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North Branch Susquehanna River
 
2009 Walleye and Smallmouth Bass Reproduction

Area 4 biologists annually assess smallmouth bass and walleye reproduction in the North Branch Susquehanna River. The smallmouth bass assessment is done via daytime backpack electrofishing at 16 sites in July; the walleye assessment is done via night boat electrofishing at 4 sites in October.

During 2009, smallmouth bass and walleye reproduction in the North Branch Susquehanna River were modest at best. The average catch rate of young-of-the-year (YOY) smallmouth bass in 2009 was 3.4 YOY/50 meters, which was well below the long term average of 7.7 YOY/50 meters (Figure 1). Similarly, the average catch rate of YOY walleye in 2009 was 20.89 YOY/hour, which was well below the long term average of 62.93 YOY/hour (Figure 2).

High water during spawning, hatching, and the first few weeks of life caused the modest 2009 year classes of smallmouth bass and walleye in the North Branch Susquehanna River. In fact, river flow during the spawning and hatching period is the single most important factor affecting reproduction of these species. High water years bring poor reproduction, while low water years bring good reproduction.

The modest year classes produced in 2009 may or may not affect the fishery in coming years. That will depend on the strength various compensatory factors that operate on fish populations. For example, in years of low smallmouth reproduction, growth of the few bass that are produced is often faster because there is less competition for food. As a result, a higher percentage of young bass survive their first winter than would do so in years with high reproduction.

Figure 1. Catch per 50 meters of young-of-the-year smallmouth bass in the North Branch Susquehanna River from 1986 to 2009.

Figure 1

Figure 2. Electrofishing catch per hour of young-of-the-year walleye in the North Branch Susquehanna River from 1995 to 2009.

Figure 2

 
-- Rob Wnuk, Area 4 Fishereis Manager

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