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Susquehanna River
 
September 21 – 24, 2009
Sampling Technique –Nighttime Boat Electrofishing

Fisheries Management Area 7 Fisheries Management Division biologists routinely assess the status of smallmouth bass populations in the Susquehanna River to determine trends in abundance, size structure, age structure, and growth attributes, among other attributes. During September 21 – 24, 2009, biologists conducted nighttime electrofishing surveys targeting adult smallmouth bass at four historic sampling sites located within the middle portion of the Susquehanna River from the Fabri Dam in Sunbury downstream to the York Haven Dam near Middletown. Sites surveyed were located in the vicinity of Clemson Island, Rockville, Dock Street Dam, and Turnpike Bridge (Highspire).

During 2009, age-1 (fish greater than approximately five inches in total length) and older smallmouth bass catch rates varied among sites (Table 1) and averaged 26.3 fish per hour (Figure 1). This is a slight decrease from 2008 surveys (27.5 fish per hour), and is well below the long-term (1990 to present) average of 89.1 fish per hour. Average catch rate for larger and older individuals, those fish greater than 15 inches, was 2.6 fish per hour (Figure 2). This is lower than the catch rates of larger fish over the past few years and lower than the long-term average of 6.2 fish per hour.

Table 1: Size classes (inches) of smallmouth bass captured from the Susquehanna River
during surveys conducted September 21 – 24, 2009.
Size (inches) Clemson Island Rockville Dock St Dam Turnpike Bridge
1 0 0 0 0
2 2 0 0 0
3 22 18 1 5
4 5 12 0 3
5 5 9 1 5
6 2 3 1 1
7 1 2 0 1
8 3 6 2 1
9 15 8 4 2
10 15 3 3 3
11 4 2 4 1
12 1 0 1 2
13 7 3 1 0
14 1 0 0 1
15 5 0 0 0
16 2 1 0 0
17 3 0 0 0
18 0 0 0 2
19 0 0 0 1
20 0 0 0 0

Figure 1. Average 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.

Figure 1

Figure 2. Average catch per hour of smallmouth bass 15 inches and greater in total length captured during nighttime electrofishing surveys conducted during the period of 1990 to present at four historic sites at the middle Susquehanna River.

Figure 2

During 2009 adult surveys, catch per hour of young-of-year smallmouth bass increased from 2008 to 2009 from 0.9 fish per hour to 12.7 fish per hour, respectively. This may be an indication that reproductive success of smallmouth bass during 2009 was slightly higher than anticipated despite adverse conditions attributable to repeated high flow events during late-spring and early-summer. However, as previously indicated these surveys targeted adult smallmouth bass and may not be an accurate measure of the strength of the 2009 year class. Adult surveys during upcoming years will provide better insight regarding the strength of the 2009 year class.

 
– Fisheries Management Area 7

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