WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2025 37 TABLE 2. Estimated expenses, revenue and profit/loss for F. lancifer culture using various forage/density options, based on current prevailing-cost and market data. Forage Initial Density Total Estimated Expenses Revenue ha-1 Profit/(Loss) (Direct and Fixed) ha-1 Before Taxes ha-1 Wheat (2 m-2) $2435 $2116 + $439 ($319) + $439 Wheat (6 m-2) $2537 $1943 + $393 ($594) + $393 Mixed Vegetation (3m-2) $2375 $4382 + $507 $2007 + $507 Mixed Vegetation (6 m-2) $2440 $3244 + $621 $804 + $621 Maiden Cane (3m-2) $2508 $3142 + $439 $634 + $439 Maiden Cane (6 m-2) $2573 $2651 + $439 $78 + $439 Rice (3m-2) $2473 $2587 + $310 $114 + $310 Rice (6 m-2) $2537 $2933 + $293 $396 + $293 Late Rice (4 m-2) $2473 $4216 + $507 $1743 + $507 Late Rice (6 m-2) $2537 $5811 + $332 $3238 + $332 animals had molted to the mature form, meaning growth had ceased. During the final week of the study, all crayfish over 70 mm total length were retained and measured, as would be the case in a commercial operation when the opportunity to sell somewhat smaller animals at a reduced price would outweigh any incentive to return them to the pond to potentially attain a larger size, especially if ponds were going to be drained and re-planted with wheat. Pools were drained to allow for any remaining crayfish to be counted and measured. ANOVA for treatment differences in survival, average weight, yield and harvest value was conducted using the GLM procedure in SAS to generate Least Squares Means and levels of significance for treatment comparisons. Prevailing monthly values for harvests of marketable size animals were estimated based on historical data and current market premiums. A total harvest value ha-1 was calculated for each mesocosm. Growth in length based on sampling data was plotted using nonlinear regressions (SigmaPlot for Windows 10.0) for each treatment. Production costs were estimated for each treatment based on published budgets for P. clarkii production incorporating estimated costs for conversion to F. lancifer culture (broodstock/ nursery facilities and maintenance/stocking labor). Results and Discussion High stocking densities in crustacean aquaculture usually increase total biomass but reduce survival and growth (Lutz and Wolters, 1986). Under stressful stocking densities, growth performance of aquatic animals is inhibited, negatively affecting economic benefits of intensive farming activities (Dong et al. 2022; Romaire and Villagran 2010). In this study, individual weight significantly decreased with an increase in stocking density of F. lancifer utilizing wheat, mixed vegetation, and maiden cane as forages (Table 1). Compared to the late rice treatment at 6 m-2, mean individual weight at harvest was significantly lower for F. lancifer culture using wheat, mixed vegetation, or maiden cane at the same density. Compared to F. lancifer in early rice and late rice treatments, mean individual weight in the wheat and mixed vegetation treatments was significantly larger for 2 m-2 and 3 m-2, but significantly smaller when the mesocosms were stocked at 6 m-2. Similar results have been reported in some shrimp species. For example, the growth of black tiger shrimp (Penaeus monodon) and whiteleg shrimp (Penaeus vannamei) was significantly lower when their stocking densities went from 400 m-3 to 500 m-3 and from 90 m-2 to 180 m-2 respectively (AftabUddin et al. 2020; Araneda et al. 2008). In this study, individuals stocked into mixed vegetation at 3 m-2 resulted in the largest mean weight at harvest. Survival rates of F. lancifer significantly decreased for individuals with wheat and mixed vegetation forages at densities of 6 m-2. Individuals stocked in late rice at a density of 4 m-2 showed the highest survival rate compared to the rest of the forages and stocking densities. However, individuals stocked in late rice at 6/m-2 resulted in the highest yield, revenue and profit. Although projected total expenses were somewhat higher than for typical Procambarus production, resulting profits and losses were within the normal range observed throughout Louisiana’s crawfish industry (Table 2). Stocking densities and forages evaluated here appeared to result in similar growth patterns (Figure 7). Most of the animals in the study attained sizes that were comparable to early-season (CONTINUED ON PAGE 38) FIGURE 7. Figure 7. Juveniles held for extended periods prior to stocking appeared to exhibit some degree of compensatory growth in various forage treatments.
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