Comparative Study on Feeding Physiology, Metabolic Physiology, and Energy Budget of Meretrix meretrix, Mactra veneriformis, and Ruditapes philippinarum in the Tidal Flat Aquaculture Zone

(1) Exploring the potential impacts of <i>Mactra veneriformis</i> and <i>Ruditapes philippinarum</i> on the aquaculture of <i>Meretrix meretrix</i> in the tidal flat aquaculture zone is significant for the optimization of bivalve aquaculture structure. (2) In this study, we systematically compared the differences in feeding, metabolic physiological indicators, and energy budgets of the three bivalve species in the <i>M. meretrix</i> aquaculture zone of Rudong County, Jiangsu Province, under the feeding conditions of <i>Isochrysis zhanjiangensis</i> and <i>Platymonas helgolandica</i>. (3) The results indicated that feeding with <i>I. zhanjiangensis</i> could significantly improve the feeding efficiency of the three bivalve species, and <i>M. veneriformis</i> showed the strongest feeding ability. Under <i>I. zhanjiangensis</i> feeding conditions, the clearance rate [1.373 ± 0.177 L/(g·h)] and ingestion rate [9.803 ± 1.264 mg/(g·h)] of <i>M. veneriformis</i> were significantly higher than those of <i>M. meretrix</i> [clearance rate: 0.716 ± 0.046 L/(g·h); ingestion rate: 5.112 ± 0.328 mg/(g·h)] and <i>R. philippinarum</i> [clearance rate: 0.609 ± 0.101 L/(g·h); ingestion rate: 4.351 ± 0.725 mg/(g·h)] (<i>p</i> < 0.05). In terms of energy allocation, the scope for growth (SFG) of <i>M. veneriformis</i> [133.050 ± 15.705 J/(g·h)] was significantly higher than that of the other two bivalve species. <i>M. meretrix</i> [70.550 ± 2.133 J/(g·h)] had the highest energy utilization efficiency, while <i>R. philippinarum</i> [53.688 ± 7.548 J/(g·h)] had the lowest SFG due to high excretion losses. (4) In conclusion, <i>M. veneriformis</i> shows high production potential in the aquaculture system, and its potential impact on <i>M. meretrix</i> is greater than that of <i>R. philippinarum</i>, thus requiring close attention in aquaculture management.