Changes in Fish Composition in an Eutrophic, Lacustrine River Lori McCloud St. Johns River Water Management District Russell Brodie, Florida Fish and Wildlife Conservation Commission Justin Solomon, Florida Fish and Wildlife Conservation Commission Michele LaCasse, St. Johns River Water Management District John Hendrickson, St. Johns River Water Management District
Photos courtesy of River of Lakes Heritage Corridor and Robert Burks Designated an American Heritage River in 1997
St. Johns River Downtown Jacksonville, 1968 Photo courtesy of Charles Ashton, USACE Jacksonville Photo courtesy of John Burns
Goals of Study Evaluate current fisheries data against a historical dataset for the lower St. Johns River Examine inter-annual changes in a recent fish community assessment along with associated water quality changes
Florida Fish and Wildlife Conservation Commission s Fisheries-Independent Monitoring Program (FIM) Started in northeast Florida in 2001 to monitor changes in the relative abundance of estuarine fishes in the Nassau, St. Marys and St. Johns rivers. Their program is an fisheries-independent program, so it is more of a community assessment and not tied to an individual sport-fishery. In 2005, the District contracted with the NE FIM office to expand their estuarine sampling universe upstream in the St. Johns River to capture the freshwater area of the river. The agencies work together to sample the freshwater reach of the lower St. Johns, with the District providing in-kind field services for collection.
A Historical Comparison FIM LSJRB Fisheries Assessment 2005-2007 Study Purpose: Monitor changes in the relative abundance of fishes in the lower St. Johns River Collections occurred between the mouth and Palatka using a stratifiedrandom sampling design between June 2005 -June 2007 Collection devices 21.3-m seine with a 1.8-m center bag Net with 3.2-mm stretched mesh 6.1-m otter trawl 38.1-mm stretched mesh bag with a 3.2-mm liner Fishes of the St. Johns River Tagatz 1968 Study Purpose: To document occurrence of blue crabs in the St. Johns River; capture of fish was incidental to sampling of blue crabs Collections at 12 sites between Clapboard Creek and Astor between April 1961 and November 1963 Collection devices 21.3-m seine with a funnel bag 4.6-m long Net with 4-mm stretched mesh 2.4-m trawl 12.7-mm net and 6.4-mm stretched mesh bag
Percent of Long-Term Mean from 1960-2006 Percent of Long-term Mean 80 60 40 20 0-20 -40-60 -80 Mean Annual Runoff 1961-1963* 1961 1962 1963 Deland SF Black Percent of Long-term Mean 80 60 40 20 0-20 -40-60 -80 Mean Annual Runoff 2005-2007* 2005 2006 2007-100 *Water Year, Oct. -100 Both study periods experienced greater discharge in the first year and reduced discharge in the second and third years.
8 seines and 8 trawls are collected within each zone, and the number of monthly samples collected is proportional to the number of grids within that zone Zones C, D, E & F encompass the lower basin
Sampling locations for Tagatz data in the St. Johns River
Sampling areas created from Tagatz sites within the St. Johns River
FIM sample locations combined with Tagatz polygons
FIM sample sites that are located within a Tagatz polygon
Number of Families Observed for FIM vs. Tagatz at each Location Increased number of families sampled is obviously tied to sampling effort for most sites Where effort was similar (red circled areas), the number of families sampled were similar
Number of Species Observed for FIM vs. Tagatz at each Location JI=51% JI=45% Again, increased number of species sampled is tied solely to sampling effort for most sites. Where effort was similar (red circled areas), the number of species sampled were similar, with a similarity index of about 50%.
Comparison of Salinity Regime SJR Dames Pt.: Surface Salinity Distributions Percent Occurrence 110 100 90 80 70 60 50 40 30 20 10 0 Deland+SF Black Flow Class Mean and Range Less Than 757 758-1485 1486-2535 2536-3979 Greater Than 3978 Tagatz Collections FIM Collections 0 5 10 15 20 25 30 35 Surface Salinity, ppt Salinity distributions and flow categories based on continuous monitoring from 1996 2001 Median percent rank for Tagatz: 8 & FIM: 52 Under similar flow conditions, salinities collected during the Tagatz study appear to be lower than those collected by FIM
Inter-Annual Comparison of Current FIM Dataset Canonical Scores Plot 6.0 3.8 FACTOR(2) 1.6-0.6-2.8-5.0-5.0-2.8-0.6 1.6 3.8 6.0 FACTOR(1) YEAR 2005 2006 2007
25 20 15 10 5 Mandarin Point Salinity (ppt) 0 1/4/2005 3/9/2005 4/20/2005 6/22/2005 7/21/2005 9/12/2005 10/20/2005 11/28/2005 1/9/2006 2/20/2006 3/27/2006 5/16/2006 6/15/2006 7/18/2006 9/18/2006 10/25/2006 12/4/2006 1/11/2007 3/5/2007 4/10/2007 5/17/2007 8 7 6 5 4 3 2 1 0 6/28/2005 8/22/2005 9/12/2005 10/18/2005 11/16/2005 12/14/2005 1/19/2006 2/15/2006 3/17/2006 5/15/2006 6/20/2006 7/18/2006 8/15/2006 9/20/2006 10/25/2006 12/12/2006 1/18/2007 3/20/2007 4/18/2007 5/16/2007 80 60 40 20 0-20 -40 Mean Annual Runoff 2005-2007* 2005 2006 2007 Percent of Long-term Mean -60-80 -100 Picolata Point Salinity (ppt)
Conclusions Historical vs. Current Fish Assemblage A difficult comparison due to lack of abundance information and poor sampling effort at many sites Where sampling effort is similar, we don t see a big difference in the number of species utilizing the river, however there is only about a 50% similarity in species between the two datasets Transition zone between marine and freshwater may have moved further upstream, but given the limited coverage of the historical dataset, we cannot evaluate how that impacts the fisheries Inter-Annual Changes in Current Fish Population We see a nice separation of fish species when examined by year May be due to hydrologic and climatic differences affecting water quality, but may also be due to different juvenile recruitment or other factors not examined by this study The ongoing study is a great beginning to what we hope will continue for the entire lower basin - once we obtain several years of data, it will be interesting to see how water quality influences fish communities in the lower basin
Special thanks to Courtney Hart, Dean Dobberfuhl, Jennifer Tallerico and the lower basin field crew for all of their assistance.