Large Pacu at the Shedd Aquarium in Chicago. Photo: I, Omnitarian

Here's another fish story via the Schuylkill Action Network: An article in last weekend's Mercury reported that a 22-year-old fisherman caught a pacu—a South American freshwater fish related to the piranha—in the Schuylkill River near Pottstown on Aug. 1. The angler, Josh Carmean, initially thought he'd hooked a two-pound catfish until he examined the fish's teeth.

"Pacu and piranha have similar teeth, but their jaw alignments are different. The piranha also have pointed, razor-sharp teeth with a pronounced underbite, while pacu have squarer and more straighter teeth with a less severe underbite. Also, sources reveal, the pacu are much larger than piranha, some reaching up to 60 pounds or more in the wild.

Pacus are also known to 'eat anything,' according to Deep Sea World zoological manager Matthew Kane. Though not the aggressive carnivores like piranha, the pacu's crushing jaw system can be hazardous. They are often sold to home aquarium owners as 'vegetarian piranhas.'

The pacu may have gotten a bad name as a result of owners illegally releasing them into wild waterways. Once in those waterways, like the Schuylkill River, they can dominate other species vying for available food and other resources, even displace some by introducing exotic parasites or diseases."

Pottstown is upstream from Philadelphia on the Schuylkill, the same river that will host the 2011 Philly Fun Fishing Fest on September 10. Did we mention that registration is free and now open? Might there be a special award to the angler who lands a pacu?

Who's afraid of a little (or, in some cases, actually quite large) snapping turtle? Not Philadelphians, who made dinner out of Cheldyra serpentina for decades in the form of snapper soup, a staple at city restaurants such as the Oyster House and the late Bookbinder's. The truth about snapping turtles is probably somewhere in between; these freshwater turtles can be ill-tempered when out of the water, and their bite can cause severe injury. The snapping evolved as a defense mechanism, as Cheldyra serpentina does not have the ability to retreat into its shell. However, when in the water, snapping turtles are docile and will seldom attack humans.

This spring, PWD biologists spotted two snapping turtles in the lower reaches of Tookany Creek (which becomes Tacony Creek within Philadelphia city limits). These turtles—whose carapaces, or shells, can grow to 20 inches in length—prefer to inhabit muddy areas of slow-running streams, lakes or ponds, and they can survive up to 30 years in the wild. 

For a strange-but-true story of an injured snapping turtle, WMMR-FM DJ Pierre Robert and former 76er Kyle Korver, click here.

Our post from earlier this month about American shad ascending the Schuylkill above Norristown for the first time in nearly 200 years contained a fish story of a different sort, as we mentioned that George Washington (pictured above, on the banks of some other river besides the Schuylkill) may have fed his troops Schuylkill shad during trying Revolutionary times. According to the University of Virginia's Papers of George Washington project, an article by Joseph Lee Boyle suggests whatever fish the troops were eating had been shipped in from other rivers:

"That shad were not in the Schuylkill by late March 1778 is evidenced by a letter Washington wrote to Francis Hopkinson at Bordentown, New Jersey. The Continental Navy Board had been ordered by Congress to move from there to Baltimore and Hopkinson offered some of the Navy’s stores to the General. Washington was "obliged to you for the trouble you have taken in removing the Stores and more so for the offer of the Rice, Oil and Fish…." The Marine Committee of Congress wrote to the Navy Board on 8 April, that they "approve of the offer you have made the General of Rice, Codfish and Oil for the use of the Army."

Anyone interested in the history of shad should check out John McPhee's book The Founding Fish.

When the Philadelphia Water Department's aquatic biologists investigate Philadelphia's streams and rivers to take stock of the number and variety of species inhabiting our waterways (they call this process a bioassessment), they pay special attention to mayflies. The presence of pollution-sensitive mayflies can indicate the level of biological health in a stream, and a mayfly census of sorts is just one of many tools used to monitor the quality of local stream ecosystems.

About 364 days of the year, you're not likely to encounter the version of the mayfly pictured above (which is of the order Ephemeroptera and the family Baetidae). The adult, winged mayfly lives only long enough to reproduce, surviving anywhere from 30 minutes to a day, during which time its digestive system is filled with air. More often you'll see mayflies in the nymph, or naiad, stage, during which they are wingless and mostly feed on algae. And despite its name, mayflies are common not only in May but also through June, July and August.