Friday, September 11, 2015

Such a long nose and such big teeth, it can only be the Longnose Gar, by Don Orth

The Longnose Gar Lepisosteus osseus (Linnaeus, 1758) never fails to fascinate the nature observer.  The Gars have many unique traits making them unlike most other fishes.  They are easily distinguishable by the extremely long snout, numerous sharp teeth, long cylindrical body form, bony scales and the abbreviated heterocercal tail.   Along with the Sturgeons, Paddlefish, and Bowfin, they are living representatives of some of fishes that existed over 100 million years ago.     Say what?  Yes they possess traits that were present on ancenstral Gars over 100 million years ago!
Longnose Gar captured in Virginia (photo by J.D. Schmitt)
In Virginia, the Longnose Gar is the only native Gar and is the most widespread species in North America.  The name Lepisosteus comes from a combination of the two words lepis the Greek word for "scale", and osteos which is Latin for "bony".  Similarly Lepidoptera is an order of insects, butterflies and moths, named for scale and greek pterin for wing.  In the case of the Gars, the name is used to describe the extremely hard ganoid scales.  The specific epithet osseus is also Latin for the word "bony".  Thats redundant, but you cant blame it on Linnaeus; Carolus Linneaus originally classified this fish as Esox osseus, or Gar Pike.    

No other fish in Virginia has such a hard bony covering.  The ganoid scale emerged at a time when very large toothy aquatic reptiles, the large pliosaurs and relatives were still around.   This bony covering is extremely difficult to pierce even with a sharp filet knife.   Each ganoid scale is rhomboid in shape and has an articulating dorsal peg that articulates with a ventral socket joint on the adjacent, dorsally-placed scale.  Ganoid scales have a bony basal layer, a layer of dentine, and an outer layer of ganoine (an inorganic bone salt).  Ganoid scales in gar are tightly overlapping on all parts of the body creating the diamond-shaped pattern and the rather inflexible body form.

Top: Lateral scales of Longnose Gar (photo by Uland Thomas.  Bottom: Close up of Longnose Gar scales (photo by D.J. Orth)
The gar body form is a long flexible cylinder, not designed for sustained swimming. The dorsal and anal fins are both set well back on the body, and with a large rounded tail fin that provides stability during caudal thrust.     The gar is an ambush predator that sits and waits motionless until potential prey are near.   With a rapid tail thrust andhead sweep they impale the prey fish in their long toothy mouth.    The Longnose Gar relies more on the speed of lateral movement rather than biting to impale a prey fish; there is very little biting force at the tip of its jaw.    Recently a diet study on Longnose Gar  in Charleston harbor and associated estuaries of South Carolina confirmed that the adults are opportunistic piscivores.  In this location the dominant in the diet were Atlantic Menhaden, shad, drum, killifishes, mullet, and Penaeid shrimp.   In Virginia tidal populations, the top five prey consumed by adult Longnose Gar were White Perch, Menhaden, Fundulus spp., Atlantic Croaker and Spot.
 Longnose Gar is easily distinguishable from other gars by its long, narrow snout.  The snout length is more than 13 times its narrowest width in specimens 50 mm long or larger.  Juveniles have a shorter snout, which grows proportionally faster than the body.   Other species gar can be distinguished by snout shape and pigment patterns.  The spots on the body of the Longnose Gar are smaller and generally less well developed than on Spotted Gar.

Top; Four Gars compared (Source Kentucky Dept of Fish & Wildlife Resources).
Bottom:  Skulls of Longnose Gar in lateral view and dorsal view (photo: D.J. Orth)
Gars have a bimodal system for respiration.  They can obtain oxygen via gills or via air breathing.   The lung is highly vascularized and homologous to the tetrapod lung. It occupies 10% of the volume of the fish.   It is this use of bimodal respiration that allows the Longnose Gar to be successful in many waters with low oxygen content that would otherwise be inhospitable.  Yet in hypoxic (low oxygen) conditions they may continue with normal levels of activity as they rely on air breathing.    Consequently they are widely dispersed in the lowland lakes, rivers, and streams of the Atlantic and Gulf slopes and throughout the Mississippi River and lower Great Lakes basins.

Distribution of the Longnose Gar (Source: US Geological Survey)
Longnose Gar are primarily freshwater fish; however, they have been captured in tidal rivers at a maximum salinity up to 15-21 ppt.  In some studies, they appear to move significant distances.  There also tends to be a springtime movement to smaller tributaries for spawning.     

