Restoring Geomorphic Stability and Biodiversity in Streams of the Catskill Mountains, New York, USA

BARRY P. B ALDIGO, ANNE S. GALLAGHER ERNST, AND WALTER KELLER U.S. Geological Survey, 425 Jordan Road, Troy, New York 12180 USA

DANA R. WARREN Cornell University Department of Natural Resources, Fernow Hall, Ithaca, New York 14853 USA

SARAH J. MILLER AND DANIEL DAVIS New York City Department of Environmental Protection, 71 Smith Avenue, Kingston, New York 12401 USA

THOMAS P. B AUDANZA New York City Department of Environmental Protection, Post Office Box 370, Shokan, New York 12481 USA

DOUGLAS DEKOSKIE AND JAKE R. BUCHANAN Greene County Soil and Water Conservation District, 907 County Office Building, Cairo, New York 12413 USA

Abstract.—Many stream and river channels in North America have been straightened, widened, and hardened to stabilize channel banks and beds, but these efforts have typically given little or no consideration to biological integrity of the affected ecosystems. Application of natural-channel design (NCD) techniques and Rosgen’s river classification system to mimic stable “reference-reach” morphology has helped reestablish natural stream-habitat conditions in more recent restoration projects. Stable channel morphology was restored using NCD techniques in a degraded reach in each of three Catskill Mountain streams during 2000 or 2001, in an attempt to decrease bed and bank erosion rates, reduce sediment loading, and improve water quality. Channel-restoration designs were based primarily on bank-full characteristics of nearby stable (reference) reaches and models of local stream hydrology and geometry. The effects of NCD restoration on biological integrity were assessed through before-after-control-impact (BACI) and analysis of variance (ANOVA) analyses of the changes in fish-community characteristics at treatment reaches relative to changes at unaltered control reaches after reach restoration. In general, relative species richness, total biomass, and biomass equitability increased significantly after treatment reaches were restored. The observed responses indicate that fish communities were affected by the restorations and by normal year-to-year variations in uncontrolled factors such as temperature, precipitation, and stream discharge. These findings indicate that biodiversity of fish communities in degraded Catskill Mountain streams generally benefit from use of NCD techniques to restore geomorphic stability.

* Corresponding author: [email protected]

587 588 BALDIGO ET AL.

Introduction Department of Environmental Protection (NYCDEP) and the Greene County Soil and The relations between geomorphic stability Water Conservation District (GCSWCD) have and condition of aquatic ecosystems have not implemented several demonstration stream res- been thoroughly documented, especially in toration projects in the Catskill Mountains of regard to the effects of stream restoration. southeastern New York as part of a larger Stream channels that are geomorphically un- NYCDEP program to implement stable typically have rapidly eroding or ag- multiobjective stream-management planning grading beds and banks; they also have fewer and design projects in the New York City pools than more stable reaches, and lower pool West-of-Hudson Water Supply Watershed. area and pool to riffle ratios, higher width to These restoration projects are designed to ad- depth ratios, more uniform water velocity, and dress several stream-management issues, in- higher rates of bank erosion, lateral-channel cluding flood hazards, aquatic-habitat condi- migration, and rates of sediment transport tion, water quality, fisheries, and property (Leopold et al. 1964; Leopold 1994; Rosgen protection. These channel restorations can 1996). Stream habitat within such channels produce self-sustaining reaches and satisfy can be relatively sterile and homogeneous with more than one management issue because low species diversity and distorted ecosystem designs are based on the form (geomorphol- structure or function (Rosgen 1994b; Scott ogy) and function (hydraulics and sediment and Hall 1997; Pretty et al. 2003). Single- transport) of naturally stable streams. The goal stream-stabilization efforts, often termed projects conducted used the Rosgen stream- restorations, have generally entailed harden- classification system (Rosgen 1994a, 1996) ing of stream channels and banks to either to (1) categorize streams according to bank- minimize localized bed and bank erosion, full-discharge hydraulic geometry, and (2) improve water quality, or mitigate flooding. base natural-channel-design (NCD) restora- Whether termed stabilization or restoration, tions on bankfull, flood plain, and valley char- only a small number of studies have evaluated acteristics measured in nearby stable reference the short-term effects of channel restoration streams of the desired type in a similar valley on wild fish populations and communities, setting (Rosgen 1994b). Specific changes in normal stream processes, or the consequences geomorphic stability of restored streams are in contiguous reaches (Pretty et al. 2003). not documented in the present paper. Even fewer studies have monitored long-term success of stream restoration on channel mor- In 1999, the U.S. Geological Survey (USGS), phology, fish habitat, bed and bank erosion in cooperation with NYCDEP and rates, or biological integrity. GCSWCD, began a 7-year study to assess the effects that stream-restoration projects (uti- Since the early 1990s, private and nonprofit lizing natural-channel-design [NCD] tech- organizations, as well as public agencies in the niques) had on the biodiversity and integrity Northeast, have attempted to base stream-res- of resident fish communities in three disturbed toration programs and projects on natural (unstable) stream reaches. Of the three types stream-channel morphology and fluvial pro- of biodiversity that may be measured—habi- cesses to recreate appropriate (stable for a par- tat diversity, genetic diversity, and species di- ticular stream type) bank and channel geom- versity—this paper focuses on species diver- etry and near-natural habitat and ecosystem sity, and its contribution to biological integ- structure and function. The New York City rity. Biological integrity has been defined as RESTORING GEOMORPHIC STABILITY AND BIODIVERSITY 589

