Path analysis of body weight and shell morphological traits in two Pacific abalone (Haliotis discus hannai) strains

The effect of morphological traits on the body weight of Pacific abalone (Haliotis discus hannai) was investigated by correlation analysis, path analysis and multiple regression analysis. We evaluated the relationships between shell length (SL), shell width (SW) and body weight (BW, the total wet weight) in two different strains of Pacific abalone. One strain is 'Huangxun No. 1', which is from the fifth generation of a novel strain that has experienced higher shell growth rate selection, and the other strain is a first-generation descendant of wild Pacific abalone. The results of the correlation analysis showed that both SL and SW were significantly (p < 0.05) positively correlated with BW in both strains. Path analysis showed that SL significantly affected the BW of the 'Huangxun No. 1' strain, while SW significantly affected BW at only one of the four ages tested. Both SL and SW significantly affected the BW of the wild strain at the four ages tested. The determination coefficients of SL on BW in the 'Huangxun No. 1' strain at 3, 6, 13 and 19 months of age were 0.835, 0.141, 0.834 and 0.708, respectively, while those in the wild strain were 0.476, 0.237, 0.344 and 0.141, respectively. In addition, the SL/SW in the 'Huangxun No. 1' strain ranged from 1.453 to 1.509, while that of the wild-type strain ranged from 1.389 to 1.497. The allometric growth analyses showed positive allometric growth for 'Huangxun No. 1' from 3 to 19 months of age, while the wild strain did not show such growth. These results suggest that multiple generations of selection for a higher SL growth rate may have led to variation in shell morphological traits and that shell width may be a less important factor in determining body weight in the 'Huangxun No. 1' strain, while shell length can be used as an effective morphological trait for selective breeding to increase body weight.