A team of scientists conducted research on the Malheur River from 2006 to 2007 to assess ecological conditions, major environmental stresses, and human disturbances. The purpose of the study was to examine the fish population within the river to determine their health. Fish populations are often used as indicators of the health of rivers. Understanding the condition of fish populations in a given river can help managers make decisions regarding fisheries. The scientists used an established scale of biological integrity to give a score to each site sampled. The team then compared this score to historical data for fish at that site to gain an understanding of how the population had changed over time.

The scientists found many changes in the population. For example, the team caught two species of native fish that were previously not known to inhabit the Malheur River. In addition, one species thought to exist there was absent, and several non-native species were present. Water quality had declined, and chemical presence had increased. These changes were likely due to agricultural runoff into the river. Overall, the project confirmed that the techniques used in this study could be used for long-term monitoring of fish populations, both in the Malheur River and other rivers in Oregon. The researchers suggest that these monitoring projects could help states quickly evaluate and respond to negative changes in fish populations.

Source

Henry R. LaVigne, Robert M. Hughes, and Alan T. Herlihy. Bioassessments to Detect Changes in Pacific Northwest River Fish Assemblages: A Malheur River Case Study.2008. Northwest Science, Vol. 82, No. 4.