ABSTRACTS OF POSTER PAPERS 323

ABSTRACT

A diallele cross was used in a comparative analysis of several traits of lake trout. A diallele cross is a set of all possible matings between a set of parental lines. A 3 x 3 diallele cross was made using parents from Gull Island Shoals (Lake Superior), Seneca Lake (New York), and Jenny Lake (Wyoming). The progeny were reared under uniform hatchery conditions up to 18 months of age. Analysis of variance was used to estimate the effects of female and male parentage at different life stages. In the early life stages, significant differences due to female parentage could have been the result of maternal effects rather than genetic effects. However. a significant additive effect due to male parental stock was observed for percent survival from eye-up to swim-up, a life stage during which there was high mortality due to bluesac disease. Additive male parental stock effects were also found for alevin lipid content. and alevin weight and length. This suggests than there is some additive genetic variation for these traits between the parental stocks. Pectoral and pelvic fin deformities measured at the fingerling stage were found to be due mainly to female parentage. At 12 and 18 months of age, length and weight were affected by both female and male parentage, and allometric condition factor was affected mainly by female parentage. Comparisons obtained from diallele crosses can help to determine the most suitable stocks for use in selective breeding pro- grams. This information is useful for stock selection for intensive and extensive aquaculture as well as fishery management.

Inheritance of size as estimated by principal component analysis at two temperatures in Penaeus vannamei

L. JAMES LESTER and KIM S. LAWSON

University of Houston-Clear Lake, Houston. TX 770.58 (U.S.A.)

ABSTRACT

Larvae and postlarvae from full-sib families of Penaeus oannamei were reared under controlled conditions in an experimental facility. Two sets of families were split between two temperatures and comparisons were made after larval growth and after 4 weeks of postlarval growth. Photo- graphic slides of random samples from each replicate of each family were used in conjunction with a digitizing tablet for data collection. For postlarvae from larval growth studies, a set of three partial lengths and one depth were digitized. For shrimp from postlarval growth studies, three length and two depth measurements were collected. Principal component (PC) analysis was per- formed on these data sets. Data from larval studies did not yield a satisfactory eigenvector on the first principal component; therefore, total length was used to estimate size. Analysis of postlarval growth used the first principal component score ( PRINl ) for each individual which summarized the information on size inherent in the data set. PRINl scores and single variables were used in ANOVA to obtain estimates of heritability of size at each age under each temperature. Heritabil- ities ranged from 0.02 to 0.16 for size after larval growth and 0.0 to 0.59 for size after postlarval growth. Heritabilities were larger when shrimp were grown at 22-24’C. Variation among esti- mates of heritability of size due to the variable used is described. The reason for using a multivar- iate approach for estimating size variation is discussed.