Observation of a Juvenile Gulf Sturgeon in the Santa Fe River, Florida H. Jared Flowers1,* and William E. Pine III1 Abstract – A juvenile Acipenser oxyrinchus desotoi (Gulf Sturgeon ) was collected from the Santa Fe River, a major tributary of the Suwannee River, FL, on 6 December 2006. The Suwannee River is believed to contain the largest existing population of Gulf Sturgeon; however, our specimen is only the third Gulf Sturgeon collected from the Santa Fe River. Based on these observations, we believe that the Santa Fe River should be studied further to determine its importance as Gulf Sturgeon habitat, especially in the face of future management plans that may alter the hydrology of the system. Acipenser oxyrinchus desotoi Vladykov (Gulf Sturgeon) is listed as Federally Threatened and as a Species of Special Concern by the State of Florida (USFWS 1995). Gulf Sturgeon can reach sizes of over 90 kg and 2.4 m total length, live over 25 years, and are thought to reach sexual maturity between ages 7–12 years (Huff 1975). Gulf Sturgeon range throughout the northern Gulf of Mexico from Tampa Bay, FL to the Mississippi River drainage (Wooley and Crateau 1985). They are anadromous, spending over half the year in freshwater rivers, where they generally spawn on shoals with a hard, rocky bottom (Huff 1975). The mainstem Suwannee River of northwest Florida is believed to support the largest remaining population of Gulf Sturgeon and has been frequently studied (i.e., Carr et al. 1996, Pine et al. 2001, Sulak and Clugston 1998). Its tributaries, however, have received much less attention in regard to Gulf Sturgeon research. Observations discussed in this paper suggest the tributary Santa Fe River also may provide important Gulf Sturgeon habitat. On 6 December 2006, a Gulf Sturgeon was collected from the Santa Fe River approximately 32-km upstream of the Suwannee River confl uence and 2-km upstream of Rum Island Park, Columbia County, FL, at a depth of 1 m (Fig. 1). This individual was collected during a routine quarterly assessment of the fish community in the Santa Fe River being performed by a joint group from the Florida Fish and Wildlife Conservation Commission and the University of Florida. The specimen was a juvenile, approximately 8–9 months old, with a 372 mm fork length, and 426 mm total length. The specimen was photographed and tagged with a T-bar tag in each pectoral fin (numbers 1245 and 1246), then released and observed to swim away. This Gulf Sturgeon was captured on the last day of a three-day sampling event, and sampling had occurred along the same 1-km stretch of river each day. Historically, there have been only scattered and largely unconfirmed reports of Gulf Sturgeon in the Santa Fe River, with most of these reports occurring near the confl uence with the Suwannee River approximately at river kilometer (rkm) 110-km upstream of the Gulf of Mexico (Ken Sulak, USGS, Gainesville,FL, pers. comm.). Two museum specimens of Gulf Sturgeon have been collected from the Santa Fe River upstream of the confl uence with the Suwannee River in October 1931 and in January 1974, approximately 35 and 19 km upstream of the confl uence, respectively (museum specimens, University of Florida, [UF] 4204, Gainesville, FL; Fish and Wildlife Research Institute, Florida State Board of Conservation [FSBC] F 08847, St. Petersburg, FL) (Fig 1). The FSBC F 08847 specimen is a 234-mm SL, young-of year juvenile; however, the UF 4204 specimen has been lost, and no length measurement for it is available. Are juvenile Gulf Sturgeon using the Santa Fe River regularly? If so, why? And what is the significance? It is notable that two of the three Santa Fe specimens are juveniles and all three were sampled in late Fall or Winter. Telemetry projects in Notes of the Southeastern Nat u ral ist, Issue 7/3, 2008 559 560 Southeastern Naturalist Notes Vol. 7, No. 3 the Suwannee have not observed adults moving into the Santa Fe (Carr et al.1996, Foster and Clugston 1997, Parkyn et al. 2007). Sulak and Clugston (1998) observed Gulf Sturgeon spawning in the Suwannee River between rkm 200 and 221 and found juvenile Gulf Sturgeon ≤450-mm TL in the mainstem Suwannee River from rkm 10 to rkm 237, an area of the river that includes the confl uence of the Santa Fe and Suwannee Rivers. Taking into account these wide-ranging movement patterns, large areas of the Santa Fe River are within the possible movement ranges of juvenile Gulf Sturgeon (Sulak and Clugston 1998). The Santa Fe River is tannic and similar to the Suwannee River during periods of high streamfl ow, but at low streamfl ow, the Santa Fe is much clearer and dominated by input from groundwater springs (Hunn and Slack 1983). All three Santa Fe specimens were observed during low-water periods, indicating water clarity similar to the Suwannee may not be a requirement for juvenile habitat selection (USGS gauge 02321500). Kynard and Parker (2004) found in an experimental setting that very young Gulf Sturgeon (<171 days old, younger than Santa Fe