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Residence Times, Movements and Growth of White Shrimp within Tidal Marsh Drainages Supplying Georgia Sounds


PI: Ronald Kneib (University of Georgia Marine Institute, Sapelo Island, GA, USA)

Support: Georgia Sea Grant College Program (R/FS-2-PD)

Timeframe: 8/1/96 - 2/28/98 (complete)

Project Overview:
To test the effectiveness of two marking systems (fluorescent elastomer tags and coded microwire tags) for identifying cohorts and individuals of juvenile white shrimp. The methods were intended to be applied in a subsequent Sea Grant project to: (a) determine the residence time of shrimp within different tidal drainages emptying into coastal sounds; (b) determine the degree to which shrimp move among tidal drainages within a sound system; (c) compare the size, growth and mortality rates of shrimp migrating into the sound from tidal drainages with different physical characteristics (i.e., geomorphic configurations, salinities and geographic positions with respect to distance from the coastal ocean).

Findings:

  • Two seasons (1996 & 1997) of methods testing showed that both types of tags could be effectively used to assess survival, growth and movements of juvenile shrimp. Coded microwire tags have the advantage of identifying individual shrimp and provided superior and unambiguous measures of growth rate. Neither of the tagging techniques significantly affected growth rates of marked shrimp. Of the four marking locations tested, injection of 1.1 mm coded wire tags into the musculature of the first abdominal segment yield the best combination of survival (93.8%) and tag retention (99.3%); tag injection in the uropod or telson was judged inferior because it yielded lower survival rates (86-87%) and relatively poor tag retention rates (59-71%).

  • More individuals could be marked per unit time using fluorescent elastomer tags, but this is a batch marking method and cannot be used to identify individuals. Shrimp injected with fluorescent tags exhibited virtually 100% tag retention, but certain combinations of colors and tagging locations produced slightly lower survival rates than were observed in control groups of unmarked individuals.

  • Preliminary field tests of the tags involved the capture of 25,612 individual shrimp, of which 10,844 were marked with either or both tag types. Fifty-four individuals marked with coded wire tags, and at large for 1-100 days, were recovered from tidal creek drainages on Sapelo Island. Growth rates declined with time at large and averaged < 1 mm per day for individuals marked 7-100 days prior to recapture.

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This page was updated October 13, 2006