放养密度对寒区稻-扣蟹共作模式中河蟹生长及水质的影响

Effects of Stocking Density on Growth Performance of Chinese Mitten Handed Crab (Erocheir sinensis) and Water Quality in a Rice-Crab Juveniles Co-culture System in Cold Regions

在黑龙江省绥化市北林区(127.08°E,46.88°N)稻渔综合种养基地的300 m^(2)实验单元中,设置1个水稻常规单作对照组(RM)和3个“绥粳4”水稻与体质量(1.02±0.16)g长江水系中华绒螯蟹(Eriocheir sinensis)Ⅲ期幼蟹共作组(RCC)。蟹密度分别为22 500只/hm^(2)(RCCI)、45 000只/hm^(2)(RCCⅡ)和67 500只/hm^(2)(RCCⅢ),每组3个重复。稻蟹共作组单元在距稻田埂1 m处开挖上宽0.6 m、下宽0.3 m,深0.4 m,不超过稻田总面积10%的梯形环沟。水稻6月2日插秧,7月6日投放长江水系Ⅲ期幼蟹,每天17:00投喂中华绒螯蟹配合饲料,9月下旬,统计水稻产量、养成扣蟹平均体质量,探究寒区稻-扣蟹共作模式下中华绒螯蟹与水稻的生长性能及水质理化因子变化规律。结果表明:在一个种养周期内,稻蟹共作RCCⅢ组水稻的产量显著高于对照组(P<0.05),RCCI组和RCCⅡ组水稻产量略高于对照组,但差异不显著(P>0.05);中华绒螯蟹终末体质量达(16.11±1.15)g,不同放养密度对中华绒螯蟹的终末体质量、增重率(WGR)及特定生长率(SGR)影响均不显著(P>0.05)。对整个实验期间,稻蟹共作组与水稻单作组水体的水温(TEMP)、溶解氧(DO)、pH、总氨氮(TAN)、亚硝酸态氮(NO_(2)-N)、硝酸态氮(NO_(3)-N)、总氮(TN)含量和化学需氧量(COD)等参数均无显著性差异(P>0.05)。稻蟹共作组水体的电导率(SPC)、总磷(TP)和叶绿素a(Chl.a)含量均显著高于水稻单作组(P<0.05),而正磷酸盐(PO_(4)-P)含量则显著低于水稻单作组(P<0.05)。稻蟹共作组稻田土壤的TN和TP含量均低于水稻单作组,且TN含量存在显著性差异(P<0.05)。综上,在高寒地区,稻蟹共作模式下适度放养蟹苗(67500只/hm~2)在保证大规格蟹种的同时,可以显著增加水稻产量,该模式下稻田水体的SPC、TP和叶绿素a含量显著较高,而土壤TN含量显著较低。本研究结果为寒区稻田大规格蟹种培育以及稻-扣蟹共作模式在寒区的科学构建提供理论支撑。

Chinese mitten handed crab(Erocheir sinensis)stage III juveniles with body mass of(1.02±0.16)g in the Yangtze River were co-cultured with"Suijing 4"rice in a 300 m^(2) experimental unit of the rice-fishing coculture systems in planting and breeding base(127.08°E,46.88°N)in Beilin District,Suihua City,Heilongjiang Province at stocking density of 0 ind./hm^(2)(single-rice planting control,RM),22,500 ind./hm^(2)(RCCI),45,000 ind./hm^(2)(RCCII),and 67,500 ind./hm^(2)(RCCIII)with 3 replicates per group in order to comprehensively investigate effects of stocking density on growth performance of Chinese mitten handed crab and physical and chemical factors of water quality under co-culture of rice-crab juveniles in cold areas.In the rice-crab co-cropping units,a ring ditch with an upper width of 0.6 m,a lower width of 0.3 m and a depth of 0.4 m was excavated at 1 m away from the paddy ridge,which did not exceed 10%of the total area of the paddy field.Rice was transplanted on June 2nd,and stage III juvenile crabs of the Yangtze River water system were stocked on July 6th,and fed formulated feed at 17:00 every day.In late September,the rice production and the average weight of the crabs were counted.The results showed that there was no significant difference in the final body weight,weight gain rate(WGR),and specific growth rate(SGR)of Chinese mitten handed crab with different stocking densities(P>0.05).There was slightly higher rice yield in RCC groups than that in RM group,significant difference only in RCCIII compared with others(P<0.05).No significant differences were observed in water temperature(TEMP),pH,and concentrations of dissolved oxygen(DO),total ammonia nitrogen(TAN),nitrite nitrogen(NO2-N),nitrate nitrogen(NO3-N),total nitrogen(TN)and chemical oxygen demand(COD)between RM and RCCs during the whole experiment period(P>0.05).There were significantly higher electrical conductivity(SPC),and contents of total phosphorus(TP)and chlorophyll a(Chl.a)in RCC groups than those in RM group(P<0.05),while the orthophosphate(PO4-P)content was significantly higher in RM than that in RCC groups(P<0.05).The TN and TP contents in sediment were found to be higher than in RM group than those in RCC groups,with significant difference in only TN content(P<0.05).Overall,normal growth of Chinese mitten handed crab and increase in the yield of rice were ensured within the moderate stocking density(4,500 individuals per hectare)in rice crab co-culture pattern.Meanwhile,the contents of SPC and TP in water were found to be significantly increased in the rice crab co-culture pattern,and the contents of PO4-P in water and TN in sediment to be significantly reduced.The findings will lay a foundation for the breeding of large size commercial crab in the development of integrated farming of rice and aquaculture animals,and will provide basic data and scientific theoretical guidance for the promotion of rice crab co-culture pattern in cold areas.