The effects of boat propeller scarring intensity on nekton abundance in subtropical seagrass meadows

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.