For over a century, the Monongahela River experienced widespread water quality degradation and ensuing near loss of its fisheries. Combined state and federal efforts that began in the 1970s, however, eventually led to tremendous improvement in the Monongahela’s water quality. Improved water quality resulted in gradual recoveries of sport fisheries, also accompanied by range expansions of numerous native species that were once locally exterminated and overall increases in fish population abundances. The best documentation of the Monongahela River’s recovering fish populations can be found in lockchamber survey findings. Since 1957, 94 lockchamber surveys have been conducted on the Three Rivers, including 36 on the Monongahela River. Notwithstanding these dramatic improvements, water quality problems continue to impact Monongahela River fish populations, primarily from industrial (coal mining and gas well development), municipal (sewage and landfill operations), and non-point sources (agricultural, suburban and urban run-off).

For the 2010 lockchamber surveys of the Monongahela (Figure 1), the Pennsylvania Fish and Boat Commission’s (PFBC) Fisheries Management Division Area 8 and Three Rivers biologists (Figure 2) were assisted by biologists from the West Virginia Division of Natural Resources’ District 1 (WVDNR), Ohio River Valley Water Sanitation Commission (ORSANCO) (Figure 3), U.S. Environmental Protection Agency’s Region III Freshwater Biology Team (USEPA), U.S. Army Corps of Engineers Pittsburgh District (USACE) (Figure 4), Pennsylvania Department of Environmental Protection’s Southwest Regional Office in Pittsburgh and Office of Water Management in Harrisburg (PADEP), California University of Pennsylvania (CalU) (Figure 5), West Virginia University (WVU), Duquesne University, and Marshall University.

All fish collected during the lockchamber surveys were enumerated and measured for total lengths and weights. A comparison of 2003 and 2010 findings are summarized in the following tables (Table 1 Grays Landing, Table 2 Maxwell, and Table 3 Braddock).

The results also include numbers of “remarkable species” collected. PFBC biologists thought that for a meaningful data interpretation and straightforward measure of biological integrity, fish species inherently more valuable, or “remarkable”, should be considered. Remarkable species, then, regarded appropriate for this evaluation consist of the following:

1. Nongame fish species either previously (e.g., mooneye, Pennsylvania-Threatened until 2010) or currently (e.g., ghost shiner, Pennsylvania-Endangered) protected in Pennsylvania;
2. Important sport fish species maintained by natural reproduction (e.g., smallmouth bass, walleye, and sauger); and
3. Fish species classified by ORSANCO as intolerant of pollution (e.g., smallmouth redhorse; Figure 6).

Remarkable species summarized in Tables 1, 2, and 3 are depicted in red text.

The total number of fish collected, total number of species collected, and number of remarkable species collected were higher in 2010 than 2003 at all three lockchamber locations. These results are encouraging, and are a testament to the improving fish populations of the Monongahela River. Total biomass was also greater in 2010 than 2003 at Grays Landing and Maxwell, but not at Braddock; where in 2010 less carp and smallmouth buffalo were collected than in 2003. These results are even more encouraging when we combine them with our 2003 and 2009 fish assemblage indices (Click here for the 2009 Biologist Report of nighttime boat electrofishing surveys). Those data showed no statistical differences between survey years.

Results that are particularly impressive are the long-term improvement trends (1967-2010) of total species and remarkable species collected at Maxwell (Figure 7) and Braddock (Figure 8). At Maxwell, not a single fish was collected in 1967, and only one bluegill in 1968. In 1975, PFBC began stocking walleye in the Monongahela, and these were first collected at Maxwell in 1978. Naturally reproducing sauger were first collected at Maxwell in 1988, and both walleye and sauger were collected at every successive lockchamber survey since. In 2010, 26,690 fish were collected at Maxwell, represented by 32 species total, and over a third of these species were remarkable.

Figure 8. Lock chamber survey results from 1967 through 2010 at Braddock depicting positive trends (solid and dashed black lines) for total fish species collected (blue columns) and remarkable fish species collected (red line).

Biologists from PADEP’s Office of Water Management in Harrisburg collected fish tissue samples from certain sport fish species (e.g., hybrid striped bass, white bass, and channel catfish) for contaminant analysis. These results will be used to update Pennsylvania’s Fish Consumption Advisories, published annually in the Summary Book – Fishing Regulation and Laws provided with purchase of a fishing license. Consumption advisories more restrictive than the statewide advisory of no more than one meal (one-half pound) per week apply to some species from the Monongahela. Fish consumers should consult the summary book for specific details.

PFBC biologists removed otoliths, or ear stones (Figure 9), from certain sport fish species. These calcified structures are one of the most reliable for determining the age of a fish (Figure 10).

Several factors must be considered when assessing lockchamber fisheries data. As a long-term dataset, they are suitable for depicting overall trends of species richness and composition, but cannot be used to estimate relative abundances of sport fish populations. Also, river conditions during the time of a lockchamber survey can influence catch. With this in mind, of all the lockchamber surveys conducted on the Three Rivers over the past 50 years, the findings at Monongahela River Maxwell L/D exhibit the most striking differences over time.

The findings of the 2010 lockchamber surveys of the Monongahela River have been exceptionally interesting, and several fish species collected during these surveys (e.g., hybrid striped bass and skipjack herring) are not typically collected during nighttime boat electrofishing surveys. The 2010 findings provide further evidence that in a relatively short amount of time (40 years), fish populations of the Monongahela River have rebounded remarkably. Many federal and state agency biologists qualify the Monongahela River recovery as ongoing, and remain concerned about existing and potential threats. Acute water quality degradation from potential catastrophic releases of abandoned mine pools, pollutant loadings from Marcellus Shale natural gas drilling activities, and other impacts could very easily tip the scales and reverse the ongoing recovery process of the Monongahela’s fisheries. Those fisheries, a renewable natural resource, have demonstrated high economic value by attracting international and national sport fishing competitions. Preserving the recovery made thus far and continued work to minimize/eliminate existing threats has potential to transform this river valley into an area containing some of the best sport fishing opportunities in the state.

In 2011, the Monongahela River Biological Monitoring Study will continue, as biologists from PFBC and CalU plan to conduct nighttime boat electrofishing surveys at the same locations surveyed in 2003 and 2009.