“the capability of supporting and maintain- tive to that in corresponding reference reaches ing a balanced, integrated, adaptive commu- (differentials), were evaluated before and after nity of organisms having a species composi- restoration to quantify responses and to sepa- tion, diversity, and functional organization rate the effects of restoration from normal comparable to that of the natural habitat of interannual fluctuations. The responses of fish the region” (Karr 1981; Karr and Dudley communities in the three restored reaches are 1981). By this definition, reaches subject to summarized and discussed herein. little or no anthropogenic stress would generally have high biological integrity. This study used indices of fish community density, bio- Methods mass, richness, and equitability (evenness) observed at nearby undisturbed reference Stream-channel restorations were conducted reaches as the basis to assess changes in bio- independent from fish surveys in large (0.4– logical integrity observed at restored reaches. 3.0 km) restoration project reaches on each of Biological integrity in reference reaches, al- three streams; summaries of restoration ap- though not necessarily optimal, reflects the proaches are provided below. Fish inventories natural year-to-year fluctuations in fish com- were done annually at small (87–112 m) munity indices in untreated reaches. Com- paired reference and treatment reaches one or munity data from reference reaches provide a more years before (1999, 2000, and 2001), scale to standardize or separate the effects of and 2 years after treatment reaches were re- restoration from differences that would nor- stored (2002 and 2003). References reaches mally occur in community indices at each were outside of restoration project reaches, but treatment reach before and after restoration. treatment reaches were entirely within restoration project reaches. Treatment reaches were, Though the number of studies that assess fish therefore, in a restored condition only after response to large scale stream modifications restoration project reaches were restored. The were rare, several efforts that increased habi- three study streams were Broadstreet Hollow tat heterogeneity in streams also documented Brook, the Batavia Kill, and the East Kill (Fig- a shift in fish communities, away from an over- ure 1). The treatment reaches were assumed abundance of a few species that were tolerant to be geomorphically unstable before restora- of high sediment loads, toward balanced as- tion and more stable after restoration. Because semblages with a greater number of species reference reaches were not manipulated dur- that were generally larger and less tolerant of ing the study, they provided information on high sediment loads (Riley and Fausch 1995; the natural year-to-year changes in commu- Flebbe 1999; Roni and Quinn 2000; nity indices (e.g., density, biomass richness, Dethloff et al. 2001; Shields et al. 1995, and equitability) that helped distinguish fish- 1998, 2000). The main hypothesis tested in community changes due to restoration from the present study was that increased geomor- those due to natural variations in unmonitored phic stability in restored channels would de- factors, such as water temperature, precipita- crease total fish density and increase the total tion volumes, or stream discharge. fish biomass, number or species (richness), and species (or biomass) equitability of commu- Restoration Aproach nities in the three previously unstable reaches. Absolute changes in each index at restored The NYCDEP and GCSWDC selected reaches, and annual changes in each index rela- stream-restoration project reaches that had low 590 BALDIGO ET AL.

