Brook Trout Declines with Land Cover and Temperature Changes in Maryland

Abstract

Abstract.-We examined the influence of landscape alteration and in situ stream habitat variables on brook trout Salvelinus fontinalis by using a landscape-scale, space-for-time substitution analysis and a smaller data set that tracked long-term changes in land use over time. Forested land cover within a catchment was the overall best landscape-scale predictor of brook trout occurrence at a given site; measures of impervious land cover and urbanization were also important predictors. Brook trout were almost never found in watersheds where impervious land cover exceeded 4%, as assessed from the 2001 National Land Cover Dataset (2001 NLCD); the single exception was in a stream that displayed consistently low water temperatures. Landscapescale analyses indicated that increases in water temperature and erosion were associated with increasing percentages of urbanization and imperviousness and decreasing percentage of forested land cover. Three of six brook trout populations that were followed over time were extirpated within the last 15 years (between 1990 and 2005), coinciding with increases in urbanization and impervious land cover. At these sites, water temperatures were substantially greater than at the three sites with extant brook trout. Land use amounts derived from high-resolution aerial photography showed substantially greater amounts of urbanization and particularly impervious land cover than did amounts derived from the 2001 NLCD. The differences in measured land cover between imagery types warrant caution when stating upper threshold limits of land cover, because use of imagery methods interchangeably may produce inconsistent results. Our findings suggest that brook trout are very sensitive to landscape alterations in Maryland and disappear at low levels of impervious land cover regardless of the specific mechanism involved.Populations near the periphery of a species' geographic distribution may be particularly sensitive to relatively minor anthropogenic perturbations. Brook trout Salvelinus fontinalis in the Piedmont physiographic province of Maryland are near the southeastern edge of the species' native distribution. Water temperature is vitally important (Meisner 1990;Raleigh 1982), because brook trout appear to only occupy streams with summer temperatures that remain less than 248C and they prefer much cooler streams (MacCrimmon and Campbell 1969). In addition, brook trout are found primarily in streams with high-quality physical habitat and limited amounts of silt deposition (Raleigh 1982;Argent and Flebbe 1999;Curry and MacNeill 2004), acidity (Baker andChristensen 1991;Carline et al. 1994), and other anthropogenic stressors.Declines in brook trout distribution and abundance have frequently been attributed to the degradation of streams' physical and chemical habitat conditions resulting from landscape alterations, such as forest clearing and agriculture. MacCrimmon and Campbell (1969) attributed reductions in the original range of brook trout through the late 1960s to pollution, siltation, and stre...

Use of ecological thresholds to assess recovery in lotic ecosystems

“…Thus, the values derived from our analyses should not be taken as literal thresholds. Moreover, landuse data derived from the NLCD will yield different results than landuse data derived from other sources (Stranko et al 2008) because the NLCD tends to underestimate the area of urban and suburban land cover relative to estimates based on higher resolution images (Moglen and Kim 2007). This tendency also explains why the taxon loss curves are so steep at low levels of ISC in Fig.…”

“…Substantial evidence indicates that land cover conversion to various forms of urban use negatively affects many freshwater taxa (Meador et al 2005, Roy et al 2005, Stranko et al 2008 and entire communities (Kennen 1999, Blakely et al 2006, Smith and Lamp 2008. General rules of thumb exist for levels of impervious surface cover (ISC) that are associated with stream degradation (e.g., loss of biological integrity beyond 10% ISC in the watershed; reviewed by Schueler et al 2009), but few more explicit relationships between ISC and taxon declines have been developed.…”

Factors Influencing Brook Trout (Salvelinus frontinalis) Egg Survival and Development in Streams Influenced by Agriculture

“…While brook trout remain widespread on PEI, Atlantic salmon is only present in about one third of its former rivers (Cairns and MacFarlane, 2015) and its decline has been attributed to a variety of factors, including excessive sedimentation (Guignion et al, 2010). In contrast to the situation on PEI, there is evidence of the decline of brook trout in other parts of the world that has been attributed to landscape alteration (Stranko et al, 2008). Thus, the study of the impacts of sedimentation on brook trout spawning can provide some insight into the persistence of this species on PEI despite the seemingly adverse conditions.…”

Sibship reconstruction for inferring mating systems, dispersal and effective population size in headwater brook trout (Salvelinus fontinalis) populations

“…Brook trout have been lost from over 50% of the historical habitat in Connecticut, USA, (Hudy et al 2008), and lotic populations are primarily located in small, cold headwater streams (Kanno and Vokoun 2008). Land development and resulting habitat alteration has often been associated with population declines (Kanno et al 2010;Stranko et al 2008;Waco and Taylor 2010), and climate change raises concern for the persistence of this steno-thermal species (Chu et al 2008;Flebbe et al 2006).…”