循环水养殖罗非鱼氮收支及对水质影响的初步研究

为提供实际生产理论依据,改良系统水处理工艺,开展循环水养殖系统中吉富罗非鱼氮收支和对水质情况的初步研究。起始养殖密度8 kg/m3,投饲率2%,系统循环量1 m3/h,总水量0.8 m3。试验期间溶解氧大于6 mg/L,pH 7.0～7.2,水温23～25℃。每周监测水质2～3次,监测指标包括氨氮、亚硝酸盐氮、硝酸盐氮,每2周检测1次水中总氮。用凯氏定氮法测定实验前后饲料、试验鱼体、粪便、悬浮颗粒的氮含量。结果显示,摄食氮有50.00±1.50%转化为生长氮,32.61±1.38%转化为排泄氮,17.39±4.0%转化为粪氮;58%的粪氮为悬浮颗粒物,42%为可沉淀颗粒物。     

3种微生态制剂对养殖水体水质影响的比较研究

对3种微生态制剂改善河蟹养殖池水质的效果进行分析比较。实验组各池中分别加入超浓缩光合细菌(PSB)、西菲利活菌生物净水剂、活菌净水剂以及3种微生态制剂组成的混合制剂。观察氨态氮、亚硝态氮、硫化氢、溶解氧、化学耗氧量、pH及异养菌总数等水质指标。结果表明:3种微生态制剂均能改善水质,抑制异养菌的过度增长,但对水质指标的改善各有侧重,混合制剂优于单一制剂。     

Water quality dynamics and shrimp (Litopenaeus vannamei) production in intensive, mesohaline culture systems with two levels of biofloc management

A dense microbial community develops in the water column of intensive, minimal-exchange production systems and is responsible for nutrient cycling. A portion of the microbial community is associated with biofloc particles, and some control over the concentration of these particles has been shown to provide production benefits. To help refine the required degree of control, this study evaluated the effects of two levels of biofloc management on water quality and shrimp (Litopenaeus vannamei) production in commercial-scale culture systems. Eight, 50 m³ raceways were randomly assigned to one of two treatments: T-LS (treatment-low solids) and T-HS (treatment-high solids), each with four replicate raceways. Settling chambers adjacent to the T-LS raceways had a volume of 1700 L with a flow rate of 20 L min⁻¹. The T-HS raceways had 760 L settling chambers with a flow rate of 10 L min⁻¹. Raceways were stocked with 250 shrimp m⁻³, with a mean individual weight of 0.72 g, and shrimp were grown for thirteen weeks. Raceways in the T-LS treatment had significantly reduced total suspended solids, volatile suspended solids, and turbidity compared to the T-HS treatment (P ≤ 0.003). The T-LS raceways also had significantly lower nitrite and nitrate concentrations, and the T-HS raceways had significantly lower ammonia and phosphate concentrations (P ≤ 0.021). With the exception of nitrate, there were no significant differences between the change in concentration of water quality parameters entering and exiting the settling chambers in the T-LS versus the T-HS treatment. Nitrate never accumulated appreciably in the T-LS raceways, possibly due to denitrification in the settling chambers, bacterial substrate limitations in the raceways, or algal nitrate assimilation. However, in the T-HS raceways nitrate did accumulate. The T-HS settling chambers returned a significantly lower nitrate concentration and significantly greater alkalinity concentration than what entered them (P ≤ 0.005), indicating that denitrification may have occurred in those chambers. There were no significant differences in shrimp survival, feed conversion ratio, or final biomass between the two treatments. However, shrimp in the T-LS treatment grew at a significantly greater rate (1.7 g wk⁻¹ vs. 1.3 g wk⁻¹) and reached a significantly greater final weight (22.1 g vs. 17.8 g) than shrimp in the T-HS treatment (P ≤ 0.020). The results of this study demonstrate engineering and management decisions that can have important implications for both water quality and shrimp production in intensive, minimal-exchange culture systems.     

Territorial and agonistic interactions between farmed and wild cod (Gadus morhua)

Studies of contest competition between wild and farmed fish have mostly focused on fish with strongly territorial behaviour. Little is known about species with more plastic social behaviour, such as Atlantic cod (Gadus morhua L.), a species that can either aggressively defend territories or shoal. There is also concern that cod that escape from farms will compete with wild populations. We examined dyadic contest competition between wild and farmed juvenile cod using an intruder–resident experimental set‐up in the laboratory. No prior residency advantage was observed, but the differences between farmed and wild cod were clear. Farmed cod were more submissive than wild cod and fled earlier during contests, which suggests that wild fish often out‐compete farmed intruders. Both fish types initiated aggression earlier against fish of the same background. A multivariate analysis of 11 different behavioural traits indicated that a group of 59% of farmed fish were behaviourally very similar to the 55% most submissive wild fish. These results suggest that wild juvenile cod may be quite robust towards competition for food and shelter from juvenile farmed cod, but further research is needed to verify this pattern.     

