Category Archives: Radio-tracking

Movements of Wild Radiotagged Brook Trout

On May 16 we released back into Beaver Brook four radiotagged brook trout we had captured by electrofishing 2 days earlier. The adventure was chronicled in a series of three posts (Day One of Operation Brook Trout, Day Two Operation Brook Trout, Day Three of Operation Brook Trout). The radiotags used should allow us to follow them for 160 or more days. Since these fish are adults we may actually be able to observe, for the first time in Shu Swamp, spawning in the fall.

Here is a map of their movements to date (different colored pins represent locations of different trout):

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So far things are going quite well. All four tags are still attached to their respective trout – a very unlikely outcome with the hatchery-reared fish we have released (over half of fish can’t be tracked beyond 2 weeks). Furthermore, they have moved very little if at all from their original release sites, anywhere from 100 meter maximum to as little as 1 meter. All three trout have stayed very close to the location at which they were captured. In fact three of the trout were originally PIT-tagged in our March electrofishing survey and have shown remarkable fidelty to the sites of capure back then.

As a basis of comparison here are the results of radiotracking of five hatchery-reared brook trout of similar size we released last spring and summer:

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Note the increase in scale in this map. Only one of the trout (101) managed to retain its tag (or possibly die) the life of the tag. You can easily see how these fish moved a lot more. 101 moved all the way to the Beaver Lake spillway before running way back upstream and settling down.

You can access all the radiotracking maps through the Radiotracking Trout Data page.

Strolling Snapper and Muskrat Love

A few weeks ago, while radiotracking trout I ran into this guy hogging the trail. If you listen carefully you can hear every 20 seconds the chirp of  a radiotag. One of our wild trout is only a few feet away.

I cautiously got a little closer and notice these appetizing hitchhikers on the snapper’s carapace.

Three juicy leeches

Three juicy leeches

At least I assume they are just along for the ride. It’s hard to believe a leech could rasp its way through a turtle shell. Later that day, I ran into a muskrat couple frolicking at the upstream footbridge (actually they were doing more than that but this is a family website). I took video as they were amazingly unconcerned by my presence. but unfortunately the quality is terrible. Instead I leave you with this classic, and one of my personal all time unfavorite songs, “Muskrat Love” by Captain and Tennille . It’s well worth watching though if only because of the dancing muskrat puppets, Captain’s amazing muskrat chirps piano solo, and Toni Tennille’s fashionable (for the time) Dorothy Hamill hair.

Day 3 of Operation Wild Brook Trout

Last Friday (5/16) the four tagged wild brook trout were released back where they had been caught. The videos show the release of two of the four. Brian’s doing the releases and Maryanne is doing the camera work.  In the first video showing the release of trout #106 (named for the radiotag code), you can actually see the thin wire of the antenna trailing from the fish. Towards the end of the second video, the trout (I think this is #107) darts back to its original release location.

We have been tracking the four for a week. Thus far, unlike the hatchery trout, these guys have generally stayed put. Yesterday I used my GoPro camera o try to locate the whereabouts of a tagged fish once we had pinned down their location using the radiotracking receiver. In the video below you can see on the bottom right two, possibly three, trout hanging out just above the sandy bottom. Presumably one of these trout is #106 located about 30 meters upstream from its release site. At the same time I was filming this, Maryanne saw two more trout a few meters upstream.

Day 2 of Operation Wild Brook Trout

The plan yesterday was to test the swimming performance of the 4 wild brook trout we caught electrofishing. The reason we want to do this is based on the results we are getting from our radiotelemetry studies on hatchery trout released into Shu Swamp. We see a lot of downstream movement right after release. We believe that one factor that may influence  movement patterns of hatchery trout released  is that they are not in top  physical condition. We notice a lot of fin damage due to the high density conditions in the hatchery.


Hatchery trout showing damage to the caudal fin, oen pectroal fin, and a deformed opercular plate.

Furthermore hatchery fish may not get all that much exercise since the flow rates in the hatchery are much lower than they are in a stream. To test this we determine the water speed necessary to cause swimming fatigue (called critical swim velocity). In the lab this is done by placing the fish in a special swim tank similar to an Endless Pool” for people. The fish swim upstream against the flow and the flow can be gradually increased until fatigue is observed. This video, using a juvenile brook trout, shows what should happen. Fatigue occurs when the fish rests its tail against the downstream grid and stops swimming.

