主要环境因子和混养对单环刺螠幼螠成活和生长的影响

Effects of Main Environmental Factors and Polyculture on Survival and Growth of Juvenile Echiuran Worm Urechis unicinctus

采用生态实验方法研究温度、盐度、底质、饵料及与不同生物混养对体质量1.11~1.19 g的单环刺螠(Urechis unicinctus)幼螠成活和生长的影响。单环刺螠幼螠饲养在50 cm×40 cm×35 cm的塑料箱中,每箱15个,加入5 L盐度25的海水,底质为40目沙,投喂螺旋藻粉+鼠尾藻粉+海参开口料混合饵料(2 mg/个幼螠),水温控制在10℃、15℃、20℃、25℃和30℃。盐度实验中,水温为20℃,盐度为15、20、25、30和35,其余同上。底质实验中,设无底质、泥、泥沙、天然海沙、40目和60目沙6个处理组,盐度25,水温20℃,混合投喂藻粉,其余同上。饵料实验设置螺旋藻粉(投喂量为6 mg/个幼螠)、混合藻液(小新月菱形藻和扁藻按投喂量各3mL/个幼螠)、螺旋藻粉+混合藻液(螺旋藻粉投喂量为3 mg/个幼螠,小新月菱形藻和扁藻按投喂量各1.5 mL/个幼螠)、混合藻液+海参开口料(海参开口料投喂量为3 mg/个幼螠,小新月菱形藻和扁藻按投喂量各1.5 mL/个幼螠)、混合藻粉(螺旋藻粉+鼠尾藻粉+海参开口料3种饵料投喂量均为2 mg/个幼螠)共5个饵料处理组,海水盐度25,水温20℃,底质为40目沙。混养实验分为5组,幼螠密度为200只/m^(2),分别混养日本蟳(Charybdis japonica)、脊尾白虾(Exopalaemon carinicauda)和矛尾复虾虎鱼(Synechogobius hasta)各26.67只/m^(2),66.67只/m^(2)和11.43尾/m^(2),温度为20℃,盐度为25,底质为40目沙。混养蟹的养殖箱中放入2根直径为10 cm的PVC管。混养组单环刺螠不单独投喂饵料。结果表明:适合幼螠成活的环境条件为水温15~25℃、盐度为20~30,底质为幼螠的成活不可缺少,但不同底质和饵料对幼螠成活率无显著影响;幼螠最适生长温度为20、盐度25~30,沙底质组的增重率显著高于泥底质和泥沙混合底质,但沙子颗粒大小无明显影响;投喂(混合藻液+螺旋藻粉)或(混合藻液+海参开口料)的两组幼螠增重率较高;虽然虾螠混养组的幼螠增重率低于蟹螠混养组和鱼螠混养组,但其成活率显著高于其他两组,虾螠混养组中的虾增重率明显高于单养虾。综合来看,虾螠混养是较为适宜的幼螠养殖方式。

Effects of environmental factors including water temperature, salinity, sediment, diet, and polyculture with different organisms on the survival and growth of juvenile echiuran worm Urechis unicinctus with body weight 1.11~1.19 g were investigated by ecological experimental methods. The echiuran worm juveniles were reared in a plastic box of 50 cm×40 cm×35 cm with 5 L sea water with salinity 25 at bottom sediment of 40 mesh sand at a rate of 15 individuals per box, and fed mixture of Spirulina powder + Sargassum powder + larval sea cucumber feed(2 mg/larvae)at water temperature of 10℃, 15℃, 20℃, 25℃ and 30℃. In the salinity test,the salinity was kept at 15, 20, 25, 30, and 35 at water temperature of 20℃, and the rest was as the same as above. In the sediment test,six treatment groups were set up including without sediment(control group), mud, silt, natural sea sand, and 40 mesh sand and 60mesh sands, at salinity of 25 and water temperature of 20℃, with the rest conditions as the same as above. In the diet test, 5 types of diets were set up including Spirulina powder(feeding amount of 6 mg/larvae), mixed algae liquid(Nitzschia lunata and Platymona platyphylla of each 3 mL/larvae), Spirulina powder + mixed algae liquid(Spirulina powder at feeding rate of 3 mg per larvae, Nitzschia lunata and Platymonas per at a dose of 1.5 mL per larva), mixed alga liquid + sea cucumber feed(sea cucumber feed feeding at feeding rate of 3 mg per larvae, N. lunata and P. vulgaris at 1.5 mL per larva), and mixed alga powder(Spirulina powder + Sargassum powder + sea cucumber feed at feeding amount of 2 mg/larvae)at water temperature of 20℃, and a salinity of 25 with 40 mesh sand bottom. The polyculture test was divided into 5 groups, with a density of 200 larvae/m^(2), including the polyculture of echiuran worm with Japanese crab(Charybdis japonica)at 26.67 animals/m^(2), ridgetail white prawn(Exopalaemon carinicauda)at 66.67 ind./m^(2), or goby(Synechogobius hasta)at 11.43 ind./m^(2), at water temperature of 20℃, salinity of 25, and 40 mesh sand sediment. Monoculture of echiuran worm, Japanese crab, ridgetail white prawn and goby was used as the control group. There were 2 PVC pipes with a diameter of 10 cm in the breeding box of polyculture crab. The echiuran worm juvenile in polyculture group did not feed with other specialized baits. It was found that the temperature of 15~25℃ and salinity of 20~30 was suitable for the survival of echiuran worm juveniles.The juveniles did not survive without substrate, without significant difference among the different substrates. The juveniles had the best weight gain rate under water temperature of 20, salinity of 25~30, and the substrate of sand. There was higher weight gain rate in the juveniles fed the diet(Spirulina powder and mixed algal liquid;mixed algal liquid and sea cucumber feed)than that in the juveniles in the other groups. There was poorer weight gain rate in the juveniles in the polycuture with shrimps than that in the juveniles in the polyculture with crab and fish, and the survival rate was just the opposite case. Furthermore, the shrimps in the polyculture group had significantly higher weight gain rate than the shrimp in the monoculture group, so the echiuran worm juvenile was more suitable for polyculture with ridgetail white prawn.