水培大蒜技术在水产养殖中应用可能性初步研究

旨在研究水培大蒜在水产养殖中应用的基础性问题。通过在红斑马鱼(Brachydanio rerio)养殖缸中浮床种养大蒜(Allium sativum L.)试验,研究水培大蒜对红斑马鱼自然死亡率的影响试验;通过在异育银鲫(Carassius auratus gibelio)养殖缸中浮床种植大蒜试验,研究水培大蒜对养殖水体水质的影响。结果表明:当大蒜种植量达到4.75 g/L时斑马鱼的自然死亡率显著增加,这可能与溶解氧的降低有关;大蒜种植使得水体总磷、总氮、氨氮、高锰酸盐指数和亚硝态氮水平均发生显著下降,其中对氨氮的影响最显著。水培大蒜可以改善养殖水体水质,但要注意控制种养密度,水培大蒜在水产养殖中的应用具有一定的前景。     

Comparative ecologies of domestic and naturalised rainbow trout in northern Lake Huron

Northern Lake Huron (Ontario, Canada) supports the largest concentration of freshwater salmonid cage culture farms in Canada and receives inputs of domestic‐strain rainbow trout (Oncorhynchus mykiss) through escapement. We assessed the potential effects of these domestic fish on the naturalised rainbow trout of this ecosystem by comparing their respective ecologies. Mature adults were sampled from spawning tributaries, primarily in spring, and to a lesser extent in fall. Fish of domestic origin comprised ~80% of rainbow trout sampled from sites near cage culture facilities but <20% of rainbow trout sampled from more distant sites. Domestic adults in spawning condition (gametes free‐flowing) were present in the spawning tributaries in both spring and fall sampling seasons, whereas naturalised fish in spawning condition were only observed in the spring. Domestic adults were younger and smaller (in length), appeared to have shorter lifespan and had a higher male to female ratio compared with their naturalised counterparts. Growth rates (change in length with age) of naturalised and domestic females in the wild were similar, but domestic males grew more slowly than naturalised males. Domestic females also produced smaller eggs than naturalised females. Food web positions (inferred from δ¹³C and δ¹⁵N) of domestic and naturalised fish were very similar but varied more strongly with body size in the former. Domestic‐strain rainbow trout of cage culture origin can survive, grow and attempt to spawn in northern Lake Huron and have the potential to compete for food, mates and spawning habitat with naturalised rainbow trout.     

船载摇摆胁迫对斑石鲷血液生化指标的影响研究

为了探索鱼类在船载摇摆条件下的应激响应和适应性,为深远海大型养殖平台养殖工艺设计与模式构建提供基础数据和理论依据,利用机械摇摆台模拟船载工况,研究了不同摇摆周期和时间条件下斑石鲷的血液生化指标变化情况。结果表明:(1)短时间摇摆条件下(5 min),摇摆周期10 s组的斑石鲷与空白组无显著性差异;摇摆周期5 s组的斑石鲷血清葡萄糖显著降低、皮质醇和肾上腺素指标显著升高、肌糖原和肝糖原无显著差异。(2)长时间摇摆条件下(60 min),摇摆周期5 s组和10 s组之间斑石鲷无显著性差异。但是,与空白组相比,血清葡萄糖指标均显著降低,皮质醇和肾上腺素指标也均显著升高,肌糖原和肝糖原指标无显著差异。(3)水质变化情况显示,摇摆60 min对于水温、盐度、pH、溶解氧、氨氮等的影响不显著。根据试验结果认为,短期小幅摇摆对斑石鲷不会造成较大影响,而大幅度剧烈摇摆会引起斑石鲷一定程度的应激反应。     

河蟹青虾混养池塘循环水净化效能的初步分析

在河蟹青虾混养池塘构建封闭式循环水养殖系统,并对其净化效果和养殖效益进行了初步研究。结果表明：该系统对水体TN、TP、NH4＋-N和CODMn的平均净化效率分别为27.33%、56.14%、43.91%和39.59%。经湿地净化后的水质能够达到GB3838-2002地表水Ⅲ类排放标准,平均纯收益达53769元/hm2。     

Growth and feeding of Patagonian pejerrey Odontesthes hatcheri reared in net cages

An experiment was performed to evaluate the performance of Patagonian pejerrey during net cage rearing in the oligomesotrophic reservoir Exequiel Ramos Mexía. Survival, growth, nutrition and reproduction were evaluated for two lots of pejerrey, initial weights 4.0 and 2.5 g, reared in net cages for 22 and 14 months respectively. Fish were stocked at 29 and 48 individuals m^?3 densities and fed with an experimental pejerrey feed. During the experiment, temperature fluctuated between 6.6 and 19.6 °C. The two lots did not show substantial differences in survival (pooled survival at the end of the experiment >80%) and the thermal‐unit growth coefficient (TGC), daily feed intake and feeding efficiency were 0.43±0.19, 1.70±0.80 and 53.6±9.9 respectively. Digestive tract analysis showed that caged pejerrey can consume substantial quantities of natural food, taking advantage of its planktivorous condition. Pejerrey showed high percentage survival, slow growth and early sexual maturation in captivity. The use of the TGC is proposed as a model for describing the growth pattern of this species and other pejerrey under culture conditions.     

耕水机在罗非鱼精养池塘的应用效果分析

选择两组罗非鱼(Tilapia)精养池塘作为研究对象,通过设置实验塘和对照塘的方法,研究耕水机的使用对精养池塘水质变化情况和养殖效果的影响.结果表明:与对照池塘相比,实验池塘的水质稳定,池水化学耗氧量的平均值降低了1.56 mg/L,总悬浮物的平均含量下降了24.3028 mg/L,总氨氮的平均浓度下降了0.2418 ...