In which we electrocute fish

One of the benefits to being a wildlife intern is that I get to handle animals.  Usually it’s limited to the arthropods and herps I find out in the field, but sometimes it’s even more exciting.  Most recently, Michelle and I were sent out to check on fish populations on Forest Service and BLM land.  There’s a decently sized stream that runs through both FS and BLM land which has a number of indigenous species (Lepidomeda alicia, Rhinichthys osculus, and Catostomus platyrhynchus) as well as the accurséd Salmo trutta.

As an aside, I need to say that the BLM riparian vegetation was in infinitely better shape than the FS parcel thanks to more responsible grazing methods.   Just sayin’.

<i>Lepidomeda alicia</i>, leathersides, are not for eating.

Lepidomeda alicia, leathersides, are not for eating.

As I expected, in order to estimate the number of fish in a stream it’s necessary to capture them.  What I wasn’t prepared for was the equipment: a forty-plus pound backpack full of electronics and a very large 24 volt battery.  It turns out that the preferred methodology for catching fish is to use this Ghostbusters cast-off to run an electrical current through the water.  The field wreaks temporary havoc with their little nervous systems which causes them to drift aimlessly into our waiting nets.

We were warned beforehand that there’s usually low mortality with this technique, but not non-zero.  Larger fish have greater surface area and therefore take a harder hit from the current and have a tendency to die.  The current was actually very mild; I unthinkingly shoved my hand in the water to grab a fish while the stunner was running and only spasmed slightly. I’m marginally larger than even a brown trout, so I think that it’s fair to say that it wasn’t a horrible experience for them especially given that we didn’t lose a single fish.

Our field office doesn’t have waders large enough for me, so I didn’t get to wield the stunner.  Instead, I was given an even better job which I know sounds crazy—what could be better than electrocuting fish—but it’s true.  I was take-the-fish-out-of-the-net-to-put-in-the-bucket guy.  That means that I got to handle the fish directly and admire them and their nematode parasites.

Michelle proudly holds the <i>Salmo trutta</i>, brown trout, I accidentally dropped.  Repeatedly.

Michelle proudly holds the Salmo trutta, brown trout, I accidentally dropped. Repeatedly.

Now, prior to this field excursion, I had appreciated fish as theoretically pleasant creatures.  Now I desperately want to take ichthyology courses so I can handle more of them.  I can’t begin to describe what fantastic and beautiful pieces of engineering these things are.  For example, the Salmo trutta (May their tribe decrease!) secrete mucus which makes handling them, or presumably eating them, much more difficult.  I personally dropped the same brown trout at least five times while trying to pose for a photo. Michelle got a better picture with it just because I had stunned it already. I was also sort of secretly hoping that one of the larger fish might spontaneously die so that I could dismantle it but that in no way changed how I treated them.

We swept each stretch of creek twice: the first time was to catch as many fish as possible so that the second sweep would yield no more than 40% of the first catch. By doing so, we made the statistical witchcraft that estimates the total population more accurate. It meant a lot of work though. We caught several hundred on the first pass at one site. Luckily, doing a proper job the first pass makes the second a breeze.

The data that we gathered was some of the first for this particular system, so more will be gathered in the next few years as the monitoring continues. There’s some talk of (Euphemism alert!) “removing” the brown trout seeing as they’re an unwelcome species from Europe imported for sport fishing. The hope is to introduce trout endemic to Utah and restore the stream to its former native glory. Until then, most of the focus is on adjusting grazing schedules to repair the riparian communities along the banks. Having seen photos of what this stream looked like a few years ago, I’m proud of my field office’s handling of the situation.

Nelson Stauffer, BLM Cedar City Field Office, Over and out.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.