| In order to give the necessary support to the sustainable development of the scallop mariculture, a series of expriments were conducted through December2012to August2013. Those experiments include:1) investigation of the spatial and seasonal variation of the biological and abiotic factors in the seawater column;2) tracking the growth condition under different sowing density;3) tracing the food source of scallop by fatty acids and stable isotopes technologies;4) research on the effects of temperature on oxygen consumption and ammonia excretion of P. yessoensis and selected strain Hai da jin bei. Results showed that:1. The bottom dissolved nutrients were high at December and August, while the surface dissolved nutrients did not show obvious regular pattern. The bottom dissolved nutrients were significantly higher than the surface at August. The chlorophyll concentration was highest at August, and there was no significant differences between the surface and bottom. Nanoplankton was dominated in the surface, while microplankton was dominated in the bottom during June to August2013.2. Four treatments were deployed with the sowing densities of4000ind/mu(A),5500ind/mu(B),7000ind/mu(C) and9000ind/mu(D). The results showed that shell height (SH), body weight (BW), relative growth rate of shell height (GRH), relative growth rate of body weight (GRW), daily shell height gain (DHG) and daily body weight gain (DWG) were significant difference among these treatments (P<0.05).All the growth parameters of B and C were significantly higher than those of A and D. The relationship between SH and growth time (t) was SHA=39.803e0.0016t, r2=0.9076; SHB=38.871e0.0022t, r2=0.9883; SHC=38.871e0.0022t, r2=0.9883; SHD=38.871e0.0022t, r2=0.9883. The relationship between BW and growth time was, BWA=3.4184e0.0053t, r2=0.9263; BWB=3.2587e0.007t, r2=0.9826; BWC=3.4064e0.0067t, r2=0.9632; BWD=3.4064e0.0067t, r2=0.9632. The condition index rearched the maximum at March2013.The lowest mortality appeared at the treatment of5500ind/mu.3. Sowing scallop was characterized by significant diatom markers such as high content of EPA and high ratio of C20:5N3/C22:6N3, which indicated that the diatoms were the main food source. Fatty acid biomarkers of bacteria were also found in scallop tissue in considerable amounts, which suggested that there were substantial bacterial input into the food of the scallops. Higher level of DHA indicated the characteristic of Protozoa. An isotope mixing model suggested that scallop was consuming82%benthic boundary layer (mainly diatom, bacteria, Protozoa).4. The experiments on the oxygen consumption rate (OR) and ammonium excretion rate (NR) of the scallop were carried out Seasonally in accordance with the natural seawater temperature (5℃,10℃,15℃and20℃) by flowing water methods. OR and NR were affected significantly by temperature (P<0.05). For P. yessoensis, the OR ranged from0.81to1.78mg/(g·dw·h), and the NR ranged from0.02to0.07mg/(g·dw·h). Both of OR and NR reached maximum at15℃. The relationship between temperature (T) and OR or NR could be described by OR=-0.2311T2+1.2372T-0.0042(r2=0.8421), NR=-0.0057T2+0.0345T-0.0002(r2=0.5149). For the selected strain Hai da jin bei, OR showed the same trend as the P. yessoensis, and ranged from0.34to1.42mg/(g·dw·h). But NR of Hai da jin bei was showed opposite trend to the P. yessoensis. The relationship described as OR-0.2221T2+1.3105T-0.6276(r2=0.9957), NR=0.0206T2-0.0957T+0.1363(r2=0.9968)respectively for Hai da jin bei. Under the same conditions, the OR of P. yessoensis were significantly higher than Hai da jin bei at5℃and15℃(P<0.05). For the ammonia excretion rate, P. yessoensis was significantly higher than Hai da jin bei at15℃(P<0.05), but Hai da jin bei was significantly higher than P. yessoensis at5℃and20℃(P<0.05). |
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