Written by Audrey Looby, Ph.D. student, Fisheries and Aquatic Sciences
Over the past three years, I have been spent days trying and at times failing to catch fish on a lake or watching videos of baby Florida bass swim around a tank, all in order to conduct the research that made up my master’s thesis as a student at NCBS. I hoped to find out the characteristics of submerged aquatic vegetation that would maximize fish habitat to benefit freshwater restoration efforts. I’m excited to say I have now completed my research projects, earned my master’s degree, and published two peer-reviewed articles—both of which are now currently available as open access articles in the journals Environmental Biology of Fishes and Frontiers in Conservation Science.
About submerged aquatic vegetation
Submerged aquatic vegetation, or SAV for short, refers to vascular plants growing completely below the water’s surface in fresh, estuarine, and marine waters. This includes seagrass species like the ones found around Cedar Key, as well as a variety of other species found throughout the world. SAV can provide various ecosystem services, including reducing erosion and improving water clarity and quality. SAV also provides important habitat for fishes, with at least nineteen freshwater fish families occupying or relying on vegetation for refuge, food resources, reproduction, and nursery habitat.
Unfortunately, SAV is decreasing in lakes around the world including here in Florida. SAV restoration may be able to reverse this global trend, particularly if the original stressors that led to the decline are removed. SAV restoration can take the form of direct plantings or other methods like removing certain fish species to indirectly increase SAV. For restoration efforts like direct plantings, however, to be effective, managers need to know how to create the most optimal environment for fish habitat if increasing fish populations is one of their goals.
About the research
For my master’s thesis at the University of Florida, I tried to figure out what we should plant and how we should plant it to inform how SAV restorations can best apply their resources and to try to define what constitutes optimal aquatic vegetation for fish habitat. As part of an adaptive restoration effort in Lake Apopka, FL, I conducted field sampling using fyke nets and trotlines to examine how fish communities responded to the SAV we had planted. While my fish catch was low (I only caught 6 fish on all of the 29 trotlines I deployed), I was still able to use the data to show that fish communities changed and fish biomass increased with an increase in SAV patch or meadow size.
The field sampling allowed me to look at general trends in fish use of SAV, but I wanted to be able to test more specifically what characteristics of SAV fish might prefer. I used choice experiments to look at specific SAV preferences of hatchery-raised, yearling Florida bass, as a species and age-class of particular interest for fisheries and lake managers. After spending hours watching them swim around tanks, I analyzed the data to show they preferred SAV over no SAV and taller, larger SAV collection sources, but they did not seem to care as much about SAV species, species diversity, or diversity of collection sources.
My research demonstrates that SAV does increase fish habitat use, that planting larger, taller SAV in greater patch sizes will effectively increase freshwater fish habitat use, and that SAV species, species diversity, and diversity of collection sources may not be as critical to consider when planning restoration for fish habitat use. Said in an even shorter way, Florida freshwater fishes generally like underwater plants and generally like more of them. These results expand existing knowledge of fish habitat use of SAV and will inform future management efforts to conserve and restore fish communities by focusing on specific SAV characteristics such as patch size and height of collection sources used for planting.
Thank you to everyone who supported the effort!
I could not have conducted this work without funding and assistance from the St. Johns River Water Management District and support from the US Geological Survey Wetland Aquatic Research Center and Shogaloo Fisheries, Inc. I also want to thank my co-authors and master’s committee for all of their help in planning, executing, and writing the research. I am so grateful, as well, to all of my labmates, NCBS, the NCBS community, and others who provided help conducting my research and providing a wonderful place to work while completing my master’s.
After finishing my master’s, I’m thrilled to be able to stay at UF and NCBS to continue on to earn my PhD. I am now applying all of the lessons I learned during my time studying freshwater fishes and SAV to focus my new research efforts on fish sound production and coastal soundscape ecology. I look forward to continuing to work at NCBS and in Cedar Key for the rest of my time in graduate school!