Figure 1. Location of three demonstration stream-restoration projects in the eastern Catskill Mountain State Park and the New York City (west-of-Hudson) Water Supply Watershed. geomorphic stability. The reaches typically had not always, the same reference reaches used high rates of bed and bank erosion and copi- for geomorphic-design purposes. ous sediment supplies that tended to produce overwide and shallow channels, rapid chan- Study Reaches nel migration, homogeneous riffle habitat, and high concentrations of total suspended sol- Fish communities at reference and treatment ids, especially where clay-rich deposits were reaches were typically surveyed once, each exposed. The NYCDEP and GCSWCD July or August from 2000 through 2003, ex- implemented restoration projects in the three cept for the East Kill and Broadstreet Hollow restoration project reaches to increase stabil- Brook, which were not sampled in 2001. Sur- ity, alleviate negative impacts on water qual- veys were also done in 1999 at both reaches ity, minimize damage to public infrastructure on Broadstreet Hollow Brook. and private property (lands and structures), Surveys at Broadstreet Hollow Brook were maintain riparian structure and function, and completed in July or August of 1999, 2000, improve stream habitat and fisheries. All res- 2002, and 2003. This stream flows into torations used the Rosgen (1994a, 1996) Esopus Creek about 35 km northwest of stream-classification system and based chan- Kingston (Figure 1). The treatment reach was nel-geometry designs mainly on bank-full- 0.1 km long and about 3.2 km upstream from channel characteristics of nearby stable refer- the confluence with the Esopus Creek. The ence reaches of the same type and on regional treatment reach had a drainage area of about hydraulic-geometry relations (natural-channel- 23 km2; discharge averaged 0.09 m3/s, and design principles). The reference reaches used wetted-width averaged 5.4 m during the four for fish surveys appeared to be stable in gen- surveys. The corresponding reference reach, eral, but stability was not a requirement nor 0.7 km upstream from the treatment site, had was it assessed in detail. Fish-reference reaches an average discharge of 0.07 m3/s and average discussed in this study were sometimes, but wetted-width of 4.7 m. The restoration- RESTORING GEOMORPHIC STABILITY AND BIODIVERSITY 591

project reach was 0.34 km long and was re- m during the four surveys. The restoration stored in September and October of 2000. project reach was 0.73 km long and was re- Additional information on the restoration stored in the July and August of 2000. Addi- project and the watershed is available at http:/ tional information on the watershed and the /www.gcswcd.com/stream/ (accessed Decem- restoration project is available at http:// ber 2004) and in the provisional stream-man- www.gcswcd.com/stream/(accessed December agement plan http://www.gcswcd.com/ 2004). stream/broadstreet/smp/ (accessed December 2004). Fish Communities

