71.6 on your radio dial–All Flatheads All the Time!

Southeast Nebraska fisheries biologists have been doing some extra sampling and work with flathead catfish in Branched Oak Reservoir for the past several years.  Please take some time to review a couple of previous blog posts about that work, http://outdoornebraska.ne.gov/blogs/2010/08/flathead-tagging/ , http://outdoornebraska.ne.gov/blogs/2011/07/field-work/ .  This year that has been taken to a whole ‘nother level.

As I have blogged before, flathead catfish in Branched Oak Reservoir have been collected and tagged over the past couple, three years.  That work is being done to learn some things about the habitats those flatheads are using, their movements, and potential angler impacts.  In reality, pointy-headed fisheries biologists do not know a whole lot about flathead catfish in reservoirs.  We are learning more all the time at Branched Oak!

To kick that knowledge up another notch, our fisheries biologists started putting radio transmitters on flathead catfish recently.  I got to go along and help capture the first of those fish to get radio transmitters so I have some pictures to show and stories to tell.

Before I do that, I must back up and tell you that actually this is not the first time radio transmitters have been placed in Branched Oak flathead catfish.  Our Nebraska Game & Parks Commission fisheries biologists tried implanting transmitters into Branched Oak flatheads last year.  Those initial attempts were made by capturing the flatheads and then surgically implanting the transmitters inside the body cavity of those fish.  Let me tell you what we learned from that–”it don’t work”!  Those transmitters were surgically implanted inside the fish, and we discovered that within a matter of days the flatheads would somehow expel the transmitters from their body!  Do not ask me how, I did not watch them do it, and it makes no sense at all, but somehow the flatheads that had transmitters implanted inside them last year managed to reject those transmitters out of their bodies!  All I know can be summed up in that line from the movie Jurassic Park, “Life finds a way”.  I do not know how a flathead catfish could expel a radio transmitter from its body cavity, but somehow they did it, and apparently did it with ease as it took very little time.

This year we had a different plan.  First of all, let me show you a livewell full of flatheads captured after less than 20 minutes of electrofishing.

That livewell has about as many flatheads in it as can be held for a short period of time.  When that many fish are captured, we have to turn off the electricity and start working on the fish.  You can see that we capture all sizes of flatheads with the electrofishing boat, everything from 4 inchers up to over 40 pounds.  The radio transmitters are being placed on a variety of sizes of fish, from 12 inches up to over 40 pounds.

Here is a picture of the radio transmitter on a work glove to give you an idea of the size of the transmitter.

Here is another view of the back side.

You can see that there are small transmitters and a battery sealed inside an epoxy/plastic sleeve.  There is an antennae that trails from the transmitter, and stainless steel surgical wires used to attach the transmitter to the fish.  The batteries/transmitters are activated just before being placed on the fish.  If I remember right, the battery life is guaranteed for 75 days, but may last for as long as twice that much.

You already know that those transmitters would not stay inside the fish after being surgically placed there, so this year there was a new plan.  The transmitters are being placed externally on the fish, wired to the fish in the same way the plastic tags have been wired to Branched Oak flatheads in previous years.  That is done by running parallel hypodermic needles through the fish, something that is not easy to do on a large flathead.

Then the wire attached to the tags is threaded up the hypodermic needles and through the fish.  Once the needles are extracted the wire can twisted off on the opposite side.

Here is another shot of the process, it takes at least a couple of guys to handle fish; when one of those big fish decides to flop or squirm someone easily can be impaled by a hypodermic needle.  To my knowledge, no fish biologists have had tags or radio transmitters attached to them, yet.

Here is what the radio transmitter looks like, along the side of the fish, when it is all done.

Additional red dangler tags were placed near the adipose fin of the flatheads that received radio transmitters.  If they should manage to lose a radio transmitter, the red tag will tell us that they had a transmitter, and if an angler catches one of the radio-tagged fish it can be identified by the number on the red tag.

Yes, the radio transmitters will dangle along the side of the fish with the antennae trailing behind.  Similar external transmitter placement has been used for other species of fish, has worked well, and we do not expect the flatheads to have any discomfort or behavior modification with these radio transmitters attached.

Each transmitter “broadcasts” on its own frequency.  The transmitter sends out a “ping” every few seconds.  Here is what the radio receiver looks like.

Pointy-headed fish biologists will be able to cruise around Branched Oak using a receiver “wand” in various configurations to pinpoint the location of each transmittered fish.

By manipulating the direction of the receiver wand a person can determine the direction the signal from a particular tag is coming from.  A boat can be maneuvered, following the signal, until it is determined to be over the fish or very close to the fish.  As I am writing this, there already have been at least a couple of successful “trackings” of transmittered fish.  It appears that the distance the transmissions can be detected depends on a number of factors including weather, water conditions, and even boat traffic.  Signals can be detected at a distance of up to a couple hundred yards.

Why do all of this?  There are a couple of reasons for doing the radio-tagging of Branched Oak flatheads.  First of all, the position of radio-tagged fish will be determined on average a couple of times per week, during different periods of the day and night to determine habitat use.  At this point I am not aware of any plans to follow any individual fish for a period of hours to determine movement patterns.  That would take more man-hours of work time and by determining a position at a point in time we will learn about habitat use and have some ideas about movement patterns.  In addition, to evaluate the efficiency of our electrofishing gear, attempts will be made periodically to recapture some of the radio-tagged fish.

On the day I got to go along to help, we had a goal of putting transmitters on 18 flatheads.  Our goal was to place radio transmitters on 3 fish in each of six different size groups from 12 inches up to as large as we could capture.  We had some good “fishing” on the day I went along and placed transmitters on all 18 flatheads we wanted to in a little over half a day on the water.  I have not talked to the field crews recently, but believe they were going to try to place transmitters on another dozen fish.  More fish will be transmittered later so that we can have active transmitters out there through the next several months.  There will not be a bunch of flatheads in Branched Oak with radio transmitters, far less than the numbers that have already been tagged, but I imagine at some point some angler is going to catch a Branched Oak flathead with a radio tag.  If you do, please leave the radio tag on the fish; look for the red dangler tag near the adipose fin and record that tag number for us, and then release the fish as soon as possible with all of its tags still attached.

Here is what one of the biggest fish looked like right before being released.

Let me finish by sharing some opinions and observations before I quit rambling. . . .

A fellow fisheries biologist and I were talking the other day about the world-class channel catfish fishery up on the Red River near Winnipeg, Canada.  Many anglers know about that fishery and dream of fishing it.  Simply put, they have something special up there largely because of special regulations that allow very limited harvest of those big channel cats.  Lots of Americans travel up there just because it is likely the best trophy channel catfish fishery on the continent.  You can say I am crawling way out on my home-state Nebraska branch again, but I believe we have developed something very similar for flathead catfish at Branched Oak Reservoir!  Admittedly, the total catch & release regulation for flathead catfish, and wipers, at Branched Oak was implemented because we need every predator we can get in there eating white perch.  That may have been the intent, but I can tell you the result has been an exceptional flathead catfish fishery, as good if not better than any in the country.  There are lots of flatheads in Branched Oak, they are reproducing on their own, and that population has fish from a few inches in size all the way up to over 50 pounds.  There are lots of waters where folks can catch flathead catfish, and catch some big flathead catfish, but I will bet few, if any of them, especially reservoirs, rival Branched Oak for the numbers of flatheads including lots of trophy fish.  What we have there is something special, in its own right just as special as the channel catfish fishery on the Red River up north.  Maybe all of this extra work being done with the Branched Oak flatheads will give us an even greater appreciation of what we have there?  I hope so.

Lastly, I know some of you hard-core flathead anglers are dying to know where we find all of those flatheads in Branched Oak.  If you look closely at the photos I posted you will get some clues; we work the fish and release them near where they were captured.  I have to show you one other photo, take a close look at this area. . . .

Before we turned off the electricity and started working on fish, just before I snapped this picture, you would not believe the number of flatheads, including big flatheads, that were boiling the water in the area shown.  There were dozens of them, the water was alive with flatheads.  If you wanted a secret from a pointy-headed fish biologist, there you go, the fish are in there if you can only get them out!

I gotta go now, I am sitting here watching realtime locational data beamed by satellite from Branched Oak flatheads directly to my computer.  Fish #DD71.6, a fat 45-incher, is getting active, cruising towards one of my favorite Branched Oak fishing spots.  If I leave now, I will be able to get there and have my line in the water just about the time she starts feeding!  FISH ON!

(Just kidding, the technology we are using is not that advanced, I have to go out there and put in my time just like everyone else)