Banded pygmy sunfish
| Banded pygmy sunfish | |
|---|---|
 | |
| Not evaluated (IUCN 3.1) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Perciformes |
| Family: | Elassomatidae |
| Genus: | Elassoma |
| Species: | E. zonatum |
| Binomial name | |
| Elassoma zonatum D. S. Jordan, 1877 | |
The banded pygmy sunfish, Elassoma zonatum, is a species of pygmy sunfish endemic to the United States, where it is found from Indiana and Illinois to Texas to the Atlantic coast. It prefers densely vegetated bodies of slow-moving water. This species can reach 4.7 cm (1.9 in) in total length, though most do not exceed 3.5 cm (1.4 in).[1]
Distribution
The banded pygmy sunfish is a dwarf fish that can live in rivers, streams, lakes, ponds, and even swamps. This species is historically found only in the continental United States, with relatively little change in distribution. One exception to this is minor decreases in species distribution due to habitat loss. They have historically been residents of the Mississippi River drainage system and Gulf coastal plain region. Currently, they are found from the lower Roanoke River drainage in North Carolina to the southern to middle parts of the St. Johns River in Florida. Also they are found west to the Brazos River drainage in Texas and north to lower Wabash River drainage in Indiana and Illinois.[2] Being a member of Elassomatidae, this species of pygmy sunfishes is no different in habitat strategy. It prefers to live in slower to still water conditions with higher sedimentation content, hence the swamps and ponds. However, the human development of wetland habitat over the ages has caused a decrease in banded pygmy sunfish and other pygmy sunfish habitat. Though the banded pygmy sunfish can retreat to lakes, streams, and rivers when wetlands are being drained, they need the wetlands for breeding.[3] Thus, the true reason for the disappearance of the banded pygmy sunfish from certain areas is not just a loss of any habitat, but the loss of its breeding habitat. When this happens, the population eventually dies off, leaving an area that can no longer support the species.
Ecology
Stomach contents of 46 individual banded pygmy sunfish (26 of which were spawning adults) collected at Mound, Louisiana, were examined for food identification. The main food identified included insect larvae (mostly from the family Chironomidae), small crustaceans, and snail eggs. The crustaceans and snail eggs combined constituted the majority of the content. Next in quantity were insect larvae. Minute amounts of algal spores were ingested by these fish. These algae were most likely taken in accidentally with other prey in the presence of algal blooms. Lastly, no other fish species or banded pygmy sunfish larvae were found in the stomach contents.[3] The banded pygmy sunfish lives in rather eutrophic conditions such as swamps and ponds. They are able to live in sedimentation levels that make oxygen availability less than 0.5 mg/L of water. Very few fish species can survive in this hypoxic condition. The only other notable fish that have an impact on E. zonatum are live-bearers (Poeciliidae), the grass pickerel (Esox americanus), and bowfins (Amia calva).[4] The bowfins are known to be occasional predators on the pygmy sunfish family. Occasionally, the grass pickerel and live-bearers are competitors for food with the pygmy sunfish. Other than fish, water snakes and fish-eating birds are known to be enemies. Water beetles and Ondonta nymphs are known to be competitors for insect larvae.[3] Wetland habitat is important for spawning habitat, but it is also an important habitat for food and protection. It provides dense plant matter (especially Ceratophyllum) for cover against predators and as a laying area of snail eggs. This habitat is also excellent as a source for insect eggs and larvae. Thus, the human development of wetland habitat not only affects Elassomatidae, but several other species of fish and insects, as well.
Life history
Banded pygmy sunfish are spring spawners which usually spawn in March. Eggs are laid on ceratophyllum if it is available, as it is in most wetland areas. If not enough ceratophyllum or similar vegetation is available, then eggs are scattered out on rocky bottoms in still water. The entire spawning process takes about 5-6 min. After the eggs are laid, the male chases the female away from the nest site, since she would cannibalize the eggs. This species of pygmy sunfish can spawn two or three times in a year as determined by ova regrowth. About 96-970 eggs will be in a clutch depending on a female size range of 2.25 cm to 3.5 cm in length, respectively, as well as on the fecundity of the female. Egg diameter ranges from 3.7-3.8 mm. The egg, on average, takes 110 hours before it begins to hatch. The newly hatched larvae are tadpole-like in shape with four pairs of gill arches with a rhythmic gill movement. The eyes are without pigment and no mouth is developed at this stage. Protein from the yolk enters the body through diffusion into the blood stream until the mouth is fully developed. Larvae are recorded from 3.5-3.7 mm in length and the juveniles are from 8.0-8.5 mm in length. The time it takes for newly hatched larvae to mature into full-grown adults is on average 100 days. Cooler temperatures of 21-23°C are optimal for growth. Adults are sexually mature at one year of age.[5][3] The average lifespan of a banded pygmy sunfish is around 2.5 years, with the maximum recorded age at three years.[6]
Management
Certain members of Elassomatidae have been listed as threatened species, but the banded pygmy sunfish is one of the few widespread enough to stay off that federal list. No state agency has listed the banded pygmy sunfish as threatened, either. Habitat loss is the most immediate threat to this species. As wetland habitat is lost due to industrialization and agriculture breeding habitat and important food species disappear with it. Efforts are in place today to manage wetland habitat across the country. The federal standards of the USDA are to retain a minimum of 2% wetland in every state territory in the eastern United States. While no agency or refuge is set up to protect this species, the conservation of wetland habitat acts as an umbrella for the species to maintain its population numbers. Fortunately, this resilient species can survive in eutrophic conditions and warmer temperatures. While some members of Elassomatidae can hybridize, E. zonatum can not.[7]
Monitoring of this species has been done by seining and performing sample counts. Certain habitats with high population densities should be set aside for protection. So far, no invasive species has been noted to compete with or prey on the banded pygmy sunfish.
References
- ↑ Froese, Rainer and Pauly, Daniel, eds. (2013). "Elassoma zonatum" in FishBase. April 2013 version.
- ↑ 'Elassoma zonatum'. Fish Base. Last modified October 6, 2010. http://www.fishbase.org/summary/speciessummary.php?id=3366
- 1 2 3 4 Barney, R. L., and Anson, B. J. 1920. Life History and Ecology of the Pygmy Sunfish, Elassoma Zonatum. Ecology 1:241-256.
- ↑ Killgore, Jack, and Hoover, Jan J. 2001. Effects of Hypoxia on Fish Assemblages in a Vegetated Waterbody. Aquatic Plant Management 39:40-44.
- ↑ Mettee, M. F., and Scharpf, Christopher 1998. Reproductive Behavior, Embryology, and Larval Development of Pygmy Sunfish. American Currents, Winter 1998.
- ↑ Jones, W. J., and Quattro, J. M. 1999. Phylogenetic Affinities of Pygmy Sunfishes (Elassoma) Inferred from Mitochondrial DNA Sequences. Copeia 1999:470-474.
- ↑ Quattro, J. M. et al. 2001. Gene-Gene Concordance and the Phylogenetic Relationships among Rare and Widespread Pygmy Sunfishes (Genus Elassoma). Molecular Phylogenetics and Evolution 18:217-226.