Last week, when colleague Phil Willink showed me photos sent to him by the Illinois Department of Natural Resources (IDNR) I was excited by what I saw; an elongate fish with a toothy snout, like an alligator with fins instead of legs, the tell-tale traits of a gar. But this wasn’t just any gar, the ornate olive blotches over the head, body and fins indicated it was a spotted gar (Lepisosteus oculatus); the focus of my dissertation at the University of Michigan. Seeing field photos of spotted gars is always great, but learning the location of the find absolutely thrilled me: this fish came from Chicago waters! After thoroughly reviewing the photos and checking spotted gar distribution maps, I got in touch with Steve Pescitelli, the IDNR Biologist who had sent the photos, for more information about this fish.
During a routine electrofishing survey in the North Shore Channel, IDNR biologists were monitoring for invasive Asian carp; thankfully they found none, but instead turned up a spotted gar, one of seven extant species of an ancient family dating back to the dinosaurs. Underappreciated and historically maligned, this is a unique and potentially important discovery for researchers, environmentalists and gar enthusiasts alike as it’s the first-ever recorded in the Chicago Area Waterway System (CAWS), and the western-most occurrence associated with Lake Michigan. After its discovery, the fish was measured to be thirty-one inches, photographed and safely returned to the water.
So why is this find significant? Spotted gars can serve as important ecological indicators of ecosystem health generally requiring clear water and large amounts of submerged aquatic vegetation to thrive, habitat that is also important nursery area for game species such as largemouth bass and yellow perch. These habitat preferences also differ from other more common Illinois gar species (i.e. longnose and shortnose gars), which are more tolerant of turbid environments. This brings up two big questions: given these habitat preferences, how did this fish get here and what does it mean?
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The path this spotted gar took to the Windy City is uncertain but rest assured we are investigating! The fish may have moved north from the Des Plaines River and through the lock system, or perhaps taken an extended trek along the shores of southern Lake Michigan, although suitable habitat is sparse along the lakefront. Curiously, other recent occurrences like the finding in Mazonia State Wildlife Area and lower Des Plaines River are all in what was previously considered an area of disjunction in the spotted gar’s distribution, a “dead zone” of sorts.
Recent studies (including my own research at Shedd) suggest that in a given population of a species, there are individuals that “stay put,” some that move a little bit and some that may have more of an “explorer” behavior, traveling longer distances than the norm. All of these individuals are likely important for perpetuating the species in the short-term as well as the long evolutionary haul, particularly in the face of habitat loss or climate change. This spotted gar may be one of those “explorers,” wandering to newly-available, improved habitat, perhaps with others yet to follow.
We cannot say for certain that finding a lone spotted gar will lead to others; and we can draw few conclusions from just one fish. Ideally we would find more fish in the same area, and therefore determine if this sighting was an anomaly or has greater implications. If we speculate that this fish is representative of others, we could presume that habitat in part of the CAWS, or somewhere nearby, is of relatively good quality. This sighting is certainly an intriguing, potentially positive find for the CAWS even if it’s only one fish; it just might be indicative of an improving ecosystem. Thanks to the efforts of Illinois DNR, I’ll definitely be trying to spot this primitive fish whenever I look into the waters of the Windy City!
Dr. Solomon David joined Shedd in 2012 as a postdoctoral research associate in the Daniel P. Haerther Center for Conservation and Research. His work focuses on migratory patterns of nearshore fishes in Lake Michigan and the importance these migrations play in Great Lakes ecosystems.