USGS' and Loyola University New Orleans' innovative research techniques played a role in the decision to downlist the Okaloosa Darter, a freshwater fish endemic to northwest Florida, from Endangered to Threatened in 2011, and the removal of the fish from the U.S. Endangered Species Act in 2023.
The Science Issue and Relevance:
Effective management of endangered species requires an understanding of temporal and spatial variability in population size and age structure. Specifically, long-term, quantitative data on population size and age structure are needed to detect the effects of acute and chronic anthropogenic activities on endangered species. Unfortunately, historical data are often absent or of insufficient quality to reliably assess ecological impacts. This problem has proven to be especially critical in the management of freshwater stream fishes in North America. Few quantitative, long-term databases exist to evaluate the natural fluctuations of, or the effects of management actions on, populations of stream fishes. Lack of information frequently results in restrictive limitations on human activities within watersheds that support fishes with special conservation status. The Okaloosa darter (Etheostoma okaloosae), which is endemic to Eglin Air Force Base (AFB) in northwest Florida, is typical of this management dilemma.
The Okaloosa darter resides among vegetation and woody debris along the margins of only six clear flowing streams in northwest Florida. In fact, over 95 percent of the fish’s limited habitat can be found on Eglin Air Force Base, one of the world’s largest conventional weapons testing facilities, just east of Pensacola, Florida. Their limited geographic range, habitat degradation due to historical land use practices, and competition from a darter species thought to be introduced resulted in the inclusion of the Okaloosa darter under the U.S. Endangered Species Act (ESA).
Methodology for Addressing the Issue: Using innovative sampling and biometric techniques over the past two decades, researchers from USGS and Loyola University New Orleans used a combination of three-pass removal and point count observations with mask and snorkel to estimate the number of these 50-mm (2-inch) fish in six small stream systems. The research team established that by using visual methods, they were observing an average of three times the number of darters than were captured using the more traditional seine nets. Their data were used by the U.S. Fish and Wildlife Service to develop the rule to downlist Okaloosa darters from endangered to threatened in 2011, complete a species status assessment for potential delisting in 2019, and remove the species from the ESA in 2023. With an estimated total number of darters around 500,000, and commitments by Eglin AFB to continue habitat restoration efforts, the outlook for the Okaloosa darter appears secure. Monitoring the darter will continue to ensure that these fish remain part of the northwest Florida landscape.
Future Steps: While continuing to monitor the Okaloosa darter with similar methods at historical sites, the team expanded their efforts into habitat restoration areas and sections of stream where a new highway crosses all six streams. Darters were marked with latex dyes to estimate movement, site fidelity, and longevity. Researchers determined that one marked darter lived at least eight years, which is a record for the genus. Fire opens stream canopies, which has proved to be an important factor in increasing numbers of darters. There is also interest in the role beavers play in modifying Okaloosa darter habitat. Techniques developed to sample small stream fishes and analyze collected data could fill information gaps for similar imperiled species in the southeastern United States.
Below are multimedia items associated with this project.
Below are publications associated with this project.
Determination of recharge areas that supply decades old groundwater to creeks inhabited by the threatened Okaloosa darter
Response of imperiled Okaloosa darters to stream restoration
Movement and longevity of imperiled Okaloosa Darters (Etheostoma okaloosae)
Population genetic structure and conservation genetics of threatened Okaloosa darters (Etheostoma okaloosae)
Weapons testing and endangered fish coexist in Florida
Comparison of visual survey and seining methods for estimating abundance of an endangered, benthic stream fish
Effects of fin clipping on survival and position-holding behavior of brown darters, Etheostoma edwini
Modeling unobserved sources of heterogeneity in animal abundance using a Dirichlet process prior
Okaloosa darter Etheostoma okaloosae
Research on the Okaloosa darter focuses on competition and habitat use
Selected vertebrate endangered species of the seacoast of the United States-the Okaloosa darter
- Overview
USGS' and Loyola University New Orleans' innovative research techniques played a role in the decision to downlist the Okaloosa Darter, a freshwater fish endemic to northwest Florida, from Endangered to Threatened in 2011, and the removal of the fish from the U.S. Endangered Species Act in 2023.