Fish surveys were done in July of 2000–2003 Fish community surveys were done at the at reference and treatment reaches in the treatment reach and the reference (control) Batavia Kill, about 42 km north-northwest of reach in each stream 1 or 2 years before resto- Kingston (Figure 1). The treatment reach was ration and 2 years after restoration. Fish in 1.4 km upstream from a small flood-control survey reaches were collected from seine- reservoir and 22 km upstream from the blocked, 87- to 120-m-long stream sections confluence with Schoharie Creek (Figure 1). during three or four successive passes using a The treatment reach had a drainage area of battery-powered backpack electrofisher and about 17 km2; discharge averaged 0.06 m3/s three fish netters. Fish from each pass were and wetted-width averaged 4.7 m during the identified by species, and the lengths and four surveys. The reference reach, 1.9 km up- weights of individual fish more than about stream from the treatment reach, had an aver- 150 mm long were recorded. Lengths and age discharge of 0.06 m3/s, and average wet- weights of fish smaller than about 150 mm ted-width of 4.8 m. The restoration project were obtained from 40 to 50 individuals of reach was 1.6 km long; the lower two-thirds each species; thereafter, total weights and of this reach was restored in the fall of 2001; counts by species were recorded in batches of and the upper third was restored in the fall of 10–50 individuals. Fish were returned to the 2002. Additional information on the water- stream after all processing was completed. shed and the restoration project is available at http://www.gcswcd.com/stream/(accessed Data Analyses Decemeber 2004). The number of fish captured during each pass Surveys were done at both reaches in the East was used to estimate annual mean population Kill during July or August of 2000, 2002, sizes and 95% confidence intervals (CI) for and 2003, about 40 km north-northwest of each fish species and for the entire fish com- Kingston (Figure 1). The treatment reach was munity by the Moran-Zippin method of pro- 11 km upstream from the confluence with portional reduction (Zippin 1958) and Schoharie Creek, had a drainage area of about Microfish (v. 1) software (Van Deventer and 45 km2, an average discharge of 0.29 m3/s, Platts 1985). Species diversity (the number and an average wetted-width of 8.4 m during of fish species, or richness), and Shannon- the three surveys. The reference reach, 0.1 km Wiener diversity (species equitability) were upstream from the treatment reach, was con- calculated through standard methods tiguous with the upper end of the restoration (Whittaker 1975). Indices of community project reach. Discharge at this reach averaged equitability were calculated using (1) the num- 0.34 m3/s, and wetted-width averaged 12.4 ber of individuals of each fish species, and (2) 592 BALDIGO ET AL. the total weight of each species at each reach. fering responses among the three streams). Al- Total community density (number of fish/m2) most all differentials used to test for effects of and biomass (grams of fish/m2) at each reach restoration were normally, or nearly normally, were estimated from the total number or bio- distributed (tested through a normal prob- mass of all fish divided by the surface area of ability plot with 0.95 confidence intervals). each survey reach. The overlap of 95% C.I.s Only the combined biomass equitability data was used to assess absolute differences (P < were not distributed normally. Differences for 0.05) in indices of community density and all analyses were considered significant when biomass between reaches or within reaches P-values were less than 0.05, unless otherwise among sampling dates. These assessments are noted. analogous to two-tailed Student’s t-tests. Fur- ther evaluation of community responses to Results and Discussion restoration at treatment reaches relied on ANOVA and BACI methods (Steward-Oaten Findings from the fish-community surveys and et al. 1986; Underwood 1994). analyses of community-index responses to restoration are treated separately below. Due to Community indices of density, biomass, rich- the paucity of directly comparable studies, the ness, and equitability at each treatment reach related discussions are somewhat limited and were scaled or standardized to the same index are included, for the most part, with the find- measured at corresponding reference reaches ings. to calculate index differentials. A differential ∆ ( ) was calculated as the product of each in- Community Density dex value at a given treatment reach minus the index value at its corresponding reference Total community density (total number of reach for a given survey period (year). The fish/m2) was greater each year after restora- BACI method tests for changes in mean index tion (2002 and 2003) than during the 1 or 2 differentials at treatment reaches before resto- years before restoration at treatment reaches ration (1999 and 2000) and after restoration in Broadstreet Hollow Brook and the East Kill (2001, 2002, and 2003) through a one-fac- (Figures 2B, 2C), but not in the Batavia Kill tor ANOVA within a single stream or though (Figure 2A). Mean density differentials (∆ a two-factor ANOVA combining data from density) increased significantly at Broadstreet all three streams. Findings from the one-fac- Hollow Brook by 0.91 fish/m2 (n = 4, P = tor ANOVA are based on a sample size (n) of 0.067) after the restoration, but decreased in 4 at the Batavia Kill and Broadstreet Hollow the other two streams (Table 1). Mean index Brook. Conclusions based on tests with such differentials at the East Kill cannot be tested a low sample size may be disputed; neverthe- for significant change because only one sur- less, the results quantify the differences in the vey was completed before restoration. Results magnitude and direction of community re- of the two-factor ANOVA indicate that ∆ den- sponses and illustrate that response mecha- sity for the combined treatment reaches did nisms may differ among the three restored not change significantly after restoration (Table reaches. The two-factor ANOVA tests for (1) 2). Although density of fish communities at differences in each index differential before and the East Kill and the Batavia Kill treatment after restoration, (2) differences in index dif- reaches increased after restoration, densities ferentials among the three streams, regardless at their corresponding reference reaches of restoration, and (3) factor interaction (dif- changed such that the differentials were RESTORING GEOMORPHIC STABILITY AND BIODIVERSITY 593

