Captive Care Notes: Gars (Family Lepisosteidae)
Because of their toughness, gars are easy to keep in the home aquarium as long as you're able to supply a steady diet of live fishes, or wean them over to other high-protein fare. Young gar, because of their fast metabolism, will waste away if not fed at least a couple of feeder-size guppies a day. But be forewarned: Properly fed young gar grow quickly and can reach a foot or so within the first year. Adult gars can be trained to eat thawed frozen smelt and beefheart. Aquarist Ray Wolff feeds pond-kept gar injured bait fish; when the gar begin to associate Ray with food, he gradually switches their diet to floating pellets.
Keep gar in as wide an aquarium as possible to prevent injury to their large snouts, with plenty of floating and submerged plants to provide cover. Avoid driftwood and rockwork except in exceptionally large aquaria. It goes without saying that gars can't be kept with other fishes not much larger than themselves, although larger, more active tankmates can harass sedentary gars. Under the right conditions, you can expect a gar to live in the aquarium for many years, even decades.
Because they can breathe atmospheric air, gars are none too fussy about water conditions. Since they can tolerate higher temperatures, some aquarists keep them with large tropical piscivores, such as oscars and jack dempseys. Keep the tank covered as any surface-dwelling fish is a jumper. But don't keep the tank so tightly covered that no atmospheric air gets inside. Even in highly oxygenated aquaria, gars need to "break" to avoid drowning.
Young gars can be collected with dip nets and small seines in shallow, still waters with lots of vegetation. Carefully remove all the vegetation from the net or seine before making another pass; camouflaged within those plants, leaves and twigs may be the fish you're looking for. Young gars can also be collected at night, when they float near the surface and are easy to net once you learn to distinguish their shape from that of floating debris. Aquarium stores occasionally sell fish mislabeled as Alligator Gar; these are almost always the more common (and much smaller) Shortnose Gar or Spotted Gar.
Aquarium gar spawnings are rare. In fact, I know of only one. In 1998, legendary fish breeder Hiroshi Azuma induced captive Spotted Gar to spawn after 23 years of trial and error. The gars were conditioned in a 400-gallon aquarium, which they shared with six Longnose Gar, on a diet of live and frozen fish, frozen and dry krill, live crayfish, and floating pellets. Water temperature varied seasonally from 24-30C (75-86F). pH was 4.8-6.4. GH was 3-4. Four 40-watt fluorescent bulbs were on 12 hours a day, with a 7-watt night light above the tank. Water quality was maintained with a wet-dry filter and monthly water changes of 33-50%. Courtship behavior was first noted in May when daylength and temperature began to increase. The gars were both five years old. The female measured 49 cm (19.3 in), the male 45 cm (17.7 in). In June the gars were moved to a 118-gallon tank, 70% of which was filled with water from the old tank. The other 30% was aged for five days in an aerated tank. Water parameters at time of spawning were 28.7C (83F), pH 6.4, GH 3.0. Light was mostly artificial, with two 80-watt flourescents on 12 hours per day, with a 7-watt night light on the ceiling. Spawning began at 2 a.m. Azuma could not see the gars, but he could hear them beating at the surface with their fins. Spawning ceased around dawn. The adults were separated shortly thereafter. About 2500 eggs were stuck to plants, stones and the tank bottom. The eggs were moved to hatching tanks with water mixed from the spawning tank and the aging reservoir. Water temperature was 26.5C (80F). By mid-June more than 95% of the eggs had hatched. The fry became free-swimming and started feeding on newly hatched brine shrimp three days after hatching. Growth was extremely rapid. The fry were 3.9 cm (1.5 in) and taking zebrafish fry 12 days after hatch. Larger fry cannibalized smaller fry. By late November the baby gar were 28.8 cm (11 in) long.
Government fish hatcheries are experimenting with alligator gar, hoping that hormone injections will induce captive spawnings. Private John Allen National Fish Hatchery in Mississippi and Tishomingo National Fish Hatchery in Oklahoma have spawned the Alligator Gar a combined three times and have gotten the young to feed, but optimal culture conditions have yet to be determined. Researchers at the Mexican Ministry of Fisheries have had success with a rather low-tech breeding operation. During the last week of May or first week of June, one female and four male Alligator Gars are placed into 10 x 5 m (33 x 16 ft) earthen ponds lined with branches of casuarina, a kind of pine, which serve as a substrate to catch the adhesive eggs. The gars are placed in the morning and usually spawn that night or the next. The fry are fed daphnia. Propagated fry from this facility have been used to determine that an Alligator Gar's intestinal tract is fully formed five days after hatching, at which time the larvae can be weaned to accept a floating artificial feed that's 50% crude protein. Mexican researchers also found that an anti-thyroid compound is successful in reducing cannibalism among captive Alligator Gar larvae.