Okaloosa darter, (Etheostoma okaloosae) The Science Issue and Relevance:
Effective management of endangered species requires an understanding of temporal and spatial variability in population size and age structure. Specifically, long-term, quantitative data on population size and age structure are needed to detect the effects of acute and chronic anthropogenic activities on endangered species. Unfortunately, historical data are often absent or of insufficient quality to reliably assess ecological impacts. This problem has proven to be especially critical in the management of freshwater stream fishes in North America. Few quantitative, long-term databases exist to evaluate the natural fluctuations of, or the effects of management actions on, populations of stream fishes. Lack of information frequently results in restrictive limitations on human activities within watersheds that support fishes with special conservation status. The Okaloosa darter (Etheostoma okaloosae), which is endemic to Eglin Air Force Base (AFB) in northwest Florida, is typical of this management dilemma.
The Okaloosa darter resides among vegetation and woody debris along the margins of only six clear flowing streams in northwest Florida. In fact, over 95 percent of the fish’s limited habitat can be found on Eglin Air Force Base, one of the world’s largest conventional weapons testing facilities, just east of Pensacola, Florida. Their limited geographic range, habitat degradation due to historical land use practices, and competition from a darter species thought to be introduced resulted in the inclusion of the Okaloosa darter under the U.S. Endangered Species Act (ESA).
Researchers used a combination of three-pass removal and point count observations Methodology for Addressing the Issue: Using innovative sampling and biometric techniques over the past two decades, researchers from USGS and Loyola University New Orleans used a combination of three-pass removal and point count observations with mask and snorkel to estimate the number of these 50-mm (2-inch) fish in six small stream systems. The research team established that by using visual methods, they were observing an average of three times the number of darters than were captured using the more traditional seine nets. Their data were used by the U.S. Fish and Wildlife Service to develop the rule to downlist Okaloosa darters from endangered to threatened in 2011, complete a species status assessment for potential delisting in 2019, and remove the species from the ESA in 2023. With an estimated total number of darters around 500,000, and commitments by Eglin AFB to continue habitat restoration efforts, the outlook for the Okaloosa darter appears secure. Monitoring the darter will continue to ensure that these fish remain part of the northwest Florida landscape.
Future Steps: While continuing to monitor the Okaloosa darter with similar methods at historical sites, the team expanded their efforts into habitat restoration areas and sections of stream where a new highway crosses all six streams. Darters were marked with latex dyes to estimate movement, site fidelity, and longevity. Researchers determined that one marked darter lived at least eight years, which is a record for the genus. Fire opens stream canopies, which has proved to be an important factor in increasing numbers of darters. There is also interest in the role beavers play in modifying Okaloosa darter habitat. Techniques developed to sample small stream fishes and analyze collected data could fill information gaps for similar imperiled species in the southeastern United States.
Okaloosa darter on sand substrate - Multimedia
Below are multimedia items associated with this project.
- Publications
Below are publications associated with this project.
