Grouper and snapper movements and habitat use in Dry Tortugas, Florida

Home ranges, activity patterns, and habitat preferences in and around no-take marine reserves (NTMRs) were evaluated for 5 exploited snapper-grouper species in diverse coral reef habitats in the Dry Tortugas, Florida. Movements of ultrasonic tagged reef fish were determined using a calibrated array of omnidirectional hydroacoustic receivers. Average home range sizes were 2.09 ± 0.39 km2 (n = 28; total length, TL = 45 to 66 cm) for red grouper Epinephelus morio, 4.17 ± 1.75 km2 (n = 5, TL = 48 to 55 cm) for yellowtail snapper Ocyurus chrysurus, 1.44 ± 1.04 km2 (n = 2, TL = 57 to 75 cm) for black grouper Mycteroperca bonaci, and 7.64 km2 (n = 1, TL = 70 cm) for mutton snapper Lutjanus analis. Red grouper and yellowtail snapper moved moderate distances (from 700 to 900 m) with moderate frequency. Observed movements for black groupers were relatively small and infrequent. Mutton snappers appeared to make short, frequent movements. A tracked gray snapper L. griseus made long-distance nocturnal migrations. Several exploited-phase groupers and snappers crossed into and out of reserve boundaries. They were most likely to do so in locations where boundaries were positioned over contiguous coral reef and close to home-range centers. We found that home ranges for red grouper, black grouper, and yellowtail snapper were relatively small in comparison to NTMR area. Our observations suggest that the Dry Tortugas NTMRs may reduce exposure to exploitation for these and other species with limited home ranges, especially where NTMR boundaries do not overlie contiguous reef.