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  1. Ashely Moreland, Student Technican
  2. Arnold
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Posted on July 15, 2011 | Permalink

Student Technican Experience - Week 3

Type: Freshwater
Region: Western
Location: Potomac River

At the beginning of the week, another intern and I were sent out to western Maryland to work with a few members of DNR that were partaking in a five year brook trout survey. The goal of their project was to catch, tag and release brook trout in Big Run, a tributary stream of the Potomac River, in hopes of catching them again the following year and seeing how much they’ve grown and how far they moved in the stream.

The process of actually obtaining, transporting and tagging these fish was rather labor intensive. In a previous year, DNR sectioned off the stream by measuring out 61 separate 50-meter-long sites. Each site needed to be checked for trout. This meant that block nets needed to be set up between all of the different sites so that the fish couldn’t escape their site and skew the data when we entered the water. After blocking off the first few sites, a crew of several people would enter the first site. One person would be handling electrofishing equipment, at least two others would be following with dip nets, and another person would be in the back to carry a bucket to put the fish in. The person with the electrofishing equipment would stun the fish, help with identifying it and, if it was a brook trout, it would be caught by the people with the dip nets and tossed into the bucket. This part of the job required a lot of patience, as every site needed to be walked through at least twice and tripping and slipping on the same slime-coated rocks more then once was quite the test of endurance.

After a site had been walked through at least twice, the fish were then transported and handed off to a few other members of DNR that would be doing all the data collecting. The transporting of the fish was also difficult since about 3000 meters worth of stream needed to be covered and hiking the fish from the stream to the road was difficult enough to do in waders. Once the bucket did reach the data site, the freshly caught fish were ‘drugged’ so that they’d remain motionless while they were measured for length, weighed, and scanned for a pre-existing tag. If the fish wasn’t already tagged, its adipose fin would be snipped off for a genetic sample and to help visually identify a recaptured fish in the future, and a small microchip would be placed under its skin either using a large needle or by making a small incision in the fish’s underside. After collecting data on the fish, they were allowed a short time to recover before being released into the same site they were caught from.

Since this wasn’t the first year that DNR was catching these trout, we did recapture several fish that had received tags previously. Although we didn’t have time while in the field to see exactly how much traveling these fish had done in a year, we were able to see how much some of the fish had grown and what kinds of injuries they’d received since they were last caught. After two long days of electrofishing and tagging, we had caught about 500 new and untagged trout and about 150 previously tagged trout. Although this is less than DNR had caught in the previous year, which was about 800 fish total, the recapture of trout in Big Run would still be considered successful since tagged fish were caught and some conclusions about growth and movement could be made.

Tags: Brook Trout