Determination of recharge areas that supply decades old groundwater to creeks inhabited by the threatened Okaloosa darter
The Okaloosa darter (Etheostoma okaloosae) is a diminutive, perch-like, benthic fish that inhabits only six small, clear, and shallow creek systems that flow almost entirely within Eglin Air Force Base in the panhandle of northwest Florida. Listed as Endangered by the U.S. Fish and Wildlife Service (USFWS) in 1973, improvements in erosion control and habitat restoration led to the Okaloosa darterAuthorsJames E. Landmeyer, W. Scott McBride, William B. TateResponse of imperiled Okaloosa darters to stream restoration
The Okaloosa Darter Etheostoma okaloosae is a small percid endemic to six stream drainages in northwestern Florida. The U.S. Fish and Wildlife Service listed Okaloosa Darters as endangered in 1973 and downlisted them to threatened in 2011 because of habitat improvements and increasing abundance across much of their geographic range. Delisting is possible if remaining recovery criteria are met, incAuthorsDavid B. Reeves, William B. Tate, Howard L. Jelks, Frank JordanMovement and longevity of imperiled Okaloosa Darters (Etheostoma okaloosae)
Movement and longevity studies inform management and conservation plans for imperiled organisms. We used a mark–recapture study to reveal information about these key biological characteristics for imperiled Okaloosa Darters (Etheostoma okaloosae). Okaloosa Darters were captured from 20 m reaches at six separate streams, marked with VIE on the left or right dorsum according to the side of the streaAuthorsDaniel E. Holt, Howard L. Jelks, Frank JordanPopulation genetic structure and conservation genetics of threatened Okaloosa darters (Etheostoma okaloosae)
Imperiled Okaloosa darters (Etheostoma okaloosae) are small, benthic fish limited to six streams that flow into three bayous of Choctawhatchee Bay in northwest Florida, USA. We analyzed the complete mitochondrial cytochrome b gene and 10 nuclear microsatellite loci for 255 and 273 Okaloosa darters, respectively. Bayesian clustering analyses and AMOVA reflect congruent population genetic structureAuthorsJames D. Austin, Howard L. Jelks, Bill Tate, Aria R. Johnson, Frank JordanWeapons testing and endangered fish coexist in Florida
Okaloosa darters (Etheostoma okaloosae) are small fish found only in a few streams in the Florida panhandle. This species has been listed since 1973 as endangered due to habitat alteration resulting from erosion, the potential competition from brown darters (E. edwini), and a limited geographic distribution. In recent years, however, Okaloosa darters have benefited from improved resource managemenAuthorsHoward Jelks, Bill Tate, Frank JordanComparison of visual survey and seining methods for estimating abundance of an endangered, benthic stream fish
We compared visual survey and seining methods for estimating abundance of endangered Okaloosa darters, Etheostoma okaloosae, in 12 replicate stream reaches during August 2001. For each 20-m stream reach, two divers systematically located and marked the position of darters and then a second crew of three to five people came through with a small-mesh seine and exhaustively sampled the same area. VisAuthorsF. Jordan, H.L. Jelks, S.A. Bortone, R.M. DorazioEffects of fin clipping on survival and position-holding behavior of brown darters, Etheostoma edwini
Advent of the polymerase chain reaction (PCR) has allowed conservation biologists to use small portions of tissue to obtain genetic material for population genetic and taxonomic study. Fin clips are used extensively in large-sized fishes, but it is unclear how clipping enough fin tissue for genetic analysis will affect survival of smaller fishes such as minnows and darters, which are among the mosAuthorsC.E. Champagne, J.D. Austin, H.L. Jelks, F. JordanModeling unobserved sources of heterogeneity in animal abundance using a Dirichlet process prior
In surveys of natural populations of animals, a sampling protocol is often spatially replicated to collect a representative sample of the population. In these surveys, differences in abundance of animals among sample locations may induce spatial heterogeneity in the counts associated with a particular sampling protocol. For some species, the sources of heterogeneity in abundance may be unknown orAuthorsR.M. Dorazio, B. Mukherjee, L. Zhang, M. Ghosh, H.L. Jelks, F. JordanOkaloosa darter Etheostoma okaloosae
Abstract not supplied at this timeAuthorsN.M. Burkhead, J.D. WilliamsResearch on the Okaloosa darter focuses on competition and habitat use
Abstract not supplied at this timeAuthorsN.M. Burkhead, J.D. WilliamsSelected vertebrate endangered species of the seacoast of the United States-the Okaloosa darter
No abstract available.Authors