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Susquehanna River
 
September 28-29, 2010 and October 12-13, 2010
Sampling Technique – Nighttime Boat Electrofishing

Figure 1
Figure 1: Fisheries Biologist Aide Sean Reese (L) and Susquehanna River Biologist Geoff Smith (R) measure, weigh, and take scale samples for age and growth analysis from adult smallmouth bass at the Susquehanna River near the Pennsylvania Turnpike Bridge. (Photo: J. Frederick – PFBC)
Fisheries Management Division biologist routinely assess the status of the smallmouth bass population in Susquehanna River to estimate current population levels, size structure, age and growth attributes, among other parameters. During September 28 and 29, 2010 and October 12 and 13, 2010 Fisheries Management Area 7 biologists conducted nighttime electrofishing surveys, targeting adult smallmouth bass, at four historic sampling sites located within the middle portion of the Susquehanna River between the inflatable dam near Sunbury and the York Haven Dam. Sites surveyed were located at Halifax, PA (Clemson Island vicinity), Rockville, PA (Rockville Bridge vicinity), Harrisburg, PA (Dock Street Dam vicinity), Highspire, PA (Pennsylvania Turnpike Bridge vicinity).
Figure 2
Figure 2: A nice, adult smallmouth bass from the middle Susquehanna River
near the Pennsylvania Turnpike Bridge (Photo: S. Reese - PFBC)
During 2010, size distribution (Table 1) and catch rates of age-1 and older smallmouth bass varied among sites with a reach-wide catch rate of 42.68 fish/ hour (Figure 3). This is an increase from the 2009 catch rate (23.91 fish per hour) but still lower than the historic median catch rate (1990 – present) of 85.05 fish/ hour (Figure 3). The reach-wide catch rate of larger and older individuals, those longer than 15 inches in total length, was 9.35 fish/ hour (Figure 4). This catch rate is the second highest on record and above the historic median for this reach of 7.05 fish/ hour (Figure 4).
Table 1: Size classes (inches) of smallmouth bass captured at the middle Susquehanna River during nighttime electrofishing surveys September 28-29 and October 12-13, 2010.
Size (inches) Clemson Island Rockville Dock St. Dam Turnpike Bridge
1 0 0 0 0
2 0 0 0 0
3 0 0 0 0
4 3 17 4 1
5 22 42 6 0
6 37 16 2 1
7 10 6 1 1
8 6 4 5 0
9 8 3 6 1
10 5 3 1 0
11 1 1 3 0
12 11 0 3 2
13 7 1 6 2
14 5 1 8 2
15 1 0 6 1
16 5 0 2 3
17 0 1 7 2
18 2 1 2 6
19 1 2 2 1
20 0 0 0 0

Figure 3
Figure 3: Catch per hour of smallmouth bass age-1 and older captured during nighttime electrofishing surveys conducted during the period of 1990 to present at four historic sites at the middle Susquehanna River. Blank values are years for which no surveys were conducted or age data does not exist.

Figure 4
Figure 4: Catch per hour of smallmouth bass 15 inches and longer captured during nighttime electrofishing surveys conducted during the period of 1990 to present at four historic sites at the middle Susquehanna River. Blank values are years when surveys were not conducted.

As mentioned previously, catch rates of large smallmouth bass were above historic median. This may be attributable, at least in part, to increased flow at the time of sampling. Smallmouth bass often seek refuge in near-shore areas corresponding to our survey sites, away from the high velocities areas in the main channel, consolidating the fish into a smaller portion of the channel. These fish occupying the near-shore habitat during high flows are more susceptible to the electrofishing gear.

Currently, there are strong numbers of large smallmouth bass in the middle Susquehanna River for anglers to enjoy. However, overall density of smallmouth bass is below the long term average, so much so, that the Commission will invoke catch and immediate release angling restrictions in 2011. Details pertaining to the cause of these declines remain under investigation, but are believed to be due to reduced recruitment and survival of young. For more details visit: http://fishandboat.com/susquehannabass.htm

 
– Susquehanna River Biologist Geoff Smith and Area 7 Fisheries Manager Kris Kuhn

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