The Effects of Boat Propeller Scarring on Nekton Growth in Subtropical Seagrass Meadows

—An increasing boating population has led to extensive propeller scarring in many shallow seagrass meadows, and research has focused on relating scarring to nekton abundance; however, little information exists on the impacts on habitat functionality. In this study we moved beyond simple measures of faunal density as an indicator of habitat quality by comparing the growth rates of common estuarine nekton in different levels of propeller scarring in Redfish Bay, Texas. Growth rates of selected fauna were examined by using field enclosures and otolith microstructure analysis. Otolith microstructure analysis on pinfish Lagodon rhomboides indicated no difference in growth rates at various scarring intensities. We conducted field growth enclosure experiments on a common decapod crustacean, the white shrimp Litopenaeus setiferus. White shrimp showed significantly lower growth in highly scarred areas than in reference sites. These results suggest that regions of low-level propeller scarring (less than 15%) may have little effect on small-scale habitat quality. However, higher levels of propeller scarring may affect habitat quality; therefore, more information is needed to characterize the large-scale effects of propellers at higher scarring intensities. Many species use seagrass meadows as a primary ‘‘nursery’’ habitat (Minello 1999; Beck et al. 2001; Stunz et al. 2002a; Heck et al. 2003). Specifically, seagrass meadows are a structurally complex habitat type providing protection from predation and increased growth rates for associated fauna (Orth et al. 1984; Rozas and Odum 1988; Rooker et al. 1998; Stunz et al.