Tuesday, January 04, 2011

Silver Creek Intern's Report, Part 2

This is the second part of Silver Creek Preserve intern Dominique Lucio's report on his summer at the preserve. Today, he explains ecological monitoring, including electro-shocking fish.

The majority of the work I helped with this summer falls under the category of monitoring. The first type of monitoring was the Preserve’s bi-monthly transect water monitoring. This full-day job consists of visiting five points on the Preserve, two in the main current, and three in tributary creeks just before they meet Silver Creek.

At each point channel width and flow readings are taken. In addition to flow measurements, we took water temperature, and dissolved oxygen and pH levels. It was truly amazing watching the water levels rise and flow speeds increase as the spring turned to summer, especially since Silver Creek is entirely spring fed.

This means there is no snow melt to raise water levels; instead aquatic vegetation grows so dense and high that it literally pushes the water up and out. This plant life is also partially responsible for the booming fish population, since the trout feed primarily on insects that hatch in droves from the vegetation all spring and rise to the surface to mate, after which they fall into waiting mouths.

I also was introduced to temperature logger collection, downloading, and replacement. Essentially a small plastic device records temperature every few hours while submerged. On a monthly basis, I would collect these loggers, download the data they had collected to the Preserve’s computer, restart them, and place them back in the stream.

This data gives not only a sense of temperature change with the seasons, but also on a larger time scale, showing yearly trends and fluctuations. These loggers are also useful in showing whether or not projects such as water cooling through streamside willow planting are truly effective.

This summer a local group known as Idaho Water Engineering (IWE) began a project to map the entire aquifer system for the area in order to revise water rights as debate rises between groups with agricultural, residential, and conservation interests. I was able to help install anchor stations for their monitors on and off the Preserve. In my last two weeks on the Preserve, I was lucky to help a graduate student from Denmark check these stations and install a few more of her own. I also helped Maria gather several more transects to better understand the exchange between tributaries and Silver Creek itself.

The next type of monitoring was by far my favorite: electroshocking. When I first heard the term, I admit I pictured sticking electrified probes in the stream and counting the fish that floated up unconscious, but realistically I knew The Nature Conservancy would not allow anything of the sort.

Nonetheless, my expectations weren’t too far off. Daytime shocking took place in sections where the water was shallow enough to walk through. It consisted of several people with nets walking alongside a Fish and Wildlife Service (FWS) raft that carried a generator which sent a current between chains it dragged and probes two FWS interns kept underwater ahead of the raft.

Fish are naturally drawn to the current they can feel in the water, and when they enter the current between the probes and the chain, they briefly stop swimming. It is in these few short seconds that we would scoop up the fish and drop them in large collection bins to be counted. This collection gives the Preserve and the FWS the best estimate of overall fish populations in the stream.

I was also able to help another intern map local stream sediment and vegetation types and levels. Because there is no springtime snowmelt to wash sediments downstream, silt and vegetation can build up, slowing the water’s flow, and in turn warming the stream.

Since Silver Creek’s trout prefer the constant cold temperatures of the spring fed system, increasing temperature can be a serious threat since it allows better suited brown trout to take over rainbow trout habitat.

For the entire month of June, Matt spent each day measuring bank vegetation type, stream width, depth, sediment depth, and sediment type. I was happy to help by heading out across the valley following creeks and measuring preset GPS points. This monitoring allowed me some of the best time to explore the region and its plethora of beautiful and complex habitats. Some days the deep water and sticky mud turned out to be quite adventurous as well.

Tomorrow: Read the final installment of Dominique's report.

Photo: Brown trout measured during electro-shocking surveys, by Matt Miller.

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