Survey finds ‘abundant’ bass, catfish populations

HARRISBURG – The Pennsylvania Fish and Boat Commission recently released results of surveys by agency biologists who concluded the Susquehanna River is home to a healthy, abundant population of smallmouth bass and channel catfish.

But, they concede, problems continue. Here are some of the key results:

Smallmouth Bass

From Oct. 22-28, fisheries biologists conducted nighttime electrofishing surveys targeting adult smallmouth bass at four historic sampling sites located within the middle portion of the Susquehanna River between Clemson Island and the Pennsylvania Turnpike Bridge.

Sites surveyed were near Clemson Island, Rockville, the Dock Street Dam and the Pennsylvania Turnpike Bridge near Highspire, Dauphin County.

Of note, the catch rate of smallmouth bass in 2018 was the fifth-highest on record since standardized surveys began in the middle section of the Susquehanna River in 1990. In addition, the surveys revealed a strong population of adult bass ranging in size from 6 to 20-inches, as well as record numbers of trophy-sized bass measuring 18-inches or longer.

“The findings of this survey continue to reveal a strong smallmouth bass population,” said Geoff Smith, PFBC Susquehanna River Biologist. “Because we’re seeing fish in all size categories, we believe the population will remain strong for years to come.”

On The Recovery

Biologists from the Fish and Boat Commission provided this further explanation of why they think the smallmouth bass population has recovered–

“According to our biologists, the primary reason for the population recovery is improved recruitment after several years of reduced disease-related mortality of young-of-year Smallmouth Bass that resulted from Largemouth Bass Virus (LMBV) in concert with a host of other factors.

“Smallmouth Bass populations are typically driven by one strong year class and more numerous poor or weak year classes, where that strong year class supports the fishery for several years.

“At the height of outbreaks, we observed normal poor year classes caused by high stream flow or colder temperatures during and after the spawn; however the conditions that created strong year classes, low stream flows and warm temperatures, also coincided with large-scale mortality.

“As a result, several years of poor recruitment occurred consecutively resulting in substantially fewer “new” fish being recruited into the population, resulting in the decreased adult abundance.

“Since 2012, we have observed a few moderate to strong year classes within the population as disease prevalence has waned. During that time, disease prevalence has remained at around 10 percent or less as opposed the highs of the mid-2000s when we observed lesions on 67 percent of smallmouth bass surveyed in the middle Susquehanna River.

“We now have a more robust population with multiple year classes, including a large number of juvenile fish, that can withstand the fluctuations in the population (natural or otherwise) should they occur.”

Former Commission Executive Director John Arway, who was deeply involved in the Susquehanna River Study and the smallmouth bass issue, had this to say about this year’s survey results:

“There is a fundamental theory in ecology called inertia and elasticity. I remember a paper published by Dr. John Cairns from VPI in the late 1970’s which explained that biological communities in natural systems are like rubber bands. You can stretch them a long way and as long as they don’t break from the stress imposed by human insults, they can withstand tremendous pressures. I believe that is what happened to the Susquehanna. The algae blooms and oxygen depletion that stressed the fishery from 2005 to 2010 have not reappear because of changing environmental conditions. Primarily higher and cooler water levels at critical times for old and young bass. Therefore we have seen a recovery in bass populations. It is not time to declare victory and assume that conditions will remain like this for the near future.

He continued, “If we see the algae blooms again which will again lower instream dissolved oxygen levels to dangerous conditions for fish, we should expect similar results that we saw in 2005. Unfortunately there are some who believe that today’s conditions are a new baseline and would prefer to ignore the lessons from our past. If we are not diligent in reducing nutrients and sediments to achieve the TMDL requirements for the Chesapeake Bay, we could very well see 2005 happen again in our river. We don’t control Mother Nature but do control what we do to our land and water. Add in endocrine disrupting chemicals (EDCs), pesticides and herbicides, malfunctioning STPs and a host of other stressors which we know very little about, the challenges still exist. Unfortunately this press release doesn’t tell both sides of the story. I guess positive spin sells more licenses than reality.

Arway quoted Benjamin E. Mays, who said, “The tragedy of life is often not in our failure, but rather in our complacency; not in our doing too much, but rather in our doing too little; not in our living above our ability, but rather in our living below our capacities.”

“That’s my opinion as a fish biologist now watching from afar from a couch in Lamar. I still plan to fish the river and take the pulse of the bass so I will be speaking out for the fish as necessary,” Arway concluded.

Channel Catfish

In a second report, PFBC biologists outlined the findings of adult channel catfish surveys conducted between 2016 to 2018. During this time, biologists surveyed eleven sites; six in the middle section of the Susquehanna River extending from Sunbury to York Haven, and five in the lower Susquehanna River from York Haven to the Columbia-Wrightsville Bridge.

Using commercial catfish bait, biologists collected thousands of channel catfish ranging in length from 12 to 31-inches.

While equipment used in the survey is not capable of collecting younger fish, typically those under 12-inches, the number of catfish in the angler-preferred length of 24-inches or longer was good in both the middle and lower sections of the river with no evidence of overfishing.

Ongoing Study

There is an ongoing study of the Lower Susquehanna River by DEP, the Fish and Boat Commission and the U.S. Geologic Survey to determine what caused a significant decline of the smallmouth bass population several years ago.

Commission surveys from 2005-2012 found severely reduced numbers of smallmouth bass due to illness in the lower Susquehanna and lower Juniata rivers. Populations started to improve beginning with surveys in 2013 through the 2018 survey.

The Commission launched the S.O.S. – Save Our Susquehanna campaign in 2015 to raise funds for water and soil conservation projects along the Susquehanna River to address the illness and elevated mortality rates of smallmouth bass populations.

Preliminary results of the study released in 2015 found the two most likely causes for the population decline of smallmouth bass in the Susquehanna River are endocrine-disrupting compounds and herbicides; and pathogens and parasites.

Based on those and other scientific results, groups like the Fish and Boat Commission and the Chesapeake Bay Foundation-PA strongly encouraged DEP to list the lower Susquehanna River as impaired.

DEP did not list the lower Susquehanna as impaired for aquatic life in the most recent listing submitted to the U.S. Environmental Protection Agency in 2016.

The Fish and Boat Commission supports the continuation of the Susquehanna River Study and listing the lower Susquehanna as impaired.

Several interesting or concerning factors were identified over the course of the [Susquehanna River] study that need more investigation regardless of the response of the Smallmouth Bass population. Water quality factors like presence of herbicides and pesticides and other endocrine disrupting compounds, occurrence of nuisance algae and harmful algal blooms, and the tributary mainstem dynamics of the Susquehanna still need to be better understood.

Similarly, a number of fish health concerns, like intersex and melanosis, as well as the identification of several parasite and pathogens still need further investigation. The Susquehanna River Study provided us the opportunity to continue to adapt and refine our investigation as we gathered more data and better understand the factors and discover things that might have otherwise been overlooked.

Among these was a study done in collaboration with Michigan State University and funded by Pennsylvania Sea Grant and Pennsylvania Department of Environmental Protection that demonstrated the ability for LMBV to affect juvenile Smallmouth Bass.

Until this time, LMBV was not known to affect Smallmouth Bass; they were simply thought to be a carrier. This finding helped to resolve some of the outstanding spatial and temporal questions that other identified factors failed to address. We need to continue to ride the momentum to work to understand some of these other issues as well. While not all of what was found can be directly relatable to the Smallmouth Bass issues, they may have other ecological or human health implications that need to be understood as the ramifications may be equally if not more important.”


For more information and the results so far, visit DEP’s Susquehanna River Study Updates webpage.