Spatial and temporal distributions of pelagic biota using hydroacoustic surveying at Gray's Reef National Marine Sanctuary, Georgia
Doyle, Katherine Rose
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The target strength distribution and abundance of pelagic organismsin Gray's Reef National Marine Sanctuary was sampled over the course of three years. The target strength distributions ranged from -78 to -45 dB for alltimes of day, at all locations. Diel vertical migration is apparent inthe Fall yet muted in the Spring due to a strong thermocline. This parameter does not seem to be influencedby the presence of colonized hard bottom in that the same range of target strengths aresampled throughout the experimental program. The abundance data found that, there are generally more uniformlydistributed fish per cubic meter in the "surface" layers and a patchy distribution in the"bottom" layers. Whether or not habitat affects abundance is inconclusive. Larger numbers of fish were seen over reefhabitats, yet corresponding numbers of fish could be found in areaswith little or no habitat also.