Unfortunately when we tried to determine swim performance in the wild trout, they would not cooperate. They just rested against the downstream grid even at very low speeds. We tried a number of approaches to get them to swim but to no avail. The fish we are using are pretty big – 8 to 10″. On the other hand there has been no problem testing swim performance in smaller 5-6″ fish. For now it’s back to the drawing board.

After giving up for now on swim performance tests, we moved on to tagging. In short order Brian had radiotagged the 4 fish and they were groggily recovering in their temporary holding tanks. Each fish received a PIT tag (if it didn’t have one already) and a radiotag. In the figure on the right you can see the incision in the abdominal cavity where the tag is implanted. The antenna leaves the body through a small puncture above 2 inches posterior to the incision. The trout will be released today. These tags should last about 160-180 days. They emit a individually coded radio pulse once every 20 sec. To extend the battery life we have the tag active for 12 hours during daylight.

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You can find more about the tagging procedure at the Tracking Trout link.

Day 1 of Operation Wild Brook Trout

Over the next three days, we are catching, radio-tagging and releasing wild brook trout living in Shu Swamp. The plan is to compare their movements and habitat preferences to the hatchery-reared brook trout. The tags we are using can last 5 – 6 months so we may even see evidence of spawning if we are really lucky. Over the summer we hope to tag and release 10 wild trout. We just received our first batch of 5 tags and today we set out to catch 5 wild trout to take back to the Hofstra Animal Lab for a short stay: swim performance tests, tagging and then release, all within the next 48 hours. Sounds like a fun weekend at the health spa doesn’t it?

Maryanne, Brian, and I met up with Steve DeSimone, CSHFH director and operator of the backpack electrofisher you see here.

We immediately startied catching fish. The problem was they were the hatchery fish we released last month. We knew because we checked them with our portable PIT-tag reader which allowed us to identify each individual. All in all we caught and released six of the 28 we had released. Three of these had been detected before at the PIT-tag antenna downstream at the railroad bridge entering Beaver Lake, and one had been detected at the spillway antenna a mile away just 5 days ago!

Fortunately things started to pick up. All in all we managed to catch 4 wild trout, one short of our goal, before we ran out of stream to fish (we reached Frost Mill Road Dam). Three  of the trout had PIT-tags attached at the previous electrofishing event back in early March and one was newbie.

Along the way we also caught some other critters including some spiny-cheeked crayfish:

And a few YOY brook trout including this beauty (be sure to compare its size to the one shown at the March survey link.

YOYAs usual there were some beautiful wildflowers in bloom. Anybody know what this is?

We lso had a surprise visit from about 30 students from Pasadena Elementary School in Plainview who were there to release the fingerlings they had raised through the TITC program. They got to see the brook trout we had caught as well as the crayfish featured above. The adults we had caught might very well have had their origin a few years ago in a Long Island TITC classroom maybe even their own! I think they were really excited to think that maybe their “babies” might one day reach adulthood in its native habitat.  As part of the TITC experience, participating classrooms visit CSHFH in November to learn about brook trout and see the egg fertilization process. Their visit was featured on Long Island News .

The four “keepers” were transported in coolers and now reside in the animal facility at Hofstra. Here is one that is about 10″ and a 1/2 pound:

Wild trout back at lab

Tomorrow they all go for a swim and a quick surgical procedure. Stay tuned!

Underwater video of released brook trout

Maryanne and Brian released 20 PIT-tagged trout and 5 PIT-tagged/radio-tagged trout Wednesday. This is most likely our last release for the season and the project. When I was at the swamp today I took this video of one the trout (at least I think it is) using my new GoPro Hero 3 camera. You can see the trout initially in the bottom left frame. Best viewed in full screen.

