Understanding trout biomass assessment

[wcosner2]

Hello all,

I am conducting research for a senior thesis for college on trout stocking in Pennsylvania and for the life of me, cannot figure this out.

Trout biomass is measured in lbs/acre or kg/ha. How exactly is the acre or hectare calculated for streams? Is it simply the surrounding watershed area?

Also, how are different stream sections designated as different classes of wild streams? Is it the area from the bank of the stream up to the edge of the watershed that exclusively drains that area and excludes the watershed area above this specific section of stream?

I would appreciate any help you all can give.

Thanks,

Willie

 

[lycoflyfisher]

I would encourage you to reach out directly to the PA Fish and Boat Commission for the most accurate answer. You will either want to talk to your local area fisheries manager or talk to the Coldwater Unit Leader. You could start by calling the Centre Regional Office and asking for contact information for the Coldwater Unit.

 

[Mike]

Lyco is correct about those whom you should contact. Your regional fisheries management office is at Nockamixon, about 10 mi from Upper Black Eddy. Additionally, there were articles in the Pa Angler and Boater magazine that described the process. One was written by Leon Creyer in the early 1990’s. Others probably appeared in the late 1979’s and very early 1980’s. You would need to seek the archives of that publication.

 

[troutbert]

The area units are simply for the area of the section of stream surveyed.

They usually survey about 300 meters. They take a few measurements of the width of the stream. (The wetted width, not the channel widith).

Then multiply the average width times the length of the section surveyed, which gives you the surface area of the stream section surveyed.

 

[Mike]

A standard 300 m sampling site, which would be 10% of a 3 km section, the standard minimum percentage of a section sampled when population estimates are run, would have ten width measurements taken..one every thirty meters. Likewise, if a section is 6 km long, then typically two 300 m sites would be run within the section, and so on. Ten widths would be taken at each, the mean (avg) width of each site calculated, the two site widths averaged generating a mean of mean widths, and then that mean (avg) width applied to the entire section to generate a section area. That’s the area upon which population estimates are based, expressed in kg/ha, and that’s also how section areas are generated for trout stocking purposes since stocking rates are based on area (number of trout to be stocked per acre of water). 2.47 acres in a hectare

 

[salvelinusfontinalis]

Mike,

Is there a margin of error?
Ex : +/- 2%

Or would you consider the numbers pretty accurate when it comes to sampling?

 

[Mike]

Mean widths are surprisingly similar from survey to survey, which could be separated by 1 yr or 20 yrs. It’s common to find a 0.1 to 0.3 meter variation in sampling sites that avg 4-8 meters wide for example. If a site averages 25 m wide, the variation across the years seem to run around .5-2.0 meters. There could be larger variations in either case mentioned above, but I am talking about more typical comparisons. One specific larger change on a smaller stream that I recall was in Locust Ck, Section 02, a wild and stocked section in Schuylkill Co. because of a long, wide pool created by a blow-down. This was unusual.

As an aside, would I fish this section for wild trout only? You bet!

 

[salvelinusfontinalis]

Thank you Mike