Gs. Su et al., GENETIC AND ENVIRONMENTAL VARIATION OF FEMALE REPRODUCTIVE TRAITS IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS), Aquaculture, 154(2), 1997, pp. 115-124
The variation and covariation of reproductive traits were studied by a
nalyzing data from 2020 females divided into 377 full sib families and
covering five generations of three lines-a random mated control line
(C), an egg size (+) line (E) and a body weight (+) line (Y), in a sel
ection experiment with rainbow trout conducted at Davis, California. V
ariance components were estimated from a single trait animal model and
covariance components from a two-trait animal model by using a deriva
tive-free restricted maximum likelihood algorithm. Pooled over the thr
ee lines, the estimates of heritability were 0.65 for spawning date, 0
.14 for spawning body weight, 0.60 for egg size, 0.55 for egg number,
0.52 for egg volume and 0.13 for fertility-hatchability. The estimates
in line C were lower for spawning date, spawning body weight and egg
number, and higher for egg size and fertility-hatchability than those
in line E and line Y. Full-sib family effects caused by factors other
than additive genetic effects were considerable for spawning body weig
ht but small for other traits. Genetic correlations were estimated fro
m data pooled over the three lines. Spawning date had significant gene
tic correlations with spawning body weight, egg size and egg volume (0
.51-0.73) as well as with egg number (0.25). Significant genetic corre
lations were also found for spawning body weight with egg size, egg nu
mber and egg volume (0.47-0.67); and for egg size with fertility-hatch
ability (0.35). As expected, the genetic correlations between egg numb
er and egg volume and between egg size and egg volume (0.81 and 0.48)
were strong and significant due to the partial auto-correlations origi
nating from commonality among biological components and methods of mea
suring these traits. The estimated genetic correlations between spawni
ng body weight and egg production traits (egg size, egg number and egg
volume) were positive, so that direct selection for growth rate or eg
g production traits-should result in favorable correlated responses. T
he low heritability of body weight, the moderately high heritability o
f egg volume, and the strong genetic correlation between spawning body
weight and egg volume, suggest that combined selection for body weigh
t and egg volume could be an effective alternative selection method fo
r improving growth rate and also reproductive capacity in rainbow trou
t. (C) 1997 Elsevier Science B.V.