Counting Trout

A brown trout sitting high in the water waiting for a snack.

During the late summer fishery biologists from Vermont Fish and Wildlife take to the field and conduct population sampling efforts on many of our streams and rivers. The Battenkill is included among the waters that are sampled on an annual basis. In fact, the Battenkill is the largest waterway that the state samples and as such it is quite a production.

For those unfamiliar with how fish counting efforts are conducted, allow me to describe the process briefly. The process involves the use of electricity to mildly stun fish, allowing the fish to be netted and placed in a live well. The electricity is created via generator that is held in a canoe. Each generator has plugs for two wands that have a circular ring at the end that introduces the electricity to the river. In the case of the Battenkill, three canoes are employed with a total of 6 wands being used. Each canoe is managed by an individual that pulls it upstream. This is not an easy job! Along with the biologist (who has a net as well as the wand) there is a back up netter who has a bucket to collect fish. The fish are transferred into a live well as the teams move their way upstream. Upon completion of a pass through a designated section the trout are transferred to in stream live wells for the biologist to weigh, measure and then return to another in stream live well. There is a minimum of two passes through a section. If the depletion from the first to the second pass is not sufficient (indicating there are a large number of trout still to be captured) a third pass is needed. Ideally only two passes are done.

A team of fishery technicians probes a root wad to

capture trout hiding under the woody cover.

As the biologist measures and weighs the trout, another team member records the length and weight of every trout captured. Only after all passes through a section are completed and all fish can be weighed and measured are the trout redistributed back into the general area of the stream from which they were captured. The overall process is quite laborious but the folks doing the work are professional and quite efficient and mindful to handle the fish with care. Mortality from this process is extremely low; often zero.

The Battenkill mainstem is sampled in the same three locations every year. There is a riffle (376 feet) and pool (316 feet) in the "Lesko" stretch and a long (720 feet) stretch of varied habitat at the Cemetery Run section of river. All told, 1412 feet of river are sampled - from bank to bank. This year the sampling was done under ideal conditions (seasonally normal "low" flows, cool water temps and clear water). The two days of sampling were expertly managed by Courtney Buckley, who is the district biologist for the Battenkill. She led a team of folks from Vt Fish and Wildlife and the Green Mt National Forest that did a fine job. It should be noted that both sections have had various habitat enhancements, though this was done well over a decade ago. Both sections have also seen recruitment of new large wood that makes for good to excellent fish habitat.

As an interesting aside, several trout that were captured carried scars from being chased by one of the many predators that subsist along the river. While we anglers are often bemused when a family of mergansers decides to hunt where we were planning to fish, the presence of avian and fur-bearing predators is another indication of a healthy, robust ecosystem.

If you have made it this far I am sure you are waiting to find out exactly how things went. In a word, great! The numbers of trout counted were excellent both in numbers and across an impressive size range that indicates a healthy river (brook and brown combined - there were a small number of brookies counted up to 11.9" but only about a dozen overall). All three sections that were sampled had excellent numbers of fish. Combining all three sample sites the numbers are as follows (measured a couple different ways):

Size range Qty Percent of total

Total Counted 353 ------

Young of Year (less than 5") 148 42

5 - 5.5" (sub "catchable") 4 1

6 - 20.9" ("catchable" sized trout) 201 57

This is a nice mix of incoming fish at the young of year class and larger fish that are defined as catchable. As good as these numbers are, for an angler it is the catchable fish that are of most interest and what the population of that class of fish looks like. I have broken this down into a variety of size ranges and the percentage of those size ranges represented within the "catchable" class of trout (201 total trout).

Size range Qty Counted Percent of total

6" - 9.9" 126 63

10" - 11.9" 41 20

12" - 15.9" 20 10

16" - 19.9" 11 5.5

20"+ 3 1.5

These numbers show a very healthy representation across a number of size and age classes. While the fish are not aged by taking scale samples, it can be surmised that there are at least 5 age classes represented and perhaps several more.

Since trout per mile is an oft quoted statistic, you may be wondering how the numbers above translate into this common measurement. Trying to estimate the number of trout per mile is an inexact science. That said, we can make some rough estimates, particularly given that this year the conditions were so favorable. Since we know the total length sampled (1412 feet), we know that it is necessary to multiply the number of trout captured by 3.74 to bring us to "trout per mile" standard.

It has to be stressed that these are very rough estimates (biologists will enter the data into a program that gives a more exacting but still estimated number). Even with that caveat, I believe one can say with some degree of confidence that the trout per mile estimate is "about" the following:

Size Per Mile Rough Estimate

All 1320

Young of Year 554

Sub catchable 15

6" -9.9" 471

10" - 11.9" 153

12" - 15.9" 75

16' - 19.9" 41

20+" 11

What do these numbers mean? In the case of the Battenkill, the river appears to be quite healthy. When doing research for my book, I detailed a number of different years' worth of population data and 2024 stacks up with the best of them. Again, it is important to stress that these numbers are rough estimates. There are some areas of river, more than a few in fact, that likely hold fewer trout than what was observed during the sampling efforts. A few other areas likely hold more fish. Where in-stream cover is lacking, the number of trout will be correspondingly affected, while robust in-stream habitat has a positive effect. This has been proven year after year. Healthy riparian areas are also vitally important - in the Battenkill itself as well as its tributaries.

Courtney Buckley, district fisheries biologist, holds a nice trout taken from the Cemetery Run population sampling efforts. Care to guess its length? Email me at ddclyons1@aol.com with your guess (to a tenth of an inch) and I will send a selection of flies to the person who comes closest (or nails it) by September 30th. If there is a tie, the flies go to the first person who submits.

From my point of view, the good numbers seen in these sections of river justify additional in-stream habitat work where practical. Fortunately, Trout Unlimited has identified the Battenkill as a priority water and there is a goal to add additional habitat to the river and importantly, its tributaries. At the same time, the Battenkill Watershed Alliance has been working hard to invigorate riparian areas with numerous tree plantings to compliment what TU has done. The Trout and Salmon Foundation have also been active partners and hopefully will be for years to come.

If you wish to help with the continued success of the Battenkill don't hesitate to reach out to the Southwestern Vermont, Clearwater, or Adirondack chapters of Trout Unlimited. Also consider donating to the Battenkill Watershed Alliance (BKWA.ORG) and by all means join in some of the field work being done on the river - tree planting, habitat restoration, spawning redd surveys, trash clean up days. There are never too many people to help make a difference.

Finally, thanks to all the folks at Vermont Fish and Wildlife, New York DEC, and the Green Mountain National Forest for the work you do to make our woods and water better places.

Next up - big, nasty flies.