Response of fish assemblages and habitat to stream restoration in the Ashokan Watershed

Science Center Objects

Background: Streams are ecologically, culturally, and economically important systems that are subject to impacts from a large array of human activities. There has been a relatively recent increase in efforts to manage, protect, and restore streams that have experienced physical, chemical, and biological degradation. Unfortunately, interest in any single restoration effort tends to be relatively...

Background: Streams are ecologically, culturally, and economically important systems that are subject to impacts from a large array of human activities. There has been a relatively recent increase in efforts to manage, protect, and restore streams that have experienced physical, chemical, and biological degradation. Unfortunately, interest in any single restoration effort tends to be relatively short lived, and despite spending >$1 billion annually in the U.S. on stream restoration, little or no effort is devoted to evaluating the effectiveness or ecological success of most restoration projects (Bernhardt et al., 2005; Roni and Quimby, 2005). The limited post-restoration monitoring that occurs in many restoration projects is generally focused on ensuring that design implementation was achieved – rather than ‘effectiveness monitoring’ to determine effects of the restoration on habitat and biota (Roni et al., 2018). A number of recent publications including Stream Restoration and Enhancement Projects: Is Anyone Monitoring? (Bash and Ryan, 2002) highlight growing concern that the effects of one of the most commonly used stream management actions are largely unknown and opportunities to inform future management actions are being lost.

A young-of-the-year Brown Trout typical of streams in the Ashokan watershed.A young-of-the-year Brown Trout typical of streams in the Ashokan watershed.

The watersheds of the Catskill Mountain region form the backbone of the New York City drinking water supply and as such are carefully managed by the New York City Department of Environmental Protection and a number of stream management programs. Restoration projects are frequently utilized to stabilize stream beds and banks, reduce sediment loads, and increase or sustain the quality of potable waters. Aquatic ecosystems are partly regulated by stream geomorphology, however, and the effects of stream restorations on biological assemblages are rarely measured and, thus, unknown or poorly understood. In one of the few such assessments, Baldigo et al. (2010) found that fish communities and trout populations generally benefitted from Natural Channel Design (NCD) stream restorations in 4 of the 6 study reaches. Concurrent improvements in stream habitat and trout suitability indices occurred at the 4 reaches where fish communities benefitted from restoration while comparable habitat improvements were not observed at the two reaches where fish communities did not respond positively. The effects of increased channel and bank stability on fish assemblages were not fully assessed because only subjective/qualitative bank data were available from habitat surveys. Central conclusions were that NCD efforts do not always positively affect fish assemblages and that the response of aquatic biota at additional stream-restoration sites needs to be assessed across the region to: (a) quantify the relationship between the condition of fish assemblages and bed/channel stability, (b) determine the effects that various restoration design principles practices (e.g., the use of wood) have on fish assemblages, and (c) ensure that fish assemblages in restored reaches are not adversely affected. In addition to ensuring that targeted restoration efforts have not degraded local fisheries, these data can also help guide and optimize future stream-restoration efforts by watershed managers in the Catskills and throughout the Northeast.

Each summer, Ulster County Soil and Water Conservation District (UCSWCD) directs one or more water quality protection or improvement stream restoration projects. These projects generally aim to address reach scale geomorphic and/or hillslope instability (or otherwise reduce inputs of suspended sediment), and therefore differ notably in the objectives and designs of more traditional NCD stream restoration projects. As a result, despite their widespread application, little is known about the effects of these projects on fish populations, the quality of trout habitat, and the physical factors that drive fish response. 

Objective: The primary objective of this study is to determine the effects of stream restoration projects on fish assemblages, trout populations, and trout habitat quality. New insights will help refine expectations, resource targets, and design principles for future restoration projects in the region. Specific goals of this study are to: (a) define the relations among stream stability (bed and bank), other geomorphology features, habitat quality, and the condition of fish assemblages, and (b) identify the factors that are most responsible for positive and (or) negative responses in local fish populations and communities following restoration.

Approach/Methods: The following approach will be implemented gradually as appropriate stream restoration projects are planned. Once a target restoration site is identified, the USGS and UCSWCD will use the Rosgen stream classification system (Rosgen, 1994, 2014) to identify a comparable reference site to be monitored concurrently. Monitoring of the restoration and reference sites will begin at least two summers prior to construction (e.g., for a 2022 project, sampling would occur in 2020, 2021, and in 2022 prior to stream disruption). Three years of post-restoration monitoring will commence the following summer (e.g., 2023, 2024, and 2025 for a 2022 project). Through this framework, 6-8 restoration sites will be targeted for monitoring.

