Tag Archives: population analysis

Horizontal Water Sampling

01/09/2016 Eric Hanson Leave a comment

This sampling technique is great for surveying various depths in a body of water. You lower the opened horizontal cylinder down into the water at the depth you want to sample and let loose a weight. The weight travels down the string that hits a switch which closes the ends (through a rubber elastic band). This technique is great for giving you a representative sample at a specific depth. The design of the contraption is pretty much always similar to these.

While I was studying the life history of the Mohave Tui Chub in California, we used this technique to survey the zooplankton distribution in Lake Tuende and MC Spring.

Lake Tuende at the Desert Studies Center

Skills

Four Square Mile Survey

01/08/2016 Eric Hanson Leave a comment

For the three summer TERM employment opportunities I had with the USFWS, I participated in the four-square-mile breeding waterfowl survey (FSM). These are incredibly fun surveys to do, and I hope to be able to do more of them in the future. I got to canoe down a water basin with a partner and identify wetland birds and waterfowl as we paddled down a lazy stream. I even got to do it from an air boat at the Arrowwood NWR one time. That was a difficult one as the birds were scared up by the boat and started circling the body of water.

I also was able to participate in some rocket netting in North Dakota on a wildlife preserve. It was quite fun, and we didn’t decapitate too many individuals. Many of the birds got banded, but a lot just had to be tallied and let go.

The FSM survey entails recording pairs of breeding pairs of waterfowl or wetland birds and whether or not they are hatch year, or after hatch year (determined by plumage) in a four square mile area. See some images below on what a typical wetland looks like in North Dakota and South Dakota.

ducks — Shovler top right, green wing teal left

Several waterfowl on a wetland in the prairie pothole region — A typical scene for counting breeding pairs of waterfowl on a wetland in the prairie pothole region

Skills

Electroshock Fishing

01/06/2016 Eric Hanson Leave a comment

Electroshock fishing is a fine art. Turn up the power too much and the muscles contract so hard you kill the fish, but not enough power and it doesn’t do anything. While I was attending Minnesota State University: Moorhead (MSUM), we used a backpack electroshock fishing setup to collect fish samples throughout some of the close by lakes.

Enjoy this wikipedia article on electrofishing. Also, this youtube video.

Skills

Fish Mark and Recapture

01/05/2016 Eric Hanson Leave a comment

When working with a post doc student from North Dakota State University, we studied the life history of the endangered Mohave Tui Chub, we conducted several mark and recapture studies to determine the population on several bodies of water. The two main ponds we focused on were, Lake Tuende and MC Spring on the grounds of the Desert Studies Center at Zzyzx, CA.

mtc — A very large example of the Mohave Tui Chub

We clipped the right pectoral fin on all of the fish we caught in our minnow traps one day, and repeat the experiment the next day to see how many individuals we recaptured. To determine what the population is, you multiply the number of individuals marked the first day by the number of animals captured on the second visit divided by the number of marked animals captured the second day (See wikipedia article for math notation).

Learning Through Life