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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. [ABSTRACT FROM AUTHOR]

A 45-day trial was conducted to study the effect of seawater total alkalinity (TA) level up- and downregulation on the growth performance and calcification of Haliotis discus hannai Ino, while seawater pH was maintained at pH NBS = 8.1. Although seawater was not acidified, the results showed that TA downregulation caused a significant reduction (P < 0.05) in the somatic tissue growth of juvenile abalone, while TA upregulation significantly increased growth performance (P < 0.05). Similar to the impacts of pH reduction, TA downregulation also induces a decline in CO 2 buffering capacity, which may be the reason why somatic tissue growth was reduced, as lowered CO 2 buffering capacity was reported to shift the acid-base balancing of abalone. Parts of the periostracum layer weremissing and exposed the inner shell layers of the individuals from the TA-downregulated group. Scanning electron microscopy (SEM) results showed calcium carbonate densely deposited onto the inner shell in the control and TA-upregulated groups, while sparsely deposited calcium carbonate was observed in the TA-downregulated group. The C: N ratio in the shell of individuals from the TA-downregulated group was significantly lower than that of the other two groups, indicating that less inorganic carbon was added to the shell. As a result, abalone grew lighter and thinner shells in TA-downregulated seawater. Although seawater was not acidified, TA downregulation also caused a reduction in the calcium carbonate saturation state (Ω), which induced the erosion of the surface shell and the interruption of calcium carbonate generation. In conclusion, although seawater pH remained at ambient levels, the lowered CO 2 buffering capacity and Ω induced by seawater TA downregulation also showed a detrimental effect on the growth and calcification of Pacific abalone. The impact of ocean acidification on the growth of abalone should not be assessed using only seawater pH and/or p CO 2 but rather taking into account all of carbonate chemistry, particularly the CO 2 buffering capacity. Abalone cultivation is suggested to be carried out in seawater with a higher level of CO 2 buffering capacity and Ω, which can be achieved through integrated culture with seaweed or increasing the seawater TA level. • Although seawater was not acidified, TA down-regulation also reduced the growth performance of the Pacific abalone. • Seawater TA up-regulation significantly increased the growth performance of the Pacific abalone. • CO 2 buffering capacity should be considered in assessing the effects of ocean acidification on abalone. • Abalone cultivation is suggested to occur in seawater with a higher level of CO 2 buffering capacity. [ABSTRACT FROM AUTHOR]