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Little Juniata River
Blair & Huntingdon Counties
 
August 2 – 4, 2010
Sampling Technique – Towed Boat (two) Electrofishing

From August 2 through August 4, 2010 a portion of the Little Juniata River flowing through Blair and Huntingdon counties was reexamined to evaluate the status of the naturally reproducing brown trout population and to estimate the contribution to the fishery from stocked fingerling brown trout. The Little Juniata River originates at the confluence of Spring Run and Kettle Creek in the vicinity of the City of Altoona and flows northeasterly to the Borough of Tyrone and then southeasterly to its confluence with the Frankstown Branch of the Juniata River in the vicinity of the Borough of Petersburg. Historically, the Little Juniata River fishery was impaired by poor water quality originating from a variety of point and nonpoint sources; however, during the 1970’s improved water quality allowed the Pennsylvania Fish and Boat Commission (PFBC) to begin stocking fingerling brown trout from the Village of Ironville downstream to the Village of Barree in an effort to establish a fishery. Numbers of fingerling brown trout stocked varied over the years, and currently the PFBC stocks 30,000 fingerling brown trout (approximately two – four inches in length) annually during spring into this portion of the river to bolster the naturally reproducing wild brown trout population residing in the river.

The Little Juniata River from the east (downstream) border of Ironville downstream to its mouth (13.7 miles) is currently managed by the PFBC through Catch-and-Release All Tackle regulations. The Pennsylvania Department of Environmental Protection under Chapter 93 currently designates the Little Juniata River as Trout Stocking, Migratory Fishes, from its source downstream to Logan Spring Run and Cold Water Fishes, Migratory Fishes, from Logan Spring Run downstream to its mouth. Numerous coldwater tributaries (Sandy Run, Tipton Run, Spruce Creek, among others) and springs enter the Little Juniata River along its 32 mile path to the mouth, and the river is characteristic of a small, limestone spring influenced river, somewhat unique to Pennsylvania for a flowing water of its size.

During August 2010, PFBC biologists from the Division of Fisheries Management conducted an electrofishing survey at three historic survey sites located in the vicinity of the villages of Shoenberger, Pemberton, and Barree. Two towed boats were used to electrofish the river while a processing crew measured, weighed, and marked all captured trout to facilitate a population estimate (Figure 1). Sites ranged in length from approximately 260 to 510 yards. Species captured during the survey included wild brown trout, hatchery brown trout, hatchery rainbow trout, smallmouth bass, rock bass, black crappie, white sucker, northern hog sucker, blacknose dace, longnose dace, bluntnose minnow, cutlips minnow, river chub, shield darter, tessellated darter, and slimy sculpin. To facilitate differentiation from wild brown trout residing in the river, all fingerlings stocked during 2009 and 2010 were marked by removing the adipose fin, a small fleshing fin just anterior to the tail fin that does not regenerate.

Figure 1. Electrofishing crew using two towed boats at the Little Juniata River in the vicinity of the Village of Barree during August 2010.

Figure 1

A total of 2,240 individual brown trout between two and 19 inches in length were captured during both passes of the two-pass mark-recapture electrofishing survey, of which 83 (approximately 4%) were missing their adipose fin and consequently were determined to be stocked fingerlings originating from the 2009 or 2010 plants (Figure 2). Based on these results, the estimated abundance of wild brown trout greater than or equal to seven inches residing in the portion of the Little Juniata River from Ironville downstream to Barree was approximately 2,963 wild brown trout per mile. This estimate of wild brown trout per mile is substantially higher than estimates based on the most recent survey conducted during 1996. Additionally, the number of stocked fingerling brown trout per mile (> four inches in length) originating from the 2009 and 2010 plants was estimated at 167 fish per mile (Figure 3; Table 1).

Figure 2. Length frequency distribution of wild brown trout and stocked fingerling brown trout originating from the 2009 and 2010 plants captured at three historic electrofishing sites located in the vicinity of Shoenberger, Pemberton, and Barree during the August 2010 survey.

