Temporal genetic structure and energy dynamics of an intergrade largemouth bass population

Abstract

This study evaluated the temporal genetics and energy dynamics of an intergrade largemouth bass population in Aquilla Lake, Hill County, Texas. Frequencies of alleles associated with Florida largemouth bass Micropterus salmoides floridanus generally increased across year classes and over time for year classes; although fewer significant differences were observed between year-class allele frequencies during the post-stocking period than during the stocking period. Linear relationships among Florida allele frequencies were well-correlated, except for the relations between sAAT-B*3 and sAAT-B*4 and between sAAT-B*4 and sSOD *1. Heterozygosity and introgression were highest for age-0 fish of the 1986 year class. Collections of specific year classes over time consistently indicated decreases in the relative abundance of the northern phenotype (phenotype = electrophoretic phenotype). Relative abundance of year classes of the Florida phenotype remained relatively constant over a nine-year period; relative abundances of F1, and Fx (F[>1]) year classes were observed to increase over time. Seasonal dynamics of several organismic indices and energy composition were evaluated for three size categories. All indices, with the exception of the gonadosomatic index, showed few significant differences between sexes. Size category was a significant factor in all comparisons of monthly index values, except for the muscle index. Analysis of variance with length as a covariate confirmed that size rather than sex provided a greater influence on indices. Significant differences were observed between relative weight means of 1990 and 1991 year classes within the stock category for February and March, indicating an age-related effect on fish condition. Monthly index values were most affected by changes in prey availability and thermal conditions, and the reproductive cycle in mature fish. Total energy was most influenced by muscle energy and was lowest in March for all fish. Hepatic and gonadal energy of quality fish declined considerably with the spawn. Muscle and hepatic energy, to a lesser extent, supported gonadal growth. Variation in lipid class concentrations was influenced by season, sex, and size. Lipid classes in liver and gonadal tissues were the most variable. Triacylglycerol and cholesterol appeared to be transported from the liver to the ovary during gametogenesis.