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Macro Invertebrate Sampling Program

As we work to restore the health of the Big Wood River, it is critical to look at the overall system health - from top to bottom - to design restoration projects that can have the greatest impact on creating a healthy Big Wood River. As our community has learned, the Big Wood River is not the river it once was - the fishery began deteriorating when settlers first moved into the area, and has continued to suffer to this day.   In fact, the river is in a number of violations with the Idaho Department of Environmental Quality, further proving the overall degradation of the watershed.  

The Wood River Land Trust is working to address these issues, and the first step in addressing any problem is to better understand it!

During the winter of 2022, we launched a key program that will give us the ability to measure the health of the river without resorting to costly water quality monitoring. This new key tool in our arsenal is our macroinvertebrate sampling program.  This program will allow us to monitor trends of the health of the Big Wood River over time. 


Aquatic macroinvertebrates are small animals that live in water, are big enough to see with the naked eye, and have no backbone. These animals include many types of insects as well as other animals such as worms, mollusks, and crustaceans. Most aquatic macroinvertebrates make their homes in rocks, leaves, and the sediment of streambeds. 

Using macroinvertebrates offers certain advantages for monitoring such as their ubiquitous nature,  a spectrum of environmental responses, longer life cycles, easy sampling methods, and suitability of certain bugs for experimental studies of pollution effects. 

Because of this, monitoring aquatic macroinvertebrates has become the standard method for government agencies, scientists, and organizations like the Wood River Land Trust to keep track of trends in aquatic ecosystem health.


When the Land Trust launched our first macroinvertebrate survey, we chose sample sites where previous survey work had been done by the USGS in 2014.  While our monitoring differed from the work done by the USGS, there were enough similarities that we will be able to compare our work with the baseline USGS data.  

It is important for us to align with this USGS data because that is the only known macroinvertebrate survey that has been done in the Big Wood watershed.


Five samples are taken at each site, using a “stratified sampling design”.  This means that we choose sample sites that are as similar as possible, aside from the variable we’re testing for.  In our testing, we want to test the different effects of stream velocity, so we make sure other variables (water depth, bed surface) are the same across sample sites.

This allows us to analyze the effects of stream velocity - as velocity is a driver for much of the variation in macroinvertebrate communities.


The results will allow WLRT staff to conduct an analysis, producing summary statistics and trend reports for the season. To an extent, these summary statistics can be compared to the 2014 USGS data, and will provide a baseline for our annual trend monitoring program.

These bugs are important because they are an integral part of the food chain. They provide food for fish and other aquatic organisms. Many of them are also key indicator species. They can tell us about the quality of the water where they are found. Bugs that have a low tolerance to pollution tell us that the water they are found in is relatively healthy. If we do not find these bugs, then it could possibly be due to some sort of pollutant or other impairment to the water body. 

These trends, along with other data,will provide science based characterizations on how the watershed is faring and whether or not our streams are meeting water quality standards.


If you’d like to continue to see these and other critical science based techniques used on the Big Wood River, get involved today!  Send a donation in, or sign up to volunteer to help out when we begin surveying in late February/early March.

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