Figure 2

Figure 3. Age-0 brown trout originating from the 2010 fingerling plant. Notice the otherwise “wild” looking appearance of this fish with the exception of the missing adipose fin.

Figure 3

Table 1. Estimated brown trout abundance (number per mile of fish greater than seven inches) based on results from electrofishing surveys conducted during 1996 and 2010. The 1996 estimate is derived from electrofishing surveys conducted at the Shoenberger and Pemberton sites only as Barree was not sampled during that year. Stocked brown trout consist of only of Age-0 and Age-1 trout (> four inches in length) marked and stocked as fingerlings during 2009 and 2010 respectively.

Survey Year Estimated Number per Mile
Wild Brown Trout Stocked Brown Trout
1996 854 n/a
2010 2,963 167

The overall percentage of fingerling brown trout originating from the 2009 and 2010 plants compared to the total number of brown trout captured was approximately 4%; however, it is inappropriate to make this comparison because fish marked to facilitate differentiation from wild stocks were Age-0 and Age-1 only. Based on the length of fish captured during this survey, age can be estimated from fish aged during past surveys at the Little Juniata River and estimated age of fish captured during 2010 ranged from this year’s fish (Age-0) to Age-8. Thus a more appropriate way of estimating the percent contribution from stocked fingerlings to the fishery is to look at only Age-0 and Age-1 fish, as it is difficult if not impossible to determine origin of trout greater than Age-1 as they were not fin marked (Figure 4). In this regard, the percentage of Age-0 and Age-1 trout originating from the 2010 and 2009 plants was approximately 13% and 4% respectively. Age-0 stocked fingerling brown trout captured during this survey ranged from approximately four to seven inches in length, while Age-1 stocked fingerlings ranged from approximately nine to 11 inches in length.

Figure 4. Age-1 brown trout originating from the 2009 fingerling plant. Again, notice the otherwise “wild” looking appearance of this fish with the exception of the missing adipose fin.

Brown trout

The length and weight of a subset of fish captured during the survey was recorded to estimate overall condition of the brown trout population residing in the portion of the Little Juniata River under evaluation. By comparing the total length of a fish to its weight, the relative condition or plumpness of an individual fish or population can be determined. A common metric used by fisheries biologists to determine condition is Relative Weight. Generally speaking, a Relative Weight equal to 100 describes a fish or population of average condition, while a Relative Weight less than or greater than 100 describes a fish or population characterized by thin or plump fish, respectively. The average Relative Weight of fish greater than eight inches was 87 and the average weight (pounds) was predominantly lower than the statewide average. This indicated that the population of brown trout residing in this portion of the Little Juniata River was thinner than average brown trout populations (Table 2). Additionally, fish less than 12 inches were in better condition than fish greater than 12 inches. The thin condition exhibited by this population can be attributable to a variety of reasons including, too many fish competing for a limited resource (food, habitat, etc.) or warm water temperatures, among other things. Due to the unusually warm summer we have experienced this year, this phenomenon may be attributed to warm water temperatures, as habitat or food availability did not appear to be limiting factors.

Table 2. Average Relative Weight and weight (pounds) of brown trout captured during the August 2010 survey.

Size Group (inches) Average Relative Weight Average Weight (pounds)
Barree Site Shoenberger Site Both Sites Both Sites Statewide
8-9 96.13 89.63 93.53 0.22 0.21
9-10 93.66 85.70 89.87 0.28 0.30
10-11 90.08 83.60 86.67 0.38 0.40
11-12 89.09 86.23 87.79 0.49 0.52
12-13 80.01 84.90 82.34 0.61 0.67
13-14 82.84 86.04 84.37 0.77 0.85
14-15 81.27 90.18 85.73 0.93 1.05
15-16 81.70 85.09 83.39 1.13 1.28
16-17 77.93 92.24 86.52 1.39 1.53
17-18 83.00 80.33 81.00 1.57 1.92
All Fish 86.57 86.79 86.68    
Brown trout
Presumably wild brown trout captured during recent survey of the Little Juniata River
 
– Kris Kuhn, Area 7 Fisheries Manager

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