Effects of inbreeding on survival and growth of Pacific white shrimp Penaeus (Litopenaeus) vannamei

Abstract

The objective of this study was to investigate the effects of inbreeding on the performance of Pacific white shrimp, Penaeus (Litopenaeus) vannamei, under various culture conditions through a retrospective analysis of family performance data. Fourteen years of pedigree and eight years of performance data from Oceanic Institute's selective breeding program were used in the analysis. During this period, shrimp performance was evaluated in growout trials (in pond and raceway systems), laboratory challenges to three isolates of Taura syndrome virus (TSV), and a laboratory challenge to White spot syndrome virus (WSSV). The effects of inbreeding on growth and survival were estimated by regressing family phenotypic means (adjusted for contemporary group effects) on inbreeding coefficients. During growout, inbreeding had a small but significant effect on growth (2.6 to 3.9% reduction per 10% inbreeding) but had no effect on survival. The effects of inbreeding on survival after exposure to viral pathogens ranged from moderate (8.3% reduction per 10% inbreeding) to severe (38.7% reduction), although not all effects were significant. Furthermore, the effects of inbreeding on survival appeared to be sensitive to environmental quality, as inbreeding depression was more severe in more stressful environments (smallest effect during growout trials and largest effect during exposure to WSSV). These results suggest that moderate to high levels of inbreeding (>10%) should be avoided in shrimp breeding programs, especially when shrimp are reared under stressful conditions. In addition, the effects of inbreeding on survival appear to be significant enough to justify the use of inbreeding as a germplasm protection strategy (under certain scenarios) for genetic improvement programs.