The effects of boat propeller scarring intensity on nekton abundance in subtropical seagrass meadows
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Seagrasses play a critical role in the function and structure of coastal ecosystems, and they are an important habitat for a variety of marine organisms. Damage to seagrass beds caused by boat propeller scarring is significant in many areas. This study was designed to assess the impact of varying scarring intensities on nekton density. We selected ten replicate (10 m×25 m quadrats) sites representing four distinct scarring intensities: reference (0%), low (5% or less), moderate (5–15%), and severe (>15%). Sites were sampled in 2003–2004 for nekton during four seasons (summer, fall, winter, and spring) using epibenthic sleds. There were eight taxa numerically dominant in all seasons and an additional four seasonally dominant species. We were unable to detect a significant effect of propeller scarring on nekton density at any scarring level. Additionally, regression analysis indicated no relationship between scarring intensity and nekton density. These results suggest that propeller scarring intensities of up to ca. 27% may not impact nekton densities. However, seagrass loss, higher scarring intensity, and scale may play a critical role in determining the impact of propeller scarring on nekton.
KeywordsBlue Crab Submerge Aquatic Vegetation Seagrass Meadow Total Catch Grass Shrimp
We would like to thank the Members of the Fisheries Ecology Lab at Texas A&M University-Corpus Christi for their help on this project. Special thanks to Brooke Stanford, Ryan Fikes, Megan Reese, Amanda Bushon, and Annette Cardona for their hours of assistance in the field and laboratory, and to Steve Moore for producing Fig. 1. We gratefully acknowledge the comments and input by Chris Onuf. We would like to thank Ken Dunton of UTMSI and Richard Watson for flights over the study area. We would also like to thank anonymous reviewers for comments that greatly improved the earlier drafts of the manuscript.
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