Spotted gar

Spotted Gar
Spotted gar, Lepisosteus oculatus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Lepisosteiformes
Family: Lepisosteidae
Genus: Lepisosteus
Species: L. oculatus
Binomial name
Lepisosteus oculatus
Winchell, 1864

The spotted Gar (Lepisosteus oculatus) is a primitive freshwater fish of the family Lepisosteidae, native to North America from the Lake Erie and southern Lake Michigan drainages south through the Mississippi River basin to Gulf Slope drainages, from lower Apalachicola River in Florida to Nueces River in Texas, USA. It has a profusion of dark spots on the body, head and fins. Spotted gar are long and have a elongated mouth with many teeth used to eat other fish. They grow to 20-30 inches in length and weigh 4-6 pounds on average making it the smallest gar out of the four species of gar. The name Lepisosteus is Greek for "bony scale". Habitat for spotted gar is clear pools of shallow water and they are found in creeks, rivers and lakes.

Contents

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Abstract

The spotted gar Lepisosteus oculatus is a part of the Gar family (Lepisosteidae).They are notable for being one of the few extant fish species with ganoid scales. They have been known to hybridize with (and look similar to) Florida gars. It occurs in quiet, clear pools and backwaters of lowland creeks, small to large rivers,oxbow lakes, swamps and sloughs. It occasionally enters brackish waters. The fish is a voracious predator feeding on various kinds of fishes and crustaceans. Gars spawn in shallow water with lots of vegetation and cover. The spawning season occurs from April to May. A female can have multiple mating partners and the female is usually larger than the males it's mating with. The amount of eggs the female lays do vary and it can be up to about 20,000 eggs, but on average bout 13,000 eggs. They lay their eggs on leaves of aquatic plants. The eggs are green in color and have an adhesive coating to them that keeps them attached to aquatic vegetation. After 10 to 14 days the eggs hatch. At this stage in their life the gar are most vulnerable. The lifespan for L. oculatus varies between males and females. The maximum lifespan for a gar is 18 years old. Males mature at the age of two or three whereas females mature at three or four years old.[1] Females on average are known to be larger and live longer than the males. Females also have less annual mortality rates.[1]

Geographic Distribution of Species

The spotted Gar is native to North America and its current range is from southern Ontario to the west from the Nueces River in Texas east to the Northern coast of the Gulf of Mexico and southeast to the lower Apalachicola River in Florida. Although the Great Lakes basins encompass the most northern extent of the spotted gar in the United States, those basins are the southern Lake Michigan basin, Lake Erie basin and southern Lake Huron basin. The gar population is small in the north and is being threatened in Lake Erie by the destruction of their habitat and pollution. The gar is more common in the southern waters like the Mississippi River basin from southern Minnesota to Alabama and western Florida currently. Historical records indicate the spotted gar resided in the Thames river and Sydenham river in Ontario, Canada. Also the fish was once common in Illinois in the Green and Illinois rivers to the swamps in Union county though sporadic, the population has dwindled in these water systems because of the loss of specific habitat they need to live in which is clear pools with lots of aquatic vegetation.

Ecology of the Spotted Gar

A diet study of the Spotted gar in the Tamiami Canal, Dade County, Florida by Burton P. Hunt reports the diet of a Spotted gar consists of four species of fish; golden topminnow, warmouth, bluegill, and spotted sunfish which adds to 18.1 percent of total food volume in the stomach, while 57.5 percent of the gars stomach content was mainly shrimp.[2] Other invertebrates filled the remaining 23.6 percent of the stomach. Gar is also known to eat insect larvae and algae and they obtain this through their food chain. Herbivorous fish eat the algae and zooplankton, and then herbivorous invertebrates are eaten by gar. Also another chain would be algae are eating by herbivorous invertebrates and other carnivorous fish eat them, then they are eaten by the gar.[2] Gars do not have many predators, only carnivorous fish would eat them and it would have to be at an early life stage. Gars are a main predator in the aquatic food chain in lakes and rivers. The fish would compete with other carnivorous fish such as the bowfin (Amia calva). In a study done in the Atchafalaya River Basin, Louisiana, Gregg A. Snedden ā€œindicated that most spotted gars were shoreline oriented (P < 0.0001), preferred submerged branches as cover, and avoided areas of exposed bank (P < 0.0001).ā€.[3] During a flood pulse a floodplain provides habitat for spawning and nursery habitat for gar eggs. Movement rates were higher during the summer than during the fall and winter and rates were greater at night than at dawn during both seasons. The temperature greatly affects their moving rates and their ability to range their home turf. When the water is warmer during the spring and summer they travel more often than during the cold seasons. Snedden also advises Spotted gars eat 70 percent of their food intake at night compared to dusk and dawn.[3] Abiotic factors that affect the spotted gar by humans include destruction of habitat and increased sedimentation in the water. In 2002 the Louisiana Department of Environmental Quality, Office of Water Resources in coordination with the US Environmental Protection Agency took fish tissue samples in the Lower Mississippi River to test for heavy metals and organic compounds.[4] Spotted gar was found to be a cancer risk with high concentrations of heavy metals and organic compounds.[4]

Life History

Spotted gar spawn in the spring time in the months of April, May and June or when the water temperature is between 69.8 Ā°F and 78.8 Ā°F depending on the location. Spawning habitat includes floodplains and wetlands with an abundance of aquatic vegetation. Also shallow water is preferred estimating about 0ā€“1 m in water depth.[5] A female can have multiple mating partners and the female is usually larger than the males they mate with. The amount of eggs the female lays do vary and it can be up to about 20,000 eggs. They lay their eggs on leaves of aquatic plants. The eggs are green in color and have an adhesive coating to them that keeps them attached to aquatic vegetation.[6] After 10 to 14 days the eggs hatch. Males mature at the age of two or three whereas females mature at three or four years old. The maleā€™s average lifespan is 8 years old and the femaleā€™s average lifespan is 10 years old. Females have less annual mortality rates.[6] The maximum lifespan for a gar is 18 years old.

