Habitat associations of demersal fishes on the Charleston Bump and adjacent Blake Plateau
Wieber, Kimberly Starr
Sedberry, George R.
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The Charleston Bump and Blake Plateau, located on the continental slope off the coast of the southeastern United States, is an area of rugged hard-bottom topography and variable currents. The complexity of habitats along with the strong and unpredictable currents makes collecting, sampling, and surveying by traditional methods very difficult. Therefore, little is known about these complex bottom habitats and associated deep-water fish faunas. Video footage from submersible dives made by the Johnson Sea-Link II in 2001, 2003, and 2004 at depths between 300 ‚Äì 900 m was analyzed to characterize habitats based on bottom morphology and occurrence of deep-water corals, and to describe fish assemblages associated with each habitat. Fishes were identified and densities and diversity calculated based on the area transected. Six habitat types were described. Nezumia sclerorhynchus and Laemonema melanurum were the most abundant fishes in flat hard bottom habitat. Nezumia sclerorhynchus was also most abundant in manganese-phosphorite pavement habitat, followed by Helicolenus dactylopterus. Laemonema melanurum and N. sclerorhynchus were most abundant in mixed habitat. In high relief habitat Beryx decadactylus, H. dactylopterus, and N. sclerorhynchus were most abundant. Polyprion americanus was also frequently observed in high relief habitat. Soft sediment and coral rubble habitats occurred on dives deeper than 740 m and were both dominated by Synaphobranchus spp. Although similarity of fish faunas within habitat types was not great, there was a distinction in fish assemblages between shallower (300-650 m) and deeper (740-910 m) dives. The same distinction in fish assemblages was apparent between hard and soft bottom substrate. Species diversity, H', was twice as great in hard bottom habitats as in soft bottom and coral rubble habitats. In situ observations of noteworthy species and behavior are also provided.