Effect of Flooding from Tropical Storm Irene on Fish Assemblages in the Upper Esopus Creek Basin

Background

The Upper Esopus Creek, a popular trout-fishing and recreational stream in the heart of the Catskill Mountains, received historic flooding from Tropical Storm Irene on August 28, 2011. Streamflows approached or surpassed the 1% annual exceedance probability (>100 year) flood levels at several USGS streamgages in this basin. Short-term flood impacts on biological assemblages have been assessed in several studies, but longer-term effects, recovery, and analysis of factors affecting ecosystem resiliency have rarely been investigated.

The U. S. Geological Survey (USGS), New York City Department of Environmental Protection (NYCDEP), and Cornell Cooperative Extension of Ulster County (CCEUC) collaborated on a study of fish communities at 18 sites from 2009-2011 (prior to the flood). The pre-flood data at these sites provided an opportunity to quantify the impacts of Irene on stream fish assemblages and to assess if the degree of biological impact was correlated with the magnitude of the flood.

Objectives

The main objective of this study is to increase our understanding of the response (short- and long-term impacts) and recovery of fish assemblages to extreme hydrologic events. More specific goals are to document the impacts, recovery, and apparent resilience of brown and rainbow trout populations and entire fish communities in the Upper Esopus Creek basin.

Approach

Additional funding by CCEUC, New York State Energy Researchand Development Authority (NYSERDA) and the USGS allowed for resampling fish assemblages at 9 of the original sites during both 2012 and 2013. Data was complied, verified, and analyzed to test hypotheses that the floods would cause:

• decreases in density and biomass of fish communities,
• shifts in community structure, and
• more severe impacts on species of small fish and early life stages of large species, especially young-of-the-year trout.

Results

Analyses conducted to date indicate that:

• the fish communities across the basin were minimally affected by the flooding.
• fish assemblages at individual sites responded differently, and
• the impact and recovery of brown, and rainbow trout populations differed,
• brown trout had an enormous 2012 year class following the flood and population age structure shifted toward   younger (age 0+ and 1+) fish,
• rainbow trout populations, already declining from 2009-2011, continued to decline in 2012 and 2013

Conclusions

• local fish communities are fairly resilient to extreme hydrologic disturbance,
• individual species and sites were affected to different degrees by the flooding
• the sampling interval was critical to correct interpretation of species and community impacts
• the increase in some fish community metrics during the post flood years (2012, 2013) may be attributed more to the poor pre-flood (2011) condition of the fish community than to direct effects of the flood, and
• continued surveys at these 9 sites will help assess and interpret longer-term impacts and recovery from extreme hydrologic events

Publications

George, S.D., Baldigo, B.P., Smith, A.J. and Robinson, G.R. (2015). Effects of an Extreme Flood on Aquatic Biota in a Catskill Mountain River. Summary report #15-08. Prepared for New York State Energy Research and Development Authority.

George, S. D., Baldigo, B. P., Smith, A. J. and Robinson, G. R. (2015), Effects of extreme floods on trout populations and fish communities in a Catskill Mountain river. Freshwater Biology. doi: 10.1111/fwb.12577

Smith, A.J., Baldigo, B.P., Duffty, B.T., George, S.D., Dresser B., (2019), Resilience of benthic macroinvertebrates to extreme floods in a Catskill Mountain river, New York, USA: Implications for water quality monitoring and assessment, Ecological Indicators, v 104, p.107-115. https://pubs.er.usgs.gov/publication/70203340

Project
Location by County

Greene County, NY, Ulster County, NY,  Delaware County, NY