Biologist reports logo Slate Run

Tioga and Lycoming Counties
August 2004


Slate Run is a popular wild trout stream located mostly on Tioga State Forest Land within Tioga and Lycoming Counties in northcentral Pennsylvania. It supports a healthy population of wild brook and brown trout and meets the PFBC’s Class A wild trout stream criteria by supporting a wild trout biomass over 36 lb/ac. Slate Run has been managed under restrictive harvest regulations for many years and is currently managed under Heritage Angling Regulations. Under these special regulations fishing is permitted year-round (no closed season), anglers must use fly fishing tackle including flies with barbless hooks, and all trout caught must be immediately released back into the stream (catch and release).

Slate Run

Typical Slate Run habitat photographed during the August 2004 survey. Note the extremely clear water and clean substrate signifying minimal sediment deposition, which is indicative of a stable, well-forested watershed.

Slate Run

Area 3 staff, assisted by personnel from the PFBC Coldwater and Warmwater Units, used backpack electrofishing gear to conduct a Petersen mark-recapture population estimate on a 330-yd index site located approximately 0.4 mi upstream of the Morris Run Road Bridge crossing on August 9-10, 2004. Brook trout collected during the 2004 survey ranged from 2-10 inches while brown trout ranged from 2-15 inches. In addition to brook and brown trout, blacknose dace, longnose dace, slimy sculpins, and white suckers were also collected. The dace and sculpins were quite abundant, providing a strong forage base for the adult trout population.

Slate Run 9 inch wild brook trout
Slate Run 9 inch wild brook trout

In above picture note the clip at the top of the brook trout’s caudal fin (tail), which signifies that this fish was captured during the first electrofishing pass and marked. A Petersen population estimate is then computed by comparing the ratio of marked to unmarked trout collected during the second electrofishing pass. Population estimates were also conducted at the Morris Run Road Bridge site in 1990, 1996, and 1999. During the 14-yr sample period (1990-2004), the total number of brook trout per mile ranged from 216 (27 of which were young-of-the-year) in 1996 to 954 (660 of which were young-of the year) in 1999 (Table 1). The total number of brown trout per mile ranged from 478 (19 of which were young-of-the-year) in 1996 to 2,110 (1,416 of which were young-of the year) in 1999 (Table 2). Low brook and brown trout abundance in 1996 was likely a result of poor year-class survival due to extremely high flows during the spring (March-May) of this year, while abundance was highest for both species in 1999 when spring flows were well below average.

Slate Run 15 inch wild brown trout
Slate Run 15 inch wild brown trout

Table 1. Estimated number of brook trout per mile at the Morris Run Bridge index site from 1990-2004.

Date Total number of brook
trout per mile
Young-of-the-year brook
trout per mile (2-3 in)
Number of legal-size brook
trout per mile (>= 7 in)
1990 620 354 140
1996a 216 27 17
1999b 954 660 64
2004 525 143 196

a - Indicates extremely high spring flows
b - Indicates below average spring flows

Table 2. Estimated number of brown trout per mile at the Morris Run Bridge index site from 1990-2004.

Date Total number of brown
trout per mile
Young-of-the-year brown
trout per mile (2-3 in)
Number of legal-size brown
trout per mile (>= 7 in)
1990 1,814 925 529
1996a 478 19 158
1999b 2,110 1,416 344
2004 1,376 893 227

a - Indicates extremely high spring flows
b - Indicates below average spring flows

Biomass is the weight of fish per unit of area and is directly correlated with the number and size of fish present. Thus, as the number and size of trout increase, the biomass of trout also increases. The biomass of brook trout was lowest in 1996 (4.7 lb/ac; Table 3) when abundance was lowest (216 brook trout / mile), and highest in 1999 (15.5 lb/ac; Table 3) when abundance was highest (954 brook trout / mile). Brown trout biomass was more variable than brook trout biomass during the 14-yr period, but was also lowest (22.2 lb/ac) during the 1996 survey (Table 4). However, brown trout biomass reached its peak in 1990 (79.5 lb/ac; Table 4) even though abundance was slightly higher in 1999. The reason biomass was higher in 1990 than 1999, was because larger fish were collected in this survey (529 legal brown trout / mile in 1990 vs. 344 legal brown trout / mile in 1999). The biomass of both young-of-the-year brook and brown trout was extremely low (0.1 lb/ac) during the 1996 survey following a wet spring and much higher in 1999 (2.2 and 4.4 lb/ac, respectively) following a dryer spring, further indicating that spring flows play a crucial role in young-of-the-year survival.

Table 3. Estimated brook trout biomass (lb/ac) at the Morris Run Bridge index site from 1990-2004.

Date Total brook
trout biomass
Biomass of young-of-the-year
brook trout (2-3 in)
Biomass of legal-size
brook trout (>= 7 in)
1990 11.4 1.2 7.8
1996a 4.7 0.1 1.3
1999b 15.5 2.2 7.5
2004 14.1 0.5 9.8

a - Indicates extremely high spring flows
b - Indicates below average spring flows

Table 4. Estimated brown trout biomass (lb/ac) at the Morris Run Bridge index site from 1990-2004.

Date Total brown
trout biomass
Biomass of young-of-the-year
brown trout (2-3 in)
Biomass of legal-size
brown trout (>= 7 in)
1990 79.5 3.7 67.8
1996a 22.2 0.1 15.7
1999b 64.9 4.4 53.2
2004 31.5 3.4 22.8

a - Indicates extremely high spring flows
b - Indicates below average spring flows

This dataset provides a good example of the natural fluctuations fish populations commonly undergo. When favorable conditions are present, populations usually have a “boom” year with lower annual mortality and higher reproductive success, but when conditions degrade, populations may have a “bust” year characterized by higher annual mortality and lower reproductive success. Most fluctuations can usually be attributed to environmental factors such as acidic episodes, floods, droughts, changes in the availability of instream habitat, and changes in the forage base. If conditions degrade for a short period, most fish populations can rebound relatively quickly once conditions become more favorable. However, severe, prolonged disturbances and degradations require longer recovery periods.

The 2004 Fisheries Management Area 3 staff at Slate Run
The 2004 Fisheries Management Area 3 staff at Slate Run (left to right: Jason Detar, Josh McCormick, Bruce Hollender)

As the fall foliage continues towards its peak, anglers should take advantage of the aesthetically pleasing setting as well as the healthy wild brook and brown trout populations that Slate Run offers. Due to its extremely clear water, anglers should use a stealthy approach to avoid spooking the wary wild trout that inhabit this stream. Anglers should consult their 2004 Summary Book of PA Fishing Laws and Regulations to confirm the specific regulations that apply to the water they plan to fish.

 
-- Jason Detar, Area 3 Fisheries Techician

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