specimens) were negatively phototaxic, but that older fish did not demonstrate the same lightavoidance behaviors. It is possible that water conditions during high-fl ow periods have concealed Gulf Sturgeon from observation in other years. Food availability may be the reason juvenile Gulf Sturgeon utilize the Santa Fe River. Juvenile Gulf Sturgeon feed on riverine benthic macroinvertebrates throughout their first year, specifically aquatic insects and oligochaetes (Mason and Carr 1993). Mason (1991) found that macroinvertebrate densities in the Santa Fe River were up to twice those in the mainstem Suwannee River during both summer and winter months. More research is needed to describe how Gulf Sturgeon use the Santa Fe River. No directed sampling studies for Gulf Sturgeon in the Santa Fe River have been published, and there have been limited, unsuccessful sampling efforts associated with public sightings (K.J. Sulak, US Geological Survey, Gainesville, FL, pers. comm.). Figure 1. Suwannee and Santa Fe River systems in Florida and locations of Santa Fe Gulf Sturgeon observations (modified from Martin and Screaton 2001). 2008 Southeastern Naturalist Notes 561 Clugston and Sulak (1998) state age-0 individuals can be found in Suwannee River tributaries, based on specimen FSBC F 08847. If juvenile Gulf Sturgeon are using the Santa Fe River, it will be important to examine the impacts of future regulations proposed by management agencies and the associated potential alterations to the natural hydrology of the system. Currently, the Santa Fe and Suwannee River are listed as priority rivers for development of minimum fl ow and level regulations by the Suwannee River Water Management District (see http://www.srwmd.state.fl .us/features/ cooperative+programs/minimum+fl ows+and+levels/default.htm). Additionally, the Santa Fe River is not listed under the critical habitat designation for Gulf Sturgeon by the United States Fish and Wildlife Service (see http://www.fws.gov/alabama/gs/). Considering our recent collection and the historical collection records, the Santa Fe River should likely also be included in the area designated as critical habitat for Gulf sturgeon. Acknowledgments. We would like to thank Will Strong and Travis Tuten of the Florida FWC for the capture of our Gulf Sturgeon; Ted Hoehn, Alan Huff, Ramon Ruiz-Carus, and Ken Sulak for their help with historical information on sturgeon in the Santa Fe River; and Jim Williams for editorial guidance. Literature Cited Carr, S.H., F. Tatman, F.A. Chapman. 1996. Observations on the natural history of the Gulf of Mexico Sturgeon (Acipenser oxyrinchus desotoi Vladykov 1955) in the Suwannee River, southeastern United States. Ecology of Freshwater Fish 5(4):169–174. Foster, A.M., and J.P. Clugston. 1997. Seasonal migration of Gulf Sturgeon in the Suwannee River, Florida. Transactions of the American Fisheries Society 126:302–308. Huff, J.A. 1975. Life history of Gulf of Mexico Sturgeon, Acipenser oxyrhynchus desotoi, in Suwannee River, Florida. Florida Marine Research Publication No. 16. Hunn, J.D., and L.J. Slack. 1983. Water resources of the Santa Fe River basin, Florida. Water- Resources Investigations Report 83-4075. USGS. Kynard, B., and E. Parker 2004. Ontogenetic behavior and migration of Gulf of Mexico Sturgeon, Acipenser oxyrinchus desotoi, with notes on body color development. Environmental Biology of Fishes 70:43–55. Martin, J.B. and E.J. Screaton. 2001. Exchange of matrix and conduit water with examples from the Floridan aquifer. Pp. 38–44, In E.L. Kuniansky (Ed.). US Geological Survey Karst Interest Group Proceedings, Water-Resources Investigations Report 01-4011, Mason, W.T. 1991. A survey of benthic invertebrates in the Suwannee River, Florida. Environmental Monitoring and Assessment 16:163–187, 1991. Mason, W.T, and J.P. Clugston. 1993. Foods of the Gulf Sturgeon in the Suwannee River, Florida. Transactions of the American Fisheries Society 122:378–385. Parkyn, D.C., D.J. Murie, J.E. Harris, D.E. Colle, and J.D. Holloway. 2007. Seasonal movements of Gulf of Mexico Sturgeon in the Suwannee River and estuary. American Fisheries Society Symposium 56:51–68. Pine, W.E., M.S. Allen, and V. Dreitz. 2001. Population viability of the Gulf of Mexico Sturgeon in the Suwannee River, Florida. Transactions of the American Fisheries Society 130:80–91. Sulak, K.J., and J.P. Clugston. 1998. Early life-history stages of Gulf Sturgeon in the Suwannee River, Florida. Transactions of the American Fisheries Society 127:758–771. US Fish and Wildlife Service and the Gulf States Marine Fisheries Commission. 1995. Gulf Sturgeon recovery plan. US Fish and Wildlife Service, Atlanta, GA. Wooley, C.M., and E.J. Crateau. 1985. Movement, microhabitat, exploitation, and management of Gulf of Mexico Sturgeon, Apalachicola River, Florida. North American Journal of Fisheries Management 5:590–605. 1University of Florida, Department of Fisheries and Aquatic Sciences, 7922 NW 71st Street, Gainesville, FL 32653. *Corresponding author - jfl ow@ufl .edu.