The Delaware and Hudson River

As part of my sampling I returned to my sites in the Delaware and Hudson River to continue sampling. As promised I took more pictures while in the Hudson River, but first the Delaware River pictures.

Good to see quite a bit more water in the stream, than when I was there last time. Area that was completely exposed had better coverage.

You might not be able to see it here, but there are two lamprey nests immediately under the breaking water.

Another area that was completely exposed before that now was almost completely covered. The rocks had no algae growing on them so they could only have been covered by the water very recently.

Other species are extremely active at this time of year. Here is a small fish that was probably hatched last month. This is probably a black-nosed dace, but not promises, my larval fish id is not that good.

Here is a male damselfly (Calopteryx sp.). These are very attractive species because their bodies are usually metallic and shiny, and the wings are often dark or dusky. These come out early in the season and lay their eggs.

Here is one videos of the damselflies going about their business. The male is the prettier darker winged animal. He stands guard over plants that females will use to lay their eggs. He will chase off or attack other males, and females that have not bred with him. Males can be very aggressive they will actually grab and tear at the wings of the other individuals they don't want around.

The other video is too large for posting here so I have linked it from Youtube. Head over to here to watch it.

There you will watch the male guard over the female while she lays eggs. The eggs are laid by sawing into the plant and then depositing one egg at a time. The Oxygen the plant consumes will be stolen by the developing insect to help it grow. Once it is large enough it will hatch and head off into the world.

And what is this?! Could it be? A dead adult sea lamprey immediately next to where I sample. The spawning was complete and so any adults are either dead or dying. Now the adult bodies will drift downstream and contribute Phosphorus and Nitrogen as they decay.

Here is a close up of the lamprey, its journey is over. This animal was probably laid as an egg ~10 years, so let us say 2005. After its first year of life it weighed ~0.15g, and when it died it probably weighed close to 700g, and before it began its migration it easily could have weighed over 1000g.

I left the Delaware River and headed to the Hudson River again as planned. The weather was very warm (90F) and the sky was clear.

I worked under a bridge for the day, collecting, marking, and releasing ammocoetes.

Here is a picture of one of the sampling areas I work in.

Although eels should be common in the Delaware River I rarely see them. Here in the Hudson River they are more common. They look a lot like an ammocoete but notice the very clear eyes.

This is the same eel just with my hands for scale. I let him go shortly after this. I only collected him because he got shocked pretty good and wasn't able to move immediately so I picked him up to get him out of the current and make sure he could bury himself from predators.

This is looking upstream from where I worked. The site is in a small town park and you can see some of the playground on the right.

Almost all of this area is covered in leaves that have washed downstream, and that makes great habitat for ammocoetes. There are ammocoetes wall to wall here.

Although the water was not as high this time, it has been higher in the past. Just some of the wood that has been moved by the stream before.

That is all for now. Stay tuned for more updates.

Lecture: How do we go about understanding populations?

What do we want to know about populations of animals? How do we go about doing this? What are some models we might use? And how many fish are in my lake?

Here I introduce the topic of mark-recapture models and discuss closed population models. In future lectures I will talk about open population models.

The file is too large to post directly to this website so I have uploaded it to Youtube. You can see the video here: link.

Return to the Genesee River

I returned from my second trip this summer to the Genesee River, I only have four more left before my field work is officially done!

At this point in the year all of the adult American brook lamprey have passed along, but many of the ammocoetes are now getting to maximum size so they can undergo metamorphosis and become adults of their own. The largest ammocoete I have ever captured I captured this time (the total weight was 22.6 grams (0.80 oz for those on the English system. This does not sound like much, but keep in mind these animals may only weigh 1 g after a full year of growth, so to make it to 22 grams probably takes more than 5 years. Wait that doesn't make sense, 22 divided by 1 should be 22. Keep in mind that growth is exponential (not linear), so as an animal grows it gets easier to put on weight assuming food is around, and the rate of growth speeds up as the animal gets older.

Enough talk, let us look at some pictures.

A large dead carp (Cyprinus carpio) rotting quietly on the edge of the stream. I found another dead carp further down stream and suspect that someone fished for them a little while ago. Before you pass judgement upon wasteful fishers, I would suggest you commend this person for killing an invasive pest. Carp are not native to North America, they were brought over by Europeans who wanted a large food fish that could eat plants. Unfortunately, carp love plants, and they will consume them until they clear the bottom, while doing so they stir up mud. As a result areas with lots of carp can turn from clear water to muddy pools very quickly. Even more annoyingly they kill aquatic plants which many native species rely upon. Carp are too widespread to do much with today, but keep in mind that goldfish are closely related. Release of goldfish into the wild is very common, I should know I catch them regularly. If you have a fish that you don't want anymore, kill it and then dispose of the body, please don't release non-native fish.

The creek is starting to green up, many of these plants have grown up again since I was last here in May.

A very small lamprey ammocoete (<80 mm) just before it gets tagged.

A drift net I have been setting at night in the hopes of catching ammocoetes on the move. To date I have not yet caught any with it, but we will see if I don't catch one by the end of the summer.

 Below is a series of photos showing the steps in  marking of a lamprey.

Address the lamprey, preferably by name, also make sure to take its length and weight.

The first injection just over the gills.

Two done, two more to go.

Third one being done. Note how shallow the needle is you can still see it. I am literally just under the skin of the animal, no permanent harm and the animal is asleep so it won't even feel it.

All done, all the marks in place and the animal is ready to go back into a bucket to recover. Total time: ~1 minute.

An interesting animal I captured this time. I have now captured 1000's of animals so I have seen slight variations from wounds and birth marks in ammocoetes, but this animal appears to have a deformed tail. The tail folded back over on itself and was stuck in that format. The cartilage had already grown too stiff to unfold the tail. I suspect this animal lost the tip of its tail and it regrew incorrectly, although it is possible it has always had this deformation.

All of the green you see before me grew up in a month. Spring has sprung and we are entering summer.

A day done. The last sampling pool with all of its lampreys ready to go. Some are fully recovered others are going to take a few minutes to come all the way back around.

I will attempt to expand the reach of the blog in the future by posting lectures that deal with the theory behind the work I am doing. However, if you are not interested do not fear, I will mark them clearly so you can ignore them if you do not find them interesting.