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A Study on the Use of Hydroacoustic and Biological Surveying to Assess Fish Populations in the Altamaha and MacKay Rivers


PIs: Daniela Di Iorio and Gary Grossman (Univ. of Georgia, Athens, GA, USA)

Support: Sea Grant College Program (R/AT-9-PD)

Timeframe: 2002 - 2004

Project objectives:

  • To develop hydroacoustic measuring and surveying techniques
  • to determine the spatial and size distribution of fish along a salinity gradient in the Altamaha and MacKay Rivers.

We will carry out both trawl and gill net sampling to identify the species composition and size distribution for comparison to acoustic signatures at 5 or 6 sampling sites along the river axis.

Findings:
     A 120 kHz single beam echosounder was used to describe the spatial distribution of fish during transects in the Altamaha and MacKay river estuaries and at five stations along the main channel. Spatial distributions are compared between ebb tide and flood tide, along salinity gradients, as well as in different current velocities. Five stations along the Altamaha and MacKay rivers were sampled by 10 minute trawls and conducted simultaneously with the acoustic measurements in order to find the dominant species in the estuaries, as well as to find if a possible correlation can be deduced from comparing the composition and size of fishes in the trawl samples to the targets identified by the echo sounder.

     Thus far two experiments have been carried out to compare seasonal differences using the RV Georgia Bulldog, Marine Extension Service, Brunswick GA. The first experiment was in Oct 2002 for three days and the data have been analyzed by a postdoctoral assistant and an undergraduate research assistant (Tamarack , 2003) with further detailed analyses underway for publication. The second experiment was carried out in Apr 2003 for three days, which was partially funded by the Marine Extension Service. Bay anchovy was the most abundant species during October comprising more than 95% of the total catch from trawls, whereas the spring sampling showed a significant reduction in total catch and somewhat smaller sizes for all species, with star drum, croaker and bay anchovy the most common depending on location within the estuary.

Publications

Thesis:
Daimar Tamarack, 2003. "The use of acoustics to describe the spatial distribution of fish in the Altamaha and MacKay River estuaries", Interdisciplinary Studies undergraduate thesis, Dept. of Marine Sciences, University of Georgia.

Planned Publications:
Di Iorio, D., G. Grossman, and T.D. Bishop, 2003. "Hydroacoustic surveying of fish populations in the Altamaha and MacKay River Estuaries, GA", in preparation for Fisheries Research.


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This page was updated October 13, 2006