Dataset: ASU Fragmentation – SMURF Settlement Rate

To assess whether faunal density patterns across landscapes were driven by larval settlement, larval fishes and crab megalopa were sampled seven times from June to August 2018 on Oscar Shoal and an adjacent unnamed shoal in Back Sound, NC, USA (34°42′20" N to 34°41′60" N, 76°36′ 15" W to 76°35′17" W) using Standardized Monitoring Units for the Recruitment of Fishes (SMURFs; Ammann 2004). This brackets the seasonal timing of settlement by the majority of species that occupy local seagrass as a nursery habitat (Baillie et al., 2015). SMURFs were created from 2.5-centimeter (cm) mesh VEXAR, zip-tied to create a 1-meter long, 0.2-meter diameter cylinder with folded-end closures. To facilitate settlement and accommodate various settler sizes, each cylinder was stuffed with two sizes of plastic mesh: 3 square meters of 5 cm × 7.5 cm and 5 square meters of 1 centimeter × 1-centimeter mesh. SMURFs were secured to each landscape by a 20-centimeter sand screw and a 25-centimeter paracord line attached to the underside of the sampling unit. Floats were attached to cylinder ends for added buoyancy and to suspend the SMURFs above the seafloor.

To examine how settlement rates across landscapes differed depending upon the amount of immediately surrounding artificial seagrass, each SMURF was positioned at the 'center' of the largest ASU patch (as estimated for each irregular shape) in each landscape. SMURFs were deployed for 48 hours to maximize larval collection (Ammann, 2004) while minimizing biofouling (Tavernetti et al., 2009). After the first deployment cycle, it was noted that SMURFs retrieved closer to sunrise had higher settler abundances. Subsequent deployments were therefore timed to coincide with a 4-hour collection window surrounding sunrise. Upon retrieval, 5-gallon buckets of water were poured over each SMURF into a collection bin while the SMURF was shaken and rotated. This process was repeated a minimum of three times or until no additional fauna were observed being washed into the collection bin. Samples were sieved (0.5-millimeter mesh) and collected fauna were frozen for later identification and enumeration in the lab. All SMURFs were rinsed with fresh water and dried by sunlight before redeployment.

Known Issues:
Time_Out data are commonly missing. Length measurements were only taken for larval fish and some crabs.