Variability in growth and survival of early postlarval shrimp ( Penaeus vannamei Boone 1931)

Abstract

Growth trials with early PL (postlarvae) suggested that growth and size variability may be used as sensitive indicators of PL quality. For PL produced from a broodstock population in which IHHNV (Infectious Hypodermal and Hematopoietic Necrosis Virus) had been identified, growth was lower and size variability was greater than for PL produced from a broodstock population free of IHHNV. Histological examinations of PL confirmed that the slower growing PL were infected with IHHNV, and that the faster growing PL were free of intranuclear inclusions characteristic of IHHNV infection. Survival of PL did not differ between the two populations. Differences in both survival and growth between batches of PL within populations were significant but did not mask differences in growth between the populations. Growth of early PL was exponential rather than linear and was appropriately characterized by the instantaneous growth rate. An additional growth trial conducted with juvenile shrimp indicated that differences observed in PL growth between the two populations continued to be expressed during juvenile growth. Correlations of PL growth to larval survival and duration suggested that larval survival was a good indicator of PL quality but that larval duration was inadequate to predict growth of PL.