be detected. Some species and life stages show “ultrasensitivity” to suspended sediment. When tested against data not included in the analysis, the equations were robust. They demonstrate that meta‐analysis can be an important tool in habitat impact assessment.

Climate and land-use changes affecting river sediment and brown trout in alpine countries—a review

“…1; reviewed data in Alabaster and Lloyd 1980;Newcombe and MacDonald 1991;Berry et al 2003). Physical damage of gill and skin epithelia include thickening of gill lamellae, clogging of gills, hyperplasis and necrosis-all of which can have detrimental effects on the individual fish (Berry et al 2003;Newcombe and Jensen 1996). Published 96-h LC 50 values for salmonids exposed to natural sediments are mostly above 1,700 mg l −1 (Berry et al 2003;Newcombe and Jensen 1996).…”

“…Physical damage of gill and skin epithelia include thickening of gill lamellae, clogging of gills, hyperplasis and necrosis-all of which can have detrimental effects on the individual fish (Berry et al 2003;Newcombe and Jensen 1996). Published 96-h LC 50 values for salmonids exposed to natural sediments are mostly above 1,700 mg l −1 (Berry et al 2003;Newcombe and Jensen 1996). However, at values lower than 90 mg l −1 fish already show signs of sub-lethal stress (changes in blood chemistry, increased parasitic infection of gill tissue) and changes in behaviour such as reduced feeding rates, increased rates of coughing, and avoidance of turbid water with increasing risk for predation ( Fig.…”

“…Area below dotted straight line is measured (cross symbol) and estimated concentrations in Swiss rivers (unpublished data LHG and NADUF). Below straight line, no LC (lethal concentrations) was found (Herbert et al 1961;Alabaster and Lloyd 1980;Newcombe and MacDonald 1991;Newcombe and Jensen 1996;Berry et al 2003) al (Baglinière and Maisse 2002;Zimmer and Power 2006) and the redds are usually placed at the same sites in subsequent years (Schneider 2000). For redd construction female trout excavate a depression by removing fines and gravel creating a typical pit and tail structure.…”

Do Conservation Practices and Programs Benefit the Intended Resource Concern?

“…Sublethal and lethal effects on fish assemblages from suspended sediment include avoidance behavior, impaired respiration, reduced feeding rates and growth, reduced tolerance to disease or toxicants, increased physiological stress, and mortality (Newcombe and Jensen, 1996).…”

“…An initial hypothesis of this study was that lethal and sublethal effects (as defined by Newcombe and Jensen, 1996) of suspended sediment on fish would decrease as CSP practices were adopted and targeted CRP cropland was enrolled in either of the two watersheds. It was also hypothesized that CSP practice payments, combined with program payments for CRP, would offset any decline in net farm income (NFI) associated with changing agricultural production practices in either watershed.…”