Figure 2. Total fish-community density and biomass, and 95% confidence intervals, at paired treatment and reference reaches in the three study streams before and after restoration, 1999–2003. smaller (or negative) after restoration than sample area at the time of the survey were before restoration in both streams (Figures 2A, smaller than during the other 3 years. Only 2C). The relative response of fish-community at Broadstreet Hollow Brook were the num- density at treatment reaches in both streams, bers of fish/m2 significantly greater at the therefore, was slightly negative (Table 2). treatment reach after restoration than before. The density of fish in the East Kill treatment The inconsistent response of fish-community reach also increased significantly after restora- density to restoration is reasonable given the tion (Figure 2C); ∆ density declined (Table high level of interannual variability, initial fish- 1), however, because larger relative increases community condition, and the various geo- in density at its corresponding reference reach morphic stability issues at each restored reduced differences in density estimates be- stream reach. Interannual variations in den- tween the treatment and reference reaches sity of fish communities at the Batavia Kill during both years following the restoration ranged from about 2 to 4 g/m2 (Figure 2A), (Figure 2C). and greatly exceeded the mean change (-0.93 g/m2) possibly caused by restoration (Table The natural-channel design (NCD) restora- 1). The unusually high fish density and bio- tions did not significantly affect fish-commu- mass (per unit area) at the Batavia Kill in 2001 nity density across the three restored reaches; were expected because that summer was ex- therefore, restored stability did not lower to- ceptionally dry, and stream discharge and tal fish densities and the null hypothesis that 594 BALDIGO ET AL.

Table 1. Mean increase (+) or decrease (-) in index differentials, and the results (P-values - in parenthe- ses) of 1-factor ANOVAs assessing differences in each index, before and after restoration at the three treatment reaches. All data are normally distributed. Boldface values indicate P-values < 0.15.

Mean change in index differentials

Community index Batavia Kill Broadstreet Hollow Brook East Kill (n=4) (n=4) (n=3)

Total density -0.93 0.91 -0.84 (0.402) (0.067) (na)

Total biomass -1.68 14.34 1.48 (0.273) (0.015) (na)

Richness 5.00 0.00 3.00 (0.019) (1.000) (na)

Equitability 0.068 0.053 0.275 (species density) (0.488) (0.535) (na)

Equitability 0.363 0.031 0.343 (species biomass) (0.099) (0.137) (na) no differences in density exist before and after Community Biomass restoration, was not rejected. The original hypothesis assumed that large numbers of small Like total density, community biomass in the species, such as slimy sculpin Cottus cognatus, treatment reaches at Broadstreet Hollow blacknose dace Rhinichthys atratulus, and Brook and the East Kill were significantly longnose dace Rhinichthys cataractae in unstable greater both years after restoration than dur- treatment reaches would be replaced by fewer ing the 1 or 2 years before restoration (Figure individuals and larger species (e.g., trout) af- 2D, 2E), but not in the Batavia Kill (Figure ter restoration. This could have occurred at 2F). The ∆ biomass averaged 14.34 g/m2 the Batavia Kill, but unusually high total den- greater (P = 0.015) after restoration than be- sities during the drought of 2001 may have fore restoration only at the Broadstreet Hol- disrupted any discernible trend at this stream. low Brook treatment reach (Table 1). Results In general, densities of fish at all restored of a two-factor ANOVA that combines biom- reaches decreased on average by 0.112 fish/ ass differentials from all three streams indi- m2 (P = 0.509) relative to fish densities at the cate that (1) biomass differentials increased corresponding reference reaches. The NCD significantly on average by 5.32 g/m2 after restorations at Broadstreet Hollow Brook may restoration (P = 0.054), (2) mean biomass dif- have increased community density; however, ferentials differed slightly (P = 0.123) among normal interannual variations in other factors the streams, and (3) the response of biomass that were not evaluated in this study (e.g., to restoration differed (P = 0.03) across the precipitation, discharge, and temperature, or three streams (Table 2). differences in recruitment, survival, and pre- dation) could be the reason for the lack of sig- The NCD restorations significantly increased nificant trends in the three restored reaches. community biomass at treatment reaches; RESTORING GEOMORPHIC STABILITY AND BIODIVERSITY 595

