Freshwater Fish Sampling

Big thicket, Texas Freshwater Fish Sampling



On our way to Texas we stayed at Big Thicket for two full days. Each day the class divided into two groups.  One group would do fish sampling with Dr. Willams and the others would do canoeing and plant identifying and collections with Dr. Dennhardt.  On the first day, I was in the group doing fish sampling.  We could reach three different sites to sample.  We used methods including sein nets and electro shocking.  At each site, we catalog each fish species that was captured.  We were also able to keep fish under a permit granted to us.

  • Using seins to collect fish samples.

At our first site, we needed to hike a trail about one mile surrounded by thick woody vegetation.  Since myself and others are currently in an ornithology class we were actively seeking birds.  In this area, it can prove difficult to identify birds as we were able to hear birds but rarely saw them.  As we drew closer to the stream, we begin to see curious hollow cylinder shapes of soil pushed up from the ground from 2-4 inches above ground level.   Our professor identified them as crayfish burrows.  The cray fish would dig these borrows during the winter months of the year.  They would start by digging the borrows and stack the excess soil in a shape building up from the ground.

  • A small crayfish was captured in the sein nets and released.

As we reached the stream there were steep banks surrounding it on both sides with fallen timber crossing it in multiple areas.  Putting on our waders we entered the stream, and found the water to be about waist high.  Within our group, four of us moved up stream where we found back water that was not currently connected to the main stream.  Beginning to sein we found several different fish species, including some very large tadpoles.  After leaving the back water we took samples for the main stream.  We found that we could capture more fish species in the back water then the main stream, this could be because the small fish became trapped and concentrated during a high-water event.

Using a backpack shocker to collect fish samples.

At our second location, we could use electroshocking to capture fish.  It proved difficult to use electroshocking in the brackish water.  We were required to continually increase the voltage to be effective.   This was my first time using electroshocking in the field, and I was lucky to do so.  We were able to bring a large spotted bass to the surface along with several other species.

As our day came to an end we stopped at one final location.  The stream was covered on both sides with a dense canopy of Cypress trees.  The tree’s roots would protrude from the ground forming sharp points.  Our instructor warned us that falling on one could cause injury.  At the same time, someone made the comment “this looks like a place where snake would live,” and Dr. Willams reminded us to watch for water moccasins.  As myself and others began electroshocking the other group began seining for fish.  Shortly later our sampling was ended when others across the stream were startled by not one, but two water moccasins. A student reported they stepped on one, luckily no one was hurt.  It added some excitement to our sampling efforts.

For a full day of sampling we recorded over thirty species of fish.  This was a very fun and educational day in Big Thicket and I would be happy to return someday and continue the adventure.



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