Tulevech_Effects_of_Shoreline_Structure_on_Fish_Habitat_Use_and_Schooling_Behavior
- 1. Introduction Many estuarine habitats like salt marshes and oyster reefs necessary for fish foraging and refuge are in decline due to increasing coastal development and shoreline hardening (Gittman et al. 2015). ‘Living shorelines’ offer a promising alternative to these rigid structures, which offer limited habitat. Combining natural marsh and protective engineered structures, living shorelines can provide shoreline protection while sustaining estuarine services. Living shorelines are gaining popularity among waterfront property owners because of their longevity and lower maintenance costs, but the economic and ecological benefits have not been fully explored. Materials and Methods We hypothesized prey fish would move more frequently and school more profoundly in and around more structurally complex habitats, with living shorelines providing more refuge than traditional hardened structures. Acknowledgments I would like to sincerely thank Dr. Charles Peterson, Carter Smith, David Kochan, and Isabelle Neylan for their mentorship and instrumental support during this project. Balancing many other projects and people’s needs, they have kindly offered me the guidance and opportunities I needed to succeed. At the same time, they permitted me a great degree of independence to pursue questions and projects that piqued my own interests. I also extend my greatest thanks to the National Science Foundation, for making this REU possible for me, and to Megan Hughes, the Institute of the Environment, and the IDEA Undergraduate Research Program for all the work they have done to make amazing experiential research programs like this possible for many worthy students. I am thankful to have had the opportunity to work in Dr. Peterson’s lab and meet so many of the fascinating people at the Institute for Marine Sciences, a wonderful institution. Results Conclusions & Discussion • Shoreline structure has a statistically significant effect on the number of fish passing into and out of the habitat structure. • Frequency of movement is one indicator of overall fish activity, and thus, one way of measuring how fish utilize various shoreline structures as habitats. • School size data and qualitative observation of school tightness suggest that the presence of a predator was not the only influence on fish schooling behavior. Figure 2 suggests that habitat structure influenced fish schooling as well. • Our finding that fish activity increased with increasing structural complexity (from bulkhead to rock sill) is consistent with Gittman et al. 2015 and Toft et al. 2007, who suggest that fish abundance increases near structurally complex habitats, natural or engineered. Future Directions • Redefining replicates so distinct groups of prey and predator are present to improve statistical robustness. • Extended analysis of video clips (currently 15 minutes, potentially up to 4 hours). • Additional GoPros could be inserted to increase coverage in each tank. Steven Tulevech, Carter Smith, David Kochan, Charles Peterson1 1 Institute of Marine Sciences, University of North Carolina at Chapel Hill, Morehead City, NC From Gray to Green: The Effects of Shoreline Structure on Fish Habitat Use and Schooling Behavior How does varying shoreline structure influence prey fish behavior, specifically fish movement and schooling in the presence of a predator? 0 50 100 150 200 250 300 MEANNUMBEROFFISHPASSES Effect of Shoreline Structure on Number of Prey Fish Passes Bulkhead Natl Marsh RipRap Oyster Sill Rock Sill a a a ab b Figure 1: Mean number of individual prey fish passes (both toward and away from structure) as a result of varying shoreline structure Figure 2: Effect of shoreline structure on fish schooling size passing near the structure. Size of each school observed was recorded and the modal school size(s) near each shoreline structure are shown. • We ran a one-way ANOVA and found that shoreline structure did indeed have a statistically significant effect on fish behavior (p < 0.01). • In terms of total number of prey fish passes, the rock sill shoreline was statistically different from the bulkhead (p = 0.015), natural marsh (p = 0.004) and riprap (p = 0.027) structures (Tukey HSD) (Figure 1). • Fish frequency of movement around the rock sill was 3x as large as the bulkhead, and 5x the natural marsh (Figure 1). GoPro footage of a very large school entering the rock sill GoPro footage of a medium school entering the riprap •Size of school was also recorded in each treatment (Figure 2). All schools were classified according to a school size key from which the modal school size(s) were ascertained. Further Reading Gittman, R.K., C. H. Peterson, C. A. Currin, F. J. Fodrie, M. F. Piehler, and J. F. Bruno. Living Shorelines Can Enhance the Nursery Role of Threatened Estuarine Habitats. Ecological Applications 26, no. 1 (2015): 249-263. Krebs, J. R., and S. A. West. An Introduction to Behavioral Ecology. Edited by N. B. Davies. 4th ed. Oxford: Wiley-Blackwell Publications, 2012. Mccauley, D.J., F. Micheli, H. S. Young, D. P. Tittensor, D. R. Brumbaugh, E. M. P. Madin, K. E. Holmes, J. E. Smith, H. K. Lotze, P. A. Desalles, S. N. Arnold, and B. Worm. Acute Effects of Removing Large Fish from a Near-pristine Coral Reef. Marine Biology 157, no. 12 (2010): 2739- 750. Toft, J. D., J. R. Cordell, C. A. Simenstad, and L. A. Stamatiou. Fish Distribution, Abundance, and Behavior along City Shoreline Types in Puget Sound. North American Journal of Fisheries Management 27, no. 2 (2007): 465-80. Rock marsh sill shoreline Riprap shoreline Effect of Shoreline Structure on Fish Schooling Size Key Loner: 1 Small: 2-6 Medium: 7-14 Large: 15-22 Very large: 23 to 30 Bulkhead Natural Marsh Oyster Sill Rock Sill Riprap small small medium loners large medium loners very large Outdoor, open system tank mesocosms at IMS Prey pinfish Lagodon rhomboids obtained via seine net Predator Paralichthys spp. obtained via trawl Rock marsh sill mesocosm (4.6m x 1.25m x 0.6m, water depth 34.5-45cm) with wave dump mechanism Rock marsh sill (Rock Sill structure) setup prior to water addition Oyster marsh sill (Oyster sill structure) setup post water addition • Compare fish movement and schooling data to prey survivorship data, to explore potential behavior differences among lethal predator feeding and nonlethal predator presence. In this study, we sought to determine how estuarine shoreline structures influence fish habitat use and schooling behavior by quantifying frequency of movement around structures in the presence of a predator.