thus, the hypothesis—that increased stabil- ass (net loss of 1.68 g/m2) at the restored ity produced greater total community biom- Batavia Kill reach. Estimates of biomass at the ass in restored reaches—was accepted. The Broadstreet Hollow Brook treatment reach null hypothesis—that no differences in bio- indicate that biomass increased on average by mass existed before and after restoration—was about 9 g/m2 after restoration (Figure 2e). rejected. Results indicate that total commu- Biomass differentials in Broadstreet Hollow nity biomass at treatment reaches tended to Brook averaged -4.7 g/m2 before restoration increase after restoration in absolute terms, but and -9.7 g/m2 after restoration (Figure 2E). may decrease or increase relative to interannual Consistent biomass differentials at both changes in community biomass that normally reaches for 2 years before and 2 years after take place in all streams. Significant increases restoration produce low variance. Combined or decreases in biomass in the three treatment with a large increase mainly at the treatment reaches indicate that physical and biological reach, these data provide strong evidence of a conditions unique to each stream may dictate significant increase in fish biomass (14.34 g/ the magnitude and direction of change in com- m2) due to restoration. Thus, the BACI analy- munity biomass in response to restoration. ses, which standardize observed responses in Further evaluations of species-specific re- treatment reaches against the normal year-to- sponses might better elucidate the basis for year variations in community indices in cor- the observed variability. Large interannual fluc- responding reference reaches, help define the tuations in total biomass at all reference effects of restoration on fish communities. reaches annegall and, at treatment reaches before restoration, suggest that normal year- The main concerns with BACI analyses are to-year changes in other environmental fac- that different communities or local and re- tors must also affect biomass of fish commu- gional factors at the paired reference and treat- nities. ment reaches might produce dissimilar year- to-year changes in indices, which would in- The ability of BACI analyses to detect and validate the assumed parallel community more accurately quantify the effects of reach trends. A qualitative assessment of indices at restoration can be illustrated through exami- reference and treatment reaches in Broadstreet nation of the small decrease in relative biom- Hollow Brook and in the Batavia Kill prior to ass at the Batavia Kill (Figure 2D) and the each restoration suggests that reach pairs ex- large increase in relative biomass at Broadstreet hibited similar seasonal fluctuations before Hollow Brook (Figure 2E) following restora- treatments. Reference reaches for all three tions. Estimates of biomass at the Batavia Kill streams were selected for their close proxim- treatment reach before and after restoration ity to corresponding treatment reaches; there- varied highly from year to year, and mean bio- fore, the reference reach at the East Kill can 2 mass decreased by about 4.0 g/m after resto- also be considered appropriate for the BACI ration. The biomass differential at the Batavia analyses, despite the lack of survey replication 2 Kill treatment reach averaged -1.7 g/m be- (two sample years) before reach restoration. fore restoration and -3.4 g/m2 after restoration. Consistent differences during both peri- Communitry Richness ods (before and after restoration) lessen the effects of interannual variability and provide Annual statistics (means and confidence in- evidence (though not significant) for a nega- tervals) could not be generated for commu- tive effect of restoration on community biom- nity richness (or for density and biomass 596 BALDIGO ET AL.

Figure 3. Total fish-community richness (number of species) and species equitability (Shannon-Wiener diversity) at paired treatment and reference reaches in the three study streams before and after restoration, 1999–2003. equitability) at each reach, but the mean num- restoration differed (P = 0.016) among the 3 ber of fish species for 2 years after restoration streams (Table 2). These results indicate that in the Batavia Kill and East Kill treatment community richness at the three treatment reaches (Figure 3A, 3C) was greater than the reaches responded differently in magnitude mean during the 2 years before restoration. or direction of change to respective stream res- Richness also appeared to be relatively stable torations (Figure 3A, 3B, 3C). at all reference reaches during the study (Fig- The NCD restorations significantly increased ure 3A, 3B, 3C). Richness differentials in- community richness at treatment reaches; creased significantly (P = 0.019) by 5.0 spe- thus, the hypothesis—that increased stabil- cies after restoration only at the Batavia Kill ity increases the number of fish species in re- treatment reach, although it also increased on stored reaches—was accepted. The null hy- average by 3.0 species (P not available) at the pothesis—that no differences in richness exist restored East Kill reach (Table 1). Results of before and after restoration – was rejected. The the two-factor ANOVA, using combined rich- 60% increase in the number of fish species on ness differentials, indicate that 1) restoration average after restorations has several impor- increased community richness by an average tant implications. First, the NCD restorations of 2.43 species (P = 0.003), 2) richness dif- had a strong effect on species richness. Sec- fered (P = 0.101) among the three streams, ond, biodiversity (a critical component of bio- and 3) the response of community richness to logical integrity) can recover relatively quickly RESTORING GEOMORPHIC STABILITY AND BIODIVERSITY 597

