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Add To Calendar 21/02/2017 09:30:0021/02/2017 09:50:00America/ChicagoAquaculture America 2017Ecophysiological-modeling-based Analysis of Red Drum Stock Enhancement in Texas:  An Update Room 7The World Aquaculture Societyjohnc@was.orgfalseanrl65yqlzh3g1q0dme13067DD/MM/YYYY

Ecophysiological-modeling-based Analysis of Red Drum Stock Enhancement in Texas:  An Update

William H. Neill* and Robert R. Vega
 
 Department of Wildlife and Fisheries Sciences
 2258 TAMUS (Texas A&M University System)
 College Station, TX 77843-2258
 wneill@tamu.edu

We have revised our previous analysis to force compliance with growth and frequency data observed for gill-netted red drum identified genetically as having come from hatcheries operated by Texas Parks and Wildlife Department's Division of Coastal Fisheries.  Growth rates of these 190 recovered hatchery fish (HF), taken in 17 bay-year-season samples, implied that 28 % of targeted HF, on average, were outside the 300-500-mm TL range subjected to genetic analysis.  Taking these "dark" HF into account, and optimizing the presumed rate of HF mortality upon release at 91 %, resulted in maximized goodness-of-fit between modeled and observed proportions of HF in the gill-net catch.For all 17 samples, the emergent relation was %HFmod = 2.37 + 0.82*%HFobs, with R2 = 0.64.  Restricting the analysis to the 12 samples with 3 or more recoveries gave %HFmod = 0.91 + 0.95*%HFobs, with R2 increased, to 0.76.

Our ecophysiolgical analysis of stocking, juvenile-abundance, and sport-fishery-catch data for red drum in Texas is thus amended, as follows:  Assuming 91 % HF mortality over first 2 days after release, subsequent growth rates equivalent to those of recovered HF, and with other reasonable assumptions in place, we estimate that for the 1990-2011 year classes of red drum, a total of 23,160,000 individual fish have survived and grown to enter the fishing "slot" (20-28 inches TL) in Texas bays 2-8.  Of this total, 1,670,000, or 7.2 %, have been HF.  These HF have supplanted 296,000 WF, or 1.3 % of the total.  Thus, net HF contribution to the stock at slot entry is estimated to have been 1,374,000 fish, or 5.9 % of the stock.




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