不同混养鱼类和投喂方式对鱼蚌综合养殖水体化学特征的影响

选用草鱼(Ctenoparyngodon idellus)、银鲫(Carassius gibelio)、鲢(Hypopthalmichthys molitrix)、鳙(Aristichthysnobilis)作为本研究的混养鱼类,通过围隔实验检验了不同混养鱼类组合(草鱼+鲫+鲢+鳙或鲢+鳙)和配合饲料投喂方式(投喂或不投喂)对三角帆蚌(Hyriopsis cumingii)养殖水体化学特征的影响,实验为期155 d。结果表明,实验设计的混养鱼类组合可显著影响鱼蚌综合养殖水体的Ca2+、总碱度(Alk)、总硬度(HT)和总磷(TP)水平;投喂配合饲料可显著影响Ca2+、Alk、HT、氨氮(TAN)、TP和化学耗氧量(CODMn)。采用混养组合(草鱼+鲫+鲢+鳙)且投喂配合饲料的围隔内溶氧(DO)水平和透明度(SD)较低,Ca2+、HT、TN、TP、TAN和CODMn水平较高;采用混养组合(鲢+鳙)且不投喂的围隔内DO和SD水平较高,而Ca2+、HT、TN、TP、TAN和CODMn水平较低。随养殖时间延长,各组围隔内Ca2+水平下降,TN、TP、TAN和CODMn水平升高。实验期间,DO与SD水平呈正相关;DO和SD与TAN、TN、TP、Ca2+和CODMn水平呈负相关。因此,鱼蚌综合养殖中,控制CODMn和TAN浓度,维持Ca2+稳定及较高的DO水平是水质管理的基本目标。

Effects of co-cultured fish and feed supplement on water chemistry characteristics of freshwater pearl mussel farming

Integrated culture is widely used in freshwater pearl mussel (Hyriopsis cumingii) farming; however, water chemistry characteristics relating to H. cumingii farming are poorly understood. To assess the effects of co-cultured fish (grass carp, gibel carp, silver carp and bighead carp or silver carp and bighead carp) and formulated fish feed supplement (with or without feed supplement) on water chemistry characteristics, a 155-day field experiment was carried out in land-based enclosures. Four treatments including GGSB-F (co-cultured fish grass carp, gibel carp, silver carp and bighead carp were fed formulated feed), GGSB-NF (co-cultured fish grass carp, gibel carp, silver carp and bighead carp were not fed formulated feed), SB-F (co-cultured fish silver carp, and bighead carp were fed formulated feed) and SB-NF (co-cultured fish silver carp and bighead carp were not fed formulated feed) were established. The results indicated that the combination of co-cultured fish species could significantly affect Ca²⁺, total alkalinity (Alk), total hardness (H_T) and total phosphorus (TP), while the feed supplement regime affected Ca²⁺, Alk, H_T, ammonia (TAN), TP and chemical oxygen demand (COD_Mn). Dissolved oxygen (DO) and secchi depth (SD) were lower, while Ca²⁺, H_T, total nitrogen (TN), TP, TAN and COD_Mn were higher in the GGSB-F enclosures. Conversely, DO and SD were higher, but Ca²⁺, H_T, TN, TP, TAN and COD_Mn were lower, in the SB-NF enclosures. During the experimental period, Ca²⁺ decreased, while TN, TP, TAN and COD_Mn increased. DO and SD were positively correlated with each other and negatively to the levels of TAN, TN, TP, Ca²⁺ and COD_Mn. Therefore, water quality management programs should include controlling the concentration of TAN and COD_Mn at the levels below the critical values, and maintaining Ca²⁺ and DO at high and constant levels.