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(D. S. Jordan, 1877)
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The southern studfish has its historical distribution in the upland tributaries of the Alabama River in Alabama (except the Tallapoosa River system); in northern Georgia, in a few of the headwater tributaries of the Chattahoochee River; in the upper Chattahoochee River drainages in northern Alabama and southeastern Tennessee; and the Tennessee and Cumberland River drainages in eastern Tennessee.
Currently, the studfish still occupies all the historical distribution areas and seems to be holding a sustainable population in comparison to the northern studfish (Fundulus catenatus), which is seemingly being replaced in these areas. The decrease in some small areas, although not significant, as in Alabama, and the failure to collect additional specimens from previous samples may indicate this species has been extirpated from the Cahaba River system. The southern studfish is also thought to be replaced in the Tallapoosa River system by the stippled studfish (Fundulus bifax). The cause of this decline is the increase in road runoff into these waterways and competition for food and breeding areas.
Prey and predators
The southern studfish's larger crushing teeth are correlated with its diet of 80% mollusks and crustaceans, although the younger specimens collected also contained small insects and invertebrates. The development of their teeth is a key factor in the diet of the species; as an individual matures, it will go through an ontogenetic shift in diet. The amount of food consumed is greatest in the months preceding and during spawning, and lowest during fall and early winter. This species' direct competitors are other top minnows and killifish also native to these areas, such as the central stoneroller (Campostoma anomalum), the coosa darter (Etheostoma coosae), and the trispot darter (Etheostoma trisella). The predators of this species are in the families Centrarchidae (in particular, the genus Micropterus) and Percidae.
Some abiotic factors that may affect this species is that they are very limited in geographic distributions and/or in characteristics of their environments, especially with respect to water temperature, dissolved oxygen concentration, and salinity. Ambient temperature is often thought of as the key abiotic condition influencing the distribution and abundance of aquatic organisms, increasing the areas needed for laying eggs. This is due to its pervasive increase of chemical activity. However, both ambient temperature and salinity are key factors in the success of this species because of their effects on distributions of aquatic organisms. Some human influenced abiotic induced factors are caused by the alteration of road crossings and urbanization of runoff areas. This factor effects both the structure of the aquatic habitat but also the biology of this habitat.
This species prefers margins, pools, and backwaters of creeks and small rivers, with moderate to high gradients, a permanent flow of clear water, and the bottom usually consisting of sand, gravel, rock, and occasionally an admixture of silt. F. stellifer is most commonly found in shallow, sandy backwaters near clear creeks with gravel bottoms. Males establish and defend small territories in shallow, quiet-water spawning areas. Spawning occurs between late April and early June. This species does not migrate or prepare a nest. Sexual maturity is reached in the second full spawning season for both sexes, with females having a maximum ovum diameter of 2.75 mm. The average size of this species is 8.01 cm. Maximum age appears to be just over two years for both sexes, as the oldest specimens collected were estimated at 28 months of age. Although this species is not migratory, its distribution is affected by the alterations of road crossings mentioned by a study done in north Georgia on the Etowah Basin streams. These alterations affect the structure of these aquatic ecosystems, changing how these species travel, eat, and spawn.
One major management effort to protect the southern studfish and other killifish and top water minnows, located in Alabama, focuses on the watershed features and current biological and habitat conditions of Hatchet Creek. This management effort was established by the Alabama Department of Environmental Management with the support of the Geological Survey of Alabama. The focus of this effort is to research and develop strategies of future management based on water quality variation, stream hydrology, watershed features, land-use patterns, and biological conditions.
- Michael J. Ghedotti, Andrew M. Simons, Matthew P. Davis, R. M. Wood. 2004. Morphology and Phylogeny of the Studfish Clade, Subgenus Xenisma (Teleostei: Cyprinodontiformes). Copeia Vol. 2004, No. 1; pp. 53–61.
- Rebecca C. Fuller, J. D. McEachran. 2001. Patterns in Male Breeding Behaviors in the Bluefin Killifish, Lucania goodei: A Field Study (Cyprinodontiformes: Fundulidae). Copeia Vol. 2001, No. 3; pp. 823–828.
- J. W. Fisher. 1981. Ecology of Fundulus catenatus in Three Interconnected Stream Orders. American Midland Naturalist Vol. 106, No. 2; pp. 372–378.
- Kerstin L. Edberg and Steven L. Powers. 2010. Life-History Aspects of Fundulus stellifer (Southern Studfish) (Actinopterygii: Fundulidae) in Northern Georgia. Southeastern Naturalist Vol. 9, No. 1; pp. 119–128.
- E. O. Wiley. 1986. A Study of the Evolutionary Relationships of Fundulus Topminnows (Teleostei: Fundulidae) Am. Zool. Vol.26, No. 1; pp. 121–130.
- Patrick E. O'Neil and Thomas E. Shepard. 2005. Hatchet Creek Regional Reference Watershed Study. Water Investigations Program. Open-file report 0509.
- Tulane University. Dept. of Biology. 1969-1970. Tulane studies in zoology and botany. Vol.16 1970.