Biological assessment of western USA sandy bottom rivers based on modeling historical and current fish and macroinvertebrate data
Hughes, R., M. Zeigler, S. Stringer, G. Linam, J. Flotemersch, B. Jessup, S. Joseph, G. Jacobi, L. Guevara, R. Cook, P. Bradley, AND K. Barrios. Biological assessment of western USA sandy bottom rivers based on modeling historical and current fish and macroinvertebrate data. River Research and Applications. John Wiley & Sons Incorporated, New York, NY, 38(4):639-656, (2022). https://doi.org/10.1002/rra.3929
While NMED Surface Water Quality Bureau (SWQB) has been able to develop quantitative nutrient and sediment thresholds for implementation of narrative criteria in wadeable streams, no assessment procedures have been developed for non-wadeable rivers. The highly altered nature of these waterbodies in New Mexico and the lack of adequate datasets resulted in a lower prioritization for threshold development plans. Therefore, these systems, which are the water sources for much of the population in the state, have gone unassessed for nutrients and sediment. Their characteristics have been so greatly altered by dams, diversions, and channel alterations that traditional means of developing thresholds such as reference condition and stressor response analysis are not applicable. This project used existing chemical, physical and biological data, and regional expertise from multiple sources to develop a BCG for the middle Rio Grande, i.e., Cochiti to Caballo Reservoirs. The Middle Rio Grande is the highest priority since the Rio Grande Silvery Minnow Recovery Plan focuses on this reach and Albuquerque, New Mexico’s largest city, and many water users are located there. The BCG will be used to develop quantitative thresholds for implementation of existing criteria which will improve the state’s ability to sustain, restore, and preserve river resources.
Biological monitoring is important for assessing the ecological condition of surface waters. However, there are challenges in determining what constitutes reference conditions, what assemblages should be used as indicators, and how assemblage data should be converted into quantitative indicator scores. In this study, we developed and applied biological condition gradient (BCG) modeling to fish and macroinvertebrate data previously collected from large, sandy bottom southwestern USA rivers. Such rivers are particularly vulnerable to altered flow regimes resulting from dams, water withdrawals and climate change. We found that sensitive ubiquitous taxa for both fish and macroinvertebrates had been replaced by more tolerant taxa, but that the condition assessment ratings based on fish and macroinvertebrate assemblages differed. We conclude that the BCG models based on both macroinvertebrate and fish assemblage condition were useful for classifying the condition of southwestern USA sandy bottom rivers. However, our fish BCG model was slightly more sensitive than the macroinvertebrate model to anthropogenic disturbance, presumably because we had historical fish data, and because fish may be more sensitive to dams and altered flow regimes than are macroinvertebrates.