Do not eat Gar eggs!   Unlike the Paddlefish, Sturgeon and Bowfin, the eggs of Gars are not used for caviar.  In fact they are highly toxic to mammals and birds, but not fishes.     This remains an unsolved mystery.   One  presumes that fishes would be a primary source of predation on Gar eggs,  yet this egg toxin does not deter fishes from eating the eggs.  Why evolve an egg toxin specific to mammals and birds?  

Many authors suggest that there is no sexual dimorphism in Longnose Gar other than females being larger than males .  However, Long and Ballard  in collections of breeding Longnose Gar, reported that adult females possessed a silvery body coloration, while males had a golden cast to their scales.   Patrick McGrath analyzed morphometrics of male and female Longnose Gar and demonstrated that males had a longer anal-fin base and wider heads and mid-snouts than females.   

Longnose Gar may spawn in relatively barren shorelines or quiet vegetated habitats.  Longnose The female spawns with one to several males who use their snout to nudge and position the female, followed by a simultaneous release of eggs and sperm.     Gar lay sticky eggs on bottom, often in weedy bays on submerged vegetation.  The dark eggs are about 3mm in diameter and poisonous for humans to eat.   The may hatch in 6 days at temperatures between 18-20C.  By day four the embryo still has a large yolk sac and has developed an adhesive organ on the head.  The adhesive organ is larger than the embryonic eye.  By the time of hatching and yolk sac absorption, the eye size is larger than the adhesive organ.  The adhesive organ on its head helps the embryo to attach to vegetation and other structures where they hang vertically.  They lose the adhesive organ when snout and mouth is fully formed and feeding can commence. 
Top: Drawings to two stages of larval Longnose Gar with (left) and without (right) adhesive organ. Bottom: Photograph of larval Gar with adhesive organ.  (Source).

The smallest juveniles have an appearance very different from adults.  The small juveniles have a long lateral stripe, shorter snout, and long caudal ray filament.     At this stage, the Longnose Gar are surface feeding on copepods, cladocerans, and aquatic insects before making the transition to piscivory.

Longnose Gar are not classified as a game fish; however, in recent decades they have begun to gain a specialized following.  The Texas State Record Longnose Gar was a 50 pound 5 ounce specimen taken from the Trinity River in 1954.   The Longnose Gar is a special challenge for the interested angler.    However, this specialized fish is best pursued with a specialized fishing technique.   You simply do not want to embed a treble hook into the bony jaw of the Gar.  Neither you nor the Gar will be happy about the outcome.  One of the alternative techniques is the use of a rope lure.   With this method the unbraided rope gets tangled in the teeth as the Gar attacks the bait.  
Rope lures used specifically to target Gars (source)

Also, bowfishers have always known that the Gars are a suitable target as they lie motionless near the water surface -- easy targets for an accurate bowfisher.   While bowfishers have quietly targeted Gars for sport and an occasional meal, recently bowfishing tournaments have become popular.   And the tournaments have raised an ethical dilemma regarding the harvest and subsequent waste of native Gars.   We will  see if tournament organizers treat Longnose Gar and other Gars differently in future tournaments. 

Jason Emmel with a Longnose Gar bowfished in Virginia. (Photo: J.D. Schmitt)
Can I eat them?   Yes, but it takes a very different approach to cleaning.  First you nail the head and tail to a board.   Then you use sharpened tin snips to cut through scale jacket straight along the backbone to the tail.  This will reveal two strips of white flesh.  Meat is firm and has a color and texture that resembles chicken or alligator more than a flaky fish filet.  Gar fillets may be dredged in a batter and fried in hot oil.    For more about catching, cleaning, and eating Gars, view this video. 

Fossil Gars have been found in North America, South America, Africa, India, and Europe, though the origins of this group remain highly uncertain.    Perhaps the ancestral Lepisosteiform fish arose before or during the Cretaceous, which began 145 million years ago.   This ancestral fish arose in the late Jurassic before the breakup of the supercontinent Pangea.    Closest relatives to the Gars are Bowfin (Amia calva).  The most recent phylogenetic analyses support the hypothesis that these two groups have a common ancestor and form a basal-sister group (Holostei) to all other bony fishes (Teleostei).   
Longnose Gar have largely been ignored in the development of fisheries management programs.   Although other Gars (Alligator Gars and Tropical Gars) are declining in many areas, there is little directed effort to monitor status of Longnose Gar populations throughout its range.  No estimates exist for sport or commercial harvest and the effect on populations.   

Scales may have been used as arrow points by Native Americans    Some artisans are using Gar scales to make earrings.   
If you are interested in more information about the family Lepisosteidae, the Gars, then check out this website now!  

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