Table 2. Results of before-after-control-impact analyses summarizing mean changes in index differentials after restoration of the three treatment reaches, and results (P-values) of two-factor ANOVAs assessing differences in combined index differentials (1) before and after restoration, (2) among the three streams (regardless of restoration), and (3) factor interaction (differing responses among the three streams). [n=11; boldface values indicate P-values < 0.15.]

P-values for differences in index differentials Community index Mean Before-after Stream-to- Interaction change restoration stream Total density -0.112 0.509 0.238 0.185

Total biomass 5.32 0.054 0.123 0.030

Richness 2.43 0.003 0.101 0.016

Equitability 0.101 0.260 0.270 0.176 (species density)

Equitability 0.207 0.004 0.016 0.063 (species biomass) in disturbed streams after restoration, pro- in the evenness or balance of fish populations vided that other stream sections contain source within the treated reaches. In other words, populations. Third, if the increased number the few general or opportunistic species that of species is coupled with an increased range are tolerant of harsh or extreme environmen- in tolerance to environmental conditions in tal conditions and low habitat diversity, and restored reaches, then these fish communities that typically dominate fish communities in can be expected to be more resilient or adapt- unstable reaches before restoration, did not able to ecosystem perturbations than commu- appear to be substantially replaced by a more nities in disturbed stream reaches. Thus, the balanced fish-species assemblage, which might NCD techniques used in this study should be better suited to greater habitat diversity be given serious consideration if restoration and less extreme environmental conditions. goals include increasing fish biodiversity in Numeric domination of fish communities by disturbed stream systems. a small number of species appears to continue at restored treatment reaches; thus, the spe- Community Equitability cies with the largest population (largest proportion of the community) may or may not Neither variations in density (numeric) change after restoration. equitability within each treatment reach (Fig- ures 3D, 3E, 3F), nor shifts in density- Though NCD restorations did not drastically equitability differentials within individual alter the numeric balance of fish species, they streams (Table 1) or in all three treatment strongly influenced the distribution of spe- reaches combined (Table 2) identified signifi- cies biomass within communities at restored cant changes that could be attributed to res- treatment reaches; biomass equitability was toration. These findings indicate that the res- higher both years after restoration than be- torations did not cause any significant change fore restoration at treatment reaches in all three 598 BALDIGO ET AL. streams (Figure 4A, 4B, 4C). Biomass- equitability differentials were 0.031 greater (P = 0.137) after restoration than before restoration at Broadstreet Hollow Brook, 0.363 greater (P = 0.099) at the Batavia Kill, and 0.343 higher (P not available) at the East Kill (Table 1). Results of ANOVA using biomass- equitability differentials from all three streams indicate that (1) restoration increased biomass-equitability differentials significantly by 0.207 (P = 0.004), (2) biomass-equitability differentials differed (P = 0.016) among the three streams, and (3) the response of biomass equitability to restoration also differed (P = 0.063) among streams (Table 2).

These findings support the hypothesis that increased channel stability increases the equitability of species biomass in restored reaches. The null hypothesis—that no differences in biomass equitability exist before and after restoration—was rejected. Increased biomass equitability in restored reaches indicates Figure 4. Biomass equitability (Shannon-Wiener) that the restorations significantly improve bio- for fish communities at paired treatment and reference reaches in the three study streams before logical integrity in previously degraded and after restoration, 1999–2003. streams. For example, total biomass of fish communities at the East Kill and the Batavia Kill treatment reaches before restoration consisted almost entirely of one or two small prey spe- Related studies cies (as high as 99% slimy sculpin, blacknose dace, and/or longnose dace), with few or no The authors are unaware of any studies that top predator species. After restoration, biom- describe the response of fish communities to ass and the proportion of brown trout Salmo restoration of stable-stream geomorphology trutta, brook trout Salvelinus fontinalis, and through natural-channel-design principles. A rainbow trout Oncorhynchus mykiss increased, few diverse studies, however, show that other whereas biomass (and proportion) of minnow types of restorations benefited fish populations species decreased. The fish communities that and communities in a manner similar to that were established in restored reaches generally observed in the restored Catskill Region resembled the natural, evenly balanced fish streams. Manipulation of coarse or large woody communities in corresponding reference debris in streams has been investigated far reaches. The NCD restorations, therefore, more than any other stream-improvement helped to reconstitute more diverse, balanced, technique. For example, addition of large and complete fish communities and enhanced woody debris in 15 streams in the Northwest the biological integrity of these aquatic eco- was correlated with lower water velocities, in- systems. creased total pool area and numbers of pools, RESTORING GEOMORPHIC STABILITY AND BIODIVERSITY 599 as well as increased density of juvenile coho, and equitability following restoration indicate cutthroat, and steelhead trout in relation to that the normal structure and function, and those in reference streams during summer or thus biological integrity of resident fish com- winter periods (Roni and Quinn 2000). Place- munities are also improved in previously de- ment of drop-log structures in six small Colo- graded reaches. These data, however, describe rado streams also decreased water velocity and the response of fish communities to restora- increased pool volume, depth, and cover, and tion over a relatively short period of time. Con- typically increased the abundance and biom- tinued monitoring of fish communities in ass of age-2 brook, brown, and rainbow trout these reaches and in additional restored (Riley and Fausch 1995). Addition of stone reaches, therefore, is necessary to verify that spurs, which are somewhat analogous to the the changes observed during the first two years rock veins used in our NCD restorations, to following restoration are sustained over the stabilize banks of several incised or rapidly long term. The improvements in fish com- eroding warmwater streams in Mississippi munities were likely related to increased habi- usually (but not always) increased species rich- tat quality, quantity, and diversity and in- ness and significantly shifted community com- creased geomorphic stability generated by the position away from colonist cyprinids and NCD restorations. Additional analyses and small centrachid species and toward higher interpretation of habitat and stability data are densities and biomass of large catostomid, underway to confirm that NCD techniques ictalurid, and centrarchid species (Shields et increase geomorphic stability, and that habi- al. 1997, 1998, 2000). Though not a ma- tat condition and stream stability are corre- nipulative study, fish communities in lated with the integrity of fish communities. geomorphically degraded streams of the coastal plain of Maryland had low diversity and were Acknowledgments dominated by a few tolerant taxa; however, less impacted streams had more balanced spe- The authors extend their appreciation to Britt cies assemblages and higher indigenous spe- Westergard, Rebecca Pratt, and Christiane cies richness and abundance (Scott and Hall Mulvihill of the USGS; Christina Falk, Phillip 1997). Although none of the above efforts used Eskeli, Mark Vian, and Elizabeth Reichheld NCD techniques, the observed effects on resi- of the NYCDEP; Mathew Horn of Cornell dent fish communities demonstrate that find- University; and Rene VanShaack of the ings of the present investigation are not unique GCSWCD for technical support. This research and that a variety of restoration techniques was funded by the New York City Depart- can have beneficial effects on stream ecosys- ment of Environmental Protection, the Greene tems. The effectiveness of various techniques County Soil and Water Conservation District, probably differ; however, potential differences and the U.S. Geological Survey. cannot be assessed at present from the available information. References In conclusion, significant increases in species richness and biomass equitability in treated Dethloff, G. M., H. C. Bailey, and K. J. Maier. 2001. reaches clearly demonstrate that biodiversity Effects of dissolved copper on select hematological, biochemical, and immunological parameters of wild of fish communities in small streams in the rainbow trout (Oncorhynchus mykiss). Archives of En- Catskill Mountains is positively affected by vironmental Contamination and Toxicology NCD restorations. Increases in fish biomass 40(3):371–380. 600 BALDIGO ET AL.

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