Okaloosa darter

OkaloosaDarter.jpg

Okaloosa darter: Etheostoma okaloosae

Taxonomic Classification

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Percidae
Genus/Species: Etheostoma okalossae
Common Name: Okaloosa darter

Listing Status

Federal Status: Threatened
FL Status: Federally-designated Threatened
FNAI Ranks: G1/S1 (Critically Imperiled)
IUCN Status: EN (Endangered)

Physical Description

The Okaloosa darter is a small darter that reaches a body length of only two inches (5.1 centimeters).  This darter species has a green-yellow to red-brown coloration with five to eight brown spots along the lateral surface of its body, and a well established spot above the base of its pectoral fin.  Male Okaloosa darters develop an orange band along the edges of its first dorsal fin (Florida Natural Areas Inventory 2001).  As an obligate bottom dweller, they have no swim bladder, which enables a fish to control its buoyancy.

Life History

The diet of the Okaloosa darter primarily consists of mayfly nymphs, caddisfly larvae, and midge larvae (Ogilvie 1980).

Okaloosa darters breed between the months of March and October, with most breeding activities occurring in April and a peak breeding period in October.  In one Okaloosa darter study, a mean average of 79 ova (eggs), of which 29 were mature, were found among 201 females sampled.  Eggs attach to vegetation once they are released.  Female Okaloosa darters reach sexual maturity when a standard length of 1.2 inches (3.1 centimeters) is reached (Ogilvie 1980).   

Habitat and Distribution

Okaloosa Darter Distribution MapThe Okaloosa darter inhabits small streams that are fed by ground water seepage from the surrounding sandhills (U.S. Fish & Wildlife Service 1998).  The majority of Okaloosa darter habitat is located within Eglin Air Force Base’s (Eglin AFB) boundaries, but they can also be found in adjoining portions of Okaloosa and Walton counties in Boggy and Rocky bayou of the Choctawhatchee Bay drainage (Burkhead and Williams 1992).  

Threats:

The main threat to the Okaloosa darter is the introduction of the brown darter (Etheostoma edwini) to its habitat.  Brown darters are thought to out-compete the Okaloosa darter for food and other resources (Burkhead and Williams 1992).  Sedimentation of streams is also a threat to the Okaloosa darter as the sediments can cover sites where eggs are laid.  Other threats include an increase of pollutants in streams.  With Eglin AFB committed to continued conservation of the Okaloosa darter, the secondary threats will occur primarily as a result of off-base development and land-use conversion.

Conservation and Management

The Okaloosa darter is protected as a Threatened species by the Federal Endangered Species Act and as a Federally-designated Threatened species by Florida’s Endangered and Threatened Species Rule External Website.  Eglin AFB’s Jackson Guard Unit has made on-base conservation a priority.  Eglin AFB has reclaimed clay pits near stream headwaters and improve road crossings to reduce sedimentation and improve habitat for the darter.

Federal Recovery Plan External Website

Other Informative Links

Florida Natural Areas Inventory External Website
International Union for Conservation of Nature External Website
U.S. Fish & Wildlife Service Okaloosa Darter Recovery Plan External Website
U.S. Geological Survey External Website

 

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References

Burkhead N.M. and Williams J.D.,1992. Okaloosa Darter  Etheostoma okaloosae. Pages 23-30 in C.R. Gilbert, editor. Rare and Endangered Biota of Florida. Volume II.  Fishes.  University Press of Florida, Gainesville, Florida, USA.

Florida Natural Areas Inventory.  2001.  Field guide to the rare animals of Florida.            http://www.fnai.org/FieldGuide/pdf/Etheostoma_okaloosae.PDF External Website

Ogilvie, V.E. 1980.  Unpublished Florida Game and Freshwater Fish Commission Endangered Wildlife Project E-1. Annual Progress Report.  Tallahassee, Florida. 19 p.

U.S. Fish and Wildlife Service. 1998. Okaloosa Darter (Etheostoma okaloosae) Recovery Plan (Revised). Atlanta, Georgia. 42 pp.


Image Credit Photo courtesy of Noel Burkhead, USGS



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