Current Management

Today humans are impacting this fish species by destroying habitat, aquatic vegetation, and creating sedimentation in the waters of North America. Waste and chemical drainage into lakes and rivers causes chemical buildup and contamination of the water. Consequently, the water becomes murkier and causes predatory fish to have high Mercury (Hg) levels or accommodate carcinogenic compounds into their body.[7] Spotted gar desire clear pools of water, and anthropogenic factors can decrease their survivability. This species is not on the U.S. Fish and Wildlife Service federally endangered species list, although in some Northern states it is on special concern lists. In Canada the fish is designated as threated by the Committee on the Status of Endangered Wildlife in Canada. For Canadian waters the spotted gar is protected by the Species at Risk Act and the federal Fisheries Act. The Habitat Stewardship Program for Species at Risk works to protect the spotted gar and its habitat. Current management plans for spotted gar include: increasing water quality, minimizing or avoiding pollution, analyzing contaminated samples.[8] The most important biological decline of the species is habitat destruction. First without the habitat gar require they cannot grow and reproduce normally resulting in a decrease of the population. Gars need the areas to spawn and lay their eggs in aquatic vegetation, without the proper spawning habitat their eggs will be less likely to hatch or will be more vulnerable to predators or anthropogenic factors.

Management Recommendations

This species should be monitored and managed by electroshocking. Electroshocking would be conducted in shallow areas of lakes and rivers where there is gar habitat. After shocking numerous places a population sample can be made and then biologists can base a management plan on the sample population of the certain water system. Population sampling could occur every few months or annually. Sampling to monitor the species could be to visually monitor. Be in a boat or on the shore and visually count the number of gar and observe their condition. Anglers could fill out surveys for how many spotted gars they have caught or for bow anglers to report how many spotted gars they shot each time. Underwater technology such as a camera could be used to look for spotted gar. Certain shallow areas could be outlawed for fishing and those areas could be sampled to compare the population to the fishing areas. Spotted gar has few predators therefore no invasive species are threating the fish and need to be removed. When dealing with abiotic factors recommendations for spotted gar management would be to first know the factors that affect the gar and from there managers and environmentalists can set guidelines for the advantage of the species. Harbor improvements, filling, dredging and destruction of shoreline habitats negatively affect the fish and should be stopped. These actions result in habitat loss and could ultimately decrease the population after a few generations of repetitive negative activity. The water quality should have a designated quality level and biologists should check the levels often and address the issues if the level is low quality. Industrial corporations and pollution should be addressed and dumping chemicals, waste and organic compounds into the waters and environment should be monitored and stopped. Citizen who use lakes and rivers that gar are present in should be educated on their important role in the aquatic ecosystem and have a joint effort to help keep gar present for many generations to come. Research in main rivers should be conducted on gar tissue samples to test for contaminants. Spotted gar is not a popular game fishing species to anglers, but to bow fishers they are a prized species to shoot. Promoting gar fishing would help the conservation of the species. Increasing their popularity with anglers would help the fish to have a better environment because if anglers fish for them the anglers care about the habitat they flourish in and they will fight to protect it.

External links

References

  1. ^ a b Murie DJ, Parkyn DC, Nico LG, et al. 2009. Age, differential growth and mortality rates in unexploited populations of Florida gar, an apex predator in the Florida Everglades. Fisheries Management and Ecology. 16: 315-322.
  2. ^ a b Hunt, Burton. 1953. "Food Relationships Between Florida Spotted Gar and Other Organisms in the Tamiami Canal, Dade County, Florida." Transactions of the American Fisheries Society. 82: 13-33.
  3. ^ a b Snedden, G.1999. Diel and seasonal patterns of spotted gar movement and habitat use in the lower Atchafalaya River basin, Louisiana. Transactions of the American Fisheries Society. 128:144-154.
  4. ^ a b Watanabe, Karen. 2003. "Fish tissue quality in the lower Mississippi River and health risks from fish consumption." Science of The Total Environment. 302.1-3:109-126.
  5. ^ DFO. 2010. Recovery Potential Assessment of Spotted Gar (Lepisosteus oculatus) in Canada.DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2010/047.
  6. ^ a b Alfaro RM, Gonzalez CA, Ferrara Am.2008. Gar biology and culture: status and prospects. Aquaculture Research 39: 748-763.
  7. ^ Hayer, Cari-Ann.2008. "Influence of Gravel Mining and Other Factors on Detection Probabilities of Coastal Plain Fishes in the Mobile River Basin, Alabama." Transactions of the American Fisheries Society.137: 1606-1620.
  8. ^ Brim, M.S., D. Bateman, R. Jarvis. 2000. Environmental Contaminants Evaluation of St. Joseph Bay, Florida. Publication No. PCFO-EC-00-01. U.S. Fish and Wildlife Service, Panama City Field Office, Panama City, Florida. Vol 1 - Vol 2.

Spitzer, Mark. Season of the Gar: Adventures in Pursuit of America's Most Misunderstood Fish. U of Arkansas Press, 2010.