Comparative growth and survival of inbred and outbred Penaeus (marsupenaeus)japonicus, reared under controlled environment conditions:: indications of inbreeding depression

This study quantifies the effects of inbreeding on growth, survival (and associated yield), of domesticated Penaeus (marsupenaeus) japonicus for inclusion in selective breeding programs of the future. To make this assessment, we systematically bred two generations of inbred (F = 28-31%) and outbred families with known parentage and inbreeding coefficients. During the 2 production years, we assessed growth, survival and yield. The estimated inbreeding depression coefficient (standard error) was -3.34 +/- 2.55% for growth and -3.43 +/- 3.59% for overall survival. The consistency in both size and direction of the inbreeding depression coefficients for two fully independent traits lends support to the hypothesis that inbreeding reduces growth and survival, even though the coefficients were not statistically significant due to high variability among animals and a relatively small effect. When growth and survival were combined, yield was depressed by an estimated -6.53 +/- 4.08%. Mortality was highest in the first growth stage (PL30-PL80), with 75.1% survival for inbred crosses compared with 82.5% survival for outbred crosses. In the second (PL80-PL124) and third (PL124-PL156) growth stages, survival ranged from 92.5% to 95.1% with little difference between inbred and outbred crosses. This study demonstrates that a level of inbreeding can be tolerated by penaeids but can cause a degree of inbreeding depression and reduced production. However, there was variation in inbreeding depression between families. The knowledge that inbreeding in penaeids can cause reduced production through inbreeding depression highlights the need to maximize the genetic diversity in founder stocks, and consider rate of inbreeding in selective improvement programs. (C) 2004 Elsevier B.V. All rights reserved.