By Phillip Parsley
Springs in the middle St. Johns River basin are known for their clear water, intrinsic beauty and unique wildlife viewing opportunities. Every year tourists and residents spend countless hours swimming in headspring pools or paddling down spring runs enjoying the breathtaking scenery of wild Florida. However, recent natural events as well as anthropogenic influences have altered our perceptions regarding the health and vulnerability of some of these springs. Researchers and stakeholders have started to notice that lush aquatic vegetation has been replaced by dense algal mats and fish abundances have drastically reduced and been replaced by exotic fish species as habitat and water quality deteriorates.
While numerous studies exist that describe water quality of springs in the St. Johns River basin and include information on plant and invertebrate communities, information describing the fish communities of these springs is lacking. In order to better understand the complexities of these fish assemblages, primary goals of this project were to determine an efficient sampling protocol for eight springs and their associated spring runs in the St. Johns River basin that will provide baseline data on community fish assemblages; and to document the presence of exotic fish species utilizing springs and how their abundances may change seasonally.
The springs and their associated runs in this study are Alexander Springs, Gemini Springs, Juniper Creek, Rock Springs, Salt Springs, Silver Glen Springs, Spring Garden (also known as DeLeon Springs), and Wekiva Springs (Figure 1).
FWC standardized river sampling protocols were followed as closely as possible. However, some of the spring runs contained areas of dense aquatic macrophytes and a standard electrofisher boat was not practical. An airboat electrofisher was used instead in these types of areas to avoid the unnecessary destruction of critical vegetation. Also, a smaller boat we called the “mini-shocker” (Figure 2) was used in Rock Springs Run due to the narrow nature of the run and shallow areas where an electrofishing boat could not access.
A total of 406 sites spread across the eight study springs have been sampled since this project began in March 2019. 204 sites were sampled during the first round of sampling in summer 2019 collecting a total of 21,933 fish comprising 59 different species. 202 sites were sampled in winter 2019-20 and this netted 15,705 fish and 56 different species. As one may expect, Bluegill (14.9% of total combined catch), Redbreast Sunfish (13.7%), Spotted Sunfish (12.6%), and Largemouth Bass (6.3%) were the most common sportfish encountered as far as total abundance. Largemouth bass also comprised over one-fourth (25.3%) of the total percent biomass across all samples, with Bowfin (19.3%), Florida Gar (8.8%), and Lake Chubsuckers (8.7%) the next highest contributors.
Five exotic fish species were collected during both rounds of sampling. Blue Tilapia (n=153), Brown Hoplo (n=23), Dimerus Cichlid/Chanchita (n=4), Vermiculated Sailfin Catfish (n=62), and Walking Catfish (n=6) were all found to occur in multiple spring runs, however, they only represented 0.7% of the total catch and 4.3% of total biomass, both very miniscule portions of the entire sample. Standard electrofishing procedures do not appear to be the best method for capturing an accurate representation of the numbers of exotic fish species occurring in the springs so in the future utilizing alternative methods could provide us with better information.
The Bluenose Shiner (Figure 3), a state listed threatened species, was collected in Rock Springs Run and the Wekiva River. Isolated populations of this species occur in the St. Johns River Basin and this fragmentation makes it vulnerable to extirpation from this region. Finding this species in some of our study waterbodies was a positive and brainstorming is already underway as far as future research projects that could contribute to better understanding how best to conserve this species.
Through days of field work over the past year we believe we have developed efficient sampling procedures for our study systems. By using those protocols, we now have extensive sampling that yielded a total of 37,638 fish and 63 different species. Calculating similarity indices between sample seasons will help us better analyze how these community assemblages may change in each spring as well. Hopefully, the data collected in this study can provide future researchers insights and direction on the best way to make decisions regarding the health and viability of these springs as unique ecosystems.