'No easy answers' to bass dying in Susquehanna, researcher says
When it comes to the health of the Susquehanna River, the Pennsylvania Fish and Boat Commission and the Department of Environmental Protection don't agree on much.
But they do agree that smallmouth bass are dying at an epidemic rate, and Vickie Blazer, a biologist from the U.S. Geological Survey, is perhaps the best person to find out why.
Earlier this month, Blazer was in Harrisburg for a forum on the health of the river the night before the federal Environmental Protection Agency ruled that the lower Susquehanna is not an impaired river.
Rather, the federal agency said, the dying bass make it impossible to make a determination without more study. That was DEP's recommendation. The Fish and Boat Commission wanted the more aggressive impairment designation, arguing it would spur state and federal action sooner.
This spring, Blazer sampled bass on the river, though some days there were so few fish it became hard to conduct the work. This summer, she will return to study the spawn class.
In her presentation, Blazer outlined all of the physical problems that have besieged bass in the Susquehanna since 2005:
During that bombardment, the Susquehanna went from one of the best smallmouth fisheries in the world to a river where anglers can't legally catch fish for months at a time. Sampling has shown that 99 percent of bass are more than a year old — which is no way for a species to survive.
- Small raised legions,
- Benign skin tumors,
- Fungal infections,
- Heavy parasite loads,
- Eggs growing in male sex organs,
- Males having the protein that is a precursor for egg yolks.
I hadn't seen that before. If the babies aren't surviving, the species won't persist. It happened once to the Striped Bass in Chesapeake Bay, in the 1970's, before the moratorium, where the recruitment was so low that essentially no young were being produced. The stripers recovered pretty well after a 5 year moratorium, but it was never really clear what happened to cause the failure of reproduction, although climatic factors are thought to have contributed to just plain old overfishing of the spawning stock.
The bass' immune systems are so weak, Blazer said, "these fish are getting infected by whatever is in the water."
And the research so far suggests a lot of "whatever" is in the water:
- Too much phosphorus,
- Too little dissolved oxygen,
- Too much nitrogen,
- Too many parasites,
- Too many hormones acting as endocrine disruptors.
In the business, we call that "multiple stressors." More than one can operate at one time, and the effects can be greater than additive. It's also pretty hard to diagnose and fix the most important contributors.
Post a Comment