I had no idea this trout was there until I viewed the video later. Most of the radio-tagged trout are tracked to undercut banks where it is very difficult to verify that the trout is actually there instead of just the tag. So we plan to use the camera to get visual verification of a tagged trout’s presence at the signal source. I have the camera mounted on a a short telescoping pole to allow me to submerge it from the surface. The camera has a wireless feature that allows you to control it and view a live feed through an app on a smart phone. Unfortunately wireless doesn’t underwater. So instead we just have to film “blindly” and once the camera is brought back to the surface reestablish the wireless connection and then review the film through the smart phone app.

Data on 2013 Radiotracked Brook Trout Are Now Online

I am finally caught up with entering the radiotracking data we collected this spring and summer into our online map. Last year we tagged and tracked 11 immature (6” or less) brook trout. Starting in April of this year we have tagged and tracked an additional 16 immature brook trout and 5 mature (8” or greater) brook trout. We will be releasing an additional 6 immature trout in the next week.

View this Larger “User-Friendly” Map”
View this Larger Map for “advanced users”

Here are some highlights of the data collected thus far (to view specific fish just click on one of the two links and make sure the only the box for at particular fish or fishes is checked):

  • 7 trout were not located after release.
  • A large majority of the tags were discovered detached from a trout. We have strong evidence that at least in some cases this was caused by predation (see for example 27).
  • Both immature and large trout showed the greatest movement right after release.
  • However larger trout moved more and all four of the large trout which we were able to track after release entered Beaver Lake. None of the immature trout moved that far downstream.
  • One of the large trout (101) returned upstream after entering Beaver Lake and remained for several months well upstream in Beaver Lake. The other three disappeared in the lake as summer temperatures rose into the upper 70’s.
  • Patterns of movement among immature trout varied considerably but can be divided into two two general types:
    • Movers. Examples include 20, 23, 25, 22b
    • Stayers. Examples include 17, 18, 19, 24, 21b, 28

LITU’s Radiotagged Trout – Final Results

Tracking of the five mature brook trout we released in Beaver Brook this past spring and summer is done. Of the five fish we released, one (104) disappeared right after release. That probably means it was eaten. The other four moved downstream and entered Beaver Lake. One trout made it to the entrance of Beaver Lake three days after release, at which point it did not move again. Either the trout was eaten or it dropped its tag. Two others moved deep into the lake and never returned to Beaver Brook. Both of them appeared to have stopped moving this summer. I suspect conditions were lethally hot by that time (temperatures were well over 78 by late June). Finally, 101, released in early April, traveled all the way to the Beaver Lake spillway within one week of release and then returned to Beaver Lake the same day. It spent the next three months in a 200 yard upstream stretch above the concrete bridge before the tracking signal was lost in mid July. Here is the map of their movements:

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Bass eats one of our radiotagged trout

2013-08-15 13.10.03

This isn’t the greatest picture but what you are looking at is a 12-15 inch largemouth bass hanging out near the footbridge at Shu Swamp pond (near the railroad). What makes this guy interesting is that he is currently possessing an active radiotag (#27) I originally implanted in a brook trout we released on July 25 at the concrete bridge 600 meters upstream. This trout spent several weeks hanging around about 50 meters downstream from the dam until moving well upstream about a week ago where we detected it on August 12. Sometime in the following three days he was predated by this bass.Yesterday walked down to the pond looking for #27 and started detecting the signal. It was strongest when we pointed at this particular bass. When the bass moved the signal moved.

More PIT-tagged and Radio-tagged Trout Released

Last Friday we released 34 PIT-tagged 8-9″ brookies into Beaver Brook just upstream of the concrete bridge. Three of them were tagged with the three remaining large radiotags donated by LITU. I was helped by my two graduate students, Maryanne and Brian, as well as two of the Commack High School crew, Eric and Alinur.

The two trout  that were released April 10 are still alive and kicking. One has remained in the same spot well upstream since April 25 while the other is still in the same general area in the lake sincei it entered the lake April 20 despite the fact that surface water temperatures have reached 29 C (84 F). While I couldn’t get a visual confirmation on this trout signal strength was changing when pointing the antenna at fixed spot indicating it was moving.

I checked the whereabouts of the newly released radiotagged fish yesterday and was able to locate all three. One was at the release site, another was about 25 yards upstream, and the third was at the mouth of Beaver Brook where it enters the lake. Surface temperatures in all three places were around 21 C (70 F).