PHOENIX — Have the redear sunfish at Lake Havasu really gone quagga crazy? Have these panfish that really can fill a pan, and are widely regarded as one of the better fish species to eat, found a surplus of invasive quagga mussels to munch?

A mystery remains: Redear sunfish at Havasu have been reaching world record sizes. But why, exactly? Let’s dive into this piscatory puzzle.

Five years ago, “panfish” took on a new meaning.

We’re at the time of year when Lake Havasu tacked its world-record pin on the fishing map. On February 16, 2014, Hector Brito caught a 17-inch, 5.78-pound world-record redear sunfish on a dropshot-rigged nightcrawler.

“I didn’t expect the record to last this long,” Brito said. “It’s amazing.”

This 45-mile fishing wonderland created by the Colorado River on the western-most strip of Arizona, adorned like a leather belt by the regal London Bridge, allows an angler to fish from the beach on the Arizona side and see the California mountains on the other. Some of those anglers said they witnessed a dramatic increase in the sizes of redear sunfish from 2009-2014 that — coincidence or not — occurred after invasive quagga mussels were first discovered in 2007 at Havasu.

In 2014, the U.S. Bureau of Reclamation (BOR) did a study about the effects of redear and bluegill on quagga populations and found these sunfish do consume quaggas. Even more, the redear reduced quagga numbers by as much as 25 percent. The experiments of the study were conducted in field enclosures of Lake Havasu, as well as in the BOR’s Boulder City, Nevada Fish Lab. See the updated report.

The Arizona Game and Fish Department can’t verify that redear sunfish, also known as “shellcrackers” because of their pharyngeal teeth (teeth in their throat) that allow them to crush crustaceans such as snails, are reaching unprecedented sizes due solely to quaggas as an additional food source. Other biological factors include Havasu’s food base of grass shrimp and redswamp crawdads.

Regardless, Havasu is home to some of the biggest shellcrackers on the globe.