Fish community surveys will be conducted at each restoration and reference site using multi-pass electrofishing depletion surveys (the same methodology employed in past surveys in this watershed surveys (see Baldigo et al. (2015)) with a Smithroot LR-24 backpack electrofisher and field crew of 6-9 personnel. The sampled reach length will be approximately 10-20 times the mean stream width but generally not exceeding 100 m. The USGS will measure reach surface area and take a stream discharge measurement (Rantz, 1982) near the downstream end of each reach. The USGS will also measure depth and velocity from 3 points along 10 transects in each reach.

UCSWCD will complete Level I Geomorphic Characterization, Level II Morphological Description, and Level III River Stability Prediction (Rosgen, 2014) for each restoration and reference site at the approximate time of each fish survey.  Data collection will include valley and stream type determination, bankfull discharge, bed morphology, stream/floodplain cross-sections, longitudinal profile, pebble count/bar sample, stream geometry, riparian vegetation assessment, flow regime, depositional features, channel blockages, channel stability ratings.  UCSWCD will also use the BANCS model framework for monitoring streambank erosion and assessing changes to Near-Bank Stress (NBS) as the restored stream equilibrates.  Together, this information will be used to determine the degree of stream (a) stability before and after treatment, (b) characterize the morphological features of the study sites, and (c) calculate trout habitat suitability indices (Raleigh et al., 1984).

This sampling approach will produce a dataset that is robust to many common pitfalls in ecological monitoring. First, the use of paired reference sites will allow for the data to be analyzed with a Before-After Control-Impact (BACI) statistical design (Smith, 2002; Stewart-Oaten et al., 1986) using linear mixed models with the nlme package (Pinheiro et al., 2017) in R (R Core Team, 2019). This approach relies heavily on the data from reference sites to separate the effects of natural variability (floods, droughts, etc.) from the effects of the stream restorations. Second, collecting three years of pre- and post-restoration data greatly reduces the chances of anomalous results (e.g. random fish movement) confounding the assessment of restoration effects. Finally, targeting 6-8 restoration sites increases the statistical power of the study and provides greater opportunity to identify habitat, geomorphic, or project design differences that drive fish response.


Baldigo, B.P., Ernst, A.G., Warren, D.R., Miller, S.J., 2010. Variable responses of fish assemblages, habitat, and stability to natural-channel-design restoration in Catskill Mountain streams. Trans. Am. Fish. Soc. 139, 449-467.

Baldigo, B.P., George, S.D., Keller, W.T., 2015. Fish assemblages in the Upper Esopus Creek, NY: Current status, variability, and controlling factors. Northeast. Nat. 22, 345-371.

Bash, J.S., Ryan, C.M., 2002. Stream restoration and enhancement projects: is anyone monitoring? Environ. Manage. 29, 877-885.

Bernhardt, E.S., Palmer, M.A., Allan, J.D., Alexander, G., Barnas, K., Brooks, S., Carr, J.W., Clayton, S., Dahm, C.N., Follstad-Shah, J.F., Galat, D.L., Gloss, S.G., Goodwin, P., Hart, D.D., Hassett, B., Jenkinson, R., Katz, S., Kondolf, G.M., Lake, P.S., Lave, R., Meyer, J.L., O'Donnell, T.K., Pagano, L., Powell, B., Sudduth, E., 2005. Synthesizing U.S. river restoration efforts. Science 308, 636-637.

Pinheiro, J., Bates, D., DebRoy, S., Sarkar, D., R Core Team, 2017. nlme: Linear and Nonlinear Mixed Effects Models. R package version 3.1-131 ed

R Core Team, 2019. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria

Raleigh, R.F., Hickman, T., Solomon, R.C., Nelson, P.C., 1984. Habitat suitability information: rainbow trout. U.S. Fish and Wildlife Service, Washington, D.C., p. 64.

Rantz, S.E., 1982. Measurement and computation of streamflow--v. 1, Measurement of stage and discharge. U.S. Geological Survey, Reston, Virginia

Roni, P., Åberg, U., Weber, C., 2018. A review of approaches for monitoring the effectiveness of regional river habitat restoration programs. N. Am. J. Fish. Manage. 38, 1170-1186.

Roni, P., Quimby, E., 2005. Monitoring stream and watershed restoration. CABI.

Rosgen, D.L., 1994. A classification of natural rivers. Catena 22, 169-199.

Rosgen, D.L., 2014. River Stability Field Guide, 2nd ed. Wildlands Hydrology Books, Fort Collins, Colorado.

Smith, E.P., 2002. BACI design. Encyclopedia of environmetrics 1, 141-148.

Stewart-Oaten, A., Murdoch, W.W., Parker, K.R., 1986. Environmental-impact assessment - pseudoreplication in time. Ecology 67, 929-940.

Project Location by County

Catskill Region: Delaware County, NY, Greene County, NY, Schoharie County, NY, Sullivan County, NY, Ulster County, NY