Last weekend I was informed, sort of anonymously on the inter-web, that I was a fine, lazy state worker. Ironically, that came after working my seventh weekend out of the ten since the first of the year. I recalled that yesterday when I actually got out of the office to help with some field work. I do not do that often anymore, but on occasion I get to be back on the water helping one of our field biologists. The occasion yesterday was to head up to Lake Wanahoo and pull frame nets for northern pike. I remembered how lazy I was in the wind and cold, after wiping the snot and pike slime from my nose, right after we had pulled and reset the 19th of 23 frame nets. Being lazy about wore me out yesterday!
Some of you may recall that we have been tagging northern pike in Lake Wanahoo for the past three years. That is being done to help us monitor the pike population in a new, southeast Nebraska reservoir. Northern pike are called “northern” for a reason–they are very much a cool-water fish with a circumpolar distribution. Their native range may have extended as far south as northern Nebraska, but in southeast parts of our state most of our waters are simply too warm to support northern pike. We have documented summer die-offs of northern pike in southeast Nebraska simply because the water got too warm. However, the habitat provided in new reservoirs can be suitable for northern pike even in southeast Nebraska; the extra fisheries management work being done on Lake Wanahoo northern pike will help us follow that population as Lake Wanahoo ages.
I have blogged about the pike tagging at Lake Wanahoo before, but let me give a brief description of what we accomplished yesterday and what is continuing this week. As I mentioned, there were 23 frame nets set around Lake Wanahoo. Those nets are very effective capturing pike as they move into shallow water to spawn. Shallow, marshy areas with some sort of aquatic vegetation, usually cattails or other emergent vegetation, are ideal pike spawning habitats. The frame nets are set in that habitat around Lake Wanahoo and yesterday we found 79 pike waiting in the nets for us. Once each net was pulled, the pike were placed in a livewell on the boat and then each fish was measured and checked for the presence of a tag. If no tag was present, one was placed in the fish.
Here is what the livewell looked like after pulling a net:
Here is what the tagging process looks like, the tags and tagging gun are exactly like those used to put those plastic danglers in clothes at your favorite department store:
Our video guy, Ralph Wall, made a short video of the Lake Wanahoo pike tagging a couple of years ago. Here it is, the one thing I will mention about the video is that we are NOT doing any boat electrofishing to catch any of the pike–do not need to, the frame nets are very effective.
Here is what the tags look like in the pike, look close because often the tags are covered with algae and at first glance you might not see them:
Look even closer, the numbers can be hard to see (especially for far-sighted “old” guys):
If you catch a tagged northern pike at Wanahoo, all pike have to be released immediately, record the number and please leave the tag in the fish. You can report tag returns for any tagged fish anywhere in Nebraska at firstname.lastname@example.org .
One of the fun things for me is to be able to help with a project like tagging pike, and then see those fish come “full circle” and end up on the end of my line or the end of one of my fishing partner’s line, Got Another One! , It’s a Wrap .
Yesterday we collected two of the largest pike that have been caught while tagging at Lake Wanahoo. I was not able to gawk around yesterday taking photos, I was actually working, but those fish were pushing up to 37 inches. If you want to know what they looked like, they looked a lot like this:
The pike population in Lake Wanahoo is very healthy, doing very well. This graph will give you a real good idea of the numbers and sizes of pike that can be found there:
Meanwhile, On the Western Front. . . .
I must also tell you that in the past week or so, we have had field biologists and hatchery personnel from our Valentine State Fish Hatchery collecting northern pike for eggs and milt to produce pike for stocking Nebraska waters this year. Those collections occurred on the Valentine National Wildlife Refuge and the pike spawn was in full swing this past week. Our crew in a short time collected all the pike eggs we needed to meet our stocking requests this year.
Again frame nets are very effective for capturing pike in the spring:
Pike spawn right after the ice is gone; in fact in a late spring they will begin spawning under the ice. That means pike egg collections are usually done when it is cold.
Once the pike are collected, they are hauled in large hauling tanks back to the hatchery where eggs and milt can be collected in a little more comfort. Accuse us of being lazy state workers again, but we have discovered that collecting the eggs and milt in a sheltered facility has resulted in higher fertilization rates and better production of baby northern pike. After extracting eggs and milt, the pike are hauled back to the water body from which they were captured.
Let me comment on one thing in that photo: You see the probe being held in the pan and the meter that probe is attached to. I am betting that was a pH monitor, and yes, changes in pH also can make a big difference in fertilization rates.
The semen came from a bottle:
If you are still reading, I hope that last statement got your attention: “Wait a minute, the male contribution to fertilization comes from a bottle???!!!!!” Yep, that is what I said, the semen came from a bottle. Milt was carefully collected from male pike and then placed in an “extender” solution that keeps the sperm alive and well. Again fisheries biologists have discovered that we can get better fertilization by using “extended” semen. That is probably because dilution of the milt gives us better distribution of semen to fertilize all the eggs in a pan. After the milt is added, it is all carefully mixed together using the third primary feather from the right wing of a mature, male, Merriam’s turkey (another important detail for maximum fertilization, oh yes, the eggs have to be stirred in a clockwise direction).
I have to add that all of that is done in a pan that is as free of water as possible. Again, I hope that gets your attention as we are spawning fish and trying to keep everything as dry as possible! The sperm is not activated until water is added. By keeping everything as dry as possible we can get the best distribution of sperm in a pan of eggs and then when water is added, we can achieve the highest fertilization rate possible. It may not be rocket science, but it is science, fisheries science!
Eventually, the eggs are jarred up and placed on batteries where water is circulated through the jars until the eggs hatch. Once hatched most of the northern pike in Nebraska state fish hatcheries are trained to eat artificial food and then are grown to as large as 10-12 inches before they are stocked.
With fish stockings, egg collections and a variety of other activities, once the ice melts, the Fisheries Division of the Nebraska Game & Parks Commission is busy, very busy. We have hit the water running, lazy as we may be!