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Conservation of Ancient Fishes: Reintroducing the Alligator Gar; and What About Those Carp?

Alligator gar are being reintroduced to Illinois in an effort to enhance biodiversity and establish a trophy sport fishery. © Shedd Aquarium/Solomon David.
Alligator gar are being reintroduced to Illinois in an effort to enhance biodiversity and establish a trophy sport fishery. © Solomon David.

Posted by Dr. Solomon David, research associate at Shedd Aquarium.

Gars and bowfin have been around since the dinosaurs; in fact, they’ve outlasted them. More recently, however, a modern creature has threatened these ancient fishes: humans. Misunderstood and much-maligned, these fishes were targets of eradication efforts for more than a century (1). Now, perceptions of these toothy predators may be changing. Recent interest in these “living fossils” has led to new research and even reintroduction efforts to bring back a lost species (2,3). All species of gars and bowfin are important parts of native biodiversity and ecosystem function, but could they also impact invasive species?

Bowfin showing characteristic elongate dorsal fin in the Great Lakes gallery at Shedd Aquarium.
Bowfin showing characteristic elongate dorsal fin in the At Home on the Great Lakes gallery at Shedd Aquarium.
© Shedd Aquarium/Solomon David.

Their appearance hasn’t changed much since the Cretaceous period over 65 million years ago. Gars (family Lepisosteidae) look like alligators with fins instead of legs, characterized by elongated snouts filled with sharp teeth, armor-like rhomboid scales, and the ability to breathe air. Shorten the snout (keep the teeth), add more slime and a bow-shaped dorsal fin, and you’ve essentially got a bowfin (Amia calva). It’s no wonder these fishes are often considered less desirable than more traditional sport fish such as bass, perch and walleye. Because of their menacing appearance, misconceptions about eating valuable sport fishes and perceived lack of value (often considered “trash fish”), humans have historically sought to remove gars and bowfin throughout much of their range (1). Sometimes removal  occurred indirectly by habitat modification and subsequent loss of spawning grounds (3). In fact, humans have been quite successful in some areas; the alligator gar, the largest species of the group (they can grow over 9 feet long and weigh more than 300 pounds), was driven to local extinction from the northern extent of its range in Illinois by the 1960s (3). When caught, other gars and bowfin are often simply cast aside on the riverbank. It was once illegal in several states to return gars to the water alive!

Fortunately, perceptions of these ancient fishes are slowly changing, as new research and renewed interest from anglers are garnering a more positive image of these misunderstood fishes. For example, gar fishing guides in Texas host anglers from all over the world for the opportunity to catch (and release) a 200-pound real-life river monster. Earlier this year, scientists discovered that the genetic make-up of spotted gars can help us better understand human development and disease (4,5). Further, in an effort to restore what was lost decades ago, the Illinois Department of Natural Resources (IDNR) is reintroducing the alligator gar to several Illinois rivers to increase biodiversity and create a trophy sport fishery.

Members of the Ancient Sport Fish Project team with three species of Illinois gars. Sarah King with shortnose gar (L), Heather Brooks with longnose gar (C), and Solomon David with spotted gar (R). © Shedd Aquarium/Solomon David
Members of the Ancient Sport Fish Project team with three species of Illinois gars. Sarah King with shortnose gar (L), Heather Brooks with longnose gar (C), and Solomon David with spotted gar (R).
© Solomon David

There are seven species of gars and one species of bowfin, all native to North America, ranging from southern Canada to Costa Rica. As apex predators, what do they eat? Considered opportunistic feeders, these fishes tend to consume whatever prey items are most abundant in the area, such as forage fish, sunfish, and crustaceans. Humans, however, are not part of their diets. In fact, there have been no verified cases of attack (not even the giant alligator gar), showing that these ancient fishes pose no threat to humans. As native top predators, the question has been raised, could gars and bowfin also have an impact on invasive species such as Asian carp? What does the science tell us?

Recent research from Western Illinois University (6) showed that in some cases, shortnose gars and other native predatory fishes do in fact select for Asian carp, as young carp were found in higher numbers in gar stomachs than other prey items. However, a new study (7) showed that predation by spotted gars and bowfin had no significant impact on common carp populations. Many scientists agree that alligator gars can and do consume Asian carp, but the extent to which carp comprise their diet and the impact on Asian carp populations are relatively understudied. So, gars and bowfin are eating carp, and it’s great to see a native species preying on invasive species; other recent examples include smallmouth bass preying on round goby, and lake whitefish eating zebra mussels in the Great Lakes. But, could gar predation on Asian carp make a significant ecological impact? The numbers suggest no. When discussing Asian carp, IDNR fisheries scientists speak in terms of tons of carp per river mile. Alternatively, even a successful reintroduction of alligator gars may be only one or two fish per river mile in several Illinois tributaries (note: alligator gars are not being stocked in the Great Lakes basin). Vastly different reproductive rates are also an issue. Asian carp mature around age 3 and reproduce in larger numbers than alligator gars, which don’t mature until they’re about 11 years old and may not spawn every year. There are simply too many carp and too few gars to expect a significant impact. Time, research, and the fishes will tell us how gars and other native species may impact this gargantuan threat.

Regardless of their impact on invasive species, gars and bowfin are valuable components of native biodiversity and play important roles in ecosystem function. As top predators, gars and bowfin can help prevent overpopulation of forage fishes (such as shad) and stunting in game fishes (like sunfish), therefore helping maintain ecosystem balance (1). They can also be indicators of ecosystem health. Great Lakes spotted gars prefer clear, highly-vegetated waters, which in turn are prime nursery areas for other game species such as bass and perch; finding the gar can indicate good habitat for other sport fishes. Alligator gars are also migratory fish, relying on river-floodplain connections for spawning; successful reproduction and recruitment can indicate quality habitat connectivity for other migratory species.

A bowfin is measured, tagged, and released as part of our Great Lakes migratory fishes research in partnership with the University of Wisconsin-Madison, UW-Green Bay, and The Nature Conservancy. ©Shedd Aquarium
A bowfin is measured, tagged and released as part of our Great Lakes migratory fishes research in partnership with the University of Wisconsin-Madison, UW-Green Bay and The Nature Conservancy.
© Shedd Aquarium

Shedd Aquarium’s team of research scientists is actively involved in studying native and invasive species in the Great Lakes region, as well as rivers throughout the state of Illinois that are home to ancient fishes like gars and bowfin. In our Great Lakes migratory fishes research, finding bowfin and gars was an example of successful wetland habitat restoration, indicating several fish species quickly take advantage of newly available habitat for spawning. As we continue our research efforts in the region, we seek to find ways to protect native species from disappearing from their natural range, to maintain balanced ecosystems, and ensure sustainable populations for future generations.  While we are not directly involved in the reintroduction of alligator gar, this work can benefit ecosystems and species we do spend so much time studying.

Dr. Solomon David with an alligator gar sampled during fieldwork in Louisiana. © Shedd Aquarium/Solomon David.
Dr. Solomon David with an alligator gar sampled during fieldwork with Nicholls State University in Louisiana.
© Solomon David.

A close colleague of ours, Dr. Jeffrey Stein of the Illinois Natural History Survey’s Sport Fish Ecology Lab, is leading an effort to better understand and conserve these ancient fishes. As a collaborator on the “Ancient Sport Fish Project,” we are gathering data on age, growth and other characteristics of gar and bowfin species throughout the state. The primary goal is to evaluate the status and trends of Illinois gar and bowfin populations and provide managers with objective data needed to develop strategies for a sustainable [ancient] sport fishery. Since 2015, in partnership with IDNR, the team has tagged thousands of gars and bowfin and will eventually include alligator gar in our research efforts. You can follow along with #AncientSportFish on Twitter for updates on the project!

For more information about the reintroduction of alligator gar, listen to this podcast from the IDNR or visit their website. You can also learn about Shedd Aquarium’s research on native and invasive species on our website.

 

*Shedd Aquarium in partnership with University of Wisconsin-Madison and Green Bay, The Nature Conservancy

References:

  1. Scarnecchia 1992. A Reappraisal of Gars and Bowfins in Fishery Management
  2. Illinois Department of Natural Resources 2016. The Return of the Dinosaurs
  3. Thomas & Hilsabeck 2011. Return of the Giants.
  4. Braasch et al 2016. The spotted gar genome illuminates vertebrate evolution and facilitates human-teleost comparisons.
  5. Parichy 2016. The gar is a fish… is a bird… is a mammal?
  6. Anderson 2016. http://gradworks.umi.com/10/11/10117282.html
  7. Van Middlesworth et al 2016. Food habits and relative abundances of native piscivores: implications for controlling common carp.