The Research Of Feeding Physiology Of Filter-feeding Bivalves On Uneaten Feeds And Faeces From Cage Fish Farming

Since the1970s, marine finfish cage farming were developed repidly in China.At present, traditional farming areas are mainly located in shallow coastal，and thenumber of traditional finfish cages had reached12million.Because the self-pollutionis serious,the environmental pressure of finfish cage culture has become one of themajor the problem which influence the sustainable development of the industry. Away to reduce the impact of cages farming is by co-culture filter-feeding bivalves,macroalgae etc. into cages area to remove particle organic matter and nutrient, whichnamed IMTA (Integrated muti-trophic aquaculture). in this paper, the feeding activityof the Japanese scallop (Patinopecten yessoensis), the Pacific oyster (Crassostreagigas), blue mussel (Mytilus edulis) and the Manila clam (Ruditapes philippinarum)on feces and uneaten feed were studied, so as to understand the feeding physiology ofbivalves and to provide basic theory for IMTA mode. the major results as follow:1. Feeding behaviors of Japanese Scallop Patinopecten yessoensis feeding onParalichthys olivaceus feed, feces and sediment particulates from farming cage. Inthis research, Static method were used to study Japanese scallop (Patinopectenyessoensis) feeding behavior on different food quantity and quality of flounder(Paralichthys oolivaceus) feces, residual feed, deposit and micro-algae, the potentialIMTA shellfish and fish based on the scallop was analyzed. Results showed P.yessoensis could feed fish feces, residual feed, deposit and microalgae. However,clearance rate and ingestion rate on microalgae were significantly higher than theother3experimental groups (ANOVA, p<0.01). Absorption efficiency amongmicroalgae, fish feces and residual feed groups were not significant different, butthere were significantly higher than that of on deposits. There was positive correlationbetween AE and organic content (f): AE(％)＝38.84ln(f)+72.7(R2=0.378); thereshowed linear relationship between AR and POM: AR＝0.118×POM-0.555(R2=0.329). TPM threshold for pseudo-feces production was24.09mg/L, and the scallop could regulate food intake by pseudo-feces production.2. Feeding behaviors of5species filter-feeding bivalves on Paralichthys olivaceusfeed, fecal and sediment particulates from farming cage. Static method were used tostudy5species bivalves’ feeding behavior on different food quantity and quality offlounder (Paralichthys oolivaceus) faeces, residul fed and deposition, the potentialIMTA shellfish and fish based on filtering feed bivalves was analyzed. Resultsshowed the5species bivalves could feed fish faece, residul fed and deposition.However, different species showed different feeding behaviors. Ingestion rates ofoyster, clam and scallop were significantly higher than the other2species (ANOVA,p<0.01). Absorption efficiency among residul fed were not significant different, butthere were significantly different among faeces and deposits of the5species. Therewas positive correlation between AE and organic content and significantly linearrelationship between AR and POM. TPM threshold for pseudo-feces production ofoyster, scallop and was26.24，21.64，27.00mg L-1, respectively, and the5speciesbivalves could regulate food intake by pseudo-feces production. The shellfish+fishIMTA mode, clam Ruditapes philippinarum, oyster Crassostrea gigas and scallopChlamys farreri is relatively good candidate species.3. The food sources of Pacific oyster Crassostrea giga cultivated in cage areawere analyzed and quantified by fatty acid and stable carbon and nitrogen isotopemethods. Results showed that comparing with the initial value, ratio of n-3/n-6inoyster Crassostrea gigas increased both in cage farming area and control area.However, the ratio of n-3/n-6was significantly higher in cage farming area than thatof in the control area (p <0.01).The DHA in Crassostrea gigas in cage and controlarea was significant different（p<0.05）, overall, DHA in C. gigas in cage areagradually approached to food source signiatures. Based on the simple linear mixingmodel, the contribution rate of the POM, uneaten feeds and fish feces to oyster was42%,40%and18%, respectively.After28days feeding on fish feeds or feces, stable carbon isotope in adductormuscle tissue of oyster showed a little change over time. However, scallop Chlamysfarreri only showed a little change feeding fish feed.