I got out of the office last week to “help” on a couple of different projects. I told you about one of those projects already, http://barbsandbacklashes.wordpress.com/2010/08/25/rotenone-renovation/ , now let me tell you about the other.
We have 5 fisheries regional offices around the state. Each one of those regions has at least two fisheries biologists responsible for fisheries management in their region. One of the regional offices is here in Lincoln and covers the southeast part of the state. I went on a “ride along” with some of those biologists last week on a little project they are doing which I know will be of great interest to many of you. They are tagging flathead catfish at Branched Oak Reservoir. Their goals in that tagging project are to document the habitat use and movement of flathead catfish in Branched Oak Reservoir, estimate the actual numbers of flatheads in Branched Oak, verify flathead catfish growth rates, and perhaps get some idea of angler catch of flatheads.
So one morning last week I went out with the guys to collect some Branched Oak flathheads. Let me tell you the story.
Fisheries biologists use different types of gear to collect different species of fish. Electro-fishing is an extremely effective way to collect flathead catfish. We use electrofishing boats that are built specifically for “shocking” fish. I will not give you all the details, but there is a particular electrofishing setting that brings up flathead catfish and almost no other fish.
We capture flatheads with an electrofishing boat by slowly motoring in areas likely to be holding fish. There is a generator underneath the boat driver’s seat that produces the electricity. That electricity is conducted into the water through electrodes which hang off the front of the boat.
Fish are actually attracted towards the electrodes, so when a flathead is “shocked” it comes towards the surface where it can be dipped from the water.
The flathead electrofishing at Branched Oak is being conducted in specific areas or stations that are defined by GPS coordinates. Each one of those stations represents a different habitat type.
Once the fish are dipped they are placed in a livewell on board the boat. They recover immediately after being taken out of the electrical field.
Once the fish are captured it is time for data collection and tagging.
I have blogged before about aging fish using scales or bony structures, http://barbsandbacklashes.wordpress.com/2010/04/08/how-old/ . Catfish obviously have no scales, so our only option to determine the age of catfish is to collect a bony structure. We take one of the pectoral spines to age catfish. Those spines are later sectioned in the lab and then viewed with magnification to determine age.
Once all of the data was collected it was time to tag the fish. The tags we most often use are called disk dangler tags. They are attached to the fish using stainless steel wire. Those tags are very likely to be retained for an extended length of time and they cause little or no discomfort to the fish. The fish are tagged by using a couple of parallel hypodermic needles.
Once the needles have been pushed through the fish, then the wires of the tag are threaded into the needles and through the fish.
And then they were done with the fish, back in the water they went.
Here are a couple of close looks so you can see exactly what the tags look like.
Now let me comment on a couple of things. First of all, all flathead catfish caught at Branched Oak must be immediately released; there is no harvest of flathead catfish allowed. If you catch a tagged flathead at Branched Oak you cannot keep the fish and since they have to be released, we would like them to retain their tags. So . . . if you catch a tagged flathead, note the time, date, location and size of the fish; write down the tag number and then leave the tag in the fish and release them! You can send the recapture information to the address on the tag or of course you can let me know! I will make sure the biologists working on this project get the information. Include your name and address and they will send you a letter with some information on the fish when it was originally tagged.
On the morning I went along, we collected 40-some flatheads from six different sampling stations. We did not capture any real large flatheads from Branched Oak that morning; we had several 30-32-inch fish, but those were about as large as we caught. They have captured some flatheads A LOT larger than what we caught on previous days of sampling; there are some HUGE flatheads present in Branched Oak (fish like this, http://barbsandbacklashes.wordpress.com/2009/10/07/fall-fishing/ ). We collected flatheads of all sizes up to 32 inches on the morning I was present. I have to tell you I love flathead catfish; some may think they are ugly, but in my opinion they are beautiful fish. In fact the small ones often are the prettiest.
Another reason I love flatheads is they are the biggest, baddest, top-of-the-food-chain, apex predators in many of our waters. If you think muskies are big bad predators, well let me tell you, flatheads would eat muskies! Please do not tell those little flatheads that I was calling them “cute” because someday they will probably grow up to be big enough to kick my butt!
Fish will often “puke” up their last meal when they are tossed into a livewell. Our flatheads puked up a few white perch.
There are a variety of fish that Branched Oak flatheads will eat; common carp, gizzard shad, sunfish, crappies, white perch and others. Yes, they will eat other sport fish, they are apex predators and they will eat just about anything smaller than themselves. Most of the time they likely eat whatever is most abundant. Obviously they are eating some white perch and Lord knows they can have all of them they want; common carp and gizzard shad too!
Crayfish are very important prey for small flatheads and I noticed this on one of the measuring boards used for the smaller flatheads.
Once they grow larger, flathead shift to preying on other fish, live fish.
This is just one example of what our fisheries staff is doing to make fishing better around the state. We have installed several different types of artificial habitat structures at Branched Oak and part of this project will help us evaluate habitat use by flathead catfish. I will not tell you any results now, because there are none, but I will tell you we shocked a lot of flathead catfish from both rocky habitats and woody habitats (and that would be no surprise to anyone who has spent any time pursuing flathead catfish in any environment). What is learned from this project will increase our knowledge of the Branched Oak flathead catfish population and that will help us be more responsible managers of that resource. In the process, I am sure we will learn a few things that will be very useful to anglers